Cathedral v.s. Rectangular Port Cylinders - Head To Head
09-13-2013, 12:15 PM
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Cathedral v.s. Rectangular Port Cylinders - Head To Head GM High-Tech Performance
The ultimate cathedral versus rectangular port cylinder head showdown.
The question of the day seems to involve the difference between the original cathedral-port and modern rectangular-port LS heads. More specifically, which one is better? Were we to compare two sets of production heads, there would be little comparison, as even the very best production (cathedral-port) LS6 heads (243 castings) offer nowhere near the flow and power potential of the current LS3 heads. Based on flow numbers alone, the LS3 head has the LS6 heads covered by 50-60 cfm on the intake side (though the change in chamber volume will drop the static compression ratio). The flow figures alone make the swap over to the LS3 components very desirable, especially considering the fact that the stock LS3 head will support well over 600 horsepower (we recently made 690 hp on a 468 stroker with stock LS3 heads). The downside is that the head swap from LS1/LS6 heads to LS3 heads is more involved than a simple R&R. The new heads require a 4.00-inch bore block, LS3 rockers and intake manifold as well, both increasing the cost and limiting the swap potential to 6.0-6.2L motors (and big-bore stroker variants).
Measured stock to stock, LS3 heads will offer power gains over the cathedral-port heads, but what about the aftermarket stuff? After the introduction of the LS3 heads, many enthusiasts started looking down their noses at the original cathedral-port heads, obviously not remembering how much better they were than the original small-block heads they replaced. Has the advent of the rectangular-port LS3 heads relegated the cathedral-port heads to second-tier status or is this just a case of bad PR? To answer this question, we enlisted the aid of Mast Motorsports. Included in their listing of performance components for the LS engine family was an impressive array of both cathedral and rectangular-port cylinder heads. In fact, they had the ideal set of heads for our comparison. One of our concerns for the head test was addressing the potential change in static compression ratio. Traditionally, cathedral-port heads offer smaller chambers than their rectangular-port cousins. The change in compression ratio can be as much as a full point or more, which can improve power by as much as 3-4 percent (near 25 hp on a 600hp motor).
To cure this issue, we selected a set of cathedral-port heads with 70cc combustion chambers to match the chamber volume typical in rectangular-port heads. Many aftermarket manufacturers are now offering larger chambers on their performance cathedral-port heads, as many find their way onto larger displacement strokers. Equalizing the compression ratio eliminated the variable, so we could concentrate on the power difference associated with the flow numbers, port size, and efficiency. For our test, Mast sent us a set of their cathedral-port, 11-degree, six-bolt, medium-bore CNC heads along with a set of LS3 heads that also featured an 11-degree valve angle and full CNC porting. In the tale of the tape, the cathedral-port heads offered 245cc intake ports, a 2.08/1.60 valve combination and peak flow numbers of 338 cfm on the intake and 237 cfm on the exhaust. The CNC-ported LS3 heads stepped up these numbers with an intake port volume of 256cc, a 2.165/1.60 valve package, and peak flow numbers of 372 cfm on the intake and 261 cfm on the exhaust. On numbers alone (like their production counterparts), the ported Mast LS3 heads seemed to hold a clear advantage over the cathedral-ports.
Another area of concern when it comes to any comparison between the cathedral and rectangular-port heads is cam timing. Optimum cam timing is a function of effective operating range, but another important factor is the relationship between the intake and exhaust flow. Typically, the superior intake flow offered by the LS3 head lowers the intake to exhaust flow relationship. This can be equalized (or optimized) by increasing the exhaust duration on the cam relative to the intake. On our Mast heads, the LS3 head offered both more intake and exhaust flow than the cathedral-port heads, resulting in an intake-to-exhaust flow percentage (372/261 cfm) of 69.89 (meaning the exhaust flowed roughly 70 percent of the intake). By comparison, the Mast cathedral-port head checked in slightly higher at 70.1 percent (338/237 cfm). Typically we'd see more of a difference between the two, but the intake-to-exhaust flow differed by less than 1 percent (actually 3/10 ths of a point). Despite the similarity, we decided to run two different cam profiles with the heads. Before you cry foul, know that we ran both heads with both cams just to see how each would respond.
Running a pair of heads with a pair of cams meant we had to double up on cam swaps, but it was all in the name of science, so we didn't mind putting in the extra work. For cam choices, we went right to the Comp Cams catalog and selected cam profiles designed specifically for the cathedral and rectangular-port heads. On the cathedral-port side, we chose a 289LRHR14 (PN 54-461-11) that offered .624-inch lift, a 239/247 duration split, and a 114-degree lobe separation angle. The 289LRRHR14 rectangular-port cam offered the same .624-inch lift, 239-degree intake duration and 114-degree LSA, but increased the exhaust duration to 255 degrees. LS3 cams typically offer a wider spread between the intake and exhaust than comparable LS1 cams. The idea is to help the (relatively) limited exhaust flow with additional exhaust duration. Not only would we show the difference between the two head configurations, but also the difference with their respective cams. How would the cathedral-port heads work with the rectangular-port cam and vice versa? Questions like these are what keep us up at night and why we do so much testing here at GM High-Tech.
Obviously our high-flow heads required something other than a stock 6.0L or even an LS3 short-block. Knowing the heads will support over 600 hp, we built our test motor accordingly. The 6.0L iron block was bored .030 over then treated to a forged 4.0-inch stroker crank and rods from ProComp Motorosports along with a set of dished pistons from Probe Racing.
Airflow Data
Intake Exhaust
Cath Rec Cath Rec
Lift
.100 71 74 55 61
.200 147 146 107 119
.300 221 222 155 188
.400 278 282 203 219
.500 315 330 214 236
.600 335 360 227 251
.650 338 N/A 231 N/A
.700 N/A 372 235 260
The slugs were combined with a ring set from Total Seal and a precision balance job from the boys at L&R Automotive. The combination has already exceeded 1,000 hp in boosted form, so we knew it was plenty stout and more than sufficient for our head test. The short-block was assembled first with the Comp cathedral-port cam (and new hydraulic roller lifters), FAST LSXr intake and matching 102mm throttle body. FAST also supplied the fuel rail and 75-pound injectors for our test along with an XFI engine management system. Additional components used on the motor included a complete Moroso oiling system, Fel Pro MLS head gaskets, and American Racing 1-7/8-inch headers. Equipped as such, the cathedral-port heads and cam combo pumped out 631 hp and 575 lb-ft of torque, with torque production exceeding 550 lb-ft from 4,200 rpm to 5,800 rpm.
Having dialed in the combination, we proceeded to swap out the cam. After installation of the rectangular-port cam, the peak power numbers improved slightly to 639 hp and 578 lb-ft. The increased exhaust duration offered by the rectangular-port cam (255 degrees versus 247 degrees) improved power production slightly from 5,500 rpm on up, but the improvements in top-end power came with a penalty. The increased exhaust duration had a negative effect on low-speed power, as power was down from 3,000 rpm to 4,700 rpm, the greatest difference of 20 lb-ft coming at 3,100 rpm. This should not come as a huge surprise, as increased duration usually follows this trend. Increased duration is done to increase the effective engine speed. The additional exhaust duration also decreased idle vacuum slightly compared to the cathedral-port cam, so low-speed drivability might also suffer (we never loaded the motor below 3,000 rpm).
Though the dyno test was run in reverse order, we will provide the data for the rectangular-port heads first with the cathedral-port cam. Swapping over to the Mast LS3 heads required a change in intake manifold as well. Once again we relied on a FAST LS3 LSXr intake and 102mm throttle body along with the 75-pound injectors, rails and XFI management. Given the difference in airflow, we were naturally excited about replacing the cathedral-port heads with the rectangular-port heads. Run with the Mast CNC LS3 heads and Comp cathedral-port cam, the 408 stroker produced 634 hp and 577 lb-ft of torque, meaning a difference of just 3 hp and 2 lb-ft measured peak to peak. In reality, the cathedral-port heads were within 1-2 hp at the peak, but offered as much as 20 additional lb-ft below 4,000 rpm. We suspected that the rectangular-port heads were not optimized with the cathedral-port cam, but we were still surprised to see such a small difference in power given the extra airflow offered by the LS3 heads.
The ultimate cathedral versus rectangular port cylinder head showdown.
The question of the day seems to involve the difference between the original cathedral-port and modern rectangular-port LS heads. More specifically, which one is better? Were we to compare two sets of production heads, there would be little comparison, as even the very best production (cathedral-port) LS6 heads (243 castings) offer nowhere near the flow and power potential of the current LS3 heads. Based on flow numbers alone, the LS3 head has the LS6 heads covered by 50-60 cfm on the intake side (though the change in chamber volume will drop the static compression ratio). The flow figures alone make the swap over to the LS3 components very desirable, especially considering the fact that the stock LS3 head will support well over 600 horsepower (we recently made 690 hp on a 468 stroker with stock LS3 heads). The downside is that the head swap from LS1/LS6 heads to LS3 heads is more involved than a simple R&R. The new heads require a 4.00-inch bore block, LS3 rockers and intake manifold as well, both increasing the cost and limiting the swap potential to 6.0-6.2L motors (and big-bore stroker variants).
Measured stock to stock, LS3 heads will offer power gains over the cathedral-port heads, but what about the aftermarket stuff? After the introduction of the LS3 heads, many enthusiasts started looking down their noses at the original cathedral-port heads, obviously not remembering how much better they were than the original small-block heads they replaced. Has the advent of the rectangular-port LS3 heads relegated the cathedral-port heads to second-tier status or is this just a case of bad PR? To answer this question, we enlisted the aid of Mast Motorsports. Included in their listing of performance components for the LS engine family was an impressive array of both cathedral and rectangular-port cylinder heads. In fact, they had the ideal set of heads for our comparison. One of our concerns for the head test was addressing the potential change in static compression ratio. Traditionally, cathedral-port heads offer smaller chambers than their rectangular-port cousins. The change in compression ratio can be as much as a full point or more, which can improve power by as much as 3-4 percent (near 25 hp on a 600hp motor).
To cure this issue, we selected a set of cathedral-port heads with 70cc combustion chambers to match the chamber volume typical in rectangular-port heads. Many aftermarket manufacturers are now offering larger chambers on their performance cathedral-port heads, as many find their way onto larger displacement strokers. Equalizing the compression ratio eliminated the variable, so we could concentrate on the power difference associated with the flow numbers, port size, and efficiency. For our test, Mast sent us a set of their cathedral-port, 11-degree, six-bolt, medium-bore CNC heads along with a set of LS3 heads that also featured an 11-degree valve angle and full CNC porting. In the tale of the tape, the cathedral-port heads offered 245cc intake ports, a 2.08/1.60 valve combination and peak flow numbers of 338 cfm on the intake and 237 cfm on the exhaust. The CNC-ported LS3 heads stepped up these numbers with an intake port volume of 256cc, a 2.165/1.60 valve package, and peak flow numbers of 372 cfm on the intake and 261 cfm on the exhaust. On numbers alone (like their production counterparts), the ported Mast LS3 heads seemed to hold a clear advantage over the cathedral-ports.
Another area of concern when it comes to any comparison between the cathedral and rectangular-port heads is cam timing. Optimum cam timing is a function of effective operating range, but another important factor is the relationship between the intake and exhaust flow. Typically, the superior intake flow offered by the LS3 head lowers the intake to exhaust flow relationship. This can be equalized (or optimized) by increasing the exhaust duration on the cam relative to the intake. On our Mast heads, the LS3 head offered both more intake and exhaust flow than the cathedral-port heads, resulting in an intake-to-exhaust flow percentage (372/261 cfm) of 69.89 (meaning the exhaust flowed roughly 70 percent of the intake). By comparison, the Mast cathedral-port head checked in slightly higher at 70.1 percent (338/237 cfm). Typically we'd see more of a difference between the two, but the intake-to-exhaust flow differed by less than 1 percent (actually 3/10 ths of a point). Despite the similarity, we decided to run two different cam profiles with the heads. Before you cry foul, know that we ran both heads with both cams just to see how each would respond.
Running a pair of heads with a pair of cams meant we had to double up on cam swaps, but it was all in the name of science, so we didn't mind putting in the extra work. For cam choices, we went right to the Comp Cams catalog and selected cam profiles designed specifically for the cathedral and rectangular-port heads. On the cathedral-port side, we chose a 289LRHR14 (PN 54-461-11) that offered .624-inch lift, a 239/247 duration split, and a 114-degree lobe separation angle. The 289LRRHR14 rectangular-port cam offered the same .624-inch lift, 239-degree intake duration and 114-degree LSA, but increased the exhaust duration to 255 degrees. LS3 cams typically offer a wider spread between the intake and exhaust than comparable LS1 cams. The idea is to help the (relatively) limited exhaust flow with additional exhaust duration. Not only would we show the difference between the two head configurations, but also the difference with their respective cams. How would the cathedral-port heads work with the rectangular-port cam and vice versa? Questions like these are what keep us up at night and why we do so much testing here at GM High-Tech.
Obviously our high-flow heads required something other than a stock 6.0L or even an LS3 short-block. Knowing the heads will support over 600 hp, we built our test motor accordingly. The 6.0L iron block was bored .030 over then treated to a forged 4.0-inch stroker crank and rods from ProComp Motorosports along with a set of dished pistons from Probe Racing.
Airflow Data
Intake Exhaust
Cath Rec Cath Rec
Lift
.100 71 74 55 61
.200 147 146 107 119
.300 221 222 155 188
.400 278 282 203 219
.500 315 330 214 236
.600 335 360 227 251
.650 338 N/A 231 N/A
.700 N/A 372 235 260
The slugs were combined with a ring set from Total Seal and a precision balance job from the boys at L&R Automotive. The combination has already exceeded 1,000 hp in boosted form, so we knew it was plenty stout and more than sufficient for our head test. The short-block was assembled first with the Comp cathedral-port cam (and new hydraulic roller lifters), FAST LSXr intake and matching 102mm throttle body. FAST also supplied the fuel rail and 75-pound injectors for our test along with an XFI engine management system. Additional components used on the motor included a complete Moroso oiling system, Fel Pro MLS head gaskets, and American Racing 1-7/8-inch headers. Equipped as such, the cathedral-port heads and cam combo pumped out 631 hp and 575 lb-ft of torque, with torque production exceeding 550 lb-ft from 4,200 rpm to 5,800 rpm.
Having dialed in the combination, we proceeded to swap out the cam. After installation of the rectangular-port cam, the peak power numbers improved slightly to 639 hp and 578 lb-ft. The increased exhaust duration offered by the rectangular-port cam (255 degrees versus 247 degrees) improved power production slightly from 5,500 rpm on up, but the improvements in top-end power came with a penalty. The increased exhaust duration had a negative effect on low-speed power, as power was down from 3,000 rpm to 4,700 rpm, the greatest difference of 20 lb-ft coming at 3,100 rpm. This should not come as a huge surprise, as increased duration usually follows this trend. Increased duration is done to increase the effective engine speed. The additional exhaust duration also decreased idle vacuum slightly compared to the cathedral-port cam, so low-speed drivability might also suffer (we never loaded the motor below 3,000 rpm).
Though the dyno test was run in reverse order, we will provide the data for the rectangular-port heads first with the cathedral-port cam. Swapping over to the Mast LS3 heads required a change in intake manifold as well. Once again we relied on a FAST LS3 LSXr intake and 102mm throttle body along with the 75-pound injectors, rails and XFI management. Given the difference in airflow, we were naturally excited about replacing the cathedral-port heads with the rectangular-port heads. Run with the Mast CNC LS3 heads and Comp cathedral-port cam, the 408 stroker produced 634 hp and 577 lb-ft of torque, meaning a difference of just 3 hp and 2 lb-ft measured peak to peak. In reality, the cathedral-port heads were within 1-2 hp at the peak, but offered as much as 20 additional lb-ft below 4,000 rpm. We suspected that the rectangular-port heads were not optimized with the cathedral-port cam, but we were still surprised to see such a small difference in power given the extra airflow offered by the LS3 heads.
09-13-2013, 12:16 PM
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The final test run was to combine the rectangular-port cam with the Mast LS3 heads. The combination produced the highest peak power numbers of the day (640 hp and 680 lb-ft), but only by 1 hp and 2 lb-ft over the cathedral-port head and rectangular-port cam combo. The LS3 heads did respond better to the installation of the rectangular-port cam. The cam improved power from 5,300 rpm on up, with only a slight loss in power below 3,300 rpm. Obviously there is something to increasing efficiency of the exhaust port with increased duration. Though we were happy with the results of the cam test, we were still surprised that the LS3 heads offered little or no power over their cathedral-port counterparts. Given the disparity in airflow, we expected to see 10-15 hp, but the results of this head-to-head shootout just go to show that airflow isn't everything. It also showed that you can't go wrong with either set of Mast heads on your performance LS combination.
Coefficient of Discharge
Though this may be a tad on the technical side, it might well help explain why the cathedral-port heads did so well against the rectangular-port heads despite the difference in flow. The coefficient of discharge is essentially a measurement of the efficiency of the port (actually the curtain area of the valve). The curtain area of the valve is easy to visualize. Imagine dropping a circular shower curtain down from the outside diameter of the intake valve. The length of the shower curtain would be determined by the maximum valve lift, but (more importantly), the curtain area can be calculated at every valve lift where airflow is measured (usually .100-.700-inch lift). Much like average airflow through the head port, we can take the average coefficient of discharge by combining the averages for all the lift values and then dividing by the number of lift points. The formula for coefficient of discharge is as follows: C/D=airflow/curtain area. Curtain area=valve diameter x Pi x Lift. Applying the formula to our heads, we see that though the LS3 heads offer a better coefficient of discharge at the maximum lift of .700, the cathedral-port head offered not only a superior coefficient of discharge from .100-.400 lift, but a better average coefficient of lift from .100-.600 lift. Could it be that the efficiency of the port overcame the absolute flow of LS3 heads?
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our .624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
Coefficient of Discharge
Though this may be a tad on the technical side, it might well help explain why the cathedral-port heads did so well against the rectangular-port heads despite the difference in flow. The coefficient of discharge is essentially a measurement of the efficiency of the port (actually the curtain area of the valve). The curtain area of the valve is easy to visualize. Imagine dropping a circular shower curtain down from the outside diameter of the intake valve. The length of the shower curtain would be determined by the maximum valve lift, but (more importantly), the curtain area can be calculated at every valve lift where airflow is measured (usually .100-.700-inch lift). Much like average airflow through the head port, we can take the average coefficient of discharge by combining the averages for all the lift values and then dividing by the number of lift points. The formula for coefficient of discharge is as follows: C/D=airflow/curtain area. Curtain area=valve diameter x Pi x Lift. Applying the formula to our heads, we see that though the LS3 heads offer a better coefficient of discharge at the maximum lift of .700, the cathedral-port head offered not only a superior coefficient of discharge from .100-.400 lift, but a better average coefficient of lift from .100-.600 lift. Could it be that the efficiency of the port overcame the absolute flow of LS3 heads?
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our .624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
09-13-2013, 01:05 PM
#6
TECH Enthusiast
+1, the only time I would consider a Rectangle Head is if its something like an ODR build. The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head. If you are building an X275 motor with something like 4.125" x 3.500" dimension, equaling a 369CID engine, I could see a Rectangle head thriving there, but for your average street motor, NOPE.
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09-13-2013, 01:12 PM
#8
TECH Enthusiast
It really depends on the goals of the car, and the size blower/turbo, as well as the class being raced.
For example: I plan on running in the LSX Real Street Class, my engine will have Cathedral heads, for one they keep the air velocity up, combine that with the intake I will be running you have gobs of low end torque, which is good for something that has a small turbocharger such as myself. If you are running 1/8 mile racing you can also use the same principles.
For example: I plan on running in the LSX Real Street Class, my engine will have Cathedral heads, for one they keep the air velocity up, combine that with the intake I will be running you have gobs of low end torque, which is good for something that has a small turbocharger such as myself. If you are running 1/8 mile racing you can also use the same principles.
09-13-2013, 01:51 PM
#11
What I dont like about the test is that the Fast ls3 intake isnt any better than a stock ls3 intake. We have seen them dyno back to back against a stock ls3 and lose a couple horses even on max effort setups. Im not knocking the theory. Its pretty standard knowledge and as stated before has been beaten to death. In this test though you are also comparing a Fast 102 cathedral to basically an intake no better than a stock ls3 intake.
09-13-2013, 02:12 PM
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i don't know how to do it yet........Cut and paste..
I'm going to LA Cali.....22 hr drive.
I like to keep a good conversion.
DEFYANT: The only time I would consider a Rectangle Head is if its something like an ODR build. The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
I'll take you up on that bet......once I get MY heads....
What heads are U talking about ....Not against any Mast heads what Rec. Port configuration, do you want.... 240cc Small bore heads & 11*degrees... that out flow AFR/TFS heads 220-245 so....... The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
You talking L92's with 267cc( I have bare castings) ports that flow's .355 cfms while MY mast heads flow the same # with a Cathedral size 240 cc port and it's 11 degree's...
They are good heads but technology has caught up they make small port LS7 heads and the Mast heads are the perfect Example.....Compare any Cathedral head VS Mast small bore heads as stated from above:
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our *.624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
I'm over 700. lift and a fast intake is not not my limitation for air flow... max for FAST ported is what 340-350 cfms .....you are basically saying that you have better bottom end TQ because of smaller runners..... well Mast/TFS have done that with 240-256cc runners and You can go larger in lift because the flow is extended there...... so why not go there Cathedrals flow at the best @ Mid lifts' we Now cover that....Also with Smaller port and Test bore compare TFS 245 heads...check it out for yourself... You have got be talking about factory castings or some other head manufacturer.. not Mast/TFS LS3's....everything is 11*degrees and you can also have a small port....Perfect...We beating a dead horse but it's something to talk about....Compare a simple TFS 245- 265 vs TFS ls3's which head are better and have the most Potential.....These heads flow up to 370'-380's at 650 to 700 lift...and Mid lift flows to match I ain't scared of taking it there... 700 lift...... open up the throat and bowls for bigger valves as some guy's tend to send there TFS/AFR Cathedrals heads to be reworked so am I.....tiny 240cc port's with larger valves they already out flow them in stock configuration....You talking about some L92's or LS7 heads on a 408-416
I'm going to LA Cali.....22 hr drive.
I like to keep a good conversion.
DEFYANT: The only time I would consider a Rectangle Head is if its something like an ODR build. The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
I'll take you up on that bet......once I get MY heads....
What heads are U talking about ....Not against any Mast heads what Rec. Port configuration, do you want.... 240cc Small bore heads & 11*degrees... that out flow AFR/TFS heads 220-245 so....... The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
You talking L92's with 267cc( I have bare castings) ports that flow's .355 cfms while MY mast heads flow the same # with a Cathedral size 240 cc port and it's 11 degree's...
They are good heads but technology has caught up they make small port LS7 heads and the Mast heads are the perfect Example.....Compare any Cathedral head VS Mast small bore heads as stated from above:
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our *.624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
I'm over 700. lift and a fast intake is not not my limitation for air flow... max for FAST ported is what 340-350 cfms .....you are basically saying that you have better bottom end TQ because of smaller runners..... well Mast/TFS have done that with 240-256cc runners and You can go larger in lift because the flow is extended there...... so why not go there Cathedrals flow at the best @ Mid lifts' we Now cover that....Also with Smaller port and Test bore compare TFS 245 heads...check it out for yourself... You have got be talking about factory castings or some other head manufacturer.. not Mast/TFS LS3's....everything is 11*degrees and you can also have a small port....Perfect...We beating a dead horse but it's something to talk about....Compare a simple TFS 245- 265 vs TFS ls3's which head are better and have the most Potential.....These heads flow up to 370'-380's at 650 to 700 lift...and Mid lift flows to match I ain't scared of taking it there... 700 lift...... open up the throat and bowls for bigger valves as some guy's tend to send there TFS/AFR Cathedrals heads to be reworked so am I.....tiny 240cc port's with larger valves they already out flow them in stock configuration....You talking about some L92's or LS7 heads on a 408-416
Last edited by lil john; 09-13-2013 at 02:19 PM.
09-13-2013, 02:16 PM
#14
The copy and paste function has been mastered.
I thought he ended the unattended debate a few weeks ago in this thread? https://ls1tech.com/forums/generatio...d-debates.html
I guess not
If the informtion is already here and on the web, what is the purpose of this thread outside of getting folks to argue?
I thought he ended the unattended debate a few weeks ago in this thread? https://ls1tech.com/forums/generatio...d-debates.html
I guess not
If the informtion is already here and on the web, what is the purpose of this thread outside of getting folks to argue?
With that said, rectangle port heads suck, cathedral port heads are still the ****. 'Merica. F*ck Yeah.
09-13-2013, 02:19 PM
#15
i don't know how to do it yet........Cut and paste..
I'm going to LA Cali.....22 hr drive.
I like to keep a good conversion.
DEFYANT: The only time I would consider a Rectangle Head is if its something like an ODR build. The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
I'll take you up on that bet......once I get MY heads....
What heads are U talking about ....Not against any Mast heads what Rec. Port configuration, do you want.... 240cc Small bore heads & 11*degrees... that out flow AFR/TFS heads 220-245 so....... The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
You talking L92's with 267cc( I have bare castings) ports that flow's .355 cfms while MY mast heads flow the same # with a Cathedral size 240 cc port and it's 11 degree's...
They are good heads but technology has caught up they make small port LS7 heads and the Mast heads are the perfect Example.....Compare any Cathedral head VS Mast small bore heads as stated from above:
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our *.624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
I'm over 700. lift and a fast intake is not not my limitation for air flow... max for FAST ported is what 340-350 cfms .....you are basically saying that you have better bottom end TQ because of smaller runners..... well Mast/TFS have done that with 240-256cc runners and You can go larger in lift because the flow is extended there...... so why not go there Cathedrals flow at the best @ Mid lifts' we Now cover that....Also with Smaller port and Test bore compare TFS 245 heads...check it out for yourself... You have got be talking about factory castings or some other head manufacturer.. not Mast/TFS LS3's....everything is 11*degrees and you can also have a small port....Perfect...We beating a dead horse but it's something to talk about....Compare a simple TFS 245- 265 vs TFS ls3's which head are better and have the most Potential.....These heads flow up to 370'-380's at 650 to 700 lift...and Mid lift flows to match I ain't scared of taking it there... 700 lift...... open up the throat and bowls for bigger valves as some guy's tend to send there TFS/AFR Cathedrals heads to be reworked so am I..... small port with larger valves already out flow them in stock configuration....You talking abotu some L92's or LS7 heads on a 408-416
I'm going to LA Cali.....22 hr drive.
I like to keep a good conversion.
DEFYANT: The only time I would consider a Rectangle Head is if its something like an ODR build. The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
I'll take you up on that bet......once I get MY heads....
What heads are U talking about ....Not against any Mast heads what Rec. Port configuration, do you want.... 240cc Small bore heads & 11*degrees... that out flow AFR/TFS heads 220-245 so....... The air velocity is dramatically decreased in a Rectangle head compared to a Cathedral Head.
You talking L92's with 267cc( I have bare castings) ports that flow's .355 cfms while MY mast heads flow the same # with a Cathedral size 240 cc port and it's 11 degree's...
They are good heads but technology has caught up they make small port LS7 heads and the Mast heads are the perfect Example.....Compare any Cathedral head VS Mast small bore heads as stated from above:
Conclusion
The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better ******low-speed power***** and produced peak torque lower**** than the LS3 heads *****(irrespective of cam choice). This might be attributed to the difference in **port volume, though these Mast LS3 heads featured intake port volumes of 256 cc compared to 245 cc for the cathedral-port heads. *What the LS3 heads really needed was a cam that could take full advantage of the head flow (372 cfm) offered at .700-inch lift*. *The use of our *.624-lift cam negated some of the additional flow offered by the LS3 heads, though 360 cfm at .600 lift was still a sizable jump over the 335 cfm offered by the cathedral-port heads.*
I'm over 700. lift and a fast intake is not not my limitation for air flow... max for FAST ported is what 340-350 cfms .....you are basically saying that you have better bottom end TQ because of smaller runners..... well Mast/TFS have done that with 240-256cc runners and You can go larger in lift because the flow is extended there...... so why not go there Cathedrals flow at the best @ Mid lifts' we Now cover that....Also with Smaller port and Test bore compare TFS 245 heads...check it out for yourself... You have got be talking about factory castings or some other head manufacturer.. not Mast/TFS LS3's....everything is 11*degrees and you can also have a small port....Perfect...We beating a dead horse but it's something to talk about....Compare a simple TFS 245- 265 vs TFS ls3's which head are better and have the most Potential.....These heads flow up to 370'-380's at 650 to 700 lift...and Mid lift flows to match I ain't scared of taking it there... 700 lift...... open up the throat and bowls for bigger valves as some guy's tend to send there TFS/AFR Cathedrals heads to be reworked so am I..... small port with larger valves already out flow them in stock configuration....You talking abotu some L92's or LS7 heads on a 408-416
09-13-2013, 02:22 PM
#16
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Real #'s for 240cc Mast small bore heads
INCH LIFT INTAKE FLOW (CFM) EXHAUST FLOW (CFM)
0.100 69 105
0.200 37 154
0.300 208 198
0.400 266 217
0.500 306 222
0.600 335 226
0.650 345 229
0.700 351 234
0.750 335 238
I'm going to fix that last # with bigger valves and bowl work/short side radius work...This is on a 3.900 bore Buddy
INCH LIFT INTAKE FLOW (CFM) EXHAUST FLOW (CFM)
0.100 69 105
0.200 37 154
0.300 208 198
0.400 266 217
0.500 306 222
0.600 335 226
0.650 345 229
0.700 351 234
0.750 335 238
I'm going to fix that last # with bigger valves and bowl work/short side radius work...This is on a 3.900 bore Buddy
09-13-2013, 02:25 PM
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stay in your lane....I just know how to cut and paste..I'm going to Cali.. this is not English class U get the point...... the rest of the info is readable.
09-13-2013, 02:36 PM
#18
It looks like you're ranking heads based on flow numbers (good, better, best), which if true, only shows that you're already way behind the curve here. Especially considering that the article you just copy and pasted basically discredits the value of flow numbers as the higher flowing heads made similar peak power to the cathedral ports while making less overall power. There is a lot more to cylinder heads than flow numbers and port volume. I hope you're not spending a lot of money on your build just to learn that the hard way.
09-13-2013, 03:02 PM
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so let me right this right ...They did not max the head out with the cam selected.change the cam to more of a 660 lift...I no what is going on....Also intake is a limiting factor.... Ain't no way in hell Fast can support 370-350 cfms change over to a MAST 4500/4150 and where would the same cathedral ports land...behind...We have more Potential...Period and it's also a fact.Now we have smaller runners to match that low end TQ or better stated:Better Mid lift #'s you Cathedral guy's are so crazy about we got that now and flow well into 380's to add salt to the wound.Fast is perfect for a head that's limited to 350 cfms...I'm looking @ 370 and better so yeah the Fast shot me down at anything past 350cfms....Summit or Jeg's can keep that.....I got heads that flow to 370 but I use a 320cfms limited intake....You should get better performance I just shot my self in the foot. Me find out the hard way...not going to happen...this engine's on paper and part receipts....It's been Carefully planned by me and overseen by LME....we are talking heads......I'm taking bet's once I get the heads owned & reworked I have the intake Vic Jr. and Fast injectors & 4150 T/b, i'll call Byran to see if he's dyno'ing any engines with a Cathedral port....to compare...I will not use LS3 composite intake or FAST 102t/b... I'm not willing to limit my self to 600 lift and a fast intake...
09-13-2013, 03:06 PM
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Home boy no mag can tell me fact....IF thats the case Mast heads are the best...fact.
I've help build over 8 engines with my uncle and I went to UTI this is just my 1st LS engine... There was no threat to you, u always think u know best...so I stated to: stay in you lane that's no threat but I will tell you this I'm unfuckwitable.... Your a *mark* Dude....you know what that means in the hood
I've help build over 8 engines with my uncle and I went to UTI this is just my 1st LS engine... There was no threat to you, u always think u know best...so I stated to: stay in you lane that's no threat but I will tell you this I'm unfuckwitable.... Your a *mark* Dude....you know what that means in the hood