Cathedral Port Vs. Rectangular Port
On The Tree
Joined: Oct 2011
Posts: 102
Likes: 0
From: Dirty South
I'm not so sure its impossible. Is it a good idea no probably not .,would it function yes would it perform well no. Without doing any of measure what needed is to get a match with LS3 intake to LS1 head. You would need to fill and raise the floor and the widen the port .The manifold port is 1.19 x 2.60 The roof is pretty close just square the corners up
I have a 370 and LS3 heads combo going together
Might be not quite the norm
14:1
single plane
251/271 solid roller
Gear and stall your car correctly then who gives a **** about off idle torque.... RPMs and HP wins races
Torque pulls trailers
Might be not quite the norm
14:1
single plane
251/271 solid roller
Gear and stall your car correctly then who gives a **** about off idle torque.... RPMs and HP wins races
Torque pulls trailers
I'm not so sure its impossible. Is it a good idea no probably not .,would it function yes would it perform well no. Without doing any of measure what needed is to get a match with LS3 intake to LS1 head. You would need to fill and raise the floor and the widen the port .The manifold port is 1.19 x 2.60 The roof is pretty close just square the corners up
I think what he was saying is that it's cost prohibitive. Anything is possible if you have enough money and are stubborn enough, and since the OP doesn't want to buy expensive heads, I'd say Tusky was on point.
TECH Veteran
Joined: Sep 2014
Posts: 4,892
Likes: 703
From: Mississippi
There are too many differences between a cathedral head and a rectangle port head. You can't make a 317 head into an 823 head.
I think what he was saying is that it's cost prohibitive. Anything is possible if you have enough money and are stubborn enough, and since the OP doesn't want to buy expensive heads, I'd say Tusky was on point.
I think what he was saying is that it's cost prohibitive. Anything is possible if you have enough money and are stubborn enough, and since the OP doesn't want to buy expensive heads, I'd say Tusky was on point.
Thanks my pal!! Unfortunately I been really really busy lately and haven't had time to really hang out with you guys on the site. Working a lot of hours and family takes most of my time.
Working 6 days a week 12 hour shifts will get you to say the least....
On a 402-416 it's really a choice between three heads:
Frankenstein TFS 237s
Frankenstein TFS LS3 255s
Frankenstein Ported Stage 2 LS3 OE Heads
Cheapest is the OE heads.
But all will support 416 to 7500. No problem. And all will make more than 600. Talk to Chris Frank. He'll probably say his Stage 2 heads would be tough to beat. But may sway you to the Cathedral ports. The LS3s flow so much more air, but it doesn't manifest as additional power.
Frankenstein TFS 237s
Frankenstein TFS LS3 255s
Frankenstein Ported Stage 2 LS3 OE Heads
Cheapest is the OE heads.
But all will support 416 to 7500. No problem. And all will make more than 600. Talk to Chris Frank. He'll probably say his Stage 2 heads would be tough to beat. But may sway you to the Cathedral ports. The LS3s flow so much more air, but it doesn't manifest as additional power.
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When the LS1 first came out with the cathedral ports everyone is like DAYUM them baby's can run. The the LS3's came out with all the ooh's and aah's and big flow numbers. Now the aftermarket is says "wait, what if me make some cathedral ports that flow like rectangle ports?" Best of both worlds.
IMO, the catherdral ports from AFR, TFS, Texas Speed, or any of the others are kicking serious tail. Stick with the cathedrals and make em work. I'm telling you, the aftermarket is getting back on the catherdral port band wagon.
I have jet boat with a 346 inch LS1 running cathedral AFR's and it's killing big blocks.. well, was. Bulidng a 400+ inch motor now.
IMO, the catherdral ports from AFR, TFS, Texas Speed, or any of the others are kicking serious tail. Stick with the cathedrals and make em work. I'm telling you, the aftermarket is getting back on the catherdral port band wagon.
I have jet boat with a 346 inch LS1 running cathedral AFR's and it's killing big blocks.. well, was. Bulidng a 400+ inch motor now.
Just to show you that flow numbers mean squat, here's a writeup that puts Mast 245 catherdral ports up against a pair of Mast LS3 256's with bigger valves and all. On flow numbers alone, the LS3 heads kill the cathedral port heads. On the dyno, 1 HP difference. And this is three years old. Cathedral port technology has gotten even better now. Actually, technology for both has, but yuo get the idea. Flow numbers alone don't make a good head.
http://www.superchevy.com/how-to/ght...-head-to-head/
http://www.superchevy.com/how-to/ght...-head-to-head/
TECH Fanatic
Joined: Aug 2009
Posts: 1,845
Likes: 255
From: Coast of San Mateo County Between Pacifica & HMB
On a 402-416 it's really a choice between three heads:
Frankenstein TFS 237s
Frankenstein TFS LS3 255s
Frankenstein Ported Stage 2 LS3 OE Heads
Cheapest is the OE heads.
But all will support 416 to 7500. No problem. And all will make more than 600. Talk to Chris Frank. He'll probably say his Stage 2 heads would be tough to beat. But may sway you to the Cathedral ports. The LS3s flow so much more air, but it doesn't manifest as additional power.
Frankenstein TFS 237s
Frankenstein TFS LS3 255s
Frankenstein Ported Stage 2 LS3 OE Heads
Cheapest is the OE heads.
But all will support 416 to 7500. No problem. And all will make more than 600. Talk to Chris Frank. He'll probably say his Stage 2 heads would be tough to beat. But may sway you to the Cathedral ports. The LS3s flow so much more air, but it doesn't manifest as additional power.
On The Tree
Joined: Mar 2015
Posts: 154
Likes: 12
Just to show you that flow numbers mean squat, here's a writeup that puts Mast 245 catherdral ports up against a pair of Mast LS3 256's with bigger valves and all. On flow numbers alone, the LS3 heads kill the cathedral port heads. On the dyno, 1 HP difference. And this is three years old. Cathedral port technology has gotten even better now. Actually, technology for both has, but yuo get the idea. Flow numbers alone don't make a good head.
http://www.superchevy.com/how-to/ght...-head-to-head/
http://www.superchevy.com/how-to/ght...-head-to-head/
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)."
The coefficient of discharge at the end is what you have to pay attention to (plus the 4.030" bore doesn't help the LS3 heads).
The MAST LS3 heads don't offer enough flow over the Cathedral ports with the much larger valves to make a difference. You have to really push flow up another 10-15cfm across the board with that size valve to see a difference.
I posted this in another thread:
In the test, the Cathedrals managed 106cfm/sq in and the LS3 heads offered 103cfm/sq in. That's at .400.
On avg between .200 and .400 it was 111cfm/sq in for cathedral and 107cfm/sq in for the LS3. For the LS3 head to be effective, it must flow more than the cathedral counterpart.
With the Frankenstein LS3 heads... the avg between .200 and .400 ended up being 115cfm/sq in. So, the port is more efficient and flows more...
The MAST LS3 heads don't offer enough flow over the Cathedral ports with the much larger valves to make a difference. You have to really push flow up another 10-15cfm across the board with that size valve to see a difference.
I posted this in another thread:
And that's not a huge port either. If you think about efficiency... a really efficient head hits about 1.45cfm per cc of port volume.
At 269.5cc @ 392cfm... it's you guessed it... good for 1.45cfm of flow. In other words, a very efficient port.
Now, when you compare the flow to the valve for the coefficient of discharge, we can see it's more efficient than even some of the best out there:
At .400" lift with a 2.165" valve... and 295cfm of flow, the calculation is (295cfm/(2.165"*3.14159*.400") = 108cfm/sq in. Most heads do not achieve that level of efficiency. In fact, I'd say anything over 100cfm/sq in at .400 is a very good head.
At 269.5cc @ 392cfm... it's you guessed it... good for 1.45cfm of flow. In other words, a very efficient port.
Now, when you compare the flow to the valve for the coefficient of discharge, we can see it's more efficient than even some of the best out there:
At .400" lift with a 2.165" valve... and 295cfm of flow, the calculation is (295cfm/(2.165"*3.14159*.400") = 108cfm/sq in. Most heads do not achieve that level of efficiency. In fact, I'd say anything over 100cfm/sq in at .400 is a very good head.
On avg between .200 and .400 it was 111cfm/sq in for cathedral and 107cfm/sq in for the LS3. For the LS3 head to be effective, it must flow more than the cathedral counterpart.
With the Frankenstein LS3 heads... the avg between .200 and .400 ended up being 115cfm/sq in. So, the port is more efficient and flows more...
On The Tree
Joined: Mar 2015
Posts: 154
Likes: 12
The coefficient of discharge at the end is what you have to pay attention to (plus the 4.030" bore doesn't help the LS3 heads).
The MAST LS3 heads don't offer enough flow over the Cathedral ports with the much larger valves to make a difference. You have to really push flow up another 10-15cfm across the board with that size valve to see a difference.
I posted this in another thread:
In the test, the Cathedrals managed 106cfm/sq in and the LS3 heads offered 103cfm/sq in. That's at .400.
On avg between .200 and .400 it was 111cfm/sq in for cathedral and 107cfm/sq in for the LS3. For the LS3 head to be effective, it must flow more than the cathedral counterpart.
With the Frankenstein LS3 heads... the avg between .200 and .400 ended up being 115cfm/sq in. So, the port is more efficient and flows more...
The MAST LS3 heads don't offer enough flow over the Cathedral ports with the much larger valves to make a difference. You have to really push flow up another 10-15cfm across the board with that size valve to see a difference.
I posted this in another thread:
In the test, the Cathedrals managed 106cfm/sq in and the LS3 heads offered 103cfm/sq in. That's at .400.
On avg between .200 and .400 it was 111cfm/sq in for cathedral and 107cfm/sq in for the LS3. For the LS3 head to be effective, it must flow more than the cathedral counterpart.
With the Frankenstein LS3 heads... the avg between .200 and .400 ended up being 115cfm/sq in. So, the port is more efficient and flows more...
At 115cfm/sq. in., the FRH heads are only 3cfm/sq. in. better than the cathedral heads. You think there will actually be much of a difference if 4cfm/sq. in. didn't do much for the cathedrals?
Yes. You're looking at 4cfm per sq inch - it's about efficiency of the port - remember, once you hit .500 the LS3 takes off... but the cam doesn't have high lift to use the head flow in the upper range. So, what ends up happening is the LS3 has a lot to overcome when the flow is the same as it is between those heads in the areas where the cam spends more time (.200-.500). At .500, where the LS3 starts to take off, the efficiency is the roughly the same despite there being 15cfm more flow (96 vs 97). So if they were equally efficient, then the flow numbers would matter (or if the cam had .700 lift to make better use of the port). And a 10cfm difference across the power band is about 10-20HP given equally efficient ports.
The flow numbers ultimately come into play at some point. If the efficiency was the same, the flow numbers would matter more. If the rectangle port heads are more efficient, than they will do even better. But that's always been the issue with them. They are not as efficient typically and usually do not have strong intake/exhaust ratios.
The flow numbers ultimately come into play at some point. If the efficiency was the same, the flow numbers would matter more. If the rectangle port heads are more efficient, than they will do even better. But that's always been the issue with them. They are not as efficient typically and usually do not have strong intake/exhaust ratios.
Very interesting read at superchevy about the MAST LS3 and Cathedral heads. I'd be willing to bet, on the road, the cathedrals would have felt better with the better port velocity and more low end power.
Stock for stock there is no argument but the aftermarket is quite interesting. Granted the cathedral heads have a "couple" years of extra development.
Stock for stock there is no argument but the aftermarket is quite interesting. Granted the cathedral heads have a "couple" years of extra development.
On The Tree
Joined: Mar 2015
Posts: 154
Likes: 12
Yes. You're looking at 4cfm per sq inch - it's about efficiency of the port - remember, once you hit .500 the LS3 takes off... but the cam doesn't have high lift to use the head flow in the upper range. So, what ends up happening is the LS3 has a lot to overcome when the flow is the same as it is between those heads in the areas where the cam spends more time (.200-.500). At .500, where the LS3 starts to take off, the efficiency is the roughly the same despite there being 15cfm more flow (96 vs 97). So if they were equally efficient, then the flow numbers would matter (or if the cam had .700 lift to make better use of the port). And a 10cfm difference across the power band is about 10-20HP given equally efficient ports.
The flow numbers ultimately come into play at some point. If the efficiency was the same, the flow numbers would matter more. If the rectangle port heads are more efficient, than they will do even better. But that's always been the issue with them. They are not as efficient typically and usually do not have strong intake/exhaust ratios.
The flow numbers ultimately come into play at some point. If the efficiency was the same, the flow numbers would matter more. If the rectangle port heads are more efficient, than they will do even better. But that's always been the issue with them. They are not as efficient typically and usually do not have strong intake/exhaust ratios.
