How good are the L92 heads compared to aftermarket castings?
01-05-2010, 02:29 PM
#41
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Ok, lets go ack to the point about the heads tehmselves. I've got a set on one of my vehicles. Will it make more peak power, yes. Is it more than a bit soggy on the mids and lows, defintiely. The heads don't "come on" until about 3500-4000 RPM in a stock cube motor. The catherdral ports on the same engine come in quicker, but run out of steam up top. So, it depends on what you want to do.
Are the L92's a very reasonable cost alternative to the aftermarket cathedral port heads? Yes, absolutely. They have reasonably good flow, and they have been shown to make good power. But IMHO, they are less than ideal.
Now, with regards to size. Is the port "too big"? Well, I guess the answer is, it depends on what you mean. Let supposed that you take two cylinder heads that have the same flow, but one has a bigger runner volume. What happens?
In my own personal experience going from a heavily ported 243 casting with 230+ cc's and going to a smaller port aftermarket head ~205 cc's, I picked up throttle response, drivability, and overall the car was much more enjoyable to drive.
Even though peak flow was about the same, I saw better mph (+2mph) at the drag strip with the more efficient smaller port aftermarket heads.
So, is a head that makes the same or better flow as an L92 head with 20-30cc less runner volume a better option. All things being equal, yes it is.
Look, you can get a head to flow any number you want as long as you make the runner big enough. The trick to heads is to make them flow what you need with as small a runner as possible to keep up velocity. Velocity and efficiency are what are going to work to fill the cylinder.
There are plenty of magazine tests, and plenty of first hand experience on this site with folks who have used L92 heads with good results. So, I'm not going to say you won't have good results with them. And, with many of the folks on here, cost is the number one factor over all else. So, since L92's are the least expensive option, many folks are making that their overall choice. But, for many other folks, cost may not be the number one factor.
What I expect we will see as time goes on with the L92 is the aftermarket offering that port shape while shrinking the port volume and improving deck thickness, exhaust port efficiency, while retaining the overall intake port shape.
I believe Mast is already offering a head "Mast Black Label" like what I'm describing. I have not had a chance to test them or any of the other heads that are using the LS3/L92 port.
Can you cam a car to "crutch" the issue of having a big soggy intake port and a less than optimal exhaust? Yes, you can do things with the valve events to promote cylinder filling, and you can put a big exhaust lobe to bleed down the exhaust side.
It also comes down to what you have for supporting hardware (intake, rockers, etc...) if you are starting form a "green field", then it may color your choices as opposed to if you already had for instance a Cathedral port FAST intake.
Are you planning to go towards forced induction where you probably want a thicker deck?
How big a motor are you looking to build?
Like I said, I think the L92 is a good economy piece. But, like I said, price is not always the only motivator....
Are the L92's a very reasonable cost alternative to the aftermarket cathedral port heads? Yes, absolutely. They have reasonably good flow, and they have been shown to make good power. But IMHO, they are less than ideal.
Now, with regards to size. Is the port "too big"? Well, I guess the answer is, it depends on what you mean. Let supposed that you take two cylinder heads that have the same flow, but one has a bigger runner volume. What happens?
In my own personal experience going from a heavily ported 243 casting with 230+ cc's and going to a smaller port aftermarket head ~205 cc's, I picked up throttle response, drivability, and overall the car was much more enjoyable to drive.
Even though peak flow was about the same, I saw better mph (+2mph) at the drag strip with the more efficient smaller port aftermarket heads.
So, is a head that makes the same or better flow as an L92 head with 20-30cc less runner volume a better option. All things being equal, yes it is.
Look, you can get a head to flow any number you want as long as you make the runner big enough. The trick to heads is to make them flow what you need with as small a runner as possible to keep up velocity. Velocity and efficiency are what are going to work to fill the cylinder.
There are plenty of magazine tests, and plenty of first hand experience on this site with folks who have used L92 heads with good results. So, I'm not going to say you won't have good results with them. And, with many of the folks on here, cost is the number one factor over all else. So, since L92's are the least expensive option, many folks are making that their overall choice. But, for many other folks, cost may not be the number one factor.
What I expect we will see as time goes on with the L92 is the aftermarket offering that port shape while shrinking the port volume and improving deck thickness, exhaust port efficiency, while retaining the overall intake port shape.
I believe Mast is already offering a head "Mast Black Label" like what I'm describing. I have not had a chance to test them or any of the other heads that are using the LS3/L92 port.
Can you cam a car to "crutch" the issue of having a big soggy intake port and a less than optimal exhaust? Yes, you can do things with the valve events to promote cylinder filling, and you can put a big exhaust lobe to bleed down the exhaust side.
It also comes down to what you have for supporting hardware (intake, rockers, etc...) if you are starting form a "green field", then it may color your choices as opposed to if you already had for instance a Cathedral port FAST intake.
Are you planning to go towards forced induction where you probably want a thicker deck?
How big a motor are you looking to build?
Like I said, I think the L92 is a good economy piece. But, like I said, price is not always the only motivator....
01-05-2010, 02:53 PM
#42
I seem to remember someone on here filling the runners on an L92 head with epoxy, and picking up as much as 70ft-lbs on a 427ci iron block, without sacrificing any horsepower.
*EDIT* Found it...L92 head 427 makes 700HP n/a!
*EDIT* Found it...L92 head 427 makes 700HP n/a!
The engine is a 4.060" bore x 4.100" stroke piece built by someone else using a 6.0 cast iron block with 6.125" rods and flat top pistons. The heads and intake were already on the engine when it came in and due to time constraints I don't know how much they were milled but they were unported. We filled the intake runners and fully ported them along with filling and completely reshaping the runners and plenum in the fabricated intake. We then dyno'd the engine with the existing cam (248/258-114, .630/.630) and picked up MAJOR amounts of torque while making 5-10 more HP.
As for the power curve, after the head and intake mods, the engine's torque curve was drastically widened and improved the average power under the curve. If you will note, the old peak tq occurred at 5900 while the improved heads lowered it to 5200 RPM while maintaining the peak hp RPM level. The tq at 4700 RPM was improved by 70 lb/ft! The engine also needed 2-3 degrees fewer ignition timing to make peak power. I would call that a sizeable difference in output from nothing more than an improvement in port velocity.
As for the power curve, after the head and intake mods, the engine's torque curve was drastically widened and improved the average power under the curve. If you will note, the old peak tq occurred at 5900 while the improved heads lowered it to 5200 RPM while maintaining the peak hp RPM level. The tq at 4700 RPM was improved by 70 lb/ft! The engine also needed 2-3 degrees fewer ignition timing to make peak power. I would call that a sizeable difference in output from nothing more than an improvement in port velocity.
Last edited by KCS; 01-05-2010 at 03:06 PM.
01-05-2010, 03:20 PM
#43
6600 rpm clutch dump of death Administrator
We did similar things with the Buick heads for the Gen I SBC. My buddy has several old 353" B/SM motors that came with Buick heads. The floor of the port is filled with 3/4" of epoxy. Buck in the day on the old Ford motors I had friends who made "port plates" for the exhaust side which bolted between the headers and the head itself to shrink the exhaust port volume as well.
01-05-2010, 03:32 PM
#44
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We did similar things with the Buick heads for the Gen I SBC. My buddy has several old 353" B/SM motors that came with Buick heads. The floor of the port is filled with 3/4" of epoxy. Buck in the day on the old Ford motors I had friends who made "port plates" for the exhaust side which bolted between the headers and the head itself to shrink the exhaust port volume as well.
We used to do that to the Turbo Buick heads before they had any aftermarket castings.
The Cleveland 4 Barrel and Boss heads were the same way. We could run a smaller lobe on the intake (like the LS guys like to do) to help the velocity with the big port volume.
Those were all OEM heads that were patched together. Now people just design and cast a set of heads.
Ahh the old days, the parts really sucked!
Robin
01-05-2010, 08:55 PM
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Strange. I ordered some for the LS9 heads...and that is what they came up with. GM lookup and the 09 GMPP mag says that the LSA uses its own intake valve, but it is solid stem. Not that i am questioning you, but I would like to know for myself. May have to order some of them in and post up what i find!!
I'll let you know what I find.
Jim used to be good at telling me what parts were in what heads, but alas he is gone also.
Robin
01-06-2010, 08:46 AM
#46
Well i held the valves in my hands as a form of vicarious glory (since i will prob never own either car ha) and looked them over well. The intake is def titanium, but I am pretty sure the exhaust is lighter than the normal or inconel exhaust valve you would see in an LS3/L92 head, and im pretty sure the exhaust on the LSA was heavier. Maybe I can get them in again and remeasure.
01-07-2010, 02:58 PM
#47
The misconception with L92 heads "not making power" comes from not looking at the specs all around. For peak HP major race applications, they may not always be the best, but in a h/c street car they are incredible. They completely change power delivery from the peaky cathedral port setups with big cams to major low end monsters with smaller much more friendly cams and still near the same pk numbers. They make killer power from much small cams, and they make TQ so early. With CNC heads and the same cam John mentions above in the 22x/23x range we have made 478rwhp and upper 45x rwtq on the stock LS2 bottom end and it idles and drives absolutely like stock. Note that those are unmilled heads and stock gaskets, so you are dropping the compression quite a bit from stock and still getting that HP and TQ. That cam leaves room for a thinner gasket and/or milling for compression and could make even more power with even better manners.
Like with most arguments on here, people simply argue peak HP numbers when that is in no way the whole story. Average hp/tq means alot, and where it makes the power.
Like with most arguments on here, people simply argue peak HP numbers when that is in no way the whole story. Average hp/tq means alot, and where it makes the power.
01-07-2010, 03:16 PM
#48
No flycutting at all. They could have worked possibly milled to a 65cc but we would have had to check PTV just to make sure. Could have and DO are 2 different things.
I am unsure as to why everyone thinks with ANY cam and the L92 heads on a stock LS2 shortblock that you always have to flycutt. That is normally from someone putting a huge cam in there that does not recognize what the L92 heads really do. Or incorrect valve event timing.
No offense intended at you spectre. I just mean i have seen and heard this on numerous occasions. People love big cams and sometimes get hung up on them when trying to produce peaky power. The heads are not all about that. They work well for their intended purpose. Esp for the price.
I am unsure as to why everyone thinks with ANY cam and the L92 heads on a stock LS2 shortblock that you always have to flycutt. That is normally from someone putting a huge cam in there that does not recognize what the L92 heads really do. Or incorrect valve event timing.
No offense intended at you spectre. I just mean i have seen and heard this on numerous occasions. People love big cams and sometimes get hung up on them when trying to produce peaky power. The heads are not all about that. They work well for their intended purpose. Esp for the price.
Last edited by Beau@SDPC; 01-07-2010 at 03:54 PM.
01-09-2010, 05:32 PM
#49
No flycutting at all. They could have worked possibly milled to a 65cc but we would have had to check PTV just to make sure. Could have and DO are 2 different things.
I am unsure as to why everyone thinks with ANY cam and the L92 heads on a stock LS2 shortblock that you always have to flycutt. That is normally from someone putting a huge cam in there that does not recognize what the L92 heads really do. Or incorrect valve event timing.
No offense intended at you spectre. I just mean i have seen and heard this on numerous occasions. People love big cams and sometimes get hung up on them when trying to produce peaky power. The heads are not all about that. They work well for their intended purpose. Esp for the price.
I am unsure as to why everyone thinks with ANY cam and the L92 heads on a stock LS2 shortblock that you always have to flycutt. That is normally from someone putting a huge cam in there that does not recognize what the L92 heads really do. Or incorrect valve event timing.
No offense intended at you spectre. I just mean i have seen and heard this on numerous occasions. People love big cams and sometimes get hung up on them when trying to produce peaky power. The heads are not all about that. They work well for their intended purpose. Esp for the price.
I think when time gets closer for me to start putting everything together and starting the swap, Ill just give you a call and talk in person reguarding a cam choice.
01-10-2010, 01:02 AM
#50
I am a large proponent of cathedral port heads. I think l92 heads can do some nice things for the money, but beyond mild head and cam results everything I've seen has been dissapointing. With a nitrous 408 in mind I would stick to an aftermarket cathedral port option.
02-07-2010, 03:03 PM
#51
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Well i held the valves in my hands as a form of vicarious glory (since i will prob never own either car ha) and looked them over well. The intake is def titanium, but I am pretty sure the exhaust is lighter than the normal or inconel exhaust valve you would see in an LS3/L92 head, and im pretty sure the exhaust on the LSA was heavier. Maybe I can get them in again and remeasure.
I was finally able to pull the LSA heads off the shelf and take a look at the parts. I was wrong and John was wrong.....well John was closer than I was
I weighed the valves from 4 combinations. Of course GM OEM Valves
Intake Exhaust
L92 110 Grams 92 Grams
LS3 88 Grams 92 Grams
LSA 119 Grams 89 Grams
LS9 74 Grams 71 Grams
The Casting number on the LSA head was 4863 and the LS9 head it was 1771
I was suprised that the casting numbers were different as I thought they used the same casting with a different head bolt size on the LS9.
Since the valves in the LSA are not the same as anything else (as I had thought) I wonder what the are the differences.
Might find some description in the parts book who knows.
Maybe Jim can chime in.
Robin
02-08-2010, 08:51 AM
#52
GM lists those LS9 valves as the sodium filled. I presume i was talking about the LS9 - LSA valves when i said the exhaust was heavier. But it has been a few moons since i posted. Since the LS9 still comes in at a 1.59 then it seems to be a pretty good idea to try and use them in a "lightweight" build. They are not pricey, and work well. I would imagine the LSA is prob some lighter allot inconel. Just a guess though.
02-08-2010, 12:09 PM
#53
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The misconception with L92 heads "not making power" comes from not looking at the specs all around. For peak HP major race applications, they may not always be the best, but in a h/c street car they are incredible. They completely change power delivery from the peaky cathedral port setups with big cams to major low end monsters with smaller much more friendly cams and still near the same pk numbers. They make killer power from much small cams, and they make TQ so early. With CNC heads and the same cam John mentions above in the 22x/23x range we have made 478rwhp and upper 45x rwtq on the stock LS2 bottom end and it idles and drives absolutely like stock. Note that those are unmilled heads and stock gaskets, so you are dropping the compression quite a bit from stock and still getting that HP and TQ. That cam leaves room for a thinner gasket and/or milling for compression and could make even more power with even better manners.
Like with most arguments on here, people simply argue peak HP numbers when that is in no way the whole story. Average hp/tq means alot, and where it makes the power.
Like with most arguments on here, people simply argue peak HP numbers when that is in no way the whole story. Average hp/tq means alot, and where it makes the power.
going back to the "big ports,soggy bottom end" stigma of the L92s...besides improper cam selection,if the heads aren't ported correctly this could also effect port velocity in a bad way..i mean,if your going for a mild 6.0 street/strip build how much porting is actually needed?the heads already flow 300+cfm out of the box..IMO,if it's not broke don't fix it..i'm sure there have been some heads screwed up by well meaning folks who want to get X amount of cfm and big numbers only to have hurt the low and midrange power..
the proper VJ and blend would be all that's needed in most mild setups,IMO..and would still give decent power in the low 400 + cube range..
02-08-2010, 12:35 PM
#54
Stock untouched heads bolted on have shown killer power. Sometimes it is best to to try and reinvent the wheel when they are proven as such, and you do not need to spend the extra money because the power you were looking for is already there.
I think the idea of a soggy bottom end (whatever that means) is from the related compression drop from bolting them onto a 6L block (LQ4 or even LQ9 or LS2). Raise the compression and I am sure that it will boost the numbers everywhere.
I think the idea of a soggy bottom end (whatever that means) is from the related compression drop from bolting them onto a 6L block (LQ4 or even LQ9 or LS2). Raise the compression and I am sure that it will boost the numbers everywhere.
02-08-2010, 12:36 PM
#55
OK I know this doesn't relate to the original post but I have some info to share.
I was finally able to pull the LSA heads off the shelf and take a look at the parts. I was wrong and John was wrong.....well John was closer than I was
I weighed the valves from 4 combinations. Of course GM OEM Valves
Intake Exhaust
L92 110 Grams 92 Grams
LS3 88 Grams 92 Grams
LSA 119 Grams 89 Grams
LS9 74 Grams 71 Grams
The Casting number on the LSA head was 4863 and the LS9 head it was 1771
I was suprised that the casting numbers were different as I thought they used the same casting with a different head bolt size on the LS9.
Since the valves in the LSA are not the same as anything else (as I had thought) I wonder what the are the differences.
Might find some description in the parts book who knows.
Maybe Jim can chime in.
Robin
I was finally able to pull the LSA heads off the shelf and take a look at the parts. I was wrong and John was wrong.....well John was closer than I was
I weighed the valves from 4 combinations. Of course GM OEM Valves
Intake Exhaust
L92 110 Grams 92 Grams
LS3 88 Grams 92 Grams
LSA 119 Grams 89 Grams
LS9 74 Grams 71 Grams
The Casting number on the LSA head was 4863 and the LS9 head it was 1771
I was suprised that the casting numbers were different as I thought they used the same casting with a different head bolt size on the LS9.
Since the valves in the LSA are not the same as anything else (as I had thought) I wonder what the are the differences.
Might find some description in the parts book who knows.
Maybe Jim can chime in.
Robin
Interesting results Robin, thanks for taking the time to weigh the valves.
GM's catalog lists the same exhaust valve for the LSA, L92, and LS3 so I am at a loss as to why the LSA valve came up a little light.
I expected the LSA intake to be heavier since it is specific to that engine.
I'm also curious as to why there are two casting #'s because I would have expected the LS9 and LSA to share the same casting.
The LSA seems to be a nice budget boost ready head at first glance, but if it is just a L92 with better intake valves then it is not an improvement.
Jim
02-08-2010, 04:32 PM
#56
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Stock untouched heads bolted on have shown killer power. Sometimes it is best to to try and reinvent the wheel when they are proven as such, and you do not need to spend the extra money because the power you were looking for is already there.
I think the idea of a soggy bottom end (whatever that means) is from the related compression drop from bolting them onto a 6L block (LQ4 or even LQ9 or LS2). Raise the compression and I am sure that it will boost the numbers everywhere.
I think the idea of a soggy bottom end (whatever that means) is from the related compression drop from bolting them onto a 6L block (LQ4 or even LQ9 or LS2). Raise the compression and I am sure that it will boost the numbers everywhere.
given the proper selection of parts there should be no loss in low end power on a build using L92 heads,all things being equal..hell, they come stock on Vettes/ SUVs and i don't see any problems with low end power there..
02-08-2010, 07:27 PM
#58
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i was just commenting on some misconceptions about the L92/LS3s,actually their one of the best deals going for a "budget" build..who would have thought just a few yrs you could get a set of heads that flow like they do for cheap,relatively speaking?
02-08-2010, 11:08 PM
#59
Robin,
The LS9 valve weight looks to be the valve only. How much does the lash cap add to the overall valve weight? 2gms? Then compare the factory LS3 hollow intake valve and we see it's pretty light even compared to the ti intake valve and the solid exhaust valves.
The biggest difference we've seen between the LSA and LS9 heads is the larger, thicker head bolt bosses on the LS9 castings. Possibly a thicker deck area on the LS9's? The next time I get a pair of LS9 heads in I'll weigh the bare casting. Head bolts for the LS9 heads are 1mm larger in diameter and are a touch longer to account for the added alum. on the head bolt boss.
Good discussion here.
Richard
The LS9 valve weight looks to be the valve only. How much does the lash cap add to the overall valve weight? 2gms? Then compare the factory LS3 hollow intake valve and we see it's pretty light even compared to the ti intake valve and the solid exhaust valves.
The biggest difference we've seen between the LSA and LS9 heads is the larger, thicker head bolt bosses on the LS9 castings. Possibly a thicker deck area on the LS9's? The next time I get a pair of LS9 heads in I'll weigh the bare casting. Head bolts for the LS9 heads are 1mm larger in diameter and are a touch longer to account for the added alum. on the head bolt boss.
Good discussion here.
Richard
02-18-2010, 01:31 PM
#60
Just got in my bare LSA castings, they weigh 21.3 lbs.
Anyone know what a regular LS3 or L92 head weighs for comparison?
They look like a MUCH nicer casting than the L92's I've seen.
The surface finish of the deck was much better too, I just hope it's flat !!!
Anyone know what a regular LS3 or L92 head weighs for comparison?
They look like a MUCH nicer casting than the L92's I've seen.
The surface finish of the deck was much better too, I just hope it's flat !!!