Max boost with a LS GM casting head?
01-29-2009, 09:41 PM
#1
Max boost with a LS GM casting head? What is the max boost/HP a factory head casting like a 317, or 241 will hold before it flexes and pushes water, or blows the gasket. This is on a fully built studed iron block, MLS gaskets with a good tune. I have heard of 24~26psi with AFR's but the factory head is a lot lighter casting. Any first hand experience appreciated. Thanks J
01-30-2009, 02:34 PM
#5
Yah that's about what I was figuring. I need to be able to run ~26PSI with a PT88 on 370CI. Was thinking about going iron heads but the decks are alot thinner than the aluminum castings. Another issue is Im afraid of ripping the rocker arm bosses out of the factory castings.
01-30-2009, 02:55 PM
#6
Yah that's about what I was figuring. I need to be able to run ~26PSI with a PT88 on 370CI. Was thinking about going iron heads but the decks are alot thinner than the aluminum castings. Another issue is Im afraid of ripping the rocker arm bosses out of the factory castings.
what did u measure them at, what was the thickness for both castings?
y do u think the bosses will tear out? which heads the alum. or iron?
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01-30-2009, 04:03 PM
#8
Not worried about det. At boost levels over 15PSI I will be either running E85, or race gas + meth.
01-30-2009, 05:01 PM
#9
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Have you ever heard of anyone ripping the bosses for the rocker arms out ?? I havent. If they have, someone likely damaged the threads.
If the threads did need to be stronger, helicoiling them is easy.
If the threads did need to be stronger, helicoiling them is easy.
01-30-2009, 06:43 PM
#10
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I've never seen a stock head just grenade from sheer pressure. Overheating will cause a warped, or cracked head. Overboosting per application would usually produce blown head gaskets first, cylinder deformation, and detonation (which would probably take its toll on the piston/ring assembly before it trashed the heads). Am I wrong?
I'm curious on this topic also. I'm at the same altitude as stock48. I'm wondering if lack of oxygen at altitude would play a part as well. Lower oxygen level at altitude would produce lower cylinder pressures (all other factors equal).
And I'd worry about the rocker bearings shelling out before I'd worry about ripping out boss bolts.
I'm curious on this topic also. I'm at the same altitude as stock48. I'm wondering if lack of oxygen at altitude would play a part as well. Lower oxygen level at altitude would produce lower cylinder pressures (all other factors equal).
And I'd worry about the rocker bearings shelling out before I'd worry about ripping out boss bolts.
01-31-2009, 01:14 AM
#11
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i've not heard of ripping out rocker arm bolts personally.
Also if you're worried about the stock heads pushing water go with some AFR's which are thicker than stock casts and ARP head studs.
Also if you're worried about the stock heads pushing water go with some AFR's which are thicker than stock casts and ARP head studs.
01-31-2009, 03:17 AM
#12
I've never seen a stock head just grenade from sheer pressure. Overheating will cause a warped, or cracked head. Overboosting per application would usually produce blown head gaskets first, cylinder deformation, and detonation (which would probably take its toll on the piston/ring assembly before it trashed the heads). Am I wrong?
I'm curious on this topic also. I'm at the same altitude as stock48. I'm wondering if lack of oxygen at altitude would play a part as well. Lower oxygen level at altitude would produce lower cylinder pressures (all other factors equal).
And I'd worry about the rocker bearings shelling out before I'd worry about ripping out boss bolts.
I'm curious on this topic also. I'm at the same altitude as stock48. I'm wondering if lack of oxygen at altitude would play a part as well. Lower oxygen level at altitude would produce lower cylinder pressures (all other factors equal).
And I'd worry about the rocker bearings shelling out before I'd worry about ripping out boss bolts.
01-31-2009, 03:41 AM
#14
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I'd say anyone who has pulled the rockers from the heads, as done so by overtightening the bolts, and ripping the threads from the head.
It isnt due to them being inadequate for the job, its down to shoddy workmanship.
It isnt due to them being inadequate for the job, its down to shoddy workmanship.
01-31-2009, 03:52 AM
#15
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Without knowing what else was involved, I would call that a casting or metalurgy issue. Possibly too much material removed in the port. If the bolts backed out and there was a lot of back and forth movement, that could have caused that breakage there also. What did the rest of the bosses look like on that head?
What power adder are you boosting your stock heads with? I'm here in Pueblo and would like to see how you're setup works. I'm getting ready to mount up a Paxton Novi 2000RR to an LS1 and boost it till it shells out. Then I can tell you first hand. lol
But I think you're asking compound questions. What you are starting with, compression wise, will have a lot to do with the engines longevity (or lack thereof) under the boost levels you're suggesting. The cam you are running may have enough overlap to bleed off boost too. There are a lot of variables. But pressure wise, I don't think a well prepped set of stock heads are going to be your first problem.
What power adder are you boosting your stock heads with? I'm here in Pueblo and would like to see how you're setup works. I'm getting ready to mount up a Paxton Novi 2000RR to an LS1 and boost it till it shells out. Then I can tell you first hand. lol
But I think you're asking compound questions. What you are starting with, compression wise, will have a lot to do with the engines longevity (or lack thereof) under the boost levels you're suggesting. The cam you are running may have enough overlap to bleed off boost too. There are a lot of variables. But pressure wise, I don't think a well prepped set of stock heads are going to be your first problem.
01-31-2009, 04:33 AM
#16
Without knowing what else was involved, I would call that a casting or metalurgy issue. Possibly too much material removed in the port. If the bolts backed out and there was a lot of back and forth movement, that could have caused that breakage there also. What did the rest of the bosses look like on that head?
What power adder are you boosting your stock heads with? I'm here in Pueblo and would like to see how you're setup works. I'm getting ready to mount up a Paxton Novi 2000RR to an LS1 and boost it till it shells out. Then I can tell you first hand. lol
But I think you're asking compound questions. What you are starting with, compression wise, will have a lot to do with the engines longevity (or lack thereof) under the boost levels you're suggesting. The cam you are running may have enough overlap to bleed off boost too. There are a lot of variables. But pressure wise, I don't think a well prepped set of stock heads are going to be your first problem.
What power adder are you boosting your stock heads with? I'm here in Pueblo and would like to see how you're setup works. I'm getting ready to mount up a Paxton Novi 2000RR to an LS1 and boost it till it shells out. Then I can tell you first hand. lol
But I think you're asking compound questions. What you are starting with, compression wise, will have a lot to do with the engines longevity (or lack thereof) under the boost levels you're suggesting. The cam you are running may have enough overlap to bleed off boost too. There are a lot of variables. But pressure wise, I don't think a well prepped set of stock heads are going to be your first problem.
