427LS1

everyone seem to say that the L92 heads tend to lift at high boost level, why is this? what about the LS7 heads, do they lift under boost? and if not what is the difference? if i were to use 1/2 inch studs with the L92 heads, would they still lift? any info?

thanks

White_Hawk

iTrader: (3)

DP you have any links to who is saying that? Is it conjecture or is somebody actually lifting one?

-Geoff

ALLBOTTLE

iTrader: (13)

The reason people are saying the heads will lift is for two reasons.

1) very thin deck, thinner than all other gm lsX castings

2) Large bore blocks and heads have less material between cylinders to help clamp down on the gasket.

kwman

iTrader: (2)

L92 heads are also meant for a 4 bolt block where as 6 bolts would provide a little better hold as well.

ALLBOTTLE

iTrader: (13)

Even for a 4 bolt head it's on the weaker side of the spectrum.

99Fbody99

L92 deck is the same approximate thickness as all the other LSX based cylinder heads.

Dave

ALLBOTTLE

iTrader: (13)

Not after measuring the Cutaway of l92 compared to a ls6 or ls2.

When talking about deck thickness .100's is a huge deal.

Robin L

"High Boost" is a relative term. To me high boost would be over 30 PSI. To someone with cast pistons and stock rods it might be anything over 6 pounds.

The L92 is a very nice all around head at a decent price. Since it is a production part it is made in numbers that allow them to be sold at a reasonable price.

Here is a cut of an L92 head that we chopped up. I don't see this as any less than other production heads.

Because of the popularity of this head there are a lot of commets and opinions floating around. For sure it's NOT an all out race head capable of high cylinder pressures. For 85% of the high performance world it will work just fine. With proper gaskets and head bolts this head should hold as well as any production and many aftermarket heads.

I can get any head to lift with the wrong tune.


Here is the picture

camarols1

iTrader: (17)

Good post, I agree completely.
Using any production head in a boosted application will require a
more precise (conservative) tune to prevent head gasket issues.
I will be using the L92's in my twin turbo build that should be finished up soon.
I think that this head is promising for "budget builds" like mine.
If they prove to limit my power goal (which I doubt) I can always
pull them off and switch to a different aftermarket head if need be.
Many builds have made insane power with standard diameter bolts
and production GM heads without issues.
It is all in the tune!

My90Iroc

iTrader: (26)

Are they using these heads on the new supercharged vette coming out? I seem to get the impression they might be but I haven't seen anything to confirm that. If so that'll be interesting since you'll be talking about 600hp on a production car where head lifting can't be a consideration. 600 may not be a lot for what people on this board are looking to do but it's a good starting point.

89lx-ls1

iTrader: (23)

if i were to use 1/2 inch studs with the L92 heads, would they still lift? any info?

thanks[/QUOTE]


I have seen nothing about this question is there any answers i am having a problem again and this would help

ALLBOTTLE

iTrader: (13)

1/2 studs are a great way to increase the clamping force.

It's a bit of a costly process since you have to machine the block and heads as well as order custom studs (W2W has off the self studs)

mike c.

iTrader: (1)

I have a set of ported l92 heads going on my 402ci. I want to spray 200 to 250 shot. Does anyone think that will lift the heads??

corvettetimmy

I have 980 miles on my 427 with the l92 heads, and there are no signs of any problems..

Lets just say that my driver information center says I get 8.4 mpg, so I dont think that was an easy 1000 miles.. It has about 10 dyno pulls and 6 track passes on it with endless street runs up thru 4th gear without lifting off the gas.

My car made 750rwhp and 800 rwtq with 10psi boost from an f-1a and a 10deg flat timing map.. Thats not too much considering the posibilities of my setup. but, I think they are gonna be just fine.. Anyone else try yet?

Phate

iTrader: (2)

I played around with a set of L92s on my stock LS2 with the APS kit. The car didn't seem to want to take any timing after about 3800-4000. I think that we ended up with 7-8* of timing for about a 1500rpm range because the car was knocking. This obviously cost a lot of power.

Keep in mind that this was with a 72cc head where the stock head was 65cc...so even with the lower compression the car didn't want any timing...where it would take timing with the higher compression 243 castings. I have heard some talk of the exhaust contaminating the intake with these heads and maybe that was my problem. A cam swap only made things worse.

From the results that I have seen these heads seem to perform really well on naturally aspirated setups. I haven't seen any other results posted for FI cars other then Timmy's above, which are quite impressive. This leads me to believe that people just haven't put on enough sets of these to get results, or the heads are fairly hard to cam for FI cars.

Robert56

iTrader: (2)

Wouldn't the high tensile strenght standard size ARPs be a viable alternative? I choose these for my 408 and 300 shot and give about 40% more clamping force through increased torquing capabilities.
Robert

ALLBOTTLE

iTrader: (13)

You can use the l19 bolts that have a much higher tq capacity, however you have to run evans coolant, L19 is prone to hydrogen embrittlement.

Each setup is going to have it's pro and cons.