I was wondering what the maximum quench height is for an LT1. From what the previous owner of my engine (bottom end) told me, I'm running a .030 deck height. When I installed the heads, I used .039 gaskets which gives me a total quench of .069. Is this too much? The other engine/car specs are as follows:

383 LT1
11.7:1 compression
Chamber Vol. 54cc
Bored .030 over
5.7" Rods
TRW4 4.030 pistons (-4cc valve relief)
Stroke: 3.75"
Head Gasket Bore: 4.125
Head Gasket Thickness .039
Cam Specs:
Intake Exhaust
Gross valve lift at 1.6 - .544 .576
duration at .050 230 244
lobe seperation 112
valve timing OPEN 37 BTDC 90 BBDC
CLOSE 73 ABDC 37 ATDC
TH-350 w/ 2500 stall
3.55:1 rear end
'79 Vette (~3600 lbs)

If this is an unnacceptable quench, what can I do to lower it short of decking the block? Are there thinner gaskets out there for the LT1? Or is that going to raise my compression ratio too high?

Currently the car is driveable w/out knock but the timing is retarded farther than I think it should be. Is my problem mainly compression ratio (11.7:1) or quench height? I'm running GM's carbureted intake w/ a Holley 750DP if it matters.

Thanks for any help,
Jason

1979 LT1 Vette


[Modified by Langadorf, 7:36 PM 6/22/2002]


[Modified by Langadorf, 9:07 PM 6/22/2002]

 

you are talking about the original LT1 and not the 1992-1996 engine right? There are thinner head gaskets out there for your sbc, whichever LT1 it is. I used a .029 compressed thickness set of victor reinz head gaskets. So far so good. Your quench height seems a bit big but if it performs well enough then if it aint broke.....
If it doesnt and you think it's due at least in part to the quench height then I'd be afriad to go any higher on the c.r. Since you would have to remove your heads to swap head gaskets though you could have a machine shop add some cc's to the heads to lower the c.r. a bit so you can use a thin head gasket without bumping your C.R.

 

Optimum quench on any 4 cycle engine is .040 ,anything over .060 and you start to loose power! Measure it physically with clay or soft solder.
GIVE ME MORE POWER SCOTTY !!!!

 

What are you running for fuel? With 11.7 comp you will need at least 102 to 106 octane. I like V-P myself.

 

You would actually be well served to install much thinner head gaskets like one of those coated .015 gaskets, and then enlarging your combustion chamber to bring compression down. Two reasons why you should have quench height closer to .040: larger quench height promotes detonation, smaller quench height promotes better mixture motion - which staves off detonation AND makes better power.

Your dial back of timing is the right thing to do because of compression and pump gas - but that is at counter purposes to the EXTRA timing that cam profile wants.

Thomas

 

To those above, I'm running the new model LT1 out of a '94 Camaro.

Where are these .015 gaskets available at?

Thanks,
Jason

 

be careful on the .015 gasket. Felpro told me theirs is only good for up to 10:1 compression. The thinnest gasket i could come up with that worked in my application was a .026.

 

What brand/part# was this .026 gasket? What kind of compression are you running?

 

i have an l98, so my part # won't help. It is a victor reinz gasket...you might wanna check with them. I'm running about 10.6:1.

 

what in the world were they thinking not decking that block to zero, with a .039 gasket you'd be right on the money with a 4 valve relief piston

 

I believe a Mr Gasket makes a LT1 gasket with specs of .026 compressed thickness and 4.1 bore. Try part number 5716.

Not sure of its limitations though.

11.7 woohoo. That is some compression, but by the current readings it is acceptable for pump gas and a LT1.

:)

 

If you are refering to a '92-96 LT1, you can get a .029 head gasket (GM Part# 10105117) that's intended for an Impala, but does the trick for us.

Jeff Kopp has the pair for $30.00 www.superchevyperformance.com

:cheers:
Donovan

 

I looked breifly at that Impala gasket, but since it was designed for cast iron heads (still LT1) there was concerns of it brinelling the aluminum head by others on different boards.

:confused: