Will I need to raise compression ?
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Launching!
Joined: Mar 2022
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Will I need to raise compression ? This cam I am getting (231/239 .594/.606 110 Lsa) seems like its on the bigger side. Will I need to raise the compression ?
If so, what pistons would y’all recommend for this cam. (Bored 30 over)
If so, what pistons would y’all recommend for this cam. (Bored 30 over)
I assume that you are building a new engine? Always spec your cam to the bottom end and heads/intake combo, not the other way around as different heads/intakes may want a slightly different cam profile 
That being said, you can run 11.5-12:1 compression on an LT1 with 93 octane no problem with that cam. Even on a stock cam and engine, there's no reason to stay at the stock 10.4:1 compression, as a lot of people swap out for the "Impala" .029 head gaskets on stock bottom ends to get to 11:1 compression. Flat top pistons produce a good flame front and SRP are good forged pistons, along with Mahle, Diamond, JE, etc are good options as well.
That being said, you can run 11.5-12:1 compression on an LT1 with 93 octane no problem with that cam. Even on a stock cam and engine, there's no reason to stay at the stock 10.4:1 compression, as a lot of people swap out for the "Impala" .029 head gaskets on stock bottom ends to get to 11:1 compression. Flat top pistons produce a good flame front and SRP are good forged pistons, along with Mahle, Diamond, JE, etc are good options as well.
Thread Starter
Launching!
Joined: Mar 2022
Posts: 247
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Yes I certainly will be. Get an lt1 and do a full rebuild. Bottom end will be stock, besides arp bolts. Spoke to Lloyd, going with his le2 set up and he said this would be a fantastic cam for nitrous.
I didnt think of getting a thinner head gasket, thanks for mentioning that. On the rebuilt engine I am going to have the block zero decked and bored 30 over. That would get the engine up into the 12s perfectly. That gasket change would help offset the cc increase of the new pistons for valve clearance.
I didnt think of getting a thinner head gasket, thanks for mentioning that. On the rebuilt engine I am going to have the block zero decked and bored 30 over. That would get the engine up into the 12s perfectly. That gasket change would help offset the cc increase of the new pistons for valve clearance.
Hold up... while generally true that larger cams do require more compression, because of increased overlap (and associated reduced cylinder pressures/ reversion at low RPMs), don't go crazy. You can put yourself into a situation of needing fuel beyond 93 pump gas in a hurry with little in return. Increasing the bore .030" (and consequently displacement) will bump the compression by itself. As already stated, LT1s are 10.4:1 factory with the pistons about .025" in the hole with a pretty thick gasket to begin with. To figure out your static and dynamic compression numbers you'll need to know the IVC (intake valve closing) event in degrees. What I'm hearing so far is also leaving quench out of the equation. Below .030" or so and you're starting to flirt with PTV contact with warmed up parts. Ideally, .035 - .042 is what you want. Consider this, with stock piston pin height at 1.565"
zero deck block, pistons flush, .026" head gasket = .026" quench, essentially.
block decked square and flat to .015" deck height, .026" head gasket = .041" quench
For a zero deck block you can also get pistons with the pin a smidge closer to the piston crown to re-create some 'in the hole' to where you're not solely dependent on the head gasket to create the quench area.
For a 355 LT1 and cam in the 230s, 11.0 - 11.2:1 would be enough for the cam, allow you run timing close to/ up to MBT (the timing that produces maximum torque at a given RPM/MAP), on E5-E10 93 octane pump gas.
Ask Lloyd what the IVC valve event is for that cam and post it up. Then we can get you a deck, piston and head gasket recipe to go with your heads (chamber volume) with a proper quench and the timing it'll want with maximum inherent knock-resistance.
zero deck block, pistons flush, .026" head gasket = .026" quench, essentially.
block decked square and flat to .015" deck height, .026" head gasket = .041" quench
For a zero deck block you can also get pistons with the pin a smidge closer to the piston crown to re-create some 'in the hole' to where you're not solely dependent on the head gasket to create the quench area.
For a 355 LT1 and cam in the 230s, 11.0 - 11.2:1 would be enough for the cam, allow you run timing close to/ up to MBT (the timing that produces maximum torque at a given RPM/MAP), on E5-E10 93 octane pump gas.
Ask Lloyd what the IVC valve event is for that cam and post it up. Then we can get you a deck, piston and head gasket recipe to go with your heads (chamber volume) with a proper quench and the timing it'll want with maximum inherent knock-resistance.
Last edited by Gojira94; May 7, 2022 at 09:49 AM. Reason: clarification
