Huntr1117

iTrader: (18)

Trying to figure out what head gasket to go with and what my compression ratio will be. LE recommended Victor Reinz 5898 that's a .026 thickness. From what I've read I want to try and get a 12:1 CR. Here's the build specs

355 LT1, machine shop said the pistons were .002 in the hole. I'm guessing thats pretty close to zero decked.

pistons are... http://www.summitracing.com/parts/uem-ic717ktd-030
Bore (in): 4.030 in. Bore (mm): 102.362mm Piston Style: Flat top, with two valve reliefs Piston Material: Forged aluminum Compression Distance (in): 1.565 in. Piston Head Volume (cc): +4.90cc Wrist Pin Style: Press-fit or floating Pin Diameter (in): 0.927 in.

heads are 56cc LE2s

cam is a LE grind 231/239

Let me know if there's anymore info needed.

Thanks

hrcslam

http://www.csgnetwork.com/compcalc.html

Try this^. Don't forget the -4.9cc from the valve reliefs in the piston. Your quench could be an issue with .026" gaskets.

I got 11.8:1, but your quench is really tight at .028".

Why do you want 12:1? What cam are you running? Also, are your connecting rods forged?

Huntr1117

iTrader: (18)

The rods are eagle forged I-beam.

Cam is a 231/239 .571/.587 109 lsa

Most posts I've read say to try and get the highest CR you can. LE even suggested I try to get to 12:1

.026 quench is pretty tight. I thought on a street/strip setup I want to try to get .035-.040 . Is there anyway I can still get this? Is there I guide anywhere that will explain quench, compression ratios and other important factors. This is all pretty new to me. I turn wrenches all the time, just never get into the technical side with calculations.

hrcslam

Yeah, the intake closing event is probably pretty late if Lloyd is recommending a 12:1 compression. The possible issue here is the quench, not the CR.

Your forged pistons and rods will help keep rod stretch under control, but at .028" quench your asking a lot from them.

If you are shooting for 12:1 SCR, I'd take the heads to the machine shop and have them mill em down to 54cc chambers. Then run a .030 head gasket (cometic makes these) for 11.8:1. Or mill to 52 and run a .036" head gasket for 12.2:1. Both will increase quench distance to a safer .032" or .038" respectively.

Those will give you higher compression and a slightly bigger quench for higher RPM's which you'll want with that cam and CID. Personally I'd shoot for the .030" gaskets and 54cc chambers.

Did you already cc out the chambers to verify their size? My LE2's are 52cc.

Huntr1117

iTrader: (18)

Lloyd still has the heads. I asked him what the CC was and he said 56. They're my brothers old le2s that I sent to Lloyd to have them cleaned and checked. He said that they've already been milled quite a bit. Hopefully not too much. I'll call Lloyd and see what he says.

hrcslam

It's amazing how much variance we get between LT1 heads and their CC's. I'd go with Lloyd's recommendation over mine or anyone else's any day of the week. But, make sure he knows about the .028" quench and possible 6500+ RPM's. If he's good with it, so should you. You'd get 11.8:1 SCR with that head gasket on your set up.

I know most people shoot for .035-.045" quench. Some run tighter than that too.

Huntr1117

iTrader: (18)

Talked to Lloyd. He cleared things up and gave me alot of useful info. He said that the .028 quench wont be an issue. He said that I could spin it to 7200 rpm and it wouldn't be a problem. He also said alot of engine builders will go even tighter on the quench. When Lloyd said that if this was his build he wouldn't hesitate to run with the .026 gaskets it took away any doubt that I had. That guy knows his stuff, I'm going with his recommendation. He also said that the 11.8:1 compared to the 12:1 I'm only looking at a difference of maybe 4 hp.

So just to be sure, with your calculations and with the .026" head gaskets I'll be at?

11.8:1 SCR and .028" quench.

hrcslam

Yes sir those numbers are what I get. Awesome, I'd go with Lloyd on this one too!