I was using a CR calculator for my LT1 from Compression Ratio Calculator - Wallace Racing

Does anyone know how much CC the relief cuts measure on the factory pistons? Stock bottom 350 not been bored.
What is the factory deck height?
If the heads were milled .003 how does that play into it.
I came up with 11.2 not sure if it's correct.

 

The stock LT1 pistons have four (4) small valve reliefs cut into them. For compression ratio calculations use 7cc.

The factory deck height is 9.025". This leaves most stock LT1 pistons .025" ..."in the hole".

Most stock LT1 heads lose 1cc of combustion chamber volume for each .006" of flat milling. If your heads were milled .003" ....... subtract 1/2 (i.e. .5) cc from your combustion chamber volume.

You're welcome!

P.S. Also ....... use this CR calculator http://www.summitracing.com/popup/ca...ion-calculator

 

Thanks,

Now I'm getting 10.85 with .039 gasket w/4.123 stock bore and stroke, 56.6 cc heads milled .003

 

Don't know what(?) you are trying to say here, but, the stock LT1 bore diameter is 4.000" not 4.123".

 

That may be the gasket bore.

 

Yes the CR calculator asks for gasket bore, not sure why.

 

Because the gasket bore minus the cylinder bore times the mean circumference equals (approximately) an area, which, when multiplied by the compressed gasket thickness produces additional uncompressed volume. All open volume needs to be accounted for.

 

at .039 seems really insignificant, but that's just my two cents.

 

I was thinking he might be referring to gasket bore diameter, but ..... 4.123" is just such a weird number for that too!

Most all common aftermarket head gaskets for an OEM 4.000" bore motor are 4.100" in diameter to accomodate overbores of +.030", +.060" and even +.090". Furthermore a 4.123" gasket is too small for any 4.125" bore motors like the SBC 400 c.i. blocks.

What makes you think you'll be using a 4.123" bore diameter head gasket? Are you ordering custom head gaskets for this 350 c.i. stock shortblock build???

 

I ordered the felpro head gasket and when the guy at the parts counter was looking in his book I saw 4.123 with a .039 thickness listed for the LT1 that works for both iron and aluminum heads. These gaskets are the copper wire ones. I could be wrong it wouldn't be the first time my memory failed me =).
Not sure why people are so prone to pass judgment on a stock short block capabilities. If I dig up an older thread, there are people running 10.2s with a stock 2 bolt, yes 2 bolt block. Failure for 2 bolt comes on at 600 hp that would make 510-520 rwhp.
Here is a 11 second car stock bottom end; https://www.youtube.com/watch?v=UXEIbILCJls

Nos setup, stock bottom end 11.9s; https://www.youtube.com/watch?v=61ZyutFhtlo

https://www.youtube.com/watch?v=U8KQbGbMkmg
Stock bottom-end? I need to get up with you and buy the same set up for mine. I have a convertible though. I have a good bit of bolt-on except h/c. Where can I get it worked on? I can't believe 10 seconds on a stock bottom. Awesome!

Plenty of evidence out there that if you set your ride up you can make that stock bottom end go far, unless you're talking to a parts salesman. The stock crank is very beefy on the lt1s but opinions vary on this topic and it's apparent that mine varies from yours on the subject.

 

No, that is a problem with "interpretation" over these message boards. Trust me, (and see my signiture below), I have a 406 RWHP heads & cam STOCK shortblock M6 LT1 car that traps 115+ in the quarter and has run a current best of 12.21 on a 2.11 second short time. I KNOW stock shortblock LT1's are very capable of 11.xx second 1/4 mile times.

What I was trying to help you out with was your selection of head gaskets , hopefully designed to increase your static compression ratio, which, (I thought), was of a concern to you?

Rather than pay $100+ for a set of Fel-Pro 1074's with a .039" compressed thickness and a 4.125" diameter ...... why not look at these:

VICTOR REINZ Part # 5898 Material: Nitroseal; Bore Size: 4.100, Compressed Thickness: .026
Category: Cylinder Head Gasket

$17.58 each.

http://www.rockauto.com/catalog/rafr...47-5898-142608

at $36 a set, which will BOTH save you money, and improve the performance of your STOCK shortblock engine build?????

Just trying to help here!

 

Thanks for the link but if the head was scribed for a 4.166 can you use a 4.100?
Supporting mods;
Headers 1 5/8 w/cat back OBX 3" no Cats.
Heads 285cfm 197cc 56.6cc chamber 1.94 stainless cheater valves actual is 1.97.
Full ported intake and ported for better fuel atomization by the injector ports.
CAI
Tune
Cam Howards 290/290 237/237 560/560 110LSA hyd. this spec is with using 1.5 rockers but I have 1.6s waiting to be installed.
Comp Cams Hyd. roller lifters and rockers.
For now as I reached my budget limit. I have other plans in the future to fine tune this setup.

 

Yes, even though the head has a 4.166" diameter scribe on it ..... you can still use a 4.100" diameter gasket.

In a "perfect" situation you would order a "custom" head gasket with a 4.166" diameter and a .015" compressed thickness, (to give you a .040" quench with your stock shortblock pistons .025" "in the hole"), but, lacking that "custom" made head gasket remember .......... the hole in the block (i.e. your cylinder bore size), is still 4.000". In essence what your are creating is a "funnel" composed of three (3) rings, 4.166" at the top, either 4.125" or 4.100" in the middle, and, most importantly ...... 4.000" at the bottom, got it?

Finally, the real reason you should use the thiner .026" gasket in your engine build is to get your static CR as high as possible partly because of the 237/237 cam you are using. You have somewhat "hogged out" combustion chambers, (at 56.6cc), in order to get that 285 cfm intake flow, but, with a more aggressive cam, (and hence a later intake valve closing point), your dynamic CR will fall. This results in a very "doggie" engine at LOW/LOWER engine RPM.

 

Future plans would included milling the deck and a nice forged 355 bottom end. Those custom head gaskets are $110 and up each out of the budget for sure this round. I ordered the VICTOR REINZ Part # 5898 for the better quenching, the head guy told me there is a wedge type gasket for better quenching but I can't find one for the LT1.
Thanks for the input.

 

You're welcome, and, of course, Good Luck with your engine build.