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head gasket and compression ratio questions

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65lkey

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Discussion starter · #1 ·
So here's the scoop on my new motor

454 .030" over, it's going in monday to get decked and have the cam bearings and freeze plugs installed and ready for assembly. the whole rotating assembly is going in too to get balanced and have the rods reconditioned with arp wave loc bolts.

My few questions are I have the trw 2465 pistons with a 25.7 cc dome (i've been using 24 in the calculators) How far should I have the block decked? I was thinking like .020"

Once I get it decked the thinnest head gasket I can find(except the shims which I was told to stay away from) is these, http://store.summitracing.com/partdetail.asp?part=SCE-013322&autoview=sku

anyone ever use these? any suggestions for head gaskets? with the zero deck, 113cc chamber (I hope), and -24cc it puts me at 11:1 compression.
 
#2 ·
Sounds like your ahead of yourself.
Have the block decked to have all 4 corners the same height.
Can't tell you a specific amount to cut without mocking it up and measuring.
You could cut the .020 you posted but that may/may not square the decks.
 
#3 ·
65lkey said:
So here's the scoop on my new motor

454 .030" over, it's going in monday to get decked and have the cam bearings and freeze plugs installed and ready for assembly. the whole rotating assembly is going in too to get balanced and have the rods reconditioned with arp wave loc bolts.

My few questions are I have the trw 2465 pistons with a 25.7 cc dome (i've been using 24 in the calculators) How far should I have the block decked? I was thinking like .020"

Once I get it decked the thinnest head gasket I can find(except the shims which I was told to stay away from) is these, http://store.summitracing.com/partdetail.asp?part=SCE-013322&autoview=sku

anyone ever use these? any suggestions for head gaskets? with the zero deck, 113cc chamber (I hope), and -24cc it puts me at 11:1 compression.
Click to expand...
If you are having it decked to zero (9.780) use the .039-.041 Fel Pro gaskets
You do not want to use copper gaskets in a street deal unless you have no choice.
 
#6 ·
If you are working with factory rods/crank/pistons then you need to do a trial assembly, figure out where "zero" will be, then have the shop machine the decks .005" less to allow for a little varience in stroke/rod length/piston compression height. Normal rebuilder Fel Pro gaskets will do the trick. Before balancing/installing pistons, do a valve to piston check, those pistons don't have much of a valve relief, esp when you start decking blocks/running oversized valves/running solid roller cams.
 
#7 · (Edited)
65lkey said:
there's these too but I've been told they don't seal very well

http://www.jegs.com/p/Mr.+Gasket/746654/10002/-1
Click to expand...
=
Are you having the block decked?
If so why not just set it at zero or there abouts & run a standard FelPro or Felpro Performance gasket
Shims will work fine with sealer like Aluminum paint, Coppercoat, Hylomar,,,
GM recommended aluminum paint on them years ago in their service manual & it is all we used back in "the day"

Ideally you normally want to end up with a total piston to head distance of 35-45 thou so decide on what gasket you want to run & deck accordingly
In an undecked block those pistons would be down about 20 thou assuming the block is straight which is a huge assumption & one reason why I deck all blocks I do unless it is a numbers deal

I can deck those too if needed but I leave the numbers by stopping short of the pad
 
#9 ·
I did a calculator and with your .030 over block at 0 deck with a .040 gasket and the 25.7 dome it works out to be 10.74 CR If you use the -24 dome it comes out to be 10.58.. If the piston ends up .010 down it would be 10.51CR If its .020 it will be 10.29CR
 
#10 ·
Paul, I'm using those SCE gaskets that .021 thickness on my 383, they fit great with the bores and dowel pins. My piston to valve clearance was right at .040 so I wasn't pushing it but I didn't want to lower compression any more by using a standard head gasket either. I didn't have the head decked because I figured in a 1975 Chevy van with 140hp stock and everything covered in oil, not to mention the(at that time) rest of the engine looked great and ran when pulled at the junk yard. Doing a mock up install wouldn't be a bad idea but a lot of work vs. double and triple checking calculation numbers which should be just as good. I used Permatex Copper Head Gasket Sealer for mine, it comes either in a brush on can with applicator ball, or spray can(couldn't find the spray can when I did mine).

Oh yeah, another factor....I think I'm about at the limit for nitrous at 10.5:1 compression. You might be dancing on eggshells if you decide to squeeze nearer to 11:1. Just something to consider.
 
Discussion starter · #11 ·
cobaltchev67 said:
Paul, I'm using those SCE gaskets that .021 thickness on my 383, they fit great with the bores and dowel pins. My piston to valve clearance was right at .040 so I wasn't pushing it but I didn't want to lower compression any more by using a standard head gasket either. I didn't have the head decked because I figured in a 1975 Chevy van with 140hp stock and everything covered in oil, not to mention the(at that time) rest of the engine looked great and ran when pulled at the junk yard. Doing a mock up install wouldn't be a bad idea but a lot of work vs. double and triple checking calculation numbers which should be just as good. I used Permatex Copper Head Gasket Sealer for mine, it comes either in a brush on can with applicator ball, or spray can(couldn't find the spray can when I did mine).

Oh yeah, another factor....I think I'm about at the limit for nitrous at 10.5:1 compression. You might be dancing on eggshells if you decide to squeeze nearer to 11:1. Just something to consider.
Click to expand...
good point I would like to eventually spray it. but I can always pull the heads off and put a thicker gasket in. I plan to pull the intake in the winters to check the lifters. so whats a couple head gaskets then too. FourEightyNine had 10.6:1 comp in his 489 with the cam I got from him. I figure a little more than that would be better in a smaller cube engine. It's a xr286r on a 107 lsa is that helps
 
#13 ·
65lkey said:
good point I would like to eventually spray it. but I can always pull the heads off and put a thicker gasket in. I plan to pull the intake in the winters to check the lifters. so whats a couple head gaskets then too. FourEightyNine had 10.6:1 comp in his 489 with the cam I got from him. I figure a little more than that would be better in a smaller cube engine. It's a xr286r on a 107 lsa is that helps
Click to expand...

With the 107 lsa it will probably be safer for the nitrous due to the overlap.....lots of factors though in a nitrous situation to think about. It sounds like you're taking your time and thinking your way through the build, I think you'll be ok.
 
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creeper72
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