Compression ratio estimates

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qwk dust

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I have a '74 318 Duster that we are working on right now. We are going to bore it .030 and use the Keith Black 167 pistons. I have a set of 302 casting swirl port heads that we will use after going with 1.88 1.60 valves. I am going to port match the heads to an RPM Air Gap and gasket match to the 1 5/8" headers. I am trying to decide what is the best way to get the highest compression ratio that is reasonable for 93 octane fuel. We have 93 everywhere here in Fl.
Question 1. If I just install the KB167s and just true up the block and install the 302 heads with no major shaving what is the expected compression ratio? I know there are variances but best estimates from those of you who had done this or similar would be great!
Question 2. Deck the block and use the 302s without shaving. Expected compression?
Question 3. Simply clean up block deck and shave the 302s ??? .020....030???? What would you expect? I don't however want to screw up the alignment for the intake manifold.

Any other suggestions? Combinations of the above would be appreciated. Also, Gasket suggestions with the above combo's. We may spray up to 100hp so keep that in mind on gasket suggestions...THANKS EVERYONE FOR ALL THE GREAT INPUT SO FAR!!! It has really been helpful!!
 
I don't know some of the variables such as combustion chamber cc's, piston design cc's (+ or _)

Go to Keith blacks website and they have a compression calculator you can use to figure up your compression.

I think 302 heads are closed chambers so you should be able to get away with 10.0-10.25 on 93. If their open chamber your best to keep it down to 9.5 to 1

Here's the link to KB's calculators http://www.kb-silvolite.com/calc.php
 
Thanks Fishy! That helps. Now to figure out the best combo. Shave heads to 55cc....0 deck block...mill block to put pistons .03 in the hole...heads to 53...heads to 58... The options seem endless. Any suggestions folks. It seems that milling the block more and less on the heads may be better for intake fitment but I am sure there is some known happy medium. This stuff is pretty darn intriguing. This is my first motor build myself since all my other cars had somebody else make the motor decisions and I just chose what I wanted. thanks again.
 
If the block deck height is actually 9.6" (which is what it's rated at) those pistons should be only .012 in the hole. Most I've seen sit a little lower than their rated though. Using .012 in the hole and combustion chamber cc of 58 cc's and a standard Fel-pro gasket thickness of .039 the compression comes up to 9.92 according to KB's calculator. That would be great for the street as long as the heads are closed chambers. It's a little high for open chambers. Once again I'm not sure what design the 302's are. If their open chamber don't mill the head any more than it takes to get it flat and don't mill the block unless it's warped. You really need to mock up the engine by putting the crank and one piston/rod assy. in to see where they sit in the hole. If it's allot lower than .012 below the deck and the heads are closed chamber style you can have it decked. If it's close leave it alone and only resurface the heads. Remember to take off .009" on the intake side of the heads for every .010 you take off the chamber side and your intake will line up. It will let the intake set lower when you mill it so when you install it don't use the cork end seals, just silicone it up.
 
thanks again fishy68. They are definetly closed chamber swirl ports. Great info on the milling of the intake vs the chamber ratio.
 
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