Anyone know how many cc's the stock 5.3 pistons are dished? I need to know this for a formula to calculate new compression ratios so I can know how much to mill off my heads.

 

I think its around 6cc.

 

A flattop piston would do wonders for our CR. I will try my calculations with -6cc and see what I come up with.

 

OK... using 3.78" Bore, 3.622" Stroke, -.008" Deck Height, 6cc Piston Volume, .060" Gasket thickness and 61cc Combustion Chambers I come up with a stock compression of 9.6998:1 for a stock 5.3. Does this sound about right and GM just rounded down to 9.5:1?

 

Now all I have to figure out is how much does it take to get 1cc off a stock 5.3 combustion chamber. I know it takes ~.0055" of deck or gasket for 1cc on a 5.3 but the chambers are a lot smaller that then piston bore. I am guessing around .0075 for 1cc?

 

I was using a 62cc chamber for the head, but actually think is somewhere in between.

I was estimating that the chamber was about 60% of the actual bore. Which would make your .0055 number take out .6cc. That would make a .0092 cut needed to remove 1cc from the chamber. Again, thats using a 60% guess. If its a 70% coverage, then you'd need to cut about .008 per 1cc. Thats not much different. So a .030 milling would net close to 3.25cc or 3.75cc based on those % guesses. The difference will be inconsequential to the final CR.

 

You are right, the stock 5.3 have 61.xx cc chambers. I should probablly use 62cc as my starting point since I likely took a little material out while I was polishing them.
Ok, using .008/cc taking .040 off will relieve 5cc and give me a 10.17:1 CR
Using .0092/cc, the same .040 would net me a 10.10:1 CR
Using the same analysis... .050 would give me 10.34 and 10.23 respectively.
I believe Snake Eater milled .050 off for a 10.3:1 on his 5.3 so that would make the .008 number about right. Snake??

I need to do some calculations and see which will put me right with a 7.35 pushrod and the new cam. I think either way the 7.40s I have now are going to be too long.

 

Yeah, if you mill them that much, that will be a long pushrod.

 

OK.. correct me if I am wrong, but here is what I come up with on the pushrod length:
Considering the stock pr length of 7.38 is perfect with the stock cam and my new cam's base circle is average .030 smaller between the two lobes. That puts my rods .015 short. Milling the heads .050 makes the rods .035 too long. This gives me a 7.345 pushrod to be back at the stock length. Therefore a 7.35 pushrod seems just about perfect for my cam and .050 milled heads.

 

BigKid

Are you running a mls gasket or a graphite? When my motor was rebuilt (2002 5.3) I saved the stock mls gaskets. When I measured the thickness on them, they were .046-0.047 thousandths compared to the .060 that everyone thinks. See if that changes anything.