13:1 Compression Stock Stroke 400??

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72DMag

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Is there anyway to get a stock stroke 3.375" mopar 400 big block into the 12:1 to 13:1 compression ratio using 75 cc heads? I looked into the KB240 pistons but even with a 75 cc cylinder head ratio will only be at 10:1 compression?

Maybe there is a combo available using the longer 6.965 hemi rods?
 
You would need a 15cc dome. It might not work very well but Diamond can build them for you if that is what you want.
 
You would need a 15cc dome. It might not work very well but Diamond can build them for you if that is what you want.

Why it wouldn't it work very well?
 
With the 15cc dome piston is that with the 6.358 RB connecting rods? With the KB240 I think the 10:1 compression ratio was using those rods. Would there be enough deck height to use the KB240 piston with a RB 6.760 rod? Thanks!
 
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If I’m remembering right the old school trick was to use a 8.0. 440 .020 piston in a 400 to get 10.0 compression. Or maybe in backward on this. Check the compression distance between the 2 pistons. Kim
 
Is there anyway to get a stock stroke 3.375" mopar 400 big block into the 12:1 to 13:1 compression ratio using 75 cc heads? I looked into the KB240 pistons but even with a 75 cc cylinder head ratio will only be at 10:1 compression?

Maybe there is a combo available using the longer 6.965 hemi rods?

that rod length dont ring any bells !!
 
The “standard” BBM Ross dome is 14cc.
If you had some pistons made to fit your rod/stroke with that dome, zero deck, 75cc heads, and a .040 gasket you’ll be at about 12.5:1

Frankly, just going for more stroke and using an off the shelf piston makes a lot of sense(unless there is a pretty specific reason you want to use the stock stroke), and wouldn’t add much to the build cost really.

The same dome volume piston used in a 451 with an 80cc head will get you to 13:1.

Chrysler Big Block: Open/Close Chamber: 400 - Dome Top: 4.375 Bore - 3.750 Stroke - 14.00CC - #99499 - Ross Racing Pistons
 
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You could also get a piston or do a combination that puts the piston above the deck. My first race engine was a 12 to 1 compression 302 SBF that had flat top pistons in it. I had the pistons .023" above the deck to get that small cubic inch engine to make that kind of compression. While it sounds a little on the crazy side it worked without issue for years. If I had to have 13 to 1 from a 400 I myself would not be interested in using a big domed piston to get it there. Decking the block and milling the heads would without question be used as well.

Tom
 
Is there anyway to get a stock stroke 3.375" mopar 400 big block into the 12:1 to 13:1 compression ratio using 75 cc heads? I looked into the KB240 pistons but even with a 75 cc cylinder head ratio will only be at 10:1 compression?

Maybe there is a combo available using the longer 6.965 hemi rods?

I have some (rare) Direct Connection TRW domes for a 400. They are basically just a huge (4.402" +.060" over) bore L2293F dome with fire slot and trough valve relief, with floating 1.094" pins. To get 13:1 with that short stroke, the block would still need milling to zero and possibly some additional head milling to compensate for the reduced dome volume once real valve reliefs were cut. The last time I used L2293Fs in a 383 +.060", it took some pretty deep reliefs to clear a moderate solid flat tappet cam (270ish duration, less than .580" lift). A longer crank may be your best bet if you have to have 13:1!
 
just an rb length after market stock length rod with bb chev pins both ends , great rod to stroke #'s , and the longer rod will reduce the head weight on your piston . alum heads so you can raise the c/r to the match the fuel your going to run . and custom racetec pistons . don't forget the stock 383 steel crank .
 
Is there anyway to get a stock stroke 3.375" mopar 400 big block into the 12:1 to 13:1 compression ratio using 75 cc heads? I looked into the KB240 pistons but even with a 75 cc cylinder head ratio will only be at 10:1 compression?

Maybe there is a combo available using the longer 6.965 hemi rods?
Sorry everyone to reopen this older thread but More options are available if you offset stroke to big block chev journals to a final 3.55 inch stroke, I haven't personally built one. I know a dude who has but I found a couple rod and piston combos that will work, if I can find my notes ill share.
 
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