will this keep my compression at or below a 10 compression,just standard 906 heads,mild street roller cam.flat tops with two valve reliefs willit take me to mid 9 compression.regular flat tops do not give the eng much pep.need a little more compression than they give.thanks

Do you have a part number of the piston? I tried to look on Summit's site but only saw flat tops.

440?

2295s?

2.029 compression distance, 12cc dome (@.030 over 4.350).

Most agree they will put you at ~10.3:1

I had these in a 446 30+ years back, that engine was never decked (old hemi hyd. grind) They had some piston slap when cold and that engine needed some racing gas mixed to be happy (or retard the timing then it ran like crap!

Too much for pump swill IMO.

Some folks mill the dome off, or mostly off?

They make flat tops that have a much higher compression distance too. Sturdy but heavy old slugs.

Assuming we are talking 440?

2355s have a 2.061 comp. height. That would get you there. 9.5 or so on "most" 440s?

These are considered pretty heavy, but have proven reliable over many years.

Aluminum heads and quench would let you go alot higher ratio with pump gas.

are you up & running now (& need more power) or are you contemplating a build? if the first one maybe some tuning or external changes could help you. if picking parts for a build do some measureing to see where you are at

i thought the shallower domed pistons were 11:1,..? whether 2.03 or 2.06 compression height and no quench doesn't make make much difference; neither are pump gas friendly.

yes,up and running just fine. this is 383 eng i have.thanks

how about flat tops with relief cuts in them will they yield a little more compression for 383 eng,906 heads,headers,mild roller cam.the regular flat tops do not help the eng performance that much.

Think 383 stuff is not so much out there. Don't really know, but a stroker has alot more choice in getting you where yo want to be.

You always have custom stuff, but I have concentrated on RBs so never looked at the Low block stuff?

Most of what I've read here is ~10.3:1.

Them ones I ran sure seemed higher than that!

She sure did not like ANY pump gas (except mixed the 110 stuff(:

I like compression, I can hear it (i'd like to think) hence why I'm going e85 on this new bullet.

So what is the part number or specs of the piston you want to use?

Your compression will be around 10.2-10.5. How big your cam is and how it is degreed in will play a significant part in detonation. Being a roller will probably help a lot. A flat top piston and old school steel shim gasket will give you slightly more compression than a regular Felpro style .039" gasket.

https://www.summitracing.com/parts/uem-kb400-040

I read these will only get you ~9:1 with 88cc heads (906s)

What flat top is in it, what year is the engine, are they stock pistons? The tallest 383 piston is the stock piston in the 68,69 335HP engine. Any replacement piston that doesn't have a dome and has valve reliefs will LOWER the compression.

Money would be better spent getting rid of those crappy open chamber heads if the shortblock is not tired..

this is a new build eng. how about those kb400 pistons,what size gasket thickness for them? 69 383 block.block is 60 over.

I don't like KB pistons, valve reliefs are huge and the dome impedes flame travel. You'll be lucky to have 9.5 with 906's and a thin steel shim gasket.

Has the block been sonic checked ? .060 is touchy on a 383.

The heads are still an issue unless you got them FREE, they are ported by someone that knew what they were doing and they are already rebuilt, otherwise any money you put into them is wasted money.

that is is about where i want to be 9.5 is better than 8.1 compression.

I don't like the current version of the kb400 piston as well as the original, but I would still use it in an application like this.
The new version has a net zero cc dome. So it's effectively the same as the original flat top, only it has valve pockets so decent sized cams will fit after you've milled the heads enough to get the cr where you want it.

KB400's, block decked so piston is down the hole .015", .027" cometic gaskets, aftermarket heads milled to 78cc, should be mid to upper 9's for compression.