What piston for my 383 build?

[__Larsson____]

Okey, new question!

What type of pistons should i use for my -68 383 with 906 heads, XE268H compcam, will the
Speed-Pro Forged Pistons L-2315NF 30 work? Or the KB Pistons?

This should not be a crazy HP motor, just enough to work good.

 

[440Coronet500]

What compression is recommended for the cam you selected? The 906 heads are open chamber and should be checked to determine combustion chamber volume. 440'

 

[451Mopar]

The 2315 piston is good with the mild cam.

 

[Dajkzo]

Hi,


440'. is correct. You have to consider the cam's timing. Do a web search on dynamic compression ratio. You'll find some decent info. The XE268H is a popular choice. Both piston choices will work, I would go with the KB because that gives you more room to machine the block and square both deck surfaces not to mention having valve reliefs. You can use the calculator at ::https://uempistons.com/p-27-compression-ratio-calculator.html and plug in your numbers.

Chuck

 

[PRHeads]

2315’s are fine in that type of combo.

 

[__Larsson____]

Hi,


440'. is correct. You have to consider the cam's timing. Do a web search on dynamic compression ratio. You'll find some decent info. The XE268H is a popular choice. Both piston choices will work, I would go with the KB because that gives you more room to machine the block and square both deck surfaces not to mention having valve reliefs. You can use the calculator at ::https://uempistons.com/p-27-compression-ratio-calculator.html and plug in your numbers.

Chuck

440? The block and head surfaces was all good, no need have them worked on, how do i measure the chambers? =S i do not no how long the rods are, wich KB pistons, the KB162 OR 400? 162 has 9,5:1 and the 400 has 10,1

 

[1 Wild R/T]

I think 451Mopar & PRHeads have covered this.......

 

[493 Mike]

I think you need stroker pistons to accommodate the 440 crank you should put in!
Mike

 

[__Larsson____]

I think you need stroker pistons to accommodate the 440 crank you should put in!
Mike

No 440 crank

 

[qkcuda]

The KB's have valve reliefs, the 2315's do not. Not an issue with that cam, but could become an issue if you upgrade it later.

 

[__Larsson____]

The KB's have valve reliefs, the 2315's do not. Not an issue with that cam, but could become an issue if you upgrade it later.

Will not upgrade. Just want it to run.

 

[Dajkzo]

440? The block and head surfaces was all good, no need have them worked on, how do i measure the chambers? =S i do not no how long the rods are, wich KB pistons, the KB162 OR 400? 162 has 9,5:1 and the 400 has 10,1

Hi

OK, let's get you a little more data on a 383. The bore and stroke is 4.250 x 3.380", deck height on a B block is supposed to be 9.25" and the rod length is 6.358". You should check out :: http://www.moparts.org/Tech/Archive/motor/36.html Most of what you need for data can be found there.

I would use the KB162. Most blocks are not exact when it comes to deck height. As long as the surface is within specs (flat, no damage) on the block you can just bore/hone the cylinders and be done with it.
With either set of KB 162 your pistons will be approx .024" in the hole depending on the exact deck height. The compression height on those pistons in 1.908. The only set of 906 heads that I checked measured to about 88-90CC on the average, they can vary. It's a safe combination with the XE268S cam. You can run pump gas and avoid pre-ignition.

I was referring to the post from 440Coronet500.


OOPS, Make that 9.98

 

[PRHeads]

OK, let's get you a little more data on a 383. The bore and stroke is 4.250 x 3.380", deck height on a B block is supposed to be 9.25" and the rod length is 6.358".

Actually, the block deck height on the B motor is 9.98”.

Basically, any off the shelf flat top piston will provide a lower CR than the 9315....... all other parameters being equal.
They’re taller and have no valve pockets.

It takes planning to do it right.
Deck the block to zero, and as part of the head reconditioning, they should be milled to 83-84cc.
Then, using generic Fel-Pro head gaskets you’ll end up with 9.3 to 9.4CR.

Without decking the block, and assuming 88cc heads...... you’d be at 8.8:1.

 

[__Larsson____]

Actually, the block deck height on the B motor is 9.98”.

Basically, any off the shelf flat top piston will provide a lower CR than the 9315....... all other parameters being equal.
They’re taller and have no valve pockets.

It takes planning to do it right.
Deck the block to zero, and as part of the head reconditioning, they should be milled to 83-84cc.
Then, using generic Fel-Pro head gaskets you’ll end up with 9.3 to 9.4CR.

Without decking the block, and assuming 88cc heads...... you’d be at 8.8:1.

Would the XE268H cam still work with 8,8:1? I dont have the money or the time to do it perfekt atm. Just need it to run good not perfekt.

 

[PRHeads]

Will it “work”?

Sure.

For 8.8cr I’d be considering less cam.

 

[__Larsson____]

Will it “work”?

Sure.

For 8.8cr I’d be considering less cam.

Why?

 

[Kern Dog]

Bigger cam for lower compression means less low rpm power.

 

[__Larsson____]

Will it “work”?

Sure.

For 8.8cr I’d be considering less cam.

So to get higher cr what should i do then?

 

[BSB67]

I think you need stroker pistons to accommodate the 440 crank you should put in!
Mike

That made me chuckle

 

[BSB67]

So to get higher cr what should i do then?

Is that a trick question. PRH answered that question in Post #13.

There is the Icon IC687 piston, but it will cost more, and won't really get you much more for you application, but an option.