Hi
Does anyone know of a company making a piston with head volume in the area of 7-10 cc?

I´m building a 383 and my DCR gets a bit high with the common 4cc volume. I´m using 3.75" stroke, 6" rods and need forged pistons size 4.030".

Thanks

 

theres quite a few flat tops with valve reliefs for 5 cc which makes 11 to 1 compression on 64cc heads. Which is fine for aluminum heads and pump gas with 230 degree cam or so... recipe for 450-500hp there.

Further dish would be in the 12-16cc range i think.

The only 7cc flattop i've seen is by Keith Black, 7cc 383 piston for 6" rods.
KB122 thats the part number

KB also has 11cc dish, KB302

 

I will use the XFI280 cam and the DCR will be appr. 8.5 . From a lot of reading that I´ve made it seems lika this is really borderline for pinging on non race gas.
Maybe you have hands on experience from this cam?

I´ve read plenty of your posts and you have built some real good motors.

BR

 

I ran 11 to 1 compression on my 383 with AFR heads and a cam that made DCR around 8.3 to 1 and had no problems. I think if you run a good aftermarket head that has a good combustion chamber you will be ok with that cam and 93 oct gas. You wont need much timing anyway with a good head. I ran 34 degrees total all the way up to 39 and didnt see any gains above 34. So i ran 34. On the dyno I started high and worked my way down to 34 and it seemed to make more torque the lower i went

 

383 , 12:1 ,TFS 195's
I'm running DCR of 8.7 (GM 847 cam ) .0.041 quench on equiv of your 91 gas with no problems
195+ degree running temps

 

If in doubt, go lower on the compression. Flattops are usually around 5-6cc total dish. Next step down is usually about a 12cc total dish volume.

You can tune anything to work, but you'll make more power with slightly lower compression and optimized timing than you will with too-high compression and timing dialed back to keep it out of detonation.

 

Thanks for your answers!

Do you think it would be better to go with a 12cc dish and end up with SCR 10.2 / DCR 7.9?

My setup is/will be: Shortblock with 3.75" stroke, 6" rods, pistons?, Brodix IK180 heads, XFI280 cam, HSR intake, 58mm TB, Hooker 2055 headers, dual 2.5" exhaust.
I will also run up to 150 hp N2O.

My previous setup 350 with flat tops and XFI268 did 12.06s / 119mph (100hp N2O)
Next seasong I would like to be well into 11s

BR

 

I calc your combo with 12cc pistons; DCR of 9.3 (w/.040 quench )

What quench are you looking at ?
It plays a major factor in likelyhood of detonation. A higher CR engine with good quench is less likely to detonate than a lower CR one with bad quench; all else being equal
In the process of building your engine you can make adjustments to get the quench in the "sweet" spot. Zero deck the block and run a 0.041 composite gasket to get desireible 0.041 quench


http://racingarticles.com/article_racing-10.html
http://www.popularhotrodding.com/eng...eze/index.html
https://www.thirdgen.org/forums/powe...ce-vs-dcr.html
http://members.uia.net/pkelley2/DynamicCR.html

 

"I calc your combo with 12cc pistons; DCR of 9.3 (w/.040 quench )"

When I use the Keith Black calculator http://www.kb-silvolite.com/calc.php?action=comp and a intake closing point of 69° I actually ends up with DCR 7.9 for 12cc dish pistons??
Heads are 64cc.

Which calculator are you using? Or am I doing something wrong in my calc?

Quench will be in the area of 0.035 - 0.04

BR

 

I don't like that one; it seem to give unrealistic high DCR numbers using the .050 + 15 seat settings.I personally don't believe 15 degrees past the .050 value has the valve close enough to the seat for compression to begin.

I use the Kelleys one ;can download it here

http://cochise.uia.net/pkelley2/dcrvb6.zip

You put your engine specs in the CR Calculator
cam specs in cam timing /overlap calculator ,
then go to the dynamic stroke calculator to calc effective stroke.

Go back to CR Calculator , tick the stroke box and it calculates the DCR

 

No, i think just do a flat top, zero deck block with standard .040-.041 MLS gasket and IK200's with that cam. Make sure you get better springs for the heads tho, that cam needs good stiff springs to work properly. 11 to 1 compression and that cam should work out well. If your nervous about it, get comp to grind it on a 111 lsa to help get DCR down a touch. DCR is just a guideline, not a true indicator of what will run on pump gas.

That above setup should be a mid high 11 second car. 150 shot will be in the mid high 10s

 

Ok, looks like I´ll follow Orr´s advice and get a set of SRP pistons with 5cc volume.
I´ll play around with the tune and hopefully get it right.

Thanks!

 

Same pistons i ran last year. Worked well