Speed Pro on (eternal?) backorder. Which one do I go with now?

[bull]

I just heard this from Mancini Racing:

Hello Curtis,

The pin height of the L2315F is 1.920. Speed Pro says @ .040 w/ 88cc =8.98 to 1.

They are not available right now, on National back order with no release date.

We do sell the 2 offerings from Keith Black pistons; the 8.5 to 1 and also the mini dome 9.5 to 1.

Let me know if you need anything else.

Thank you,

Arthur Cowan

Mancini Racing

artc@manciniracing.com

So what else is out there besides KB? What's the next best?

[firefighter3931]

Curtis,

Piston selection for 383's is very limited unfortunately. I did some digging around and found a very nice option for you. 

Diamond racing now makes a top shelf Forged lightweight slug for the 383. This is a 4.28 (.030) bore piston with 4cc valve reliefs. Plugging the numbers into the compression ratio calculator using a zero deck, .020 steel shim head gasket and 88cc chamber it comes out to 9.2:1 compression.

The pn on that piston is 51900....you'll have to contact Diamond for pricing and availability. 



Ron

[bull]

Curtis,

Piston selection for 383's is very limited unfortunately. I did some digging around and found a very nice option for you. 

Diamond racing now makes a top shelf Forged lightweight slug for the 383. This is a 4.28 (.030) bore piston with 4cc valve reliefs. Plugging the numbers into the compression ratio calculator using a zero deck, .020 steel shim head gasket and 88cc chamber it comes out to 9.2:1 compression.

The pn on that piston is 51900....you'll have to contact Diamond for pricing and availability. 



Ron

That sounds very nice. Do you know if they have any .040 over listings? I might have to shave .010 more off the cyl walls because the last guy did a dirty rebuild.

[bull]

And is this compression ratio calculator online somewhere? And what compressions range should I try to stay between to run on pump gas.

After searching for 383 stuff I'm starting to like the idea of going with a 440 more and more.

[firefighter3931]

Curtis,

Piston selection for 383's is very limited unfortunately. I did some digging around and found a very nice option for you. 

Diamond racing now makes a top shelf Forged lightweight slug for the 383. This is a 4.28 (.030) bore piston with 4cc valve reliefs. Plugging the numbers into the compression ratio calculator using a zero deck, .020 steel shim head gasket and 88cc chamber it comes out to 9.2:1 compression.

The pn on that piston is 51900....you'll have to contact Diamond for pricing and availability. 



Ron

That sounds very nice. Do you know if they have any .040 over listings? I might have to shave .010 more off the cyl walls because the last guy did a dirty rebuild.

Curtis, they do have a larger bore....i believe it is 4.31 which would be .060 over 

Go to the Diamond website and download the PDF file (it's quite large) and have a look.


Here's the online CR calculator i use : http://www.rbracing-rsr.com/compstaticcalc.html



Ron


Ps. With iron heads i would shoot for 9.0-9.5 (max) compression if you want it to run on pump gas.

[aifilaw]

I have had very good luck with Diamond pistons on the 383. and if you want something custom they have been more than willing in the past. Just something to consider if their standard offerings don't appeal.

[bull]

I need to figure out for sure if I need to go .040 over or not. I hate to go .060 over if I don't need to because you're pretty much done at that point, aren't you? I'd like to leave myself some room for one more rebuild just in case.

[firefighter3931]

I need to figure out for sure if I need to go .040 over or not. I hate to go .060 over if I don't need to because you're pretty much done at that point, aren't you? I'd like to leave myself some room for one more rebuild just in case.

Yep, a .060 overbore is usually the end unless you decide to sleeve the block....but that gets expensive.

Another option would be to order up a set of custom pistons.....not that much extra $ in the grand scheme of things. 


My feeling on it is to overbore as little as possible to maintain structural integrity. 



Ron