69Sting

After the help of the forum and finding out my motor in my 69 was internally and head correct but the block was not. I decided to turn it into a 383 Stroker motor.

My motor guy has given me some options he ran through Desk Top Dyno. 2 of these I like the torque and hp curve. But I noticed their is only one difference between them and one set has a 64cc head and the other a 72cc head. Same head just different chamber size.

Does one have an advantage over the other.

I did notice the 72cc gave me a 9.99 SCR and a 7.95 DCR using flat tops

The 64cc gave me a 10.09 SCR and a 8.035 CDR using dished piston.

HP 374@5000 torque 424@3500. for the 64cc and the 72cc is with in 2

Any advice is apreciated. I am looking for strong Mid Range using a dual plan intake (edelbrock preformer). I have the M20 (wide ratio trany, 3.36 rear)

gkull

Even with the same compression the dished piston and smaller chamber is more thermally efficient. Because less head surface area is exposed to heat which it x-mitts to the water jacket.

It will also be more ping resistant. The 64 cc even opened up a little for low lift valve unshrouding will be better

Pete79L82

Can you post the spec he plugged into DD. I can't think of any senerio that dropping the head cc 8cc's would only up the CR .1. It should be closer to 1 point in compression, not .1

joe73vette

You have to watch the shape of the dish compared to the shape of the chamber to get proper "squish" at the flat part of the head. Squish shoots the mixture towards the plug and causes good turbulence and mixture mixing. A flat top piston with a larger head will probably have better squish. Cheaper 4-eyebrow pistons might not have such good properties, though. A d-shaped dish is better than a cheaper round one. Joe

69Sting

I have chosen the 64cc with .12cc dome piston. no eybrows or D a round dome.

I would post the desk top dyno specs but it is on 5 sheets and I don't have a scanner working right now.

Thanks for the feed back...