Quote:

I'm thinking of building my 383 HP to a Blueprint/Purestock spec. It will go in either a 70-Bee or RR 4spd.

I'm curious about how to get the 9.5 cr. with the limited pistons and CC's.

I think I have the 2315 pistons and the depth is at .105 in the whole. I can't see a 79.5cc head helping much (apx. 8.3).

How do I accomplish this? Do I deck the block .070-.080 to make it work?



CDP,

I have done this same combo in my 70 Bee

To get the C.R. up you will need to deck the block and mill the heads and I think Speed Pro offers a correct flatop piston

Here are some specs on my combo

The block is the original std bore 383
I am using the original cast flatop pistons standard bore.
Speed pro plasma moly rings
The block has been decked to a piston to deck clearance of -.006. (NHRA stock elim minimum specs are -.004 (for a 70 383 335hp) in untouched form I measured the piston to deck at -.050
I am using a Fel Pro steel shim gasket for a 413 which has a compressed thickness of .020
The heads are stock unported 906's with stock size 2.08/1.74 valves with a good valve job. Additionally the heads have been milled to 80cc's (the NHRA minimum is 79.5cc's and in untouched form they were 88cc's)
All this adds up to a measured compression ratio of 10.12:1. This number would be higher with a .030 or .060 piston. Originally in untouched form I measured the CR at 8.44:1 (a far cry from it's 9.5:1 advertised CR.

The cam is a Mopar Performance stock resto cam for a 440 6 pack (same dimensions as the original 383 magnum cam except it uses a 3 bolt cam gear instead of the original 1 bolt)
The intake is the unported original.
The carb is the original 585 cfm holley
The converter is a dynamic 11 inch that stalls at 2300 (like the original converter
The ignition is a combination of Mopar Performance elctronic and FBO Ignition Box, and Coil

The exhaust is a TTI 2 1/2 H pipe with Dynomax Ultra Flow Mufflers
I am running a 4.10's in the rear and I am using a pinion snubber and I clamp the front segment of the original springs.

The car weighs between 3975 and 4015 lbs with me in it depending on the fuel load. I leave the line at around 2000 rpms and roll into the throttle (I don't stab it at green as I am running F70-14 Polyglas's) and shift between 5600 & 5700 and it goes through the traps at 5600 rpms.


I hope this helps