My 1969 383HP Restoration Build

[CompSyn]

I'd like to take the opportunity to share with the community how my engine builder and I arrived at the final build. The objective with this build was a 1969 383HP as close to factory specs as possible utilizing today's lack of available parts. This was to be an engine restoration for my numbers matching 69 383 Road Runner and not your more typical street/strip build with big cam, headers, stall converter, etc.

Going into it, I never thought the vulnerable Speed Pro L2315NF forged piston was that great of a candidate due to a shorter compression distance of 1.920' and since they are forged, heavier and noisier, right!? Well. check out my actual as-measured numbers below.

One thing to note. The engine block was square-decked which really only amounted to a clean-up pass as the decks were not found to be that far off. Kind of surprising. So squaring up the deck help close the gap of the shorter compression distance of the Speed Pro forged piston. Also, the Speed Pro pistons are 4032 forgings so they run tighter in the bore than 2618 forgings. Heavy? Not so. When weighing the stock cast piston versus Speed Pro forged piston side-by-side, they were found to be within 6 grams of each other. After shaving some grams for balance work, the difference becomes negligible at best. Best of all. I picked up the Speed Pro pistons from Summit Racing for a reasonable price of $398.99, purchased 4/2020.

I also wanted to help dispel the commonly held belief that the 383 HP, at least in 68 and 69 had a compression ratio of 10:1. Not so. That number was nothing more than marketing department hype. These engines could not be 10:1 unless they had significant decking and milling work done to them.

Side-by-side, here are the actual as-measured numbers with final calculated compression ratio at the bottom:


Stock 1969 383 HP-------------------------------------------------------383 Rebuilt with Speed Pro pistons L2315NF

Bore: 4.25-----------------------------------------------------------------------------------------------------4.28
Stroke: 3.375------------------------------------------------------------------------------------------------3.375
Rod Length: 6.358-----------------------------------------------------------------------------------------6.358
Gasket Bore: 4.354----------------------------------------------------------------------------------------4.441
Comp. Gasket: 0.020------------------------------------------------------------------------------------ 0.020
Block Deck Height: 9.978--------------------------------------------------------------------------------9.971
Top Ring Down: 0.360-----------------------------------------------------------------------------------0.380
Head CC's: 87.5--------------------------------------------------------------------------------------------86.7
Piston CC's: 0--------------------------------------------------------------------------------------------------0
Piston-to-Deck: 0.001------------------------------------------------------------------------------------0.006
Piston Compression Height: 1.932--------------------------------------------------------------------1.920
Piston/Pin Weight: 994.5 Grams------------------------------------------------------------- 1000.2 Grams

Calculated Compression Ratio: 9.34:1----------------------------------------------9.40:1

Note: These were the findings with my specific 383 engine. Your specific production 383 engine may differ.

 

[Russ69Runner]

Thanks for the insight on the 383 motor. So the 10 to 1 was not true. Makes me feel better about how this motor turned out. Could not find the fixed wrist pin piston's when doing the build and that is why we went with the piston's we did. Very happy with how the motor preforms so far. The carb came with the car along with the holley intake. So tried to keep cost down by using what I had. Now that the car is finely done putting money in Cragar rims. Have the back one's now and the front ones will be bought next month. Getting to drive the car after all those years of building it is rewarding to say the least.