[GFS] FP31 motorhead stuff

[eddee <eddee@xxxxxxxxxxxxx>]

Hello Group

I know there was always a question regarding the FP 31 'DOMED PISTONS'  that were supposedly put in the FP 31 and created a higher compression ratio than later (non 290HP) 318s
i.e.:  9 1/4 to 1  verses  9/1

I have half of the gospel.
I am 99% plus sure I have a virgin 1957 FP31 short block at the very least.
Possibly the heads were removed and rebuilt at some point,,,but EVERY indication is that the basic short block is like the day it was assembled!!!!!!!!!

A few interesting things...........................
The bearings are all marked 'DPCD' and not TRW or FED MOGUL or CL77.
Of course all bearings,,,rings,,,pistons, are 'standard' size.
I have examined the rods and crank and I find NO difference between them and 'normal' 318 parts.
I am waiting on one last 'examination' on the rods--to see if there was any factory shotpeening or if their weights are suspiciously close to each other.

One item that is no longer a mystery is the COMPRESSION HEIGHT of the pistons.
They do look like any other 318 piston.
The compression height is as follows
PISTON top of 'dome' to centerline of wrist pin = 1.822
I would give this a tolerance of + or - .002
This is the infamous compression height in our FP31s !!!!!!!!!!!!!!!!!!

One of these days,,,when I can verify a piston from a later 2bbl or 4bbl 318,,,,,I'll let you know if it the same or less.
Personally I can tell you that replacement piston manufacturers ( KEITH BLACK,,,TRW,,,PERFECT CIRCLE) all 'claim' that stock compression ratio of 9/1 is with a compression height of 1.810 to 1.815

SO MAYBE OURS WERE UNIQUE???????????

Time will tell.

ED ECKERSON
LI  NY
57  FURY
59 GOLDEN COMMANDO PROJ
57 FP31 PROJECT


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