john-dickjr
Well-known member
is there nay problems with having a machine shop enlarge a .912 pin to a .927
.912 pin to .927 pin
- Thread starter john-dickjr
- Start date
Machining the pistons for a larger wrist pin is not a good idea. it weakens the pin support bosses in the piston. You're much better off bushing the small end of the rod down. That weakens nothing.
what part are they enlarging? the rods or the pistons?
I'd think there would more issues doing the rods than doing the pistons.
No matter what the rod end will get thinner if the hole in the rod gets enlarged.
I'd think there would more issues doing the rods than doing the pistons.
No matter what the rod end will get thinner if the hole in the rod gets enlarged.
Agreed but I read it that he wants to open up the wrist pin bore in the pistons, not the rods.
Either way, bushing down to the smaller diameter would seem preferable.
Either way, bushing down to the smaller diameter would seem preferable.
john-dickjr
Well-known member
my bad, no i am wanting to know if it would hurt to open the small end of the rod from .912 to .927,StrangeRanger":tdfj1b6o said:
A stock engine would never know the difference, but a high performance engine? I dunno, but it would only be weaker on the upstroke. I suspect that if you put enough stress on such a rod that it failed there, something else is likely to break first.fastbarry":3uffwymv said:
YMMV.
How does the outside diameter of the small end of those early rods with a .912 pin hole compare to the outside diameter of a late model 300 rod with a .975 pin hole? That comparison might indicate how much extra meat there is in the older rod end.
john-dickjr
Well-known member
ok..so it would not be a issue to go the other way..so take a .975 pin down to a .927 or .912 pin..since it is just a bushing
Right
x2 
The more powerfull turbo Ford OHC 4 CYL engines started with 0.945 rods for 100 hp Pintos, went down to 0.912 for the 2300 Turbo Lima engines in the SVO and Merkur turbos which regularly hit 500 hp as 2.5 liter race cars, and to 0.866 or less for specialist Cosworth headed 2 liter 500 hp turbo engines.
Bushing rods and ring circlips are the accepted American and US practice for hardcore performance engines, and critical loads with these smaller outside diamter wrist pins are less with the smaller items than stock.
Bushing rods and ring circlips are the accepted American and US practice for hardcore performance engines, and critical loads with these smaller outside diamter wrist pins are less with the smaller items than stock.
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