TRW/SpeedPro Forged piston tolerance
- Thread starter tminer
- Start date
QuickWrench
Don't Read This
I think the .001" is per inch of bore diameter, which is in line with the old value. I'd have a hard time believing that you could run a forging with only .001" - .002" of clearance...but it would be nice.
tminer
Not quite normal
I am looking for tolerance, not clearance. Their clearance spec is .0035, so ideal diameter would be 3.7965 (std) or 3.7995 (.030 over). I am wanting to know how close they come to that spec. I believe that the .001 was the amount that they could be oversize, which would mean spec of 3.7995-3.8005 for .030 over.
I am really interested in std size, but I imagine that there is more experience with .030 overs.
Tom
I am really interested in std size, but I imagine that there is more experience with .030 overs.
Tom
tminer
Not quite normal
Since the skirt coating may add .001", the size and clearance specs may be different than I listed.
I'm really trying to determine two things: the correct bore size and whether the pistons vary enough that the cylinders need to be honed to match the individual pistons.
Tyvm,
Tom
I'm really trying to determine two things: the correct bore size and whether the pistons vary enough that the cylinders need to be honed to match the individual pistons.
Tyvm,
Tom
QuickWrench
Don't Read This
Sorry 'bout that, I'm stupid. Not enough caffeine yet...
You are off on your calc's, though. A .030 over slug would most likely range from 3.82 - 3.83", not 3.7995". You're adding .003", not .030".
FYI...
I've never installed a set of forgings that didn't require per-cylinder setup for the final hones, regardless of the engine make/piston brand. I've used TRW, BME, JE, and KB's in Buicks, Chebbys, Ford, and Mopars, and they all had to be set up individually. I've rarely seen a complete set where all 6 or 8 weren't within .001" of each other, but they always vary enough to warrant a precision hone for each one, before pressing/Spiro-Locking them to the rods.
g'luck.
You are off on your calc's, though. A .030 over slug would most likely range from 3.82 - 3.83", not 3.7995". You're adding .003", not .030".
FYI...
I've never installed a set of forgings that didn't require per-cylinder setup for the final hones, regardless of the engine make/piston brand. I've used TRW, BME, JE, and KB's in Buicks, Chebbys, Ford, and Mopars, and they all had to be set up individually. I've rarely seen a complete set where all 6 or 8 weren't within .001" of each other, but they always vary enough to warrant a precision hone for each one, before pressing/Spiro-Locking them to the rods.
g'luck.
Close??
I just finished checking 8 4.500" bore Wisecos for my HEMI
All were DEAD NUTS ON!!!
I guess it's a matter of how well the mfgr sorts his products as the sets are made up???
I just finished checking 8 4.500" bore Wisecos for my HEMI
All were DEAD NUTS ON!!!
I guess it's a matter of how well the mfgr sorts his products as the sets are made up???
I don't remember the actual #s. The skirts were coated with whatever that black coating they're using is. Their spec is .0035" but I set the last two I did at .004"; they don't make noise when cold at .004" and the skirts weren't scuffed on one I had apart subsequently.
