piston to wall clearance

[TrackPack]

What is the recommended piston to wall clearance on the old TRW 2355, and should they be run with more clearance?

 

[Demonic]

Rough answer, .006 to .009 for naturally aspirated. Those old forgings expand a bit with heat. It will vary slightly with intended use - if you're bolting a blower to it, your pistons will run hotter, so many prudent builders will run at the top of the spec.

I looked for the exact number on Summit and Jegs for the Speed Pro equivalent, but didn't come up w/ anything.

 

[BeepBeepRR]

Here are some sealed power pistons with the same number.
https://www.jegs.com/i/Sealed+Power...MIw6e11ebK6QIVjYrICh3eygomEAQYBCABEgK1BPD_BwE

 

[BSB67]

IIRC, Speed Pro and TRW said 0.002". I would put them in with 0.0035" clearance.

 

[33 IMP]

On summits site, I checked the 2355 pistons out, and a customer asked what the piston to wall should be. The answer, supposedly given by speedpro was.... .0015, one and a half thousandths. I find that very hard to believe. If those were my TRWs, I would probably set them to .004 or .005 .

 

[bm02tj]

The newer forgings have more silica and expand less than the old forgings
30 years ago they would rattle until warmed up
so more is better unless you can get the specs from an old book for year the pistons came from

 

[33 IMP]

I've got an old TRW catalog that would give the answer. Unfortunately I'm two hundred miles away from it.

 

[wyrmrider]

fordgedtrues used rhe big clerance
not the 2355
run the clesrance for a 6 pack from the fsm or trw or sealed power catalog

 

[bm02tj]

If no one can come up with an old TRW book do the next safe thing
Measure the pistons then heat in oven at 200F for 20 min then measure
that will give minimum clearance

 

[33 IMP]

fordgedtrues used rhe big clerance
not the 2355
run the clesrance for a 6 pack from the fsm or trw or sealed power catalog

The 2355 is a forged replacement for the cast 440 sixpack piston. Fsm for cast pistons would not be right for a forged piston.

 

[BSB67]

When I put my Speed Pro forged pistons in back in 1990, they called for something around 0.002". I don't recall exactly. The two local Mopar machine shops at that time were reporting some skirt stuffing at the recommended clearance. So I put mine in at 0.0035". I still have them today. The skirts look new. There was a slight slap upon start up.

This will be your choice at the end of the day, but even if you find the right manufacturer's recommendation for the piston you have, view it with caution. If it were me, I would not go any tighter than 0.003". Of course, the race guy were putting them in at 0.005"+ and going up from there.

 

[dvw]

.006" with the old TRW was common.
Doug

 

[wyrmrider]

sorry I forgot the stock 6 pack pistons wewe cast
I was always boring for theTRW's
now .003-.0035 sounds right
.006 only on worn out bores cleaned up with a minimum hone
that big shortens ring life

 

[TrackPack]

Thanks for the replies. I do remember the old forged Sealed Power and TRW's were run looser even than their specs because of scuffing.

 

[383man]

You need to check with the manufactor of the piston. Many stock cast factory pistons ran .0015 to .002 but they were cast. I can tell you the Diamond forged pistons we just put in my sons eng which is getting supercharged Diamond said run them from .005 to .007 range. With the final honing on the cylinders it came out at .0055. Myself I always check with the manufactor of the piston I use. Good luck , Ron

 

[TrackPack]

Thanks Ron,

The metallurgy has changed quite a bit, I'm sure, since these TRW's were manufactured in the early 80's. Unless someone has an old catalog.......this information is long gone. Even at that, I remember a friend putting together a 440 with 2295's in the 80's at the recommended skirt clearance and a later tear down revealed scuffing on the skirts.