Moved from the Shoveled forum to here. No response over there...


Need a little help. I've been following a thread here in Shovel land and am trying to get familiar with Shovel spec's but I'm a little bit confused after researching piston/cylinder clearances from the FSM. I always though that standard clearances for forged piston run between .002" and .0025" and .001"-.002" for cast. My service manual is a Factory 1970-early 1978 and it list clearance @ .001"-.002" in loose, and I'm good with that. but then there's this thread here
https://www.hdforums.com/forum/shove...l#post15840654

Now this guy jon is rebuilding his 83 shovel and the shop doing the cylinder work has the pistons @.007" which to me I thought was like wow that's real loose so that's when I started to look into the clearance only because I as well became new to Shovel's after owning my Evo for like 15 years now. So l came across this as well quoted from the FSM,

It did not state an actual wear limit but on page 3-1, General specifications page, it says that "piston Fit in Cylinder .001"-.002" But on page 3-17 the FSM says,
"When cylinders are worn less than .022" maximum, and reboring is unnecessary, unless they are scuffed or grooved the same pistons may be used with the replacement of the rings and the roughing of the cylinder walls to facilitate rings seating"

So my question is what is a reasonable serviceable limit? is .007" ok and can it go up to .022" (as the way I understood what I read) as the manual says or is there a typo somewhere and the serviceable limit is actually around .003"-.004". Any and all help would be appreciated.

I HAVE but am a little confused...... Thanx Bob.....

 

That .022 is a misprint. If you look at the top of the page it says:
"if the cylinders show more than .002 wear, they should be rebored/honed to next standard oversize & refitted with corresponding pistons & rings."
Says the same thing on the previous page.
I can tell you from experience that a piston fit .007 loose is going to give you trouble.
You had it right the first time. .001-.002 for cast. .002-.003 for forged.

 

That is exactly what I thought, a mis print. The reason I got into this was because there's a guy in the shovel section who is getting his motor redone and the shop say he has .007 clearance but that it won't be an issue. I felt that it was and decided to research. I'm not a builder but do have some knowledge and feel that this guy is going to have issues.... You're knowledge is helpful to me, Thank you...

 

When using ductile iron and JE or CP piston kits .007" is reasonable for hot street.

 

Randy follow the link to the thread he's talking about & see if you know what those cylinders are made of that he's using.

 

I believe they are the oem cylinders...

 

Only time you set one that loose is when you plan just running the **** out of it on the track from mile one, street engine that'll have piston slap like crazy.

 

Depends on the growth rate of the cylinder material/aluminum piston properties, at full operating temps.
On an OEM HD cylinder, I agree with Larry.
Scott

 

They are after market ZEL cylinders.... The machine shop he dropped them at measured the cylinders at 3.657" and the pistons at 6.550"....

 

Not in ductile.