Anyone have some info on rod side clearance?

[Intercooler]

After a thread last week and reading the article on GMHTP's site by Merkel engines I tried to make some sense of it today. In the article he explains to not exceed .015" side clearance from the rod to the crank but doesn't give the fix. Every motor I have put together had more He also states it sets of the knock detector and kills boost. Only way I figured this could be fixed is with a new crank and rods which there aren't any! I talked to them today on the phone and they left me very After mumbling around about the fix (they seemed a little uncertain) they told me they need an uncut crank then they crip the edges and regrind it. Does any of this make sense to anyone? I never heard of crimp a crank

 

[qtr@atyme]

after runnig a automotive machine shop for quite a few years,
about the ony fix i know of is to replace the con rod with slightly
wider one, or weld the crank up and grind it back to get the proper clearance. I've assembled my fair share of turbo 6 motors
from stock to mid 9 stage 2's and have run as much as .018"
with never a problem.
Probably the situation your experancing is caused by an
overzealous crankshaft grinder. (getting paid by job not hour)
next time you get a crank done look at the sides of the journals for grind marks. Also aks the guy very politly about his grinding
techniques (besure not to offend the guy)
I'm sure he has many years experiance but doesn't know how
fragile/particular these motors are.
Hope to been of some help, not just babbling on.

 

[Ormand]

Side Clearance

I've been discussing this with a guy on "The List", and basically, the problem with too much clearance is oil pressure. The even fire crank has more "slots" than a V8 crank, since there is leakage past both sides of each rod, while the V8 (or an odd fire six) has leakage between the paired rods, and at the sides, so there will be 9 slots on an odd fire six, compared with 12 on an even fire. When you measure clearance on a V8 or an odd fire six, you are measuring total clearance for two rods, while the measurement for an even fire six is clearance for just one rod. Also, the Buick has narrow rod bearings, which makes it more sensitive to low pressure. The Buick "Power Source" states that the difference between 0.006" side clearance and 0.008" is 30psi of oil pressure. But if your clearance is too high, its REAL hard to make it tighter. Maybe just use a bigger oil pump? Does this make any sense?

 

[earlbrown]

damn, i'm glad i don't own an oil pressure gauge. 50,000 miles ago at 147,000 i measured .048 side clearance on one of my rods. i didn't know what the spec was, but i figured it was a little on the loose side.



earl

 

[ijames]

A machinist/engine builder friend once told me that he uses pipe solder (I think) to build up the sides, then sands them back to size on a surface plate. There really isn't much side loading and the solder is about as hard as a bearing surface anyway. Next time I get together with him I'll ask for his procedure again.