engine gurus input needed

[prove_it]

I'm putting together a 4G for my friend and it went to the machine shop and came back with the crank and pistons assembled. I noticed dirt in it so I'm pulling it apart to clean it out. I noticed that the rods seem loose on the crank though. Not so much the bearing clearance but the side clearance against the crank. They move enough that you can just barely see the crank surface. Any input on this? Does this seem too loose for track drag car?

 

Refer to the fsm for clearance tolerances.

 

[prove_it]

I'm not asking for specs. I'm looking for a technical discussion. I'd like to know what others have run and what's worked and not worked for others.
I know .025" is pretty much the high end for clearance. Just want some input. This ain't my first rodeo.

 

[iceman69510]

Well without some idea of where your clearance is, "seem loose" is a bit ambiguous. If you have an actual measurement to discuss I think that would help.

 

[bazeng]

On the same note, what have others built their motors with in regards to tolerances?

Is the tendancy to go tight ie 1thou over mains and 1 thou over the big ends or loose ie 2thou / 2 thou...

As for the slop of the crank / rods, what rods are you using?

 

[prove_it]

Unfortunately I'm doing this build in his garage and he has a very limited selection of tools. I did rummage around and late last night I found a feeler gauge. It only has a few blades but it does have a .026" blade and that did fit the clearance. to me .025" is the high side of side clearances however I've heard of some running up to .030". I'm using my best guess and going with a measurement of .026" side clearance. It's only on the number 4 pistons while the others are running around .015"-.021" clearance.
For some stupid reason he went with Mahle pistons, but saved himself and bought eagle rods.
The crank was turned and the engine was bored .020" over.
On the other note when I build motors I try to keep the crank to rod clearance tight and mains looser. think about how often rod bearings go verses main failures. On my own personal engine I just built I'm running .0025" on the mains and .0020" on the rod bearings. It's kinda loose, but its solid.

Again I want a technical discussion on this, not a drama that seems to be occurring lately.

 

[prove_it]

I used eagles in my own engine and my side clearance was down around the .010" side, but that was a low mileage engine and no machine work needed. I'm curious to how this much clearance came about.

 

[CarRacer]

Do you have a dial indicator to measure crank run out? I'm still learning lots about these cars, but that might be an issue.