I started putting in my rods and pistons today, and I got to number 5 before I noticed this. The rods on all of the pistons are slid all the way over to one side on the wrist pin so it's touching the pin boss. There is no gap. When torqued down, the rods won't slide at all on the wrist pins. Everything moves freely however, no binding that I can tell. Here are some pics. There is obviously nothing I can do to correct it, except order new pistons or machine these slighly. Any help is appreciated. Thanks!

 

Rod looks offset...

 

And by that you mean...? The rods are in the correct way I believe. The rods only move all the way to the side when the bolts are torqued down. With the rod caps nested in place and the bolts finger tight there is a small gap between the rod and the pin boss. After closer inspection, there appears to be a small gap between the rod and the pin boss, maybe a couple thousanths. I'll see if I can get a feeler gauge in there.

 

True LS1 rods are off set. I don't know if they are offset in the manner that your seeing, but I would try and flip one of the rods over and see if it centers it up. Technically, flipping it over should pull it back to the center instead of into the wall.

 

I think that's a good idea.

From the picture the rods do look offset.

 

The only problem with that is that the one side of the rod has the chamfer to clear the fillet on the journal of the crank. If I flip the rods around, the rods will scrap on the fillet.

After messing around with the rods for awhile, I can see that they are not pressing against the pin bosses, but intsead "resting" on them. If the push the slide the rod over on the crank as far as I can, then there becomes a small gap of a couple thousanths. Not sure if this is enough or not. I know it would be ideal to have the rods centered on the wrist pins, but that may not be possible.

 

"holy High Def Pictures Batman!"

 

Looks to me like you have yourself a set of rods for a small block Chevy. Small block rods have an offset beam. Ls engines have the beams pretty well centered on the big end.

You are going to have to return those rods for the correct set for an LS engine.

Steve

 

They are Lunati Pro-Mod rods for and LS1 motor.

 

Steve, the rods came out of a LSX 427 motor I had.(Which dosen't change things) BTW, don't people use the Eagle SBC rods in LS-1's all the time? I know I had a 383 with those in it at one time.

 

I am betting the problem is due to the inboard pin bosses on the pistons instead of the regular style.

Man this really pisses me off. This wasn't an issue when everything was mocked in place.

 

I use inboard pin boss style pistons (FSR J&E) and have not run into that problem with Lunati LS Pro Billet rods or Crower titanium rods.

What you can do is take a bit off the offending wrist pin face of the rods to provide a bit more clearance. This is best done on a Bridgeport style mill or in a lathe with an expanding mandrel. You should be able to find a local shop to take care of that if you are not equipped to do the work yourself.

If you were closer, I'd take care of it for you.

Steve

 

What about milling a little bit off the inside face of the pin boss? Any machining I do I would like to minimize the change in weight of the rotating assembly, seeing that it has already been balanced. Since aluminum is lighter than steel, the change in weight won't be as great. I do have access to a milling machine. I could knock off .050" or so from the rod or the piston. Any reasons you would machine the rods before the pistons, or vice versa?

 

Ttt

 

You won't end up taking a lot of material off the pin boss of the rods. Thus not a lot of weight.

Looking at the pistons, you will weaken them too much if you take .050" off them.

Also, you will find it much easier to fixture the rods for machining than the pistons.

Steve

 

Hope I don't have that problem with my pro-mod rods and diamond pistons!!!

 

is the thrust off on the crank? do you have to set that on the new style engines?

 

It almost looks to me like you have the rod installed backwards. Pull that piston out and look at the connecting rod and bearings. I'm not certain about aftermarket rods but I know stock rods are chamfered on both ends because the rods are supposed to face a certain way when installed so that rod has to be machined to clear both even and odd bank cylinders. I would almost bet that is your problem. If it mocked up ok and was put together correctly then thats gotta be the problem.

 

As already mentioned, the rods are chamfered on one side only, they cannot be reversed or they will grind on the fillets on the crank journals. I agree if I could flip them around it would solve the problem, but I can't.

 

Ok, today I machined one of the rods down. I took it down .050" on the side that was giving me problems. When I put it back in, it was no longer touching the pin boss. There is now about .035" of clerance on the once problematic side, and about .070" on the other side. Does this sound okay? I'll post a pic ASAP, thanks!