Ok, this is my second topic, the guys in the driveline forum were really helpful with the first one.

I am about to start assembling my 327 shortblock. I already had the new pistons installed onto the old rods. But I didn't have the rods resized becuse they looked good and so did the crank. Right now, the old rod bolts are still in the rods.

There was nothing wrong with the old rod bolts except they could possibly be from 1967 (as was this block). Anyway, I just got the box from summit with the ARP rod bolts and the book about rebuilding small block chevy's.

Unfortunately the book says not to replace the rod bolts unless you are going to resize the rods! It says "Only install new rod bolts if you have to because the journal bore will need to be trued up when a bolt change is made," David Vizard, How to Rebuild Your Small-Block CHEVY.

Is this true? The old bolts are knurled and so are the new ones - I would have thought they would have located the cap relative to the rod identically.

Has anyone here replaced rod bolts without resizing the rods? What was the result?

Also, is this a hammer the old rod bolts out, hammer the new ones in situation? Or do I need the machine shop to do this with a press?

Thanks for your help.

 

As rpm increases, tensile loads will make the big end elongate into an oval shape. This ovalization, puts bending loads on the bolts. Good aftermarket rod bolts are recommended in for any performance application.
It is absolutely necessary to resize the rods when installing new bolts. Without it, the proper clamping loads can't be realized and failure is inevitable. Unless of course you don't bring the rpm's up at all ( which isn't likely ).

 

Well, you confirmed what the book said. I guess I still haven't wrapped my mind around it.

But I'll give the machinist a call and see if he can do the big end resize operation with the pistons already installed to the rods. I hope so.

If he can't I'll have to chose between reusing the old bolts or having him remove the pistons, do the rods, and reinstall the pistons. I guess I would probably need new pins in that case?

Anyway, thanks.

 

The pistons have to be off to do the big end resize.

No, you won't need new wrist pins.

 

Hey guys,

I just got off the phone with the local machine shop.

He again confirmed what has been said here - yes I need to recondition the rods to put in the new bolts.

HOWEVER, he told me that he can do the resize even though the pistons are already installed.

(Of course maybe his plan is to "secretly" remove the pistons first, then reinstall before he gives them back.)

He'll do the work this Saturday. I will post back here when he's done to let you know if he had to remove the pistons or maybe there is a special way to do the work with the pistons still on.

Thanks.

 

No way he can do it without removing the pistons. If he says he can, find another machine shop!

For one I don't see how he'll be able to hone the rods to size with the piston on. It physically wont fit on any rod machine I've worked with.

Second, once the rods are re-sized they need to be thouroughly cleaned to remove metal. There is NO WAY to do this with the piston on the rod.

I would run away from this guy as fast as possible.

 

I dropped off the pistons & rods to have the bolts installed after my last post. When I picked them up today I asked the machinist if he had to remove the pistons. He said no. He did resize the rods - the fresh machined surface is clearly evident.

They look good. I'll be putting the pistons & rods in the block this weekend. Will post back next week to let you know how that goes.

 

It would be interesting to see the machine he used to do that. Admittedly, I haven't seen that many rod resizing machines, but none I've seen would do it with pistons installed.