Technical Engine Building 101............a question

When building an engine its common to upgrade the rod bolts. The mating surface of the rods are ground slightly to close the rod hole and after the new bolts are installed, the rods are then resized.........supposedly because the installation of the bolts may deform the rod hole.

I purchased some new specialty rods for a Cadillac build. When they arrived they were incorrectly manufactured. This company has been making these rods a long time. The problem was that the big end of the rods were too wide. I found out about it some time later through the internet, and checked mine. They were too wide. I contacted the mfg as i could not get a response from the company I purchased them from.

The mfg agreed to replace them if I shipped them back and they were bad. They had never been out of the box except to check them. So I shipped them back. I needed a second set of these rods for another engine and rather than take a chance on getting some more bad ones, asked if I could order a known good set at the same time. They said they would do that for me since I had already had a problem with their product.

The rods came with ARP bolts installed ......but when they shipped the second set of rods, there were no rod bolts installed or included.. I contacted them again and they sold me the additional ARP bolts. Their excuse was that they had stopped installing the bolts in the rods because many people were choosing different ARP bolts than the standard ARP ones.

Now I'm wondering if I need to have these new rods resized after installation? The rods have a coating on them, and the rods that came with the bolts installed don't appear to have been resized. Does anyone know if aftermarket rod manufacturers size their rods after bolt installation, or do they just press them in and ship them? I can check size both before and after installing, but that would require installation and removal of the bolts if resizing is needed. What do your new rods look like?

 

I have to ***ume these are cap screw rods and not a bolt and nut. I if this is true you won't need to resize the rod as it doesn't have an interference fit that causes distortion.

 

I would contact the company. Explain your concerns and see what they say. If this is a rod bolt pressed into the rod, I'd ask the proper procedure they use and if honing will be needed and if they cover that.
I think that they should have covered all of this when you ordered the second set, but give them another chance to make this right. Seems like they need a bit of work on communication skills.
Oh, and have the ends properly torqued and measured before use as normal!

 

First step is to check the ARP catalog and see if they list different rod bolts for that application to see if you just got old a bill of goods. Some times it is a case of "if you have this combination you have to reun these bolts for clearance" though.

Still for your current peace of mine it is ***emble the rods with the bolts and either measure the diameter of the end with a snap gauge and micrometer or load them up and head to a local machine shop that has a Sunnen rod hone with the gauge on it that you/they can check the rods and make sure that the ends are round.

Not that it can't happen but I have never seen a case of where the rod big end was distorted by swapping for upgrade rod bolts. I haven't resized a rod since trade school but the normal method is to clamp the rod in a fixture and grind a few thousandths off the mating surfaces of the rod and the cap and then put them back together and torque them and hone them back to where they are round and the ID is on spec. That is +/- a very thin RCH over on the 4th didget of the .0001 scale.

 

I got to resize the rods for my 327 a couple years ago, it was fun to get back into it.

Yeah, we really need to know if there are rod nuts involved, to be able to answer the question.

 

@RodStRace, @Mr48chev,@squirrel

Thanks for the help guys, but much as I hate to admit it..........I had a brainfart here, one of those "Duh!" moments that seems to be happening more frequently these days. M C Empson got it right on, the rods are H beams and don't have nuts or a press fit. Its been about a year since I bought them, and somehow I got to thinking about how the stock rods bolted together instead of how the new ones did. No real excuse, just a dumb mistake on my part............ Anyway, thanks for steering me straight.

 

Glad to hear it, @ekimneirbo . Make sure you have that first cup of coffee and a checklist handy when you start ***embly.

 

Actually I'm in the process of building a cart to organize all the engine building and special tools for working on dis***embly/***embly of the engines I have. It will have places to put the crank as well as the pistons, rods, rings, lifters so they go in the right places . Trying to make it as "fool proof" as possible because it looks like I need it.........

 

I only trust a dial bore gauge for measuring, As I remember (iffy at best) rods measure slightly larger at the parting line so as to not break the hydrodynamic wedge. If it's round everywhere except the parting line and within spec, I would run them. I should add that many modern rod bearings are a little wide at the parting line to do the same thing.

 

Yes, a dial bore guage is an excellent tool for quickly checking the rods size and roundness. I have one and I will be checking/verifying all sizes before ***embly. I have some intrimics that I like for double checking sizes because they read the actual size .......so I don't set the zero on the dial bore gage incorrectly. Usually no problem on an existing rod, but helpful when machining something from scratch.