Stuck connecting rod bolt

Mac-Porsche · 02-23-2020, 10:36 AM

Rebuilding 911sc engine for first time. Used old connecting rod bolts when checking the tolerances with the plastigage - everything checked out perfectly.

Then started on the final torque/installation with the new OEM connecting rod bolts I purchased from PP. Most of the new bolts don't want to slide right in, you can get them on just enough to get the nut on, then screw them down with a wrench till they're flush. Given this is my first rebuild, I assumed that was normal.

As I was tightening down the first rod, I noticed the "wing" on the end was eating into the side (see attached picture). So I stopped and then tried to remove the bolt - cannot get it out... Tapped it a few times with a hammer with a plastic end - no luck...

Any suggestions on how to proceed? Furthermore, should the bolts fit that tight in the rods? Or should they be able to drop right in? Some do, some don't, makes me question the quality of the OEM bolts...

r lane · 02-23-2020, 01:02 PM

You should be able to tap them all in with a snug fit, and as you found out, you have to get the wings centered. If some are snug and some aren't, that might make me nervous. Is the problem the bolt or the hole. Can you remove the others and mich them. I have heard frightening stories with defective rod hardware, though I have not encountered any, but have had rod bearing problems. I do think product quality in general is going down the tubes. All you need is one guy to drop the price and quality, and everyone else follows suit. ARP, Race Ware. There are good aftermarket rodbolts out there. Bob

Mac-Porsche · 02-23-2020, 01:20 PM

I believe the problem is the bolts. At least, that was my question to the community. The ones that drop in easily, do that for all the rods. The ones that are very tight, are that way for all the rods...

I was planning on using ARP, but the machine shop I went through rebuilt them by tightening the old bolts to 32 ft-lbs. Because of that, they advised me against using ARP, as those require ~50 ft-lbs and might slightly deform the work that was done. They suggested that OEM would work fine... Which is how I ended up here.

Problem now is how to get this bolt out... I've gone about as far as I feel comfortable with, I'm afraid that hammering or using a vice bench might mess up the rod. I'm beginning to realize that it'll probably involve more shipments back and forth with a machine shop... Not the best start, but live and learn I guess...

Flat6pac · 02-23-2020, 01:42 PM

I tap them in to seat the wings. I use the flat on the vise to support rod bottom as I tap.
Removal is easier because of the stretch factor, just knock them out holding the bottom half in my hand.
Bruce

Mac-Porsche · 02-23-2020, 06:18 PM

I appreciate the replies. I've whacked at this bolt quite a few times while holding the bottom half - it won't budge in the slightest. It seems to be really stuck.

I thought about putting the bottom half in a vice and hammering it a little harder, but really don't want to run the risk of deforming/damaging the rod.

mikedsilva · 02-24-2020, 12:32 AM

Quote:

Originally Posted by Mac-Porsche

I appreciate the replies. I've whacked at this bolt quite a few times while holding the bottom half - it won't budge in the slightest. It seems to be really stuck.

I thought about putting the bottom half in a vice and hammering it a little harder, but really don't want to run the risk of deforming/damaging the rod.

In your first post you said you were using a plastic hammer? Maybe try a metal one while holding the cap in your hand, tap the conrod bolt.. the plastic would be absorbing too much of the force I think.

Neil Harvey · 02-24-2020, 11:21 AM

Mac-Porsche

Take the new bolts and the rods back to the machine shop and ask them to fit the new bolts, torque the nuts and recheck the sizes.

It doesn't matter what make of bolt you use, you have to fit the new bolts before the rod is re sized. A new OE bolt will stretch differently than an used bolt.

Resizing BE's always fit the fasteners that will be used in the engine.

Trakrat · 02-25-2020, 09:51 AM

"they advised me against using ARP, as those require ~50 ft-lbs and might slightly deform the work that was done."

I've NEVER heard of this. if tightening something to 50 ft lbs would 'deform' a machine shop's work... I'd be worried about the work they did.

cgarr · cgarr's Garage

The rods need to be sized with the bolts being used, if more torque is used then what they are sized too it can change the ID of the big end and cause a tight bearing.

eastbay · 02-26-2020, 07:47 PM

To the OP, screw an old rod nut onto the bolt leaving a few threads open so you are only hitting the nut and pound it out of there with a steel hammer.

smokintr6 · 03-02-2020, 07:57 AM

Quote:

Originally Posted by Trakrat

I've NEVER heard of this. if tightening something to 50 ft lbs would 'deform' a machine shop's work... I'd be worried about the work they did.

Metal always deforms under load. You always need to install the rods in the engine with the same bolt clamp load as the parts were machined to. This is very common practice.

I would start the process over with ARP bolts and have the machine shop torque them correctly. I would also be concerned about the different fit of the bolts. You definitely want a snug fit, because the shoulder of the rod bolt aligns the two halves of the rod, and bearing.

Mac-Porsche · 03-02-2020, 12:29 PM

Thanks all. That is the plan at this point. The rods are currently on there way (along with new ARP bolts) back to the machine shop.

I agree and felt the same way as many of you... The OEM bolts are suspect. Especially since some will just drop right it and you can actually "jiggle" them within the rod... Not good... Appreciate the responses!