Can I replace a rod bolt nut with a grade 8 from hardware store?

[WH23G3G]

I got my block back with the cam and cam bearings installed, honed, and cleaned. They are checking the crankshaft now but they said I shouldn't have to do anything to the crank but polish it. He said he was going to mic it just to make sure. I was told the pistons, rods, and rod bolts were ok. But when I was taking one of the pistons out, I dropped a rod nut somewhere in the garage and can't find it. Do I need to order the exact part number rod nut or can I just get a grade 8 nut of the same size from the hardware store? I don't want to do the wrong thing here and trash everything. I asked a couple of mechanic's and they said it would be ok. But I know there's people on here that have built more motors than some shops ever will. Do I need to use threadlocker on the mains or rod bolts?

[firefighter3931]

Personally, i would source out the proper nut for the application and not have to worry about it. 

As for torquing....just use 30wt oil on the rod bolts and torque them in stages....that's how i've allways done it. 



Ron

[Chatt69chgr]

I don't know what the tensile strength of the OEM bolt is but grade 8 is 150,000psi.  Most all ARP rod bolts have tensile strenghts of 180,000 and up--in fact, most are 190,000 to 220,000 psi.  I think I might replace all the rod bolts and nuts with a set from ARP.  Just good insurance since that bolt and nut is probably the most important one on the entire vehicle.  And did they magnaflux your rods?   

[WH23G3G]

The rods are still connected to the pistons. They have been looked at closely through a magnifying glass for stress and cracks. I've had a couple of older mechancics look at them too. The machine shop told me all I have to do is hone the block, clean it, put cam bearings in, and have them check the crank. They said the block was only lightly worn out from the previous build. He said the bores cleaned up easily. The rod and main bearings have been examined and the machine shop says the engine didn't have many miles on the build. Which is what I was told when I first took everything apart and had someone else look at the bearings. I didn't get the rods fluxed or anything special. He told me that they don't have to be replaced and that it gets more critical as you start racing the engine at higher RPM for extended use such as drag racing or course racing. Mine is going to be as stock as I can get. I will however, source out the correct rod nut from Chrysler for it. I think I saw a couple of places that had some. Just hope that a rod bolt doesn't break. The budget on this Charger project is way way out of what I expected it to cost and I've still got trim and bodywork to buy. Consensus from everyone who's checked out my engine is that it should last a long time with quality rebuild parts.

[Chatt69chgr]

You can buy a new set of ARP rod bolts and nuts, their lowest grade, but 200,000 psi for $57.95 from Summit:

http://store.summitracing.com/partdetail.asp?part=ARP%2D145%2D6002&autoview=sku

If you still want to just replace the one nut, I bet there's lots of folks on here that would be willing to send you one free for the postage.

[gtx6970]

suprised no ones mentioned the potential weight differences factor. grade 8 is probably strong enough but does it weigh the same as all the others?

personally  I'd make sure all the rod nuts were of same likeness and quality. Connecting rod hardware is the most critical internal engine component and it takes to most abuse . Just think - average 4000 rpms for how many years and miles of trying to be pulled apart  / stretched

[b5blue]

Hey guys! I did just what he is talking about long ago. If your like me, you will drive your self nuts (no pun) knowing it is not correct. It is a balanced assembly, all those nuts should be the same. 5 years from now, 500 miles from home, going 90 mph, you will be glad you waited to get the ARP set, and had the connecting rods checked out now.The MOPAR Big Block Bible, on page 90 says "check for alignment and size big and small ends with a Sunnen connecting rod reconditioner".I know how hard it is to keep coming up with more time and money, my charger sat in storage for 6 years waiting till I could come up with the cash to get it back on the road (3 kids to raise and an ex 21,000 behind on support) but your motor is the heart of your project.

[WH23G3G]

If I take all the rod/piston assemblies into the machine shop to be checked will I have to buy new pistons. Will they take the pistons off the rods to check the rod bolts? I've already got my block back with the cam and cam bearings in. Will that have to go back to the machine shop with the rods/pistons in order for them to check the rod bolts? The guys that are there doing the machining have been there for like 30 years and the shop has been there for 50 years. I know their reputation is good thats why I get all my work done. He told me I didn't necessarily have to replace the rod bolts. When they change the rod bolts will they have to oversize the rods to .020 changing my rod bearing size to .020 over? What will I have to bring to the shop other than the rods/piston and rod bolts? I don't want to anything to come apart when I put the engine back together. 

[superduperbee]

If one bolt is bad, the others may not be far behind? I would replace all the rod bolts with a new ARP set. They are not expensive, airconditioned blocks are however.

[Chatt69chgr]

The new rod bolts are the same diameter as your old ones.  Just pop the old ones out and install the new ones.  The new bolts won't have any effect on the bearing size. 

Are you assembling the engine yourself?  Did you have the rotating assembly balanced?  Just curious.

[WH23G3G]

Is it not difficult to replace the rod bolts yourself? But you still have to have the rods reconditioned if you replace the rod bolts so you may as well have the machine shop put them in too. I didn't have it balanced. So far the machine shop checked the bores and the block for defects, cleaned it inside and out, and honed it for steel rings. He also put in my Sealed power cam bearings and cam. I picked it up have it double bagged on the stand and now the machine has my crankshaft. He knew right away the crankshaft was good when he saw it. He told me he was going mic it and hopefully all it would need was a polish. The crank journals were as shiny and smooth as my newly rechromed bumpers. I thought about having everything balanced, but thought the expense was too much for what I was going for. Don't they just need the pistons, rods, and crank to balance everything? I'm going to be building the motor as stock as possible. Any power increase will come from bolt ons such as intake, exhaust, ignition. So I don't expect it to be a powerhouse. Only thing I'm going to do different inside the motor is the addition of the windage tray.

[superduperbee]

I have replaced rod bolts many times without reconditioning the rods, never had a failure.

[WH23G3G]

Do I have to have a vise? If I can't do it at home I may be able to take the pistons to one of the shops I deliver to and have them do it for less than the machine shop. If I do replace them I would like to try myself. If I decide against replacing them at all I am at very least going to buy a set of new rod nuts since I've misplaced one. I can get a set of OEM replacements from Pioneer for about $10.

[bull]

I would go out there and look harder for the nut you dropped.

[WH23G3G]

That nut is long gone now. It was back when I just inspecting the motor. I've since cleaned everything around the car, there's nothing laying under the car except the transmission and the driveshaft ready to be put back in. Everything is organized and neat in the truck. There is nothing laying around in the interior. I'll just get a new set of rod nuts if I have to.

[Big_John]

This really isn't that complicated.

First, as a matter of good practice with any performance engine rebuild, the rod bolts should be replaced. They are one of those small things that are disastrous when they fail.

Second, in the "big picture" they aren't that expensive. Yea, I know... its another $60... compared to what the expense is when they fail...its cheap insurance. I've seen people reuse rod bolts and most times they get away with it, but sometimes they don't.

Third, they are easy to change. A small brass hammer is all I have ever used. Hold the rod in one hand and hit the end of the old bolt with the hammer. It'll pop right out. Make sure everything is good and clean and put the new one in and it will lightly tap down into the  hole. If anything has to be forced, something is wrong.

BTW, I use Locktite on the rod nuts.

[firefighter3931]

Connecting rod hardware is the most critical internal engine component and it takes to most abuse . Just think - average 4000 rpms for how many years and miles of trying to be pulled apart  / stretched

Exactly....the most critical component in an engine is the rod bolt....if it fails > Game Over ! 

On any rebuild i allways swap in new rod hardware....no questions asked. 



Ron

[WH23G3G]

I don't mind buying new rod bolts and swapping them if it's not a difficult task. It's just that everytime you have to take something to the machine shop it costs at the very least over $100. So is it ok to go ahead and replace the rod bolts without taking them in for reconditiong? If the consensus is that it's ok to replace the rod bolts and go with that then I will most definitely do it. But I don't know if it's just around here or the same everywhere, but it seems like the machine shops around here are all more expensive than elsewhere in the country. Maybe because there's only a couple around.

[lisiecki1]

ARP ftw....rod bolts are not something you want to be "iffy" inside your block.......

[Runner]

if you put new bolts in you really need to get the rods resized. so youll end up being into the ordeal a couple hundred dollars.  if your going to put it back together with what you have id call around to some machine shops and see if they have a rod bolt nut laying around.