ARP is a manufacturer of high quality fasteners used mainly in racing engines. Their fasteners are made to stretch ("YIELD") at full torque. This keeps better holding pressure against whatever application they are used for. Ken gave a great description of how to torque standard "factory" bolts and fasteners. Find out if you have the ARP bolts and if so, please post here and I will type up the procedure for torquing them, it's somewhat lengthy.

Since I've got a non-stock 383 stroker, do I follow torque recommendations for a 400, since I have a 400 crank? Actually, I don't know if a 400 was a stock motor in a Vette, so I'm not sure where I find proper torque value for my 400 crank...?

Patricia/75

Since it's a 350 block, I would use the specs for the 350.

Why would you consider not changing a $5 oil seal when you have the motor apart? You wouldn't want to pull the motor or pan again to do it later.
Make sure you put A LITTLE sealer on the ends of the new seal, and on the rear bearing cap/block surface.
Joe

The procedure for torque to yield bolt depend on the very specfic bolt. Not just the size. All bolts stretch when tightened. When loosed, they return to their original shape. The is the elastic properties of the bolt. If it does not return, it will stretch again, weaken, and fail. The reason we torque the bolts is to get it in the correct range, but more so, to determine the clamping force of the bolt. How hard it's twisted really does not matter, except that the only way we can determine how hard it is clamping.

Torque to yeild bolts are different. They are tightened to the point of passing the elastic point of the bolt. It stretches, and does not return. As it starts to stretch, it "Yields" or will only clamp so hard. As we turn it more, it will maintain the same clamp force until we go to far, stretch it too much, and it gets weak. This very exact amount of plastic stretch gives us a very exact of clamping force. Much more accurate than a standard bolt and torque.

These bolts are usually tightened to a given torque to make an initial adjustment, then turned a given number of turns so it will stretch and clamp properly. This varies with each design bolt and application. Go by the mfg of the bolt, and their procedure.

The advantage, much better, more accurate. Disadvantage, only one or two uses, then throw it away and get new ones.

Ken Styer

Should I use Loctite blue (242) on the bearing cap bolts when changing out the rear main seal?

If my torque wrench is not perfectly calibrated (probably isn't), I suppose there could be some torque variance between the rear main bearing cap I work with and the other bearing caps the mfg. torqued (and which I would not touch). For instance, if the rear main cap ends up being a few ft*lb tighter or looser than all the others due to wrench calibration differences, would it wear that bearing out faster than the others or put extra strain on it? The alternative would be to loosen all bearing caps and re-torque them all with my one wrench so they'd all be identicle. Should I bother to do that? I don't have a feeling for how touchy these things are.

Thanks, Patricia/'75 with 383 that probably isn't leaking but whose seal may have been abused by an out-of-round tranny input shaft for 5k miles

I would rather see you use a torque wrench you can trust. Have yours calibrated, or test it compared to a known accurate one.
If the bolts are too loose, the bearing caps will not properly crush the bearing, and it will spin and fail. If the bolts are too tight the bearing may overcrush and not have enough clearance, and wear out quickly. Locktite on the bolts will not affect the bearing crush. This is a fairly exact requirement with out much "fudge factor". If you are more than 10% off you may have a failure. Better to be less than 5% off. If your torque wrench is off, loosening all the caps and retightening will only create the problem at all the bearings, instead of just one.

Ken Styer

I wouldn't mess with the other bearing caps unless you decide to remove all of them to allow a little clearance for installation of the rear main seal. Loctite certainly can't hurt, make sure you get the studs and nuts really clean to get the stuff to take.

Ken, thanks for explaining about the caps' torque being critical. I did not know whether the cap's torque or whether the cap-to-block mating surface dictated the bearing's tightness. I was hoping the cap's "parting line" that butts against the block was what set the bearing tightness and the bolts' torque was merely a matter of the cap not coming loose. I'm glad you clarified it's the caps' torque which dictates the bearing's tightness.

Now I'm curious: When rebuilding an engine do you ever re-machine the area of the crank that sits against the bearings (like if the crank got damaged with a bearing failure)? If so, doesn't that tweak with the bearing's tighteness when you use standard cap bolt torque?

BigFish thanks for your help; I'll plan on using 242.

Man, maybe I should leave my seal alone; I didn't realize I could mess up a bearing if something went wrong or if my wrench isn't perfectly calibrated. I'll have to stew about this one.

Don't stew about it. Take your time. The most important thing is to assemble everything CLEAN. Dirt will ruin the job. Just borrow a good torque wrench and compare it to yours. Mine acutally reads about 10% off, and I compensate for that when I do the work. You'll do fine. And it is easier to install the rear main seal if you loosen all of the caps. The crank will lift a bit, and allow the seal to go in easier. Just torque them back when you are done.

As for a repair to the block the machinist do what is called line bore. The bearing caps are bolted back in place. The the block and caps are bored in a stright line and even size. When putting the crank back in a "oversized" bearing is used. This means the outer wall of the bearing is a larger size, to make up for the metal cut from the block. If the crankshaft itself is machined to make a better surface, the bearings are "undersized". The inner measurement is smaller to match the crank size. Both work very well, and many sizes are available. This does not match new spec, but is just as good. Many crate motors are engines that have had a problem when made, and have had that corrected with different size bearings and or pistons. Not a thing wrong with them, they just don't match OEM spec in the new car.

Ken Styer