The Stovebolt Site Forums The Shop Area Engine Shop Main Bearing Cap bolts- Find replacements

So I am finally putting my 235 back together after a long disassembled slumber. I got the bearings in, put the crank in, and then started to check the rear main with plastigage before I lube it all and call it good.

As I was torquing down the rear main, one of the bolts snapped.

Where or what are a good replacement for the main bolts on our engines?

This is my second rebuild and at least the third for the life of the engine. So I am gong to replace all the bolts, because I figure they are all tired of being torqued and re-torqued. More may snap if I don't. I appreciate the help. I did find some posts on the subject, but not a real clear answer. Grade 5 or 8 seems to work, but from where?

It's possible one of the racing specialty places like ARP might have something suitable. Instead of cap screws, studs might be a better choice. When we wanted to build a really bulletproof lower end on the race engines, we would install Grade 8 studs in the block and use hardened steel grade 8 washers and nuts to secure the main caps.
Jerry

Grade 8 sounds like a fool proof choice, maybe from Fastenal?

ARP has a "Main Stud Kit, Chevy Inline 6, '54-'62, Kit #: 132-5402"

May be worth the peace of mind, but overkill.

Our hardware store in Boulder has all kinds of grade 8 hardware. Look around where you live for a fully stocked hardware store. ARP has good stuff, studs and nuts would be a good idea, reasonable prices.

Ed

$108.00+ for the ARP kit....

I may just compare prices and go from there.

I agree with Jerry.
Grade eight studs lubed when installed and torqued to specs.
A lot of people don't realize that the bolt or stud has to be stretched to hold it from working out.
Not friction.
If you do not lube when installing and torquing, you do not get the proper stretch.
Do a search for a torque chart for the grade bolt/studs you get.
You will be surprise at the different torque values for the same size fastener but different grade.

Don

The ARP Main stud kit that I ordered for my 1959 261 only fit the 2 center bearing caps. The other studs that they provide have too much of the shank showing when installed (READ: they are the WRONG length!), even after using their thick washer, so you can't torque them down.

That's the worst thing I heard today...

I was beginning to plan on using that kit too. So much for simple....

Well, just send them back and get the correct ones, they are available by the each!

Ed

you can get studs from ARP, I just went with individual ones. I have tried looking through my records for the numbers I used, but something is missing. However ARP is very good about swapping out ones that don't fit, (I tried about 3 times)I do recall having to cut the rear set because they interfered with the oil pan. They generally give you some of their special lubricant. However don't use their recommended torques, just use the factory specs.

From every one else's experiences it sounds like finding some bolts at Fastenal, or some-such, and using them may be easier/less time consuming than going back and forth with ARP.

I have some extra factory head bolts in my parts stash left over from various projects. If you decide to simply replace the one that you snapped, send me a PM letting me know if you need a long one or a short one and I'll drop one in the mail to you.

Matt

Thanks Matt, but I decided to go with all new since one snapped, I don't want the rest to snap while going down the highway or something.

I ended up getting all new bolts from "Specialty Fasteners.com"

They had individual bolts for sale in Grade 8. I wrote out all the specs and found the best matches to the original bolts. Best part they are made in the USA!

All other site I found made in USA only sold in large quantities. Bolts were only $13.00, but online sales had to be $15 or more so I bolt a bolt gauge aswell for $4 more, alot cheaper than the ARP set up. I'll try to report back about the fit when they come in and are installed.

P.S. What recommendations for bolt lube? Just straight 30W? OR spring for the ARP Lube?

SAE torque specifications are written for bolts lubed with 30 weight oil. If you use a high-pressure lube such as Never-Seez or 90 weight gear lube, etc. reduce the torque spec a little, 5% or so usually works for me. I used Never-Seez on race engine fasteners for a lot of years, and there's no reason to pay through the nose (or some other bodily orfice) for the expensive stuff from ARP. I like to put a small dab of lube under the bolt head as well as on the threads- - - -there's friction there, too, where it contacts the head or the main bearing cap.
Jerry

Would head bolts and main cap bolts be the same?

Possibly the same material and/or grade of bolt- - - -the length and amount of stretch at the specified torque would probably be different. I can recall racing connecting rod bolts that came from the manufacturer with a "stretch" specification instead of a specific torque number. We would glue a small ball bearing into center-drilled holes on both ends of the bolt and tighten them until the specified amount of stretch could be measured with a micrometer. Some of them were 7/16" fine thread, and required 90+ ft/lbs of torque.
Jerry