The Stovebolt Site Forums The Shop Area Engine Shop Grade 8 bolts for Bearing Caps

So the more I tear into my rebuilt ( not ) engine the more I scratch my head. Long story short, I bought this '59 235 from a guy in Vegas that said it was rebuilt. The more I get into it, the more it looks like they only did a top end rebuild. Anyway, I have been checking the clearance on all the bearings and the Bearing Cap bolts looked old. Since I had the bottom opened up I figured I would replace them with new ones. Took the old ones down to Ace and matched them up with new Grade 8 bolts. Came into work today and spoke to an old timer and said that the bolts needed to be ARP bolts specifically maid for Bearing Caps. Are the Grade 8 Bolts I bought from Ace not good enough? I thought Grade 8 was the strongest bolt?

I'm like your coworker. I replace cap bolts and cylinder head bolts with those designated for the job. Not saying the Grade 8 is a bad deal, but so much bolt bin stuff is offshore these days,
I am leary.

Strongest isn't always best. Often "strong" goes hand in hand with "hard" and "brittle" which can be underisable.

The advice to use ARP fasteners is spot on!
http://arp-bolts.com/

Grigg

Most head bolts and main cap bolts have a machined surface below the head of the bolt. They are also designed to stretch and hold the proper torque rating.

So I called ARP. The part number they gave me was #132-5402 and they wanted $100. They said I could get it cheaper at Summit or Jegs. So I visit those sites and they have it listed as a stud and nut kit, huh???? I don't need studs, I need bolts, I even said that to them when inquiring. They said that was the only thing listed under the year, make and size engine I provided them. So know what???

There's nothing wrong with using Grade 8 bolts, but the studs would be a better choice. Most studs have a coarse thread where they thread into the block, and fine threads at the end the nut fits. A hardened steel washer should be used between the nut and the main bearing cap and lube it with something like anti-sieze compound if you choose to go with studs.

The only time I'd reccomend using studs on main bearing caps would be on a high-output racing engine. Go with the new grade 8 bolts, and make sure they engage approximately the same number of threads in the block as the original bolts. You wont have any problems. Main bearing bolts are normally grade 8, so unless your originals are badly rusted or stretched, there's really no reason to replace them. I can usually tell by a bolt's "feel" when I'm torquing it if it's stretching excessively, but that's not a skill that can be taught over the internet. It takes a few thousand bolt-torquings to develop the feel, and even then it's not a sure thing, just a judgement call.
Jerry

So I must ask why you would want to replace them. Of course they look old but if the threads are OK and they are not damaged, why would you replace them.

Hi, thanks for the replies. To answer both Hotrod Lincoln and truckernix answers. The reason for wanting to replace them was because it did seem like one or two of the bolts " stretched " when approaching 110ft/lbs of torque. None of the bolts are rusted. The ones I removed all had three lines on the head of the bolt with either an " M ", nothing or " AP ". It's seems like a hodge podge of whatever the " rebuilder had lying around......

3 lines is grade 5
6 lines is grade 8

So it looks like they used grade 5 bolts in my engine :-(

Yes, I would be worried about them too.

So I went to my local engine builder and showed him the Grade 5 bolts I removed from the Bearing Caps. I mentioned the Grade 8 bolts I bought from Ace and both him and his engine builder said I should be fine with using them. They said the same thing Hotrod Lincoln mentioned about making sure I had enough thread to go into the Block. I should be able to finish the clearance check and button her up this weekend.

Okay just checked bolts from my 235 main caps.
Rear cap one has a TR and 3 radial lines. So old designation must not be a grade 5, it looks and seems much harder.
Number 3 cap bolt has a U on it both have thick heads, so they must be proper for the application.
Both are 3/4 hex and 9/16-12 , rear cap bolt head to thread is about 1.200, head to end is 2.436, head to.... means the head to cap contact area.
Number 3 cap bolt is 1.74 head to thread, and head to end is 3.00. Didn't check others but likely same, including short front ones.

there is not a chance I would use hardware store fasteners in an engine. If you are concerned about the bolts, just go ahead and get the stud kit from ARP. Grade 5 might actually be the correct bolt for these engines, it is strong, but will flex a little, whereas grade 8 is rather brittleish. but I don't know for sure what would have actually been specified. You said the one looks harder, just what does hard look like?

I would hunt up another block and use the original bolts before I would use hardware store bolts. Main caps move around and grade 8 is not what I would want. I would bet they were something in between a 5 and 8.

Joe

Another option might be to check with your local John Deere dealer. I had an issue with a bad bolt in the rear maincap on my 235, and could not find a proper matching bolt at any of my loac sources (even tried Fastenal). The machine shop I use suggested trying John Deere. It turns out that head bolts for a Deere Deisel engine are a match for 235 main bolts.

I originally was going to suggest a Cat dealer, but the JD maybe a good one too. You can ask ARP for the spec, I'm sure its with in the grade 8, I know that most CAT bolts are grade 8 plus.
Heres a nice bolt site

http://www.derose.net/steve/resources/engtables/bolts.html

Wow, I didn't think I would get more posts after I said I was going to just leave the Ace Grade 8's in there. I forgot to mention earlier that when I showed the original Grade 5 bolts to that engine builder, they said they looked fine and felt ok about me using them. Well, after all added posts about the NOT using the Grade 8's I installed, I've decided to remove the Ace Grade 8's and re-install the Grade 5's that were in there originally. Thanks for all the help

1. Grade 8 is always overkill on our stuff. 2. Stainless is stronger that Gr 8. 3. Always get new proper bolts when rebuilding. 4."Never say always" is not always true always. 5.To be technical, precision builders go by stretch when torqueing.

I disagree with that. Some stainless bolts can be but they aren't cheap and you won't find them at the hardware store. I'd assume all stainless to be weak unless you know exactly where they came from and what they are.
There are many different "stainless" alloys.

Grigg

I agree with Grigg as I learned on a mini tour of Totally Stainless near Gettysburg,PA. Regular Grade 8 stainless steel bolts are only slightly stronger than STANDARD GRADE 2 bolts!
They and likely other manufacturers of stainless fasteners offer
a higher quality Grade 8 stainless bolt for more severe applcations. Never use a regular stainless Grade 8 bolt in a "high stress"
application. And use the correct lubricant and torque for the stainless bolts.

Wow,so many answers that are just wrong....
216,235 and 261 engines,other than the rear main cap,have no dowels pins or registers cut into the block to locate the main caps.The caps are located by that shoulder just under the head on the stock bolt.Use any other bolt and the main cap location is lost.maybe the ARP bolt or studs have the shoulders....
This is not to say the engine won't run with the wrong bolts.

Grigg: You are right. Mixing apples and oranges will get you any result you wish. Grade 8 from ARP would be stronger than Chinese Stainless steel from Home Depot. But the point is: 17-4PH Stainless steel is a little stronger than Gr 8 when comparing SAE type quality. BTW I am not advocating using CRES or Gr 8, just the factory recommended bolt.

DrewP: Gr8 is not stainless steel, it is a carbon steel alloy.

Fast Truck: You are the person we should be following on this because you are staying on topic and giving specific engine info. I did a little checking and found out the shoulder does locate the cap fairly acurately (for that era), as you said. They are GR 5 marked. They are listed as .056 GM part No. and the bolt uses a .060 thk lock? washer. The 056 refers to the shoulder dia. being .56 or real close to 9/16. According to those who have used the studs, the non threaded portion is .56 and the threads are 1/2". That will function the same as the shoulder. The front two nuts supplied with the ARP kit will not accept a socket? SO they say a pair of 12 point nuts are needed from ARP also.

As an old fabricator and welder I can assure you that SS is NOT stronger than most common steels. There are tool steels that are much harder but they are not what goes into an engine. Typical stainless steel is less than a grade 5 bolt woud be. I do agree about the use of hardware store fasteners because so much of the ones they carry are Indian and Chinese imports and little if any quality control.

As Grigg stated there are MANY different SS alloys. I used to run into that constantly on sheet steel with 304 vs 409.
Bolts are the same way, know what you are buying.

The 17-4ph stainless steel bolts sold by "Just Stainless" are 200,000 PSI. A Grade 5 bolt = 81,000 PSI. the Chromoly studs we are talking about from ARP are 180K-190K. There are many different alloys for steel and stainless steel and many hardness and heat treatments, I assure you I know that.

I agree, stainless is actually soft stuff, some is resistive to machining not because of hardness but because of the grain structure. You can easily dent most stainless steels, especially the more difficult to machine stuff. To buy a good bolt made of it would be very costly.

Yes, correct. I thought it was a given that any replacment would be checked for the correct diameters. And this should help the original poster to determine if what he has is correct. I'd like to know what the heads are for thickness that he has?