The Stovebolt Site Forums The Shop Area Engine Shop Front Intermediate Bearing cap has a crack in it. What to do?

He fellas! I’m looking for some advise. I purchased a running 261 for my 1940 Chevy tuck and I’m in the process of replacing seals, gaskets and repainting the engine. I took the oil pan and timing cover off and as I was looking underneath I saw that my front intermediate bearing cap has a crack in it. It’s where the bolt tightens the cap down. It has not creeped all the way up yet.
If I can figure out a way to post a picture I would show you guys.
Should I leave it alone or replace the cap?
If so should I leave the original bearing shell in place or do I need to replace the single bearing shell and or all main bearings?

Thanks,
Jaydevc

Post a picture. Are you talking about a main bearing cap? Which one? Need some more information to help you without assuming what your talking about. Thanks

Here is a Picture

Ouch! I would not run that one. Check out this post.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=1011600#Post1011600

Do not run that! That has lost the torque and will fail. replace the cap.

Ok, Thanks for the advise guys!

I guess my next question is, what’s the best way to replace the cap?

'Correct' answer: Buy new cap, have motor line bored to ensure bearing fit.

Real world: Buy new cap, mic it, if its got clearance run it.

Common sense: Cost to line bore is more than a new block, running an ill fitting, new cap should work, but may fail causing more damage and $$$$ to repair than if you got a new block.

In summary: get a new block.

I wonder if that bolt has been over tightened. I would be inclined to check the others closely. For that matter I would examine the rods too.

It may be my imagination but that side doesn't seem to have a lock washer but the other side does. Is that correct?

If it was my engine and I wanted to run the rest of the life out of it I would V the crack out and weld it up. Than use a good grade 8 flat washer over it.
If you are going through the engine than I would replace the cap.

It looks like none of the main bearing cap bolts have washers.
I got to see the engine running before I bought it and it ran good with no knocks.

Early on Chev used lock washers on the main bearing bolts, but they were dropped in the later years, I think around 1955.

For all practical purposes, the block is junk if you ever want to rebuild it. However, if you are just do casual driving with it, why not just put a thick flat washer under it, retorque the cap and drive it. It will probably last a long time and you really don't have much to lose by running it. The chances are pretty good that under normal driving conditions, nothing will ever happen to it.

My vote is with Pre '68 Daves idea.

There's actually a pretty effective way to repair that crack. Thoroughly clean the bearing cap and stop-drill the crack at the upper end with about a 1/16" or 3/32" drill bit, all the way through to the bolt hole. Then V-groove the crack a little with a cutoff wheel in a Dremel tool or a die grinder and braze over it. It might be necessary to line bore the block afterwards, but it will keep the engine from being a boat anchor. A properly-prepared brass repair is just about as strong as the cast iron it's applied to.
Jerry

From what I am reading in a few other forums a replacement cap is probably your best bet.

"Find yourself some main caps, a good shop like mentioned above, probably has a box with caps they have removed from destroyed blocks, foolish if they toss them with the block. It doesnt take very long to try each cap on your block and see which one fits with the best register, and the closest fiting main alignment and parting lines. Any good machinist has or can make the rounded tip tool to improve the register. Once a cap has been found that fits well, and the alignment of the main housing bores are close, we get ready for the align honong process. I dont have to go into the align hone procedure here, but see how simply and inexpensively you can save this block. Align hone with cutting all the main caps should be around or under $200. I bet if you ask here on the HAMB, you can find a couple of used main caps that folks will give you for the shipping cost alone. This is a 100% correct way to save the block. TR "

http://www.jalopyjournal.com/forum/...4aad49274&p=6601741&postcount=20

If the cost is still about $200 that would be smarter/cheaper than finding a new block, cleaning/fluxing and using it.

I would do this before I welded up the web of a highly stressed part (the studs and the caps are the only thing keeping that 80bl crank spinning at 2000RPM in place.

Good luck line-honing an engine with 4 different-sized main bearing bores. I'd like to hide and watch while a machinist tries to find a honing mandrel for an old Stovebolt engine! Most of them got scrapped 40 years ago.
Jerry

Being the very, very, very part time junior machinist that I am let me ask:

I understand in the perfect world that you would want to cut/hone all 4 caps at the same time to keep them aligned, I would think that if the bar was set via the other three surfaces you could reasonably assure tolerance on the 4th.

Since this is the front cap that is less than ideal (the intermediate caps would be a much better candidate) but any manufacturing process would allow for tolerances that would provide for a reasonably successfully outcome.

As I said, new block is the preferred repair... but for a matching numbers motor that may not be always desirable.

Admittedly this may sound naïve, but aren't all end caps machined the same? I thought the process of fitting the cap to the crankshaft was all in the bearing.

Good luck Jaydevc!

No, the 235 (as I have also just learned) has 4 different main bearing diameters. They are listed in the manuals. I think the reason for the step is that they are bored and honed by a single tool (probibly from the rear as that is the largest opening). You need to step the diameter of the bore holes to allow the tool from the bearing in front of it to come out without scratching the newly machined surface.

Journal Diameter, Inches:
Front: 2.6835 - 2,6845;
No. 2: 2.7145-2.7155;
No. 3: 2.7455-2.7465;
No. 4: 2.7765-2.7775

I copied these from another site. They are stepped like the cam bearings are. The reason cam bearing are stepped is to allow a tool to pull them out.

Holding a half a thou on a tight machine is commonplace today. Setup is the killer. You have to use 3 surfaces to locate a 4th... to a .0005 or less tolerance.

Align honing is a newer modern technique and was not performed from the factory on any engines, its only done in the aftermarket workplace or rebuilder shops. They are only line bored to size and sent to the next machining operation. The stepped size main journal was common to all of the GM inlines of that era with the GMC's, Straight 8 Buick, Straight 6 & 8 Pontiac's and Straight 8 Olds as well as the Stovebolt's.

I'm not sure if this is about new production ONLY or a repair:

Prior to 1948, the Chevy 235 (and 216) had an initial factory align-boring of the mains' saddle bores.
- The main bearing caps were then removed, and a brass layered shim pack was installed (these shims did not extend past the bearing parting-line) .
-- The main bearing semi-finished bearing shells were then installed (note: they were eccentric walled semi-finished bearing shells with thicker crowns than parting lines !!) The main bearing saddle bore at this stage was thus NO longer round in shape because of the additional shim pack. Main caps were then re-installed.
--- The main bearing semi-finished insert shells THEN needed to have an extra final align-reaming of the shells to get the inner diameter housing round (concentric) to mate with the crankshaft journals . This was because the main bearing insert shells were not a precision fit ... (the main bearing shells had a real thick babbitt linings that needed more honing/reaming to get proper final oil clearances).

---- SO, the early engines needed an 1) align-bore; 2) a cap removal and brass shims added;3) a cap re-install with rough insert main bearing shells...... 4) then a final stage of align-reaming of the insert shells to get the babbitt thinner, and the inner bearing shell housing round.

I may be using hone/ream switched around... but from what I understand you would bore to +.002/+.003 then hone (ream) to size. Seeing the production spec had only a +/- .0005 tolerance boring to size would be a difficult one shot endevour.

How many engines of any kind have you line honed/reamed? Tell us how you did it. We're waiting with keen anticipation to hear from an expert!
Jerry

We all agreed that the best course of action is a new block. But just for giggles it would be very doable to bore/hone the block he has. Done all the time. I can give the number of a few shops that can do it and you can ask them if, for some reason, you think I am making this all up.

You may not be up for the task or think its not a good idea... ok, duly noted.

Please don't resort to personal attacks.... I can't perform open heart surgery... that doesn't mean its not done. But I can get a block bored.... evidently your skill set may not but up to the task... but there are (SHOCKINGLY!) other machinist that can.

500 line bores and counting- - - -I own a machine shop- - - -what's your number, troll?
Jerry

but you'd be right in there telling the surgeon how it's done

Bill

You just admitted on the last page to "just discovering" that the Stovebolt has 4 different housing bore sizes. You might take a hand hone that fits in a drill and call it align honing, but not many shops are going to gamble with a $2000+ honing mandrel that is designed to fit through all the housing bores at once and are the same size and chance tearing it up.

Does anybody else think of this guy when reaching for their hip waders?

First, I have reported you, Mr Lincoln. If you can't talk civilly than don't speak at all.

I have had work done by many heavy machine shops/auto shops.. I don't need to have done *ANYTHING* I pay people to do it for me if beyond my ability... you never jobbed something out?

If, in your 'professional' opinion you would not take the job fine, that's a statement of your limitations and abilities. But you are going to the illogical step of saying it CANNOT be done. That, is patently incorrect.

Hey Mr. Lincoln you seem to have a history of hating anyone who talks about boring.

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=710590#Post710590

Read that and tell me how that guy and I are saying anything different

AND THESE ARE YOUR OWN WORDS:

If the machine can be set up with four different cutters at the right spacing, making all the cuts at once is the best choice, from both an accuracy and labor time standpoint. Line-boring is also done on big-truck rear end housings, fitting the carrier bearing saddle bores after welding repairs are made. Jasper engine/transmission exchange does a lot of that type of work on heavy duty transmissions and rear ends.
Jerry

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=710653#Post710653

So you have said EXACTLY WHAT I HAVE.

What changed in the 3 years since that post??? We both agree that you can line bore a 235 (also the topic of that post).

So yeah... there's that.

Blah Blah Blah

Thats 1 set for each bore size right?
Like one set for each different big rig rear ends, one set for sbc 283's one set or 235's plus all those pesky blue oval jobs?

Is that why some shops just flat out don't do some engines?

One other thing that should be known is when you aline bore the mains on a 235, 216, 207, 261,194,230,250,292..style blocks , you better not take too much off the block when you bore the mains or you will have a meshing problem with the crank gear to cam gear, if it was a chain no big deal but gear to gear will make your hair fall out when you cant turn the crank because its too tight. There are people that know and then there is people that think they know. life is good, Have a nice day!

Last week I noticed a crack in a crankshaft counterweight:
http://s1154.photobucket.com/user/JonGoodman/media/counterweightcrack.jpg.html?sort=3&o=0

This crank was turned 10 under and polished in 1979 and neither I nor the shop noticed it then, so I have no idea when it happened. Because of the location (and because it hasn't been a problem to this point), it doesn't worry me. Any thoughts?

Jon

Caso, these mandrels are 4-1/2 feet long, and have honing stones and guide shoes almost their entire length. They are attached to a large electric drill sized drive motor that spins the mandrel via a universal joint drive shaft. So imagine trying to spin the mandrel with it only supported with one 1-1/2" wide bearing surface. Thats where the damage can occur because of it not being supported by anything more than just one housing bore in 4+ feet of length.
Yes your right about the different housing bores taking different sized mandrels. Yes, they get incrementally more expensive the larger OD they get also. So it can be an expensive investment.

Exactly! The phrase, "simply owning a micrometer doesn't make you a machinist" comes to mind. There is a lot of skill involved, and that one thing if overlooked can make a block a big piece of scrap iron.

Jerry, I believe that you have officially been nanny, nanny boo booed.

LOL! Us old geezers are used to being challenged by wet-behind-the-ears kids who were filling their diapers, or not even a gleam in Daddy's eye back when we were making a living fixing these old rigs. I spent 30+ years riding herd on a classroom full of high school kids who had read at least two issues of Hot Rod Magazine and thought they were Smokey Yunick! Some of those guys are now very successful line technicians and shop owners, and others are running racing teams.
Jerry

Just got back into town and was reading replies. I just want to thank everyone for their thoughts and advise. I didn’t mean to start such a strong debate and I know that everyone’s heart is in the right place. I love that this forum encourages the opportunity to share thoughts, ideas and experiences, all for the sake of helping each other keep these fantastic trucks on the road.
I bought this 292 for a couple of hundred bucks to replace the destroyed 216 that was originally in the truck.
I’m looking for the most cost effective repair without having sink too much more in this engine. I’m intrigued about the process of repairing the crack in the intermediate cap.
I live near Colorado Springs and I’m hoping to find a good machine shop that can drill, V-groove and braze the cap like Hotrod lincoln describes, unless you believe I can perform that repair myself. If not, I’m looking for any advise on a good shop in the area. I usually do my own mechanic work, but I’m no machinist. I can braze and weld on the ranch, it’s functional but not real pretty!
Thanks again everyone, I really appreciate it.
Jayde

I'm sure you can do that, Jayde. For something like this you can also consider using a product Harris Products makes known as "Stay-Brite". It is a silver bearing solder (tin & silver), and it melts at around 450 degrees, so you don't even need to get out the oxy-acetylene gear to use it. You can just use a propane or MAPP torch. It has a high tensile strength and shear strength. I'm sure Harris Products puts spec sheets on the web if you're curious. I've used it for a long time on things like this and have not had a single failure yet. It will bond to iron (incl cast) very well and will join dissimilar metals, also. Just be sure to use the flux they sell for it...other fluxes don't work as well and get the metal as clean as possible. It is not cheap, but a roll lasts a long time and I think you'll find lots of uses for it. I just discarded a very old Briggs & Stratton grass edger I repaired with it and even though the repaired part took a great amount of vibration and abuse, it never showed even a crack in over 30 years. It is lead-free, also. Good luck.

disclaimer: I have no connection at all with Harris Products.
Jon

If it where mine here are the options. #1 attempt to locnstitch it. #2 gas weld it with iron rod. #3 remachine a cap from steel.

Then with either a horizontal mill, boring mill, CNC horizontal machining center, or a very tall vertical mill the existing bore in the block could be reestablished. Easy stuff on the correct machine. Or someone good with a scraper could reestablish the bore in the cap. If that cap is fixed that hole will always need a hardened washer under the bolt head.