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I just got my 235 block back from the machine shop. I had them line bore it which turns out to be a big mistake. They bored it with the #2 bearing cap reversed. The cap Is now obviously egg shaped. Is there a fix for this or is the block ruined? I have a lot invested in this engine and would like to save it if possible. Thanks for your help!

OUCH! The problem with line-boring a stovebolt, or any other engine with a gear-driven camshaft is the fact that any cutting that's done into the block moves the crankshaft and the cam closer together. When I was set up to do line boring, I always made a tiny scratch cut into the block, and took most of the material out of the caps. If you can find a competent shop to try to correct the damage, have them measure the fit on the timing gears before doing anything else. Do not let the shop that did the damage touch it, or anything else you own. They've already shown their incompetence, and another bite at the apple shouldn't be an option! It might be possible to install another #2 cap, and do most of the boring on it while removing little or no more material from the block, but it would take a well-experienced master machinist to do it right. Good luck!
Jerry

I take it you mean align bore it as it wouldn't make a difference in boring the cylinders. Back when we had piles of main caps we would try caps till when one was torqued down it would not catch your finger nail at the parting line. This would usually be close enough to clean up after boring/honing. If the cap is centered front to back then you could fly cut a new bearing lock notch on the opposite side and leave it backward. A really talented machinist could measure what profile was needed in the cap, bolt two caps together with each cap surfaced with an offset so that after honing one would have the the profile needed. Look for a machinist at least in his 70's for something like this. Now the young computer guys could slap some stock up in a 5 axis mill and make one accurate to 4 decimal places but the set up cost would be way more than everything spent on the whole project.

Evan- - - -please check your private messages. Thanks!
Jerry

Yes, I meant align bore. The block was also bored .30 over and the crank ground 10/10. I have an 848 head with a new valve job and I was excited to get this thing together. Of course I have already purchased everything I need to complete this motor. I can see now why people go the route of a 350 crate motor from Mexico.. I guess I will search for some #2 caps. Thanks for your help!

I do not believe it would matter if the #2 cap is installed backwards.
The caps are marked so they match the block after the factory align bore.
Once it has been align honed with the cap backwards just remark it and use it that way.
It is not like #3 which is the thrust bearing, which could cause problems.

When I tighten the other caps down, you can drag your fingernail across them and they do not catch. The number 2 cap has a huge lip on one side. Literally the machining marks on the cap are all on one side and it is not round. I am sure the machine shop will say it is not big deal. But then what is the purpose of the align bore to begin with?

Oops! I am talking about the fingernail catching where the cap meets the block.

The rear cap is dowled to keep it perfectly inline.
The other three have a little wiggle room.
Have you tried loosening the caps and seen if they can be shifted to align?

Yes, I have tried loosening to get better alignment. When the #2 cap fits on one side it does not on the other and vice-versa. There is no way to get it fit without a big ridge where the cap and block meet. Thanks for the suggestion!

The purpose of align boring is to get the main bearing bores perfectly round, and exactly in line with each other. Stovebolts are particularly difficult to bore properly because all the main bores are different diameters and all the holes need to be cut at once, using cutters adjusted to four different diameters on the same shaft. Add the difficulty of maintaining the proper timing gear fit, and it takes an extremely skilled machinist to get the job even close to right. The bore diameter tolerances listed in my shop specifications manual are in the neighborhood of .001"- - - -2/3 of the diameter of an average strand of hair!

The machine shop owes you another block, properly prepared by a different shop!
Jerry

If memory serves me right, doesn't the center main bearing cap that does NOT have the thrust surfaces on it never align perfectly front-to-rear with the block, no matter which way you put it on? It always looks like it isn't centered. I could be wrong...

I'm with Jerry on this one!

Just wondering, are you installing the cap in the original position, or as machined position?

Good question- - - -if the cap is round and the right diameter with it bolted on the way it was machined, it can be run that way without a problem. It's really sloppy shade tree work to do it that way, but the cap doesn't care which way it's turned. The only problem I can see is that the anti-rotate tabs for the top and bottom bearing shells will be on opposite sides of the engine. Does the oil pump pickup screen attach to the reversed cap?
Jerry

This block is one of the latest produced, a 1961 casting. The cap is obviously not round and will not work no matter which way it is bolted on. On one side it does not fit flush at the parting line. Anyway, I took the block back to the shop. They gave me my money back plus the $75 I payed for the block. They now own the block and I will look for a another.
Thanks again for your responses.

Sorry about the situation, but at least they were willing to man up and take responsibility. It's possible to do a lot of checking on crankshaft fit without going to the extreme of line boring. I like to use small pieces of shim stock between the crank and a new set of bearings to see if there's any excess clearance anywhere, and it's also a good idea to bolt down the main bearings on both ends and check the crankshaft for runout in the middle with a dial indicator. Of course, if you've had the crank reground, a good machinist will check, and straighten the crank if necessary in the process of grinding it.
Jerry

Boy do I have mixed feelings here, at least you were made whole,, minus the frustration,, but I hate to see a block wasted.
Example: we broke a crank in one of the pulling tractors and damaged the "pocket" the main cap sits in, we machined the block a little wider and made a new cap a little wider ( we make all steel main caps), new line bore and good to go. saved a block that has thousands in machine work.
Apples and oranges I understand, but I hope someone finds a new cap and saves that block.

I am glad to hear that there are still stand up guys out there who make things right. I had a similar situation with an engine that a guy built for me (his engine) and I didn't discover a cracked head until 3 years after I payed him for it (long term ground-up project). He profusely apologized, and had a new head ready for me to pick up before noon the next day!
I am talking about THREE YEARS LATER! Great guy who has more pride in his work than greed in his pockets.

Others can chime in on whether or not this is feasible, but I can have a couple spare #2 main caps in my parts stash and will give you one if the machine shop can use it to salvage the block. The other three sound as though they are good, so perhaps you can install one of my extras and the shop can line bore it to match the other three without cutting any more metal except from the replacement #2 cap?

I have never had a block line bored, so I'm flying kinda blind here. Those of you with more machine shop experience, please weigh in. If this could fix 51cowboy's problem. I'll gladly donate a #2 bearing cap.

Matt

You just take a few thou off the mounting surface of the cap, torque it in place, and then bore it.

Hopefully that shop doesn't try to sell the "rebuilt" block as-is to someone like me with little to no experience in engine building. I'd look at it like a pig staring at a wristwatch and think "wow, looks like a great motor!" I decided a long time ago that if I ever rebuild a Stovebolt I'm either moving in with Jerry or I'm flying him up to move in with me while we do all the work! :-)

Truckbiz, that's what I thought, but like I said, I've never done the procedure before. It seemed to me that if you set up the boring bar exactly the way it was and installed a replacement #2 bearing cap, you could simply rebore #2 and all would be good...the other three wouldn't get touched and #2 would now by in sync with them.

51cowboy, it that interests you, consider talking to the shop to see if they would be willing to do that. If they continue to be stand up, they'll give you the old block back because it is junk to them anyway and will correct #2 with the replacement cap.

You can PM me so that I can contribute the replacement cap. The only thing that I ask in return is that you keep us posted how it works out because I think that several of us are curious!

Matt

The problem would be in setting up the boring bar to cut ONLY the cap, without making the block side bigger. Based on the machining skill that's been demonstrated so far, I think dealing with that shop any more would be roughly equivalent to getting brain surgery at a drug store!
Jerry

The mechanical engineer in me brings out theory...Jerry brings out reality!!