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

You make it sound like line boring is a rare and dangerous feat. It's done all the time. And there are machines built to do this one operation. Many boring machines utilize some sort tail stock/rest, some do not... all depends on the design.

If you had the money a Rottler F65 is 'less scary looking' than a 'standard line boring machine.

Any well stocked shop should be able to fit you a new main bearing cap with none of the fuss made here. It really comes down to the cost.

Will the cost of the machining be significantly more than the cost to get a another block and have it cleaned and fluxed. I think that $400 would be your cut off point. Another block $100-$200 (hopefully free) cleaned and fluxed $200-300.

There is nothing so positive as ignorance- - - -particularly from someone who does not know the difference in line boring and line honing.
Jerry

Laugh, but since that crack is not in a high stress area. Just stop drill it and use devcon or jb, and a hardened washer under the bolt it should last along time with no problems. It was likely cracked by who ever tried hammering it on or by tightening it, it was not a bearing failure. Maybe it was dropped and got cracked I didn't study the pics again.

The original poster, isn't looking to do anything but change leaking gaskets, paint the engine, fix the bearing cap, and drive on down the road. So why is anybody trying get his old engine prepared for a Lunar landing? If it were mine, I would take off the cap, look it over to see if it is about to become two pieces. If it is not in obvious jeopardy of coming apart, I would put it back on, add a a washer for each bolt, and drive it down the road. It is not a part that moves (like a rod bearing cap), so I wouldn't expect it to fail. If it does fail, you will have a spun bearing, worst case scenario. So, Jaydevc has a choice, buy/have built a new engine, or put this one back together and get all of the miles that are left in it.
Carl

Oh yeah, you said it cannot be done. You've given your 'advice'. Contribute or move on.

Just letting it go is a gamble. The tow home will cost more than fixing it or replacing the block. If you have some sort of towing coverage on your insurance then OK, let it ride and hope for the best.

Otherwise line bore or new block.

Here's a post from a guy that had this done...

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=710652#Post710652

Sorry Mr. Lincoln, done all the time...

Enough rambling on, its not doing anybody any good being this....

http://www.hahastop.com/pictures/Pain_In_The_Butt.htm

Line boring is done everday with no problem. You keep confusing your terminology and thinking line boring and align honing are the same thing and they are two completely different processes altogether. No body has ever disputed whether or not a Stovebolt can be line bored or not. Align honing cannot be performed on blocks that have different size housing bores like the Stovebolt, GMC Jimmy, Straight 8 Buick, Pontiac and many other engine blocks. Line boring can be performed very easily on blocks that have different size housing bores, and is the only way that they can be machined to correct out of spec housing bores. Line boring and Align honing are two completely different machining operations done with completely different equipment and objectives. Its like people that think knurling valve guides is the same thing as honing them to size.

I think this whole thread has not given the original poster much direction. I have seen cracked main caps and they ran a long time by just putting as large a washer that will fit. It was my original suggestion for him to do that. Honing has nothing to do with this problem. I have a Superior honing machine with a 14" stroke and it has pulled stones bigger than 6" It will freshen up blocks that a lot of people would bore these days. But it is a hone and it will not bore a cylinder and it certainly will not hone bearing caps. I see only a few feasible options. The cheap way would be to put a washer over it or possibly even V out the crack and weld it and it would probably run as long as the guy owns the vehicle. If the hillbilly fix would worry him, I would suggest buying another 235 and just freshen it up. If he installs a different cap, I think there is no question that he will have to take it to a machine shop to have it line bored. But most shops will want to bore the cylinders while they are at it and mill the deck whether it needs it or not. By the time he is done with the machine shop tab and a set of oversized pistons, he may have more in the engine than the vehicle is worth. Unless someone just wants to plunk $3,000 in a 6 cylinder engine, I have never seen real reason to line bore a 6 cy engine. If the block has been hot enough to warp the line bore, the deck will be crooked too. Another option that I would explore is buy a good running engine engine and installing it as is. Possibly I'm wrong, but I don't think they guy really wants to spend the money a machine shop rebuild would cost.

I do a lot of hillbilly fixes and they work. If I have bell mouthed valve guides, I see nothing wrong with reaming them straight, knurling them, reaming them to spec and then honing them a little to polish them. Valve stems have to be within spec because there is no fix for worn valve stems. But I have an old 645 Sioux that will reface them, dress the tip and champher the tip. It even does rocker arm tips.

All the realistic options were presented on the first page (replace block, line bore, just run it). It all comes down to cost when it does break.

I would bet the engine ran with the crack for a long time and will continue to run with it. Mid block, low load, putt around town truck, low rpm, I see no problem with it. If it falls apart when the bolt comes out, now you have issues.

Install a name brand stud, large flat washer, and have the cap milled on the bolt boss so it's true flat ( you could carefully hand grind it flat ), and torque it down. The crack is vertical and not in the bearing area. A stud and nut will torque a little easier then a bolt and not as likely to twist on the cap as hard using a hard washer.

In my opinion,
Joe

I'll second this, as I have one that's repaired with this exact method in mine (rear intermediate). Got well over 25000 miles on it since, no issues at all. No need to junk a block over an easy repair.

I'm a bit late to this party but.....I was building a 261 and had a similar crack on the front middle main cap. I tried other main caps but they were so far off that line boring would not correct it. So the crack was prepped and TIG welded. Then the bolt holes in the cap were spot faced on all for mains. Assembled with hardened steel washers and stock bolts.
This 261 has Ross 9-1 pistons, some head work , hotter cam and so on. It's still fine after several thousand miles of use....And that means using the performance and not parade driving down the road...

But your experience may differ....

Thanks, guys! Once again, real-world experience trumps theoretical Bovine Scatology!

Jerry

In my case if the main caps I had would have fit with normal line boring I would have preferred to do that. As it was the block still needed a light line honing....
As a note, on 235-261 the two inner main caps have no locating dowels or machined register slots in the block. It's appears only the fit of the shoulder of the main bolts locates the inner main caps. That and the bearing shell......It's a poor design compared to other period inline engine like the GMC.

I believe the idea was for the caps to self-align as they were installed, using the bearing shells and the assembly lube to create enough hydraulic force to help the caps center. No, it's not a good design, compared to later machining procedures, but a few million of those engines survived some pretty tough operating conditions.
Jerry

Well guys, I had someone that is pretty well known for welding cast in the community and he repaired the bearing cap. There were actually 3 cracks but nothing that went all the way through. I have some pics of the finished product.

https://www.dropbox.com/s/bj52w6uctz03nxr/IMG_2068.JPG

https://www.dropbox.com/s/2hc6hyrab2377i2/IMG_2069.JPG

When I pulled the bearing cap, I noticed the bearing itself looked like it had gotten hot at one time and there was some scoring. Now I’m wondering if I should check the rest of them.

https://www.dropbox.com/s/g9f6jykteemb14u/IMG_2070.JPG

I purchased some hardened washers.

What do you guys think?

That bearing is showing pretty much normal wear for a high-mileage engine. There are four layers of material on an insert bearing- - - -steel backing, a layer of copper, then a layer of soft metal similar to Babbit, and a top "flash" layer of pure tin less than 1/2 thousandth thick for quick wear-in to minor irregularities in the crankshaft surface. The bearing in the picture is worn to the copper- - - -one layer away from the steel backing that will do major crankshaft damage.

I'd suggest pulling the crankshaft out and have a competent machinist measure it for out-of-round and diameter differences from one end of the journals to the other (taper wear). If either dimension exceeds acceptable wear limits, it's time for a regrind or a crankshaft replacement. The machinist can also check the main bearing bores in the block for out of round problems, particularly the bore with the welded cap.
Jerry

Thanks Hotrod Lincoln!

Speaking of Lincoln's and not to get off topic I’m very partial to them. I’ve got a 1956 Premier, 1958 Continental mark III convertible , and a 1975 Continental Town Coupe.