My neighbor has a Chevy truck with a "freshly rebuilt" motor. He pulled the oil pan and noticed that one of the bearing caps is broken off completely on the one side. It's a 4 bolt main engine so the inner bolt is stll there as well as all of the cap except from about half way through the bolt hole out. Strange thing is that the piece (or the bolt) is NOT in the oil pan so it was probably broken off during the rebuild and they figured that there was enough steel left that it would be fine with the one bolt. His question to me was "is it ok to drive it this way?" I really don't have the expertise to tell him yes or no. I would think that it is because it's kind of like a 2 bolt main being that the inside bolt is still there, but again, I am no expert. Any advice would be appreciated. By the way, it's a stock early '80s 350 so there is no big power being made and no high RPM's being reached...
Find out who was the "fresh rebuilder" and have a serious conversation. The cap will not register if it is not all there. Time for a new cap and a line bore. The engine is salvageable. Why did your neighbor pull the pan? Is there other problems?
He pulled he pan because he thought he heard a knock. I didn't hear it run but he said it sounded like it was coming from the front of the engine. It altogether doesn't look very good. There is a ton of gasket sealer squeezed out of every possible spot on the engine and the whole thing is as filthy as an engine with 200,000 miles on it. Just curious, if the only part of the cap that's missing is the very outside edge and all the rest that makes contact with the bearing is there, plus the inner bolt, how would that affect it?
Caps are a "snap fit" in the regester,the houseing bore size would have changed when the cap was broke Tony
How would it change when the inside bolt is still torqued down? I'm not doubting what your saying, just trying to understand it.
I would be paying a visit to that so called "engine builder" with a big damn bat ! There is no reason for that to happen if the engine was built the right way the first time . I bet the mains weren't line honed ! Sounds like just shitty work ! Remember you don't get a good quality rebuild cheap ! Retro Jim
Back in the 60's I worked a few weeks in a small shop in a farming community for two brothers, Don and Dennis Pelzer, while waiting to enter the Army and a customer had a truck motor with a broken main cap, I think it was a Y block Ford but I could be wrong. They took a piece of really heavy strap iron, bent it to conform to the cap and bolted it back together. Cheap fix and it worked. Not sure I would have done it that way but the farmer didn't want to spend a bunch of money. I wish I could have absorbed 1% of what those two guys knew. They probably did too
The cap does not register on the bolt, it registers in the machined "step" in the block. With the outside edge of the main cap missing, it does not register at all. It may only be able to move a couple of hundred thousands of an inch but to an engine that is a mile of movement. Also, unfortunately, just installing another cap is not the quick fix. The main caps are cut & machined as a set when the initial machining is done the first time. After they are cut to fit the block, they are align bored and honed to be perfectly aligned and perfectly round over the length of the block. The block in the truck can be saved but it will need completely disassembled, another main cap fitted into place and the whole block align honed. Unless there is a reason to keep that particular block, it will be cheaper and quicker to get another block with a full set of intact main caps. The above is also why you must keep connecting rod caps in the proper orientation and on the same rod that they came off of. they are machined as a unit when the initial machining is performed. If a new set of rod bolts is used (such as using ARP rod bolts in a race engine) they connecting rods must be honed out as well after the new bolts are installed and torqued to spec.
if the piece of the cap isn't in the pan then it wasn't on the cap when installed, if it's broke all the way from the bolt surface to the block then it wont center between the raised edges of the block that align the cap, and the bearing shells won't be centered, no clearance for oil. no way to dissipate heat, so you get bearing death and or crank death
------------- Yep. Even if you got another block and have to bore it to fit the pistons from the broken block, it would still be cheaper to do that, than to replace the one main cap and then have the block line-bored to properly fit it. Also, if the boneheads who built that motor were so stupid and so careless as to *somehow* actually break a main cap (!!)eek and then, even worse, just leave it (!!!) eek:), it makes you wonder - what kind of shape the other caps are in (cracked or distorted and just ready to let go too???) - and also, what *other* incredibly boneheaded, dumb-ass things did they do when they assembled the rest of the engine???? Mart3406 ============================
He didn't pay to have the engine rebuilt, he bought the whole truck with the freshly rebuilt engine. Again, I am not an expert by a long shot but when I saw the engine the first thing I noticed was the fuel pump has 3 gaskets and gasket sealer gushing out between every one. I thought that was a bad sign of what else may have happened.
sound like he was lucky to find this problem when he did. that motor sounds like a disaster waiting to happen
+1 on that! From what you have described I would not trust any part on that engine, or for that matter anything else they did before selling the truck.
I swore I wouldnt get in on this one, but here goes. Find a real engine builder with a real machinist and shop. This can be easily repaired and I'm speaking from decades of experience. Whether or not you are repairing this disaster or installing 4340 billet main caps here is how the block can be saved. In Ohio especially you have many roundy round engine builders that build the SBC. 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
If its a performance engine, have the shop put a ARP stud, a washer and 12 point nut in the rear main cap for the oil pump, for a couple extra $. If they are a good and reputable machine shop, they will have the oil pump, or a dummy pump mounted on the rear main while checking and actually honing the mains. TR
I'm guessing that engine was the victim of an impact wrench mechanic! The cap was "cocked" and he buzzed it down with an impact wrench and snapped off the ear. Like others have said, chuck it. Who knows what other screw-ups he ignored in the assembly?
This motor looks like a candidate for a claimer race and hope someone claims it. From the description of the rest of the motor, I would not trust any part of it without a complete disassembly and check. Otherwise put the pan on and run it till it blows and then find another engine. As I posted earlier, fix it right or fix it again.
Come on. He pulled the pan because he thought it had a knock. He found all kinds of bad looking things when he got inside. Dirt, sludgy, broken parts. What more is there to say. Baring Divine Intervention It looks like time for a real rebuild.
Kinda sounds like your buddy fell for the bullshit line Yeah,just rebuilt the engine and its a 4-bolt main engine>" People will tell you anything to sell you something. Yank the dang engine and have a shop look at it. If its trash,probably is,find another engine for the truck. The going rate for a running 350 is less than you can rebuild that junk for.
Around here good running 350's are $75 to $150. Why mess with an abortion,line bore ,transfer parts ect. if you don't need too. If it is supposed to be some hot rod big deal maybe, but on a daily just find a donor and drive it.
Hard time finding a set of heads for $150 around here. Used to be able to find a rusty truck with one in but with scrap over $250/ton, those aren't around anymore.
Yep I was at the salvage yard the other day picking up an axle shaft my buddy working there told me the last running 350 that they sold brought $950.00 and was high miles.
That is not even good advice. Get your money back from silicone boy and take your complete engine to a reputable shop. They can replace the cap and align bore the mains and clean up the mess he made. They will use gaskets with small amounts of silicone where it is called for to properly set your engine up. Throw away society is making people think that 4 bolkt main blocks will always be around.....yeah, if you want to pay a fortune for a new casting...this one is completely serviceable.
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