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So I was reinstalling my oil pump after replacing the rear main seal in my '78 with factory 350, and was torquing the oil pump bolt to 65 foot pounds and felt it give and then spin freely. Never a good sign. When I removed it, I noticed a small chunk of the bearing cap cracked off (see photos). I think what happened was the bolt was oily and got over torqued even though I never hit 65 ft lbs on the wrench.
Is this bearing cap toast? What would you guys do?
Looks like the bolt was to short !
I don't see the bearing cap being damaged - looks like a piece of the top of the thread broke out ?
Get a longer bolt and torque by feel not crazy amount of torque
You seem to have problem with bolt torque LOL
I dunno about bolt length. It was the factory bolt. But yes, the top thread broke off and a bit of the casting came with it. The bolt is a bit buggered and won’t thread in. I’m tempted to buy a new bolt and reinstall, but I found a bearing cap on eBay for like $120 that I might get. I’m wondering anybody thinks reinstalling with the damaged bearing cap is a bad idea?
You usually can't just switch caps as they are machined with the block.
Something was WRONG when you installed the bolt - I'm not going to speculate.
I would measure the depth of the threaded hole and see what maximum length bolt you can install.
Then I would get Gr 8 bolt or L9 bolt that length or longer and cut it down or use hard washer under head of bolt to suit length- I wouldn't just buy another stock length bolt.
Or get Gr 8 threaded rod and screw in and use nut.and washer at the pump.
I dunno about bolt length. It was the factory bolt. But yes, the top thread broke off and a bit of the casting came with it. The bolt is a bit buggered and won’t thread in. I’m tempted to buy a new bolt and reinstall, but I found a bearing cap on eBay for like $120 that I might get. I’m wondering anybody thinks reinstalling with the damaged bearing cap is a bad idea?
I think installing a replacement bearing cap is a bad idea. Bearing caps do not interchange between blocks. If you change the cap, you need to disassemble the engine and have it line bored, or align honed, or whatever it takes to get the bores lined up and sized correctly. And then you need new bearings. By the time you do that you are into a complete rebuild.
I had the same thing happen to me a couple of engines ago. I replaced the bolt with a piece of Grade 8 redi-rod that I installed to full depth with blue Loctite to engage as much of the remaining threads as possible, and then added a nut and a washer. It worked fine, and I torqued it by feel, not using the factory torque spec. (That engine failed when I broke the crankshaft, but that had nothing to do with the oil pump mounting bolt.)
I am beginning to suspect the factory bolt is simply too short. How many threads engage with the factory bolt?
Swapping caps MAY require entire crank tunnel be align-honed $$$$$
FIRST: Strongly suggest you acquire a name-brand dedicated Oil Pump STUD and install that into your OE cap.
No matter what goes into cap; if it extends too far it WILL impinge into lower rear main bearing INSERT and that WILL ruin your day. You'll have to witness, measure this closely !
GM part number 3892678 bolt. 7/16 - 14 x 2". If that bolt is in the specific car line parts catalog rather than the Standard Parts Catalog that tells me it's a unique bolt for attaching the engine oil pump.
Thank you all for the replies. I guess I will not be ordering that replacement cap. The first couple threads on the factory oil pump bolt are a bit buggered and it won't easily screw into the cap. So I don't know how many threads it will catch. I have a another factory bolt on order but I like the idea of grade 8 all thread with a washer and nut with some loctite for good measure. The cap bolted in fine and this single bolt just holds the oil pump, right? So it sounds like maybe I dodged a bullet and will proceed while hoping for best. Thank again everyone.
GM part number 3892678 bolt. 7/16 - 14 x 2". If that bolt is in the specific car line parts catalog rather than the Standard Parts Catalog that tells me it's a unique bolt for attaching the engine oil pump.
Yeah so it's a specific bolt that GM uses but for some one who has understanding of what it does and is required to do it can be replaced with equivalent or upgraded fastener........................
Do this work with cap removed from block.
even better than a tap, suggest use a thread chaser to restore some of the damaged threads, but not attempt to cut more.
then test-fit the stud and measure depth so it does Not impinge on bearing insert. measure it again, then remove stud and apply RED Loctite to threads and reset to pre-measured depth. Let it cure overnite, then set cap back into place, then set pump onto cap and torque NUT to spec .NO Loctite on nut threads.
How does the insert remove? Does it just slide out and then I just slide it back in?
you will note a notch on one corner. Rotate the shell out so the notched side rotates upwards and around. Once turned about a quarter turn it'll just lift out. Reinsert is reverse.
I have that ARP stud kit in my realitivly basic 350. Worth doing.
Never heard of an internal thread chaser - tell me about it - that would sure get you out of jams
Most of us professional mechanics have a set like this. They clean the threads without cutting. Good for removing old thread sealers and loctite. And just generally cleaning threads.
Broken Main Bearing Cap
