Broken main bolt

[WilliamBill]

Has anyone had this happen? Dropped oil pan to put new pan gasket and oil pump in,and found bolt head in pan.Ends up it came from main bearing cap, cap still on with one bolt. I replaced all main bearing cap bolts with arp studs and a new oil pump, oil pressure is better due to crud removal and all seems fine

 

[GTX63]

Saw a video not long ago from a guy that bought ebay/China heads with new springs, bolts, etc. As he was tightening a head bolt, with a torque wrench, the head of the bolt twisted off.
I believe others followed.
He also bought a rebuild kit off ebay and the motor wouldn't turn over after installing the bearings.
Not saying that is your situation, but it has become a thing.

 

[WilliamBill]

The truck is an 86 with 109,000 miles onit, no telling how long it has been broken, no indication of anything wrong, probably just a rare bad bolt?

 

[fast 99]

Only seen a bolt head snap off a 6.5 diesel head.

Buy a lottery ticket. That could have turned out quite different.

 

[Bennyt]

I'm glad it worked out. I've had a few motors change clearances after stud installs.

Typically you need to line hone with studs as they apply pressure differently than bolts and are only installed hand tight if I recall.

 

[Buck69]

Did you roll new bearings in? Curious what the date stamps were.
Maybe someone has been into it?

 

[WilliamBill]

no new bearings, only actually removed the one cap to get out broken bolt. all other caps stayed put while I changed from bolts to studs. I went ahead and changed all to studs just for peace of mind, maybe more could break. They are installed hand tight, then torqued to 80 ft. lbs. There was letters stamped on pan rail, random J,H and more, don't know the reason though.

 

[Bennyt]

It's amazing how forgiving the SBC really is. In most motors, losing a main bolt and essentially 20% of the total clamping force holding the crank would be catastrophic. I'm amazed the bearing didn't spin.

 

[Blue Ox]

no new bearings, only actually removed the one cap to get out broken bolt. all other caps stayed put while I changed from bolts to studs. I went ahead and changed all to studs just for peace of mind, maybe more could break. They are installed hand tight, then torqued to 80 ft. lbs. There was letters stamped on pan rail, random J,H and more, don't know the reason though.

Usually that was for piston sizes. The factory had pistons sized in smaller increments than are used in rebuilding. Probably to make it easier to machine the blocks with more relaxed tolerances and make up the fit with the pistons.

 

[Ricko1966]

Saw a video not long ago from a guy that bought ebay/China heads with new springs, bolts, etc. As he was tightening a head bolt, with a torque wrench, the head of the bolt twisted off.
I believe others followed.
He also bought a rebuild kit off ebay and the motor wouldn't turn over after installing the bearings.
Not saying that is your situation, but it has become a thing.

So,did he get bad head bolts or was his Chineese torque wrench and his own inexperience to blame. Did he order the correct size bearings,confirm them and check his clearances? Not siding with anybody but I've seen way to many unsuccessful repairs by operator error,blamed on other things. O.P. did these stamps look factory or did it look like someone had been in there before? Sometimes an overtorqued fastener will pop a head off when things start growing due to thermal expansion.

 

[GTX63]

The head bolts were garbage, and after sending the block off to a machine shop, discovered the main and rod bearings were poorly manufactured and out of spec. Yes, he was a newbie builder but that doesn't make the fault his. If a torque spec is 80 ft lbs and the bolt breaks at 90 or 100, it is a junk bolt. Wouldn't a Chinese torque wrench be suitable for Chinese parts?
Hundreds of thousands, if not more Gen 1 small block Chevies were built and rebuilt over the past 70 years in garages and shops and under shade trees by folks who did not have micrometers and dial indicators and mega tool boxes loaded with high end snap ons. It is a matter of the drop off in the quality of parts.
He contacted the seller, who refused a refund. He then went to ebay, provided documents, evidence and verification from the shop and was refunded his money.
I would advise anyone buying build kits from ebay, "Buyer Beware".

 

[Ricko1966]

The head bolts were garbage, and after sending the block off to a machine shop, discovered the main and rod bearings were poorly manufactured and out of spec. Yes, he was a newbie builder but that doesn't make the fault his. If a torque spec is 80 ft lbs and the bolt breaks at 90 or 100, it is a junk bolt. Wouldn't a Chinese torque wrench be suitable for Chinese parts?
Hundreds of thousands, if not more Gen 1 small block Chevies were built and rebuilt over the past 70 years in garages and shops and under shade trees by folks who did not have micrometers and dial indicators and mega tool boxes loaded with high end snap ons. It is a matter of the drop off in the quality of parts.
He contacted the seller, who refused a refund. He then went to ebay, provided documents, evidence and verification from the shop and was refunded his money.
I would advise anyone buying build kits from ebay, "Buyer Beware".

I would recommend anyone be careful no matter where the buy there stuff, I've had several sets of brand name main bearings out of spec. Even called the manufacturer once letting them know their bearings were out of spec. I was told yeah that's not uncommon,but we aren't going to spend mega money to retool equipment to make bearings for a dying market. I" ve had to polish material off of cranks to get the clearances I wanted. And a bolt that breaks at 80 foot lb, breaks at the 80 foot lb, reading on a Chineese torque wrench that is actually at 120 lbs hmm whose fault is that. I've been putting stuff together and realized,this doesn't feel right,checked with another torque wrench before I did any damage,and I was right,torque wrench out of spec.Also he should have felt the engine tightening up as he put it together. Put the mains in it,spin it through a couple of revolutions,while you are torquing the mains does it feel right,? Did it get tight when you pulled that last third on the middle cap? Followed by,wow,this just got crazy hard to turn after I put that connecting rod in place. Did I get dirt between the rod cap and bearing shell,are my clearances wrong? Plastigauge is cheap. I built plenty of engines before I owned micrometers and checked end play with a home made jig and feeler gauges before I owned a dial indicator. I'm not sure how he even got the engine together without realizing it was way too tight. Sometimes you get a bad part,sometimes you have a bad tech,not an ideal situation,especially of thevtwo meet on the same project.Good parts can make up for a poor tech,a good tech can catch a bad part.

 

[GTX63]

I wouldn't say the vintage car/truck market is dying. It may at some point become more of a niche, but all one has to do is look at all of the shows and drags across the country to know the square body market is alive and well. That and the prices for old iron.
With the prices and regulations and difficulty servicing newer vehicles continuing to increase, the demand for the old stuff is not going away anytime soon.

China could have bought the tooling for domestic parts like cams, bearings, pistons, rings, etc but they chose to close their right eye with their thumb out front and design new machinery that may or may not create something close to the original. The results are mostly piss poor.

I am not exaggerating when I recall my days as a boy hanging out in many, many backyards and garages while the local motor head was putting together small and big block Chevy engines with kits from the local supplier. They did not have to spec every piece; they pulled them from the boxes, cleaned them up, eyeballed them, maybe pulled a feeler gauge out and went at it. I'll also say that the number of cam, bearing, ring, valve failures then vs now is like night and day. Youtube is full of videos exposing garbage aluminum Chinese Vortec heads.
Those who did not work on pre 2000 drivetrains at their inception really won't get how really, really bad replacement parts are today.

 

[ChuckN]

So, go gently on me, but in the 80s-early 90s when I was in shop class, plastigauge was told to us as the bare minimum. Now, that was years ago, and times change.

I was into cars back then, and then got out of it when it couldn’t afford it. The last five years has seen my return. I do plan on rebuilding my own one day for the experience.

But has actually checking the tolerances when things are torqued down gone by the wayside? Just curious. I wouldn’t be comfortable putting something together without checking things out. No judgment to others. Carry on.

 

[Ricko1966]

Count the SBC or BBC possibilities in these 2 random pictures.. And in the 80s/90s all those BOP cars would be small block chevy.Now multiply that times all the millions of highway miles in the Unted States. Car shows,truck forumns,and cars that arent daily drivers,aren't enough volume to interest most manufacturers,especially when they can sell way more LS stuff. Even lots of the SBC,BBC, and people are going LS when rebuild time comes. Good parts for Antique vehicles are going to become more and more scarce,again, the moneys not there anymore.