When good rebuilds go bad

[03BRG]

BJ8 900 miles on a new rebuild and its all down hill from there. A friend that will remain nameless had the motor overhauled by shop all seemed great car never ran better till it started to knock really bad he did the right thing shut it down and the shop that rebuilt it pulled 2 rod caps- bearings down to the shell backing. Long story after about the shop and its back into his hands. So a few of us are helping out on the tear down and find really over tighten hardware like impact tight all hardware is intact no broken hardware so.....

1) During the new rebuild should the rod bolts be replaced? ie are the replacement bolts that you can get any better then the old ones. Threads do not seem stretched so what the thought? Car is not raced standard rebuild.

2) #1 rod has the best bearing and its worse as you get to the fly wheel we have been told the motor had oil and all bearings were STD size. will be sizing everything soon when all is apart.

Well thanks for any input you have- Will update!

 

[GregW]

Hi BRG,
Even if the bolts aren't stretched, they <span style="font-style: italic">may</span> have been weakened. If you are worried about new bolt quality, you might be interested in getting ARP bolts. They are slightly different than the originals in that they don't have that little locating dowel on the head. I think you'd need to call them, when I bought a set, they weren't in their catalog. https://www.arp-bolts.com/

P.S. Sorry to hear about another botched rebuild from a supposed professional. A friend of mine had his BJ7 motor rebuilt just the opposite. The rear main cap nuts were only finger tight. :madder:

 

[stevebn2bj7]

That's why I put them together myself. If something goes wrong though, you know whom to blame

 

[GregW]

Same here brotha', and I make sure I get a warrantee. :wink:

 

[03BRG]

Thank you for the ARP info! will have him pick up the new hardware.

 

[mjobrien]

If you doubt the hardware, look at new hardware as cheap insurance. I did this with head studs that looked well used and was glad to spend the few bucks. Also checking the actual "clamped" clearance of the bearings so you know you will have proper oil clearance is important.

My 100 is being rebuilt and two of the big ends had "0" clearance. The reason it's apart now is poor oil circulation due to poor assembly and heavy dirt in the system which brought on the "Knock of Sudden Death"

PS: Yes the wife was with me when that happened

 

[wheelwright]

Alas,we have seen problems like this too.Apparently there was an entire production run of "County" bearings {made in India} that were mis-marked,they mic out at plus .003 instead of minus .003,we are re-rebuilding a factory 100-m that only made 256 miles before it went sour.This is becoming very common,parts made in 3rd world countries aren't even usable right from the box,so you would be well advised to use Plastigauge during your rebuild.You may want to check out the Joe Gibbs racing oil,we use it for break in,it has the additives oils used to have in the good old days.If your car was assembled w/an air wrench you probably should get new bolts...

 

[roscoe]

Plastigage measurements should be a part of every engine rebuild, period. Along with measuring everything you have numbers for. Replace any hardware you even think might be questionable, if it is in the bottom end, where you really don't want to have to go once you put it together.

 

[RonMacPherson]

Jon, I agree, measurements including plastigage SHOULD be part of every rebuild.

Sadly, that is not what has happened in the industry.

Due to the manufacturer's payment reductions, everything was pushed to "flat rate" and most of the major manufacturers parts were just drop in and drive quality.

That drop it and and drive philosophy has engendered itself, pretty much, throughout the automotive field in the US in the last 30 years or so.

Only on the hobby cars, or older classic cars where replacement parts may not be made to "standards" have people become aware of the necessity of "blueprint" rebuilding.

 

[roscoe]

Ron,
I come at this from aviation. I don't work on piston engines much, but I've built up a few. In powerplant class I had already assembled a set of Lycoming O-320 case halves on a crankshaft and obtained plastigage readings that were right-on. So I had already assembled it once and was ready for final assembly when my powerplant instructor put a couple of 1/8th inch long pieces of nylon fishing line, hair will do it too, on one of the crankshaft bearings while I was eating lunch. I assembled the case halves of the flat four cylinder engine and when I torqued up some of the case through studs the whole thing bound up. When I showed the instructor he looked at my plastigage measurements and said they looked fine, but I'd better split the case and see what was up. I barely noticed the problem even when I WAS looking for something. Lesson well taught and well learned. I was the demo for the class on that one and it put me a day behind.