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MG MGB Technical - Engine bolts re-use

What is the general opinion on re-using the con rod bolts and main bearing studs after replacing the crankshaft bearings (GD series engine)?
Steve Church

I don't see why not if you aren't building a very high revving race engine. Over many engine rebuilds during the last 40 years I've always re-used them without trouble.
Mike Howlett

Steve. Definitely agree with Mike. Unless you are going to upgrade to something like the ARP fasteners, you are better off with reusing the originals. The quality of currently available parts is inconsistent and erratic. Good condition original parts are, in my experience significantly more likely to hold up than many of the current "OEM quality replacement parts". Still have the block lying around the garage from the "Made in England" conrod bolts that let go at less than 300 miles after a rebuild. Never had that problem with original bolts nor quality parts like ARP/APT.

Les
Les Bengtson

Steve,
be a bit careful with the old bolts. On a recent engine rebuild of my 18V engine, I had a problem getting the con rod bolts tightened up to the recommended torqe setting. On removal it was plain to see the threads were stretching. I had to replace several of them. could have been serious. Trev
Trevor Harvey

Hi Trevor

What were you torqueing to? I have seen quite a few con rod nuts die but few bolts die. I use arp bolts on race engines and sc engines where we are looking at high power/hard use otherwise I use the standard bolts. Elastic threads usually show up when you are torqueing up, I let the torque wrench click off at least 5 or 6 times per nut to get the feel.

Peter
Peter Burgess Tuning

I guess I was being influenced by modern engine practice of using bolts that require a certain amount of stretch to perform correctly. I have been reading some posts on other car forums saying that the old bolts should not be used. None of the car forums were for cars of 60's vintage however! Thanks for the advice.
Steve Church

Hi Peter, I cannot remember what the bolts were tightened to but the wrench would have been set to the recommended setting from the Haynes manual, The engine was 40 thou over so had obviously been worked on several times before by previous owners. who knows what abuse items may have been put through in the past including the overtightening of conrod bolts.
Trev
Trevor Harvey

I was just asking as the manual leads one to believe the torque is 40 lbs/ft (diagonal split 3/8ths bolts)whereas the torque for the horizontal split 5/16ths rod bolts is 34 lbs/ft.

Peter
Peter Burgess Tuning

Peter, You may have a point there, as I got the info. from a manual that is more for the early models and only limited info on my 18V engine. I assumed the torque settings were correct for my engine, so that was probably why they stretched.
Trev
Trevor Harvey

This thread was discussed between 09/01/2012 and 12/01/2012

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