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Triumph Repair/MK3 Spit rods


When resizing MK3 Spit rods what is the big end dimension to finish to for correct bearing crush. Can't find it anywhere, only crank pin diameter and clearance on bearing. Installing ARP bolts, polished rods for fast ralley build.

Sorry Hank,

None of my manuals quote the rod bore diameter. You may be able to figure it by measuring the thickness of a new bearing shell and double that and add the rod jurnal diameter and add in one measurement of the oil clearance of .001" to .0015" and come up with what it needs to be.

I take it you are resizing them due to an out of round condition? Or a bearing shell spun in the rod. I worked for several Triumph dealerships and several BLM dealers and rebuilt many engines including Spitfires but I don't remember ever seeing the rod bore specs. I had my own mikes and did find a few out of round rods but just sent them to a auto machine shop to be sized. But I am sure most of those machine shops are long gone now as very few shops rebuild engines any more.

In the dealerships I worked in we were not allowed to resize a rod that had a bearing spun in the rod, we had to just replace it. I only had a few done that were out of round.

You might try Moss Motors tech line, they may have that info or might measure a new rod for you.


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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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