I am in the process of restoring a 1971 thunderbolt, I have the engine stripped,there appears to be no wear in the barrels & bigends as it looks like it's only done around 3000 miles, anyway I put new big end shells in, they are standard ones, when I torqued them up there appears to be quite a bit of resistance on the crankshaft journal when I move the con rod, so I took them back out and refitted the originals and they seem to be the same, it was quite a while ago that I stripped the engine so can't remember what they were like before, any thoughts on this would be greatly received.
Thanks
Ian Turner
They should not be stiff, You need an oil film so about 1 - 1 1/2 thou per inch dia (opinions vary on the exact amount.
Have you cleaned the sludge trap? I ask because i bought an '71 Lightning new and the bottom end seized within 2 years with the sludge trap full.
Thanks for that, I did use oil but I'll have another look
Hi,
Have you put the caps back on the correct rods? The all aluminium ones are numbered and must be the same number and the right way round as they must have been machined as a pair. Even the steel caps need to be kept with the original rod.
Dave.
Yes, with oil and torqued up they should move easily. How are the rod surfaces, is there any build up of lacquer that could cause tightness?
After torquing up, make sure you give the end caps a tap from a copper headed hammer to "settle" them in place.
I've heard negative things about the Hepolite big end shells. I always get mine from SRM and don't have a problem. They use tri-metal Vandervel shells. There's also plenty of NOS Glacier shells on eBay.
If you're doing it right, plastigauge the rods/shells against the crank.
Clean the rods and the shells with a dry lint free cloth before installing, the contact between the rod and the shell should be clean and dry. Once you've done the plastigauge technique and stripped and cleaned it up again, apply some competition assy lubricant/grease (I like the Driven brand) between the shell and the journal (the contact between the shell and the rod should still be clean and dry).