Hello Jack and others Technical Gurus

First off Thanks So Much for Your Time! It's
very much appreciated!

The bore on my block is ok. The machine shop
I'm using wants me to bore 20 over. My budget says don't bore and put the stock stuff back in. My question is if I do that how bad is it to put back the stock knurled 1972 pistons?

Thanks David Kelly "The A Other Pantera from Richmond, VA"

------------------
Original Post
The correct way: check the block for bore taper, for instance- 0.004 taper found in 2 cylinders (the top of a bore always wears more than the bottom). Hone the block straight (0.004 o'size) and use forged std-bore pistons, which expand more than cast or hypo-eutectic-cast. Use new moly rings which seat almost instantly.
The cheap way: check for taper as before, then hone or glaze-break the cylinders lightly for a good ring seat. Use moly rings. This setup will have you back in there in 15-20,000 miles to change pistons & rings, as that's about all the longer the new rings will last. Piston rattle and smoking from tired rings will be the symptoms, since the rings have to expand to a larger diameter at the top of the bore, then squeeze down to a smaller size at the bottom of the bore, each time they go up & down. Metal fatigue sets in and the ring seal goes away after several million trips up & down. I wouldn't knurl pistons unless the bores were honed oversize, or the piston skirts have 'collapsed' from heat and become smaller, since the bottom of your bores are likely exactly at std and knurling will expand the piston skirt diameters, creating an interference. Knurling is only good for 15-20,000 miles, due to very rapid wear.
You should just wait until you can afford the extra $300 or so for the new parts you need. Why half-ass it while you have the motor apart. Just think of that you time is worth? I know mine is worth more than that!
Likes (0)
Post
×
×
×
×