Doc - With a re-hone can the stock pitons be re used with new rings, or do you have to get new pistons made like .0005 larger? I will be going with forged pistons on my 401 rebuild and would like to not mess with the bore too much. I would like to stay under .0030 over bore.
Tony, every engine will be slightly different, because what you are actually doing is custom fitting the pistons to the bore. Get with your machinest and determine just how much you will have to hone to clean the bores up. he can measure this without any problem. If 0.010 will clean it up then go with that figure. each set of pistons will have its own demensions. So you need to have them in hand so you can determine the actual amount the final hone will be. I dont like to ''loose''fit the pistons. That is a race only thing. On any engine that is to be driven on the street, for reliability stick with buicks stock demensions. On piston clearance, rod and mains, ring gaps, ect. Then follow it up with 500 miles or the equevilant amount of run time, for break in, at low speeds with the occasional ''flash'' up to high rpm to get everything seated. Then change oil and filter and you are set for some ''heavy duty application'' as Buick says. Pistons come in various sizes from stock to compensate for wear. A piston is not round. It has some ''cam'' made into it to compensate for the forces exerted on it. As I said a good machinest knows this and will figure the right demensions into the equasion. thats what you are paying him for. Trust him. If you cant trust him, get another machinest. The relationship between you and the machinest is very important. Buy him lunch or something, it will pay off big time in the future. You would be surprised at what a gift to him or just as good, to his kids will get you. Later, Doc.
That is sound advice Doc. A buddy I have known for many years will be doing my machining. Merkel performance engines has been a family run business, around for about 30+ years here on Long Island. I hope he will let me hang around while the take care of the machining on the motor. I will probably have my pistons made by JE and use the stock rods. He will balance everything out for me and I will do the assembly. If I can kidnap TT I will have him looking over my shoulder, making sure I put it together better than the factory would. That is next winters' project, if I finish the body on the Lark by then.
Tony, the general procedure is to measure the bore taper. If the taper is more than 0.008" from the top of the bore to the bottom, then a rebore to an oversize is recommended. Read thru the Buick Service manual, it has the specs. Great book! :TU: The only way to positively know the overbore limit on a particular block is to have the wall thickness sonic checked. TT also likes to use block fill in the bottom of the cooling passages to help stabilize the cylinders. Sounds like a plan to me!
