This is probably a dumb question but if I put new pistons in do I need to put new bearings in or can I just retorque everything aand be ok
Yes you can if the Bearings are good, but if you have all of the Rods out and the bearings are original then look at the back side of the Bearings, if see that they are the low performance GM Moraine 200 types then I would up grade them to new and better types!
Ok thanks guys. One more question if I do this and put in new cam and bearings should I use break in lube on everything
If going to the trouble of new pistons and cam, why not just spend a few hundred more and have new bearings too.....cheap insurance. What will it cost if one these used bearings gets torqued or something differently and I eats a crank or rod
Unless you have some experience in engine work and you have done this before, there are a lot of ways to screw all of this up. Correct me if I am wrong, but looking back on your threads, it looks as if you want to build an engine by swapping parts around. Like I said, there are a lot of ways to screw up.
Larry is correct about the lubes. I feel there is one exception that we use and it is Torco MPZ Engine Assembly Lube HP. This product is used for high pressure points such as camshaft lobes, lifters, bearings, and valve train components. This stuff is so thick and slippery that I use it around the shop for all kinds of mechanical applications, ... not just automotive. (Tip- It works great if you put a dab of it on the mandrels of your brake/fuel line flaring tools to help get a super nice flare, especially with stainless lines.) Larry
At the very least, the OP will have to weight match them. Re-balancing the rotating assy would be alot better IMO. Replacing pistons is major surgery. At that point, why not just have a machine shop check it all out for you? I guess the question that comes to mind is why are you replacing just pistons in the first place?
If he's changing cams doesn't he need to change the lifters as well? A more aggressive cam may require new pushrods as well?
I would have all of the mentioned concerns and more. I'm not trying to be rude here, but if you're having to ask about whether or not to use certain types of lube during assembly, you probably don't have the experience to do this work properly. My experience has been that engines cobbled together by inexperienced folks rarely last long or run well/don't burn oil. Why are you only replacing pistons? There's almost no circumstance that I can think of personally where an engine needs its pistons replaced yet doesn't also need other work as well.
Need pistons changed and want to change them for more compression are 2 different things, I would at least put bearing in for sure as u stated. And if different weight balance should be considered. ...if you get lucky they might be close to factory weight. But a factory balance job is.not in the area as a good balance.
You just opened up yourself a big ole can of worms dude. I am curious . Are you putting new piston rings on them.
I was just wondering if it could b done without having to do a bunch of other things. I have a 75 motor so I figured stock 70 pistons would wake it up a bit. But I will just leave the pistons alone. I am putting a set of 71 heads on that r ported and polished and also replacing the cam and cam bearings
I had low compression 455 pistons pressed off my rods and junked them. I took used 1970 pistons to machine shop to check all measurements. Pressed those 1970 pistons on my rods. Run them at the drag strip and hammer the engine a lot. No problems. 7.50's in the eight mile at 92 (about 11.80's at 113 in quarter mile)
Also...the 70 pistons were .040 taller than the low compression pistons which helps compression and gives better burn of the fuel.
The 75/76 pistons had a .040" lower piston pin height than the 70 to 74. The 1970 piston had a shallow 22cc dish, the 71-74 34cc. The comp. is about the same using 71-74 pistons or the 75/76 pistons (they had a very shallow dish). The specs are on the site somewhere. Ray
