cast or moly??

If I can get away with it, (Yes I will mic the holes) I want to just re-ring my '74 318. It will be strictly a street car with a mild .478(?) cam (sorry, don't have the specs handy but it probably will be one of Comp's kits), duals through magnum exhaust, a Carter 600 cfm AVS over a stock intake, 904 in front of a 8 3/4 rear with (depending on what I can find and afford), 3.31 or 3.55 gears. I'm looking at Mancinni's engine rebuild kits and my question is this: Do I want cast or moly rings? I thought I read one is better than the other depending on if its a re-ring or full re-bore, but can't find a definitive answer. Of course, if the mic says so I will buy pistons too but I'm hoping to get away as cheaply as possible without worrying about having to do it again next year Also, Mancinni offers two brands of kits; Clevite and Sealed Power. SP is a little higher price. Is it worth the extra couple dollars over the Clevite products?

Thanks,
Scott

Moly is best, easiest on the bores. Cast is dirt cheap which is why the OEM's used to use it, but it eats bores.

However, Moly rings take a different hone finish to seat properly. If your 74 318 came with cast rings and you have a lot of miles it would not surprise me one bit that you would need a bore job. My 87 318 had factory moly rings and even at almost 200k miles it didn't need a bore job, regular oil changes too.

As for which brand to buy, both are/were good names, but it would not surprise me one bit if they are the same parts in different bxes anymore. Only a few manufacturers of that stuff anymore.

When you open it up you will have a dead smooth bore and I'd also say Moly though I understand cast seals a bit better if the bores have a fair amt of taper/out of round. the trick is to be patient and conservative w the ridge reamer and NOT take out all of the ridge because if you do there will be some areas around the circumference where you are past the ridge and into the wall and #1 pull the blade toward you rather than pushing it around the circumference which means you need to change positions many times as you move around the engine. Get the cheapest set of the two you mentioned and break off one of the old rings in two and grind a hook on the end and grind the edge straight across and use it to CAREFULLY clean the carbon from the grooves and .004"/.003" gap per inch of bore on the top/second rings respectively works for me and read "breakin secrets" at www.mototuneusa.com

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When you open it up you will have a dead smooth bore and I'd also say Moly though I understand cast seals a bit better if the bores have a fair amt of taper/out of round.

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Thanks guys

Robert, I understand that the bore will be smooth, but can I use new rings as is? Won't I need to hone the cross hatch in them to get them to seat?