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335 Series- 5.8/351M, 6.6/400, 351 Cleveland
Moly rings or Not???

Moly rings or Not???

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Old

May 5, 2004 | 03:51 PM

#1

66ford400

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Moly rings or Not???

It's time to buy the rings for the rebuild and I do not know what to go for. Machine shop says cast rings will be fine, but I have always heard that Moly rings are the way to go. What do you guys think Moly or not to moly that is the question?

Also getting it internally balanced, waste of money?

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Old

May 5, 2004 | 04:24 PM

#2

CJJTulsa

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Quote:

Originally Posted by 66ford400

It's time to buy the rings for the rebuild and I do not know what to go for. Machine shop says cast rings will be fine, but I have always heard that Moly rings are the way to go. What do you guys think Moly or not to moly that is the question?

Also getting it internally balanced, waste of money?

Most people will tell you moly is the way to go, but I really prefer cast, just for the ease of break-in. I've had some moly sets that didn't want to seat. I guess it's kind of like cast pistons vs. forgerd vs. hyper. Forged are nice, but there's been many engines go over 200,000 miles with cast pistons and cast rings.

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Old

May 5, 2004 | 07:53 PM

#3

dimora

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My builder says get moly. He said they are better in the long run (last longer). They cost just a bit more, but the cost is minor. I went with moly, and so far, so good.

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Old

May 5, 2004 | 11:27 PM

#4

mark a.

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CJJTulsa : Under what conditions didn't your moly rings not seat ?

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Old

May 5, 2004 | 11:37 PM

#5

TMI

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From: Fairmont

Technically, a moly ring will seat faster.

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Old

May 6, 2004 | 06:14 AM

#6

CJJTulsa

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Quote:

Originally Posted by mark a.

CJJTulsa : Under what conditions didn't your moly rings not seat ?

I have them in my 429CJ, and no problems. Had them in my 351C and that damned thing had blow-by forever. My 302 has iron rings and no problems at all, as did my 289. My wife's stepdad has been a self-employed mechanic since the early 60s and I told him about it. He said he avoids moly rings too because he's had trouble seating them. Mine might have been the way the cylinders were honed; from what I understand there is a difference between the bore finish for cast and moly rings. I've never had a problem with iron rings seating, and since what I build engines for aren't daily drivers that are going to have 150,000+ miles put on them, the iron rings should do me just fine. I wouldn't be opposed to moly again, but cast just seem like more of a "sure thing" for me.

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Old

May 6, 2004 | 12:52 PM

#7

66ford400

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Thanks for the reply's

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Old

May 6, 2004 | 06:21 PM

#8

mark a.

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I was curious because moly rings are the choice of most all engines rebuilt today. I've stuffed them in holes that I never thought would seal.and they have always sealed instantly for me. I have a boring bar & a honing tank and everything that goes with it. Perhaps your cylinders weren't finished, correctly, maby out of round, tapered, too much end gap. Your right that moly need a finer finish.I always clean cylnders with WD40 and a paper towl. before assembly, It's the best thing out there.soap & water wont cut it.

Last edited by mark a.; May 6, 2004 at 06:23 PM.

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351, 390, bore, cast, cleveland, difference, finish, ford, hone, long, moly, rimgs, rings, seat, seating

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