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Old 11-09-2012, 10:42 AM
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Cast Iron or Moly?

I am assembling a 72 402 BBC , stock dome pistons, mild cam (.550 lift), 820 Oval ports (116cc chambers). Got new cam bearings and freeze plugs, engine cleaned up std bore, std mains, .10 Rods, performer intake.
I am about to order my rings and normal we use Moly rings with our small block builds. Want to know which would be best for this build? Cast iron or moly?

This setup will be going in my 68 C10 work/towing/driver. Any help would be appreciated. Thank You



Steven

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Old 11-09-2012, 11:01 AM
How fast is fast enough?
 
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moly is a facing on a ring, not what the ring is. A ductile iron or steel ring can also be a moly ring. I'm guessing you just want a cheap set of rings though (cast rings), for the extra $15 the moly facing is worth it IMO. Other than the little extra cost there's no downside to moly and it tends to seal better and be a little more durable.
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Old 11-09-2012, 11:03 AM
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Thank You, I understand moly is a coating. I dont mind paying the extra money for some good rings at all. Im looking for the better sealing myself.
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Old 11-09-2012, 11:07 AM
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Thank You, I understand moly is a coating. I dont mind paying the extra money for some good rings at all. Im looking for the better sealing myself.
Cast iron rings with a moly inlay is the 'standard' moly ring. If you want to go up a notch, look for plasma moly rings. But in your build you really don't need the added cost of plasma moly rings. Now if you plan on using nitrous, that's a different story.

Whatever you end up choosing after doing your due diligence, be sure the machinist knows exactly what ring it is you are going to use before he does the final hone. If he says he doesn't care what rings you are using, pack up your things and find another machinist.
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Old 11-09-2012, 11:11 AM
How fast is fast enough?
 
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If you want good seal then spring for the Total Seal rings. I use those on engines I really care about and while the cost seems like a bit much compared to a cheap moly set they really do have zero leak down. Pro's say they're only worth 5-10hp which isn't much- but they also give you cleaner oil and improved vacuum which helps on the street.

Last time I bought a set I think it was about $150- and you can get a set of cheap moly rings for like $40 so again to you the sticker shock may not be worth it. I've used both and for some applications a std moly set is really just fine and sometimes I want something a little better.
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Old 11-09-2012, 11:15 AM
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Old 11-09-2012, 11:20 AM
How fast is fast enough?
 
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Total Seal has conventional as well as gapless first and gapless second ring sets. You might want to expand (no pun intended) on what Total Seal rings you're recommending to the OP.
either Gapless set has worked for me. Some people claim a gapless second cannot work because it holds pressure between the top and second ring but I have a Cutlass outside that shows different. The Gapless second set is a little cheaper, but like I said the pro's recommend Gapless top.

I believe those rings are all ductile iron as well, but it's been a while so I would check on that before you hold it to be gospel.
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Old 11-09-2012, 11:25 AM
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Originally Posted by ZPI28 View Post
I am assembling a 72 402 BBC , stock dome pistons, mild cam (.550 lift), 820 Oval ports (116cc chambers). Got new cam bearings and freeze plugs, engine cleaned up std bore, std mains, .10 Rods, performer intake.
I am about to order my rings and normal we use Moly rings with our small block builds. Want to know which would be best for this build? Cast iron or moly?

This setup will be going in my 68 C10 work/towing/driver. Any help would be appreciated. Thank You



Steven
Stick with moly or chrome these are really wear coatings on a cast iron ring, but bare iron, while breaking in quickly, doesn't provide a wear resistant enough surface so their life span is pretty short especially by today's standard where a 100,000 miles is barely broken in.

The hard coating (traditional moly or chrome, and the coming of titanium nitride and cold case nitriding) are mostly applied to the top ring which sees a lot of heat, pressure and poor to no oiling so these coatings are intended to improve resistance to abraison and mico-welding in this demanding situation.

Most second rings are plane cast iron but may include a coating such as phosphate to reduce wear and improve lubrication, the second ring works in a much friendlier environment than the top ring.

For a third ring the oil control ring, I much prefer the three piece expander type over a cast ring as the individual pieces have more freedom to conform to the cylinder wall. These are usually made of chorme plated steel or from stainless steel.

Bogie
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