Quickie question, Moly or Cast piston rings in re-honed/de-glazed cylinders?

Thanks

TC

 

Molys take longer to break in and are more sensitive to bore finish. Cast iron break in faster and are less sensitive to bore finish. Hope this helps.

 

I second mia. In automotive I ALWAYS recomend cast for re-ring and molly for re-bore.

 

Thanks for replies.

@IDIDNTDOIT

Before fitting new rings surely you get a re-hone, after a re-bore I presume a honing is done also, if this is the case what is reason for cast if re-ring and moly if re-bored?

Cheers,

TC

 

You hone in both cases, leaving you a cross-hatch pattern, but a hone will follow the contour of the bore and is not as true if the cylinders aren't bored. The moly rings are harder and won't adapt as well to any out of roundness. The cylinder can be a little egg shaped and still re-ring OK with cast rings breaking into the shape and not being an oil burner. Hope this helps.

 

every engine rebuild ive ever done ive used moly. seated right off the bat. never used any oil. as i remember, moly for bores that arent perfect, chrome for engines that are going to get a lot of dirt, and cast if you dont give a damn and are going to sell it. like i said ive done more than a few engines and always use moly.

 

Thanks for reply, IDIDNTDOIT, see your point.

But as usual, there is always conflicting views..........................

To be honest, I have ordered Moly, so I suppose I am trying to "feel good" about it, but seeing hotrod351's reply, I feel a bit better.

I will make sure that my cylinders are properly torqued before any work and will get machine shop to check trueness. If he says tolerances are off I will do a re-bore and fit oversize piston kit.

As the say HD, Hundreds of Dollars!!!!!!!!!!!!!!!!!!

TC

 

Molly is a good *****.

 

i had read about the differences in a old engine performance rebuild manual i have, somewhere around here. i also have a friend that is a certified mech. he also uses moly. i can find a article or two that talk about chrome being for extreme dusty or dirt conditions, like off road racing. there harder therefore the cylinder wears faster. i know a lot of people that stick with cast, guess that is what works for them. but as i stated, moly are good for a un-perfect bore and therefore they would also be good for a perfect bore. i do believe that its only the second compression ring that has moly in it and the top is cast. pprobelm is you can get so many different answers that you end up not knowing which ones to use. i think youll be happy with the moly. post back when you get it rebuilt.