i was wondering what would be the benefit of running either one on a 392 hemi...thats mainly a street car.
There are guys that say you don't need to run fancy-pants parts in a motor, but my thoughts are to put the best you can afford into the rotator, and design it for the end-goal. If you keep playing the game of "i'll change it later when i get my (insert speed part here)" then you spend 130grand on a car that i could recreate for 35 grand. Make the rotating ***embly something you never have to take apart.
Moly rings are the best to use with a fresh oversize bore. If you're just re-ringing without boring, then use cast rings. They will mate with an old bore better than molys will. However, cast rings will wear out sooner.
good point- do you remember the preferred bore finish for moly rings- i remember it takes a different finish but i dont remember if it's a finer crosshatch or something else.
Chrome rings take a different cross hatch as they don't seat easy. Molly rings are not as picky and they are easier on the bore than Chrome rings. If you want to go modern than plasma molly rings are the way to go. Prior to plasma molly rings the easiest on the cylinders were cast then molly after that and finally chrome rings that wear real well but are real hard on the cylinder because they are a harder material than the cylinder wall. For everyday driving I still prefer cast rings, they are real forgiving. With a clean straight bore cast rings are good for anywhere to 100-150 K miles. You should be taking a look at your innards by then anyway.
Your typical Cast ring needs only a 280 grit cylinder finish and seat reasonably fast.however Molly rings need a 400 grit finish and in race motors seat almost as quick as fire up. With full racing motors a sunken CK-10 hone is used to keep the cross hatch uniform and is basicaly necessary for a professional job. For my run of the mill motors I stick with the regular cast type rings and they give me the service I need.
Cast rings are not suitable for performance work of any kind. Period. Plain cast rings will break at the first sign of detonation. They will wear out quickly - especially on unleaded fuels. No OEM engines have had cast rings since at least the 70s - and more likely since the early 60s. I ran Speed-Pro for Federal-Mogul for about a dozen years. I was responsible for roughly 10 million dollars per year in ring business. They let me go a couple years back - so it ain't like I am pushing their products - but I do know a little bit about piston rings...
That's funny, Barry, I didn't know you were here on the H.A.M.B..... Gentlemen, the man knows of what he speaks about....
Really??? Hmmm.......I'm runnin' cast rings in a 450hp 440 with no problems whatsoever. It's the original block to the car with 250,000+ miles, so I'd rather have rings wear than the block. The 1st rebuild went 100,000 on cast rings and many of those miles were on spray (Nitrous). And the current rebuild didn't need a bore, just reringed. And it's been sprayed too. I run cast rings in 99% of the "performance" motors I build.....
There hasn't been a US made engine made since 60 or a bit earlier that did not come from the factory with either chrome or moly rings. Basic machine design Do Not run 2 simular hardness materials together ie steel shaft with br***/bronze bushings NOT steel to steel. American cars made before the mid 50s used plain cast rings, 90% of them needed to have a ring job in the 20-30 K mile range and a rebore at 45-60 from wear. Modern oils and filters make plain cast rings last longer but the moly is still the best deal. Some imports back in the 60s-70s had induction hardened cylinder bores [Toyota for one] that then used plain cast rings as the bore was harder than the rings.
The moly rings are little for forgiving on the installation also. I have seen many a time cast rings snap if you dont put them in just right.
I'm running cast rings in the mill I had in the Pusher. Over 100K of serious abuse. Makes over 400 horse and still holds good compression and p***es a leak down test. This is a motor that has seen everyday use and wore out I think 3 or 4 bodies at this point. Its comming down for a freshening this winter before it goes into the next body. I'll be able to give you good close up pics and numbers when that happens. If you can swing plasma molly rings then jump all over it but if you're building on a claimer budget then I wouldn't be afraid to throw a set of cast rings in it.
Good artical in the latest Hot Rod Mag this month about pistons and rings, a lot of information about the newest ring sizes/ material. I have recently torn down 2 motors Chevy Vortec 96 to 2000 and I am amazed at the lack of cylinder wall wear as well as guide wear. Both of these 350's were in excess of 180K miles one of them with 233K on it. I am ***uming it is due to block material and maybe a lower tension ring than were in the old motors. I had a pretty decent Automotive machine shop in the early to late 70's, all Sunnen machines. After 90K miles some of those SBC would not over bore .030, needed to go .040 or even .060. A lot of changes since then I'd say a lot for the GOOD!
You really think there's 100,000 miles on spray? Rocket scientist indeed..... Reading comprehension......look it up.....
OK, so back to the original question... ***uming a basic rebuild, even with 10:1, warm cam, etc. we often use ductile rings. It was said earlier that the oem quit using ductile rings back in the 60's...seems odd that we still have so many to choose from...what else can you find that was discontinued 50 years ago still easily available? Just be sure that the bore finish matches the ring either way you go. Either ring will give you 100K miles, you will not see or feel any difference. Flip a coin or decide on cost vs budget. As for cost, because of the very common 4" bore, we don't see much difference in price. .
Sorry I let this coast for a week while life got in the way... And did not intend to get snippy, but I actually know a little bit about the piston ring business. Buying the cheapest rings is kinda like buying a Chinese condom - you might save a dollar at the start, but something will really cost a bunch when it "pops".... The OEs stopped using plain cast rings many decades ago. Ductile iron is good stuff, and one of the two base materials of choice in the OE or performance environment - the other being steel. Both of them require a plasma-moly face coating due to the flexible, high strength nature of the base materials. Inexpensive cast rings can get by with a wire feed or mechanical insertion on the moly since the ring will fracture before the coating fails. Non-coated cast iron rings are really targeted toward super low budget rebuilds. They have no redeeming features other than the fact that they are very inexpensive. Hastings sells the plain cast stuff to the cheapo rebuilders for around a dollar per cylinder for a top, second and oil - that should be telling you something... Manufacturing COST on a quality ductile top ring with plasma-moly runs somewhere around $4 per ring.
Good point Barry, many folks ***ume ductile = cast and perhaps I made the mistake of thinking that ductile was actually what he was asking about. ...gotta quit thinking too hard about some of these posts... .
Hi engine builders. Anymore ***y RING talk? I just love it when Folks say they run tens with iron rings and 250 shot of NOS with a stock 350 chev! I must have spent $50,000 trying to run a TEN with a street car... $100 molly rings was the best deal in the whole set-up lol.
More efficient fuel management (fuel injection) and higher operating temperatures reduce oil contamination and cylinder wear. GM did some interesting studies.
Flatties, Chrys, and Desoto hemis... Hell, I'm gonna use 'em, I have the Grant Indy decals... Besides, they'll probably outlive me!
If I can swing 'em I am going to use plasma moly rings when I freshen. A lot of the time my builds are budget driven. I can go hog wild with someone else's motor but I have to keep the lights on and that sometimes requires me not having the same stuff that the really cool guys have.
Yeah...Some of the 'really cool guys' (they said they were) weren't as cool as they said. Witnessed this in 4 consecutive 10 year generations.
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