Don Terrill’s Speed-Talk

PackardV8 wrote: ↑Tue Nov 27, 2018 10:03 pm I sat in a gravel pit and passed Craftsman wrenches to Don Garlits as he took parts out of the back of his pickup and off his grenaded engine and built a junkyard block into a top fuel hemi. When Plastigage came out, I thought it was really high tech.

Drag racing might be better off if stuff like that could still be done..

It can still be done. Just not with 10k hp and not at the big show. Make the same power they did and I don't see why you couldn't use the same parts. It's not black magic.

There is no such thing as a "chrome moly" piston ring. However rings may have a chrome face material or moly face material applied to the basic ring.

Up until the 70's or so all rings were grey cast iron and chrome was often applied to the top compression ring face, especially when the engine was used in an off-road situation such as farming or construction equipment. Chrome was rarely used in passenger car production engines, although many current-production Japanese engines are using chrome faced top groove rings. Grey iron second rings where the norm, with a tapered face and either standard twist or reverse twist design. Also during this time the ring lateral dimensions were much larger, such as 5/64' and larger. When GM and others began using 1/16" compression rings, this was a really big deal.


Then "moly" top groove rings came into being, most often used in high performance V-8's of the day. However, these rings were still gray cast iron base material and they had a groove machined into the ring face which was filled with moly then lapped to shape. Problem with these rings as that any slight detonation would hammer the moly out of the ring. This is when the ductile iron base material, plasma spray moly came on the scene and has been used almost exclusively in high performance applications until just a few years ago.


Now, in keeping with twenty-first century technology, most top rings are being manufactured from steel then coated or heat treated with various chemical formulas. The steel ring is extruded into a large coil of material with close to net shape that needs little additional machining. Grey cast iron is still used for the majority of second groove rings, although new and improved face shapes like the Napier style have come into being.

I have a full set of old school Hastings .040 rings for a Chevy 292 inline 6...Looks like a chrome top ring...Free for the price of shipping!!!!

Have a 62 Willys, state of the art at the time. Original definition was chrome, service replacement "upgrade" was cast iron. Tried to find something better, failed, stuck with NOS factory cast.

engineguyBill wrote: ↑Wed Nov 28, 2018 12:54 pm There is no such thing as a "chrome moly" piston ring. However rings may have a chrome face material or moly face material applied to the basic ring.

I should have said that. I was just assuming everyone here would know there never was a chrome moly ring. I must have heard 50 people tell me that's what they had or were going to use back in the day.

Truckedup wrote: ↑Wed Nov 28, 2018 1:17 pm I have a full set of old school Hastings .040 rings for a Chevy 292 inline 6...Looks like a chrome top ring...Free for the price of shipping!!!!

Someone needed them...

Wasn't that chrome moly speaking about the metallurgy or advertising BS, like chrome vanadium, not that spray/paste on smegma?

Chrome moly is a common term referring to a family of steel grade prefixed with 41 ,like 4140 and 4130 being the most recognizable.

Chrome has been used as a ring to bore wall coating on typically the top ring ,it is not common these days as it was difficult to seat but had great surface wear resistance.

Moly or Molybdenum is a surface coating or inlay typically applied to the top ring ,the ring support structure is still iron or steel, as Molybdenum as a metal is quite malleable, but retains oil so is less prone to scuffing and seat quickly .Plasma Moly refers to the application process of the Molybdenum to the ring surface, Moly inlay is another term used to describe the production process,effectively both have the same performance.Molybdenum has a very high melting point.

One point not covered in this post is the instance of micro welding of rings to the piston ring groove seat ,this situation occurs pretty much at engine first fire up ,don't put them in dry and you wont have a problem, recently developed coating reduce the instance .But that's just me.
My first go to on any tech info is the manufacturers recommendations, not my mates!!

Cheers.

If you took all the piston rings in the world and surveyed them, I think you'll find chrome faced top rings would be most common of what currently exists.
That said I would be wary of using chrome faced for d-wall and wide sizes for a fun toy, as they can take a long time to seat, but say NPR's metric sizes, they work great.

modok wrote: ↑Wed Nov 28, 2018 8:41 pm If you took all the piston rings in the world and surveyed them, I think you'll find chrome faced top rings would be most common of what currently exists.
That said I would be wary of using chrome faced for d-wall and wide sizes for a fun toy, as they can take a long time to seat, but say NPR's metric sizes, they work great.

I have only messed with chrome rings on automotive stuff once but airplanes not only have the possibility of chrome rings but also plain, nitrided and chromed jugs. 95% of my aviation career was on gas turbine engined aircraft but I never knew of anyone having any problems seating chrome rings unless they ended up with a chrome ring in a chrome jug. Of course aircraft engines are at full load much more than a car.

modok wrote: ↑Wed Nov 28, 2018 8:41 pm If you took all the piston rings in the world and surveyed them, I think you'll find chrome faced top rings would be most common of what currently exists.
That said I would be wary of using chrome faced for d-wall and wide sizes for a fun toy, as they can take a long time to seat, but say NPR's metric sizes, they work great.

I recently re-ringed a newer Honda 750 bike...NPR ring set, top was chrome..I prepped the cylinders with a brush hone, bore gauge said the cylinders were within tolerance...I ran the engine the usual way to set the rings...After about 20 miles it still smoked a bit..But after a few more miles of "hard" use ,no more smoke and normal compression..

tresi wrote: ↑Wed Nov 28, 2018 3:37 pm

engineguyBill wrote: ↑Wed Nov 28, 2018 12:54 pm There is no such thing as a "chrome moly" piston ring. However rings may have a chrome face material or moly face material applied to the basic ring.

I should have said that. I was just assuming everyone here would know there never was a chrome moly ring. I must have heard 50 people tell me that's what they had or were going to use back in the day.

==================

As I recall about two score years ago for a while at least one of the big mail order outfits' magazine advertizements boasted their engine kits as having chrome moly rings.
PAW maybe ?

Yeah, most of the folks I knew knew twaren't so.

I took apart a all original 74 Pontiac 455 Super Duty and it had double moly rings.

The term chromoly or chrome-moly can be blamed on early Sealed Power advertising and packaging.
Anyone remember that Sealed Power originally packaged their ring sets with both Cast and the then new Chromoly top rings in the same package?
It was a bit confusing at first. They looked chrome but had that moly insert.
I suspect they were trying to bring the old wisdom about rings into the future by giving folks a choice and not upsetting their current old customer base.
It took quite a while for folks to ask for moly rather than chromoly rings.