Teflon coated piston skirts

[Mike T.]

I'm getting my 69 350 rebuilt and the rebuilder said he is going to use "Sealed Power" pistons with Teflon coated skirts.
I'm unfamiliar with that so I wanted to ask you guys. I don't want to use some "new technology" that we find out "flakes off in 10 years" or something else.
So what do you think? Is it a good idea to use Teflon coated skirts or should I go the conventional route? Thanks!!

[Al R.]

Re: Teflon coated piston skirts

I'd go conventional unless you are planning to use it for racing. As others will point out, the Teflon is for reducing friction, which in turn increases horsepower. For a street engine, this would be a waste of money that could be used elsewhere on the 69.

[Duke W.]

Re: Teflon coated piston skirts

Sealed Power is a Federal Mogul brand, so okay to use, but you should verifiy that it's the proper OE replacement part number, so you don't end up with a low compression engine.

I think the Teflon coating is primarily a break-in aid to help prevent piston scuffing - similar to Parkerizing camshafts, and it will gradually wear away with use and without consequences. I think the LS6 had Teflon coated piston skirts and maybe some other LS engines, so it's mainstream technology.

What other parts does he want to sell you? How about machining operations? I bet some are either unecessary or not correct OE replacements.

Turning over your engine to "rebuilder" without a proper plan is a recipe for disaster. The archives are full of horror stories.

Duke

[Bob W.]

Re: Teflon coated piston skirts

Mike I agree with Duke. Some builders will try and sell you stuff you don't need . So when I have a motor rebuilt I know what I want done,

No more no less.

Bob

[Tom P.]

Re: Teflon coated piston skirts

Mike I agree with Duke. Some builders will try and sell you stuff you don't need . So when I have a motor rebuilt I know what I want done,

No more no less.

Bob

And I totally agree with this-----------------------PROVIDED YOU CAN BUILD YOUR OWN ENGINE! Engine building is NOT rocket science! Of course, you need to use a machine shop that you have total confidence in. Have all the machine work done that you want done (tell the machinist what you want, DO NOT tell him HOW to do it!!!). Then bring all the parts home and do your own assembly.
Now, with that said, I fully understand that not everyone has the time, space nor desire to build their own engine, Fine, then you have to rely on a competent engine builder.
As mentioned, machine shops want to sell you stuff that really isn't needed. One of the best examples is surfacing the block decks. We all know that destroys any stamped numbers/codes and eliminates the broach marks. Machinists will oftern tell you that the block needs to be surfaced to assure that it is perfectly flat. I SAY BALONEY!!!!!!!! If the block-gasket-head interfaces were not leaking when the engine was torn down---------------THEN IT IS STILL FLAT!!!!!!! DUH! Personally, I don't want anything removed from the deck surface bacause I want all the thickness I can get from a cylinder deck surface. If the cylinder deck/head surfaces were flat when disassembled, a good composition head gasket will seal almost anything.
Personally, I like pistons with the teflon coated skirts. For a street/driver/performance engine, are they really needed? Probably not, but anything that can be done to reduce friction is a plus.

[Duke W.]

Re: Teflon coated piston skirts

It's best if an owner can do his own disassembly and assembly, and this begins with what I call a "forensic teardown", which includes measuring deck clearance of all eight cylinders before the piston rod assemblies are removed to get a handle on the compression ratio management task. Head and block level is easy to check with a machinists bar and .0015" feeler gage. A basic rule is "remove no metal unless absolutely necessary."

The owner should discuss the rebuild with the shop to make sure they understand what should be done and not done, and a specific set of instructions and parts list should be prepared by the owner and attached to the work order. The parts list should include manufacturer and part number of any part that MIGHT need to be replaced, and it's not that long.

I have detailed documents on this process that I send to those who are interested.

Duke

[Tom P.]

Re: Teflon coated piston skirts

Maybe it's good, maybe it's not. But I purchase ALLLLLLLLLLLLL my parts, usually by mail order. I determine what is needed, then order them-------------USUALLY at a substantial savings over what it would cost to have my machinist buy them and then tack on his markup.
Before ordering pistons/bearings, I have my machinist determine how much the cylinders will need to be bored and how much the crank will need to be turned. Once that determination is made, I order the needed oversize pistons and the undersize bearings. I RARELY replace the oil pump, but everything else gets replaced: cam, lifters, cam bearings, timing set, freeze plugs, rod bolts, (and I usually replace main cap bolts with studs) gaskets, etc, etc. My machinist resizes the rods, installs new bolts, fits the pistons to the bores, installs the pistons on the rods, balances the rotating assembly, then I bring it home and do a very precise assembly. And again, building your own engine IS NOT rocket science! I also build my own (and customer's) 4spds, rearends, suspensions, brakes and FI units. There is no better satisfaction, and as they say, if you want something done right, do it yourself.

[Jack H.]

Re: Teflon coated piston skirts

Specific to the original question, I'm not sure about 350 pistons, but in the 327 hi-po configuration you don't have a choice of teflon or non-teflon at least in the L2166F (HiPo 11:1) SealedPower/FedMogul/SpeedPro quality brands I prefer. So, I don't think its a question of should I use teflon coated or not. I'd be surprised if your rebuilder had a quality alternative that was non-coated unless he found some pricey NOS units. And as Duke has already noted, I don't think the teflon is at all bad, consequential, or not wanted for any reason...not to mention the other things that are more important to worry about in this endeavor.

[Mike T.]

Re: Teflon coated piston skirts

Thanks Duke, Tom Bob and Al.

This engine rebuilder has a great reputation and has been around for 30 yrs. that I know. Several of my buddies have used him through the years and highly recommend him. He runs the entire operation by himself in his shop behind his house. I visited him when I dropped the motor off and discussed his work and his views on things. He understands the importance of pad stamps and broach marks. You would think you were talking to an NCRS guy with a SWC in his garage instead of his red/red 63 Impala 409. I definitely trust his commitment to originality and matching numbers.

My motor had been left outside and was seized from rust, both throughout the intake and in the cylinders. When I took it over to him, I brought the head gaskets and he recognized them as being factory originals. He mic'd the cylinders and sure enough, it was the original bore. He is optimistic that he can clean it up at .020 over, but confident .030 will certainly be enough.

In addition to the Teflon coated piston skirts, he is going to use a Fel-pro .040" thick head gasket. The pistons in it now are double half moons, and he plans to use single half moons to compensate for the thicker head gasket. He estimates the compression ratio will be in the area of 9.3 to 1. I told him I wanted everything as original possible.
Thanks again for your help.

He's going to tear it down first, and then call me to discuss exactly what will be done and to complete a work order.


My with a sthe othhouthe 's a single maoper
s a sinis shpofpr

[Joe L.]

Re: Teflon coated piston skirts

Specific to the original question, I'm not sure about 350 pistons, but in the 327 hi-po configuration you don't have a choice of teflon or non-teflon at least in the L2166F (HiPo 11:1) SealedPower/FedMogul/SpeedPro quality brands I prefer. So, I don't think its a question of should I use teflon coated or not. I'd be surprised if your rebuilder had a quality alternative that was non-coated unless he found some pricey NOS units. And as Duke has already noted, I don't think the teflon is at all bad, consequential, or not wanted for any reason...not to mention the other things that are more important to worry about in this endeavor.

Jack-------

Non Teflon-coated pistons are available for both 327 and 350 cid engines as manufactured by Keith Black/Silvolite. These are available in both hypereutectic cast as well as forged. However, I have no problem, whatsoever, with the use of the Teflon-coated pistons. These are actually used in some PRODUCTION applications. This means they are PRODUCTION-validated which should give one a high degree of confidence in the performance and durability.

I recommend hypereutectic cast for all street applications, including those originally using forged pistons. Also, if possible, I recommend the use of flat top style pistons (with 2 or 4 "eyebrows").

[Duke W.]

Re: Teflon coated piston skirts

Thanks Duke, Tom Bob and Al.


In addition to the Teflon coated piston skirts, he is going to use a Fel-pro .040" thick head gasket. The pistons in it now are double half moons, and he plans to use single half moons to compensate for the thicker head gasket. He estimates the compression ratio will be in the area of 9.3 to 1. I told him I wanted everything as original possible.
Thanks again for your help.

He's going to tear it down first, and then call me to discuss exactly what will be done and to complete a work order.

The OE head gasket should be .018" and a .040" will drop the OE 9.5-10:1 by several tenths. Compression ratio "estimates" are about as worthwhile as somebody's estimate of which way the stock market will go tomorrow. Piston manufactures list net volume specs and you can assume the head chambers are 62cc, but it's best to measure. If the head and block mating surfaces are level, you can use a shim type gasket, and the thinnest is the .015" Fel-Pro 1094. If there's a couple of thou of warp (not likey) the thinnest composition gasket than will seal with a little warp is .026".

Leaving compression on the table will cost in terms of across the range torque power and fuel economy. A few years ago I co-authored an article in The Corvette Restorer on how to manage the CR and it's not a difficult task. If you don't remember it I can send you an e-copy, and you should give it to the engine builder.

Tell him to measure deck clearance of all eight before he disassembles the block. If you don't do that never mind anything else I said.

Duke

[Mike T.]

Re: Teflon coated piston skirts

Thanks Duke. I sure would like a copy of your article. Thanks.

[Tom P.]

Re: Teflon coated piston skirts

The OE head gasket should be .018" and a .040" will drop the OE 9.5-10:1 by several tenths. Compression ratio "estimates" are about as worthwhile as somebody's estimate of which way the stock market will go tomorrow. Piston manufactures list net volume specs and you can assume the head chambers are 62cc, but it's best to measure. If the head and block mating surfaces are level, you can use a shim type gasket, and the thinnest is the .015" Fel-Pro 1094. If there's a couple of thou of warp (not likey) the thinnest composition gasket than will seal with a little warp is .026".

Leaving compression on the table will cost in terms of across the range torque power and fuel economy. A few years ago I co-authored an article in The Corvette Restorer on how to manage the CR and it's not a difficult task. If you don't remember it I can send you an e-copy, and you should give it to the engine builder.

Tell him to measure deck clearance of all eight before he disassembles the block. If you don't do that never mind anything else I said.

Duke

Duke,
Do you know what issue that was? I have all issues of them back to 79.

[Duke W.]

Re: Teflon coated piston skirts

...Fall 2009. I emailed you a pdf of the article and have attached it here for anyone else who is interested. The online CR calculator I use is at:

http://www.csgnetwork.com/compcalc.html

Duke

Compression ratio.pdf

[Mike T.]

Re: Teflon coated piston skirts

Thanks Duke!!