Teflon buttons replace circlips?

[GB SISSON]

Does anybody have experience with teflon buttons that replace the spring circlips to retain the wristpins? I have 8 almost new .030 over pistons with rings that I want to reuse. Problem is 3 of them have damage to the shallow 'U' shaped groove in the piston. This was caused by side thrust because of a bad combination of too loose bearings combined with at least one rod that was too tight onto the floating bearing and locked onto it. About 20 years ago I saved up money for that rebuild and by the time I got the $ together the long time family machine shop had changed hands and was being run by somebody that ran the business into the ground and did very shoddy work. I have a different crank in it now which I just had turned .010/.010 and got a new set of ford rods and of course new bearings. I have carefully carved some new grooves for a larger wire circlip in the 3 damaged pistons, but am now afraid to trust them. If I can use the teflon buttons I wont have to remove the new crank and the camshaft and re-hone and buy new pistons and rings etc. I see a company that makes them to order. Heard stories of them lasting over 100,000 miles. The picture they use actually shows a stem that goes part way into the wrist pin and the button is the cap of this 'mushroom'.

 

[JWL]

I have only used the buttons in racing engines. But, how about using a double set of spiro-locks from Ross if you have grooves properly sized for that to work.

 

[Ol' Ron]

I have used aluminum buttons, they seemed to work fine. If it was me I'd uz them.

 

[Pete]

I too have used Teflon buttons in race engines.
The stem should fit the inside pin dia. fairly close.
Some pins are tapered on the inside.

 

[GB SISSON]

Thanks very much. I will look into them today.

 

[Ronnieroadster]

I have used teflon buttons in my supercharged street flatheads for many thousands of miles. You will have no problems with them.
Ronnieroadster

 

[GB SISSON]

I could not find any already made up for our flatheads and the one place I found says they are 10.00 apiece and take 6-8 weeks to make custom sizes. Besides they don't answer their phone and so I ordered 2' of teflon mechanical rod in the .750 size. Working temp 500 degrees, melts at something like 675. This was from interstate plastics. $12.75 per foot. Not sure how I will machine it yet. Neighbor has a metal lathe and I have woodworking shop. They said it machines real nice.

 

[36coupe]

I made my own for my Indians many miles ago.

 

[GB SISSON]

I made my own for my Indians many miles ago.

I think I saw a movie about you...

 

[GB SISSON]

Well I woke up in the middle of the night last night and worked out a few more details in my head. The .750 teflon rod won't be here til Monday so I had to try my methods out with a 3/4" hardwood dowel. Don't worry, I won't make any of the actual ones out of wood, though I think something like locust or a tropical wood would be fine The disc sander has a stick with a groove to hold the rod and the pivot point is half of the 3 3/16" piston creating a domed end that matches the cylinder wall's radius. I fashioned an end stop from a piece of 3/4" poly pipe with a saw kerf down it's length so the feed of the rod into the sander would be uniform. A stainless hose clamp holds the stop in place. While I am sweeping the arc with the pivot stick I am slowly rotating the rod with my fingers. After that it goes to the router jig with a 1/2" straight cutter in it. I have the depth of the router set to make a tenon or shoulder that's a nice press fit into the hole in the wrist pin. This cutter depth will no doubt change when the real teflon arrives as this dowel is a about .010 undersized. Next I lop of the head with a pull saw, and it's done. Because the router bit has it's carbide tips back cut and proud of the rest of the bit for plunge cutting, it creates a very nice 'barrel' shaped tenon that starts easily and then gets resistance as it gets half way. The completed pin assembly with both buttons installed is about .008 less than the bore which incidentally is .030 over. I'm thinking this just might work.

 

[36coupe]

Well I woke up in the middle of the night last night and worked out a few more details in my head. The .750 teflon rod won't be here til Monday so I had to try my methods out with a 3/4" hardwood dowel. Don't worry, I won't make any of the actual ones out of wood, though I think something like locust or a tropical wood would be fine The disc sander has a stick with a groove to hold the rod and the pivot point is half of the 3 3/16" piston creating a domed end that matches the cylinder wall's radius. I fashioned an end stop from a piece of 3/4" poly pipe with a saw kerf down it's length so the feed of the rod into the sander would be uniform. A stainless hose clamp holds the stop in place. While I am sweeping the arc with the pivot stick I am slowly rotating the rod with my fingers. After that it goes to the router jig with a 1/2" straight cutter in it. I have the depth of the router set to make a tenon or shoulder that's a nice press fit into the hole in the wrist pin. This cutter depth will no doubt change when the real teflon arrives as this dowel is a about .010 undersized. Next I lop of the head with a pull saw, and it's done. Because the router bit has it's carbide tips back cut and proud of the rest of the bit for plunge cutting, it creates a very nice 'barrel' shaped tenon that starts easily and then gets resistance as it gets half way. The completed pin assembly with both buttons installed is about .008 less than the bore which incidentally is .030 over. I'm thinking this just might work.

Yep nice job.
Here is the 40 not Bert Munroe.

 

[GB SISSON]

Wow, my dream bike. I have a BSA 441 Victor Special like I rode in high school. The engine must be tightening up as it gets harder to kick over every year...

 

[Dodge]

I've run aluminum and teflon both work well, If your going to make them yourself put
a nice big radius on them to have enough surface area for wear. If the radius is too small
they will wear quicker.

 

[GB SISSON]

The radius matches that of the cylinder, giving the maximum wear area. I wasn't sure that was best and wondered if that would wipe the oil from the bore in that area. The teflon buttons seem to be most prevalent in racing applications, air cooled volkswagens and motorcycles, all of which would really put them to the test. I'm sure I will be more than confident putt-putting around in my old panel at 40 mph, which is the highest speed limit on Orcas Island.

 

[GB SISSON]

Got the teflon rod yesterday, made a bunch of buttons. It machines better than the wood. I few tech questions arise as I assemble the first piston/rod assemblies. The rod is exactly .750 and so the button heads are a pretty tight 'tap with a hammer' fit. This makes me confident in some ways, but they most likely wont rotate. My tenons or stems are also a tight fit into the wrist pins. This combination will in my opinion lock the pin to some extent and make it act more like a fixed pin. Still not so bad for wear and longevity of the buttons. I can easily make the heads a bit looser so they rotate with the pin, keeping them tight with the pin if that's better. The other thing I notice is the holes through the piston must be offset as in all 4 assemblies I have done, the buttons are slightly proud of the piston on the marked forward side. Not much, but noticeable. A tighter radius to the domed end will correct this. I capped a couple of wrist pins with my buttons and placed them in the bores just to see the clearance and see about .008 total. If I keep the button head 'hammer tight' in the piston it seems like they will stay centered better and not rub the cylinder walls, but this is at the risk of stopping or slowing the free rotation of the pin in the piston. On one trial fit I made the button head about .001 under the size of the wrist pin and it (the double buttoned pin) just presses through the piston and rod with hand pressure. Is that preferable to tapping in the buttons hard after the rest is assembled. I could be over thinking this. I have been known to do this. Thanks in advance for any help. GB

 

[Jack E/NJ]

>>>I could be over thinking this. >>>

Nah. Not even close. Now you can think about the different coefficients of expansion between the Teflon, pistons & pins when they all get heated up to temperature. Then there's vibration to think about. You got all kinds of things to think about yet before you've overthunk it. 8^)

Jack E/NJ

 

[GB SISSON]

I have used teflon buttons in my supercharged street flatheads for many thousands of miles. You will have no problems with them.
Ronnieroadster

I think I'll go to sleep tonight with this endorsement instead.... Pins free to float side to side, or locked in with tight buttons, pretty much is what I wonder today. I will have a few miles to worry about the expansion coefficient, but I don't see a blower in the future, so maybe I will lay awake for 20 minutes, not all night.

 

[GB SISSON]

I guess I will go with tight buttons in the pistons. In my anxiety I was doing more searching and found someone who tore down an engine with 300,000 miles on teflon buttons and to his surprise they looked like new. It must be true, I read it on the internet.

 

[GB SISSON]

I'm goin' in.... I found a bunch more written about teflon and aluminum buttons. I see their use in aircraft engines and caterpillar diesels from the factory, and as I mentioned they are very prevalent in hot vws and motorcycles, air-cooled stuff, talking about expansion and contraction. There are some arguments pertaining to their use, ( not as heated as the thermostat wars here) but with a set of pistons at 425.00 and then having to re-use the rings or new. The pistons I have seem lightweight and are unmarked and not sure where I could buy 3 more, so that's why I'm even doing this. With the research I have done I have firmed up what has already been expressed here. I have sized the stems to be a press fit into the wrist pins and the heads are now exactly the same dia as the wrist pins so they will rotate with the pin whenever it chooses to. After pressing in the buttons I trimmed any oversize off with a fresh razor knife blade, resting the blade on the pin, and rotating it around. So far this exercise has cost me $38.45 and a little sleep at night.... Thanks for all your input. They will be going in the holes after work today.

 

[leakers]

I use them on all my flathead V8s, bangers and Indians including race and blown . Never had an issue since the very first set I made in 1977. I have used both aluminum and teflon. I always center drill mine, so that expanding heated air in the pin does not pressurise the buttons against the bore. I drill them 1/16 or 1/8 with the outer end slightly champhered with a countersink. Yes I have them tight in the pins and free to turn in the pistons. Must make sure the pin/bush is fitted exactly correctly in the rod.