Just been having a read on the American 914 site; there seems to be a move to use a square profile PRT seal made by McMaster. Here's the product; https://www.mcmaster.com/products/viton-fluoroelastomer-o-rings/ McMaster-Carr chemical resistant viton fluoroelastomer 1/8 fractional width, O-ring X profile. 2126540k152 (small end) 2146540k154 (large end) Coat with DuPont Molycote 55 O ring grease. and here’s the thread; http://www.914world.com/bbs2/index.php?s=5f371d7e59cc5ef7414b4a7aec40445a&showtopic=368062 Anyone have any experience or thoughts on these? Got to be worth a try I reckon.
Guess it depends on the state of everything else. A normal one won’t leak, if all the other components are as they should be. Wear, vibration, age, etc.
Like that a lot, the fact of having two points of contact on two different surfaces and less tightening required to form an efficient seal sounds great. Didn’t read too much about distortion issues though. Ozziedog ,,,,,,,,,,,all progress starts somewhere
The temperature range is a bit low but they would probably work – if the size is correct, and an imperial, square section, ring might not be correct for a metric groove. But what is wrong with an ‘o’ ring?
I think that one of the comments on that thread is appropriate "it didnt leak until I put oil in it" . There is another form of that "nothing goes wrong until use" concept where you just put an oversized lump of elastic polymer material in the gap and it seals perfectly until the engine runs. But for the seal to not wear it does rely on a small amount of oil making it past the moving shaft to case seal to provide lubrication, as the grease will not last forever.. The question is how much oil you are prepared to leak, or how often you want to disassemble to re-grease the surface to stop it leaking in the end.
They all blumming leak! Well not all, but enough to be darn annoying. I expect the problem is with non-original PRTs really. Yes, two. Points of contact does seem attractive.
I bought my round Viton seals from Polymax (UK based) and they worked much better than the rubber ones, but not perfectly, I still have a few that weep. Could it be my mating surfaces are not perfect, probably, so do these offer more chance of a better seal I hope so...looks interesting.
I did .. . I apologise for a different rant. Anyway, these will fill the gap well, better than an O ring and less likely to get damaged right across the sealing face, or by bypassed by small surface irregularities as they have a wider contact surface.
How did you decide which viton o-rings would be best? I recall buying a bag of them from the same supplier 10-15 years ago and finding that viton comes in several varieties. I also remember that I got about 50 for the price of about 4 at our usual VW suppliers!
I can't really remember, but similar price difference , but I did speak to one of their chaps who was very helpful and after explaining what I needed them for bought what he suggested. O ring 24.99mm ID x 3.53mm CS FKM (Viton) 75 ShA BS214V75 50 for £9.50 O-rings 21.82mm ID x 3.53mm CS FKM (Viton) 75 ShA BS212V75 50 for £9.50 A few of these were gifted out to other idiots around here
Beats the £4.50 per that VWH were charging back then. 16 x £4.50 isn't funny - they rely on you being unable to specify them then *cough* in your pocket with a straight face. This is info that should be in a sticky post.
The proper ones are the green FKM for the higher temp . When I looked into this I could get the correct size from my supplier but found the leak issue to be more with the tubes than ORings . Personally if I could be bothered I’d make alloy tubes with two ORings at each end
CSP have both standard and extra-long tubes. https://www.csp-shop.com/en/engine/push-rod-tubes-csp-109-335-021ca-29491a.html And they still use ‘o’ rings.
Too expensive, I'd rather drip a bit of oil. To be honest, if LHU made some they'd be too pricey as well. If I really wanted totally leak free and wasn't concerned with taking it apart again I'd glue the o-rings to the tubes with wellseal or something then glue them into the engine using the same. I'm a cheapskate with other hobbies too.
so the extra long ones can be used with stock lenght pushrods, they just stick into the head further and have two rings? seems a good solution. Shame they are so expensive.
