ET: Engine (Twin) ET38 Valve Circlip Install Tool, Collet Types and Pushrod Info

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bmetcalf

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PEI chose the JAP style and he was certainly familiar with all the then current designs. There must have been some good reason to choose the circlips.
 

oexing

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Probably - but I cannot think of any that makes sense. As to JAP, the first idea for the A Rapides was not JAP inspired, they did the funny screw-on /screw-you contraption , same case, I have no idea why. And only 10 years after they stopped having JAP engines in HRDs they had the wire cum collet thingy. As so often, today knowledge got lost why and how things were done. There is noone alive I think we could ask about these matters to understand.

Vic
 

vibrac

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Yes the clip should pass through the cap sometimes it doesn't but (a.) its only a smigin to remove and (b.) a flick with an electrical screwdriver while compressed will take it off
I have a small magnet on a rod I hang about to catch the loose collets.
As weight is so important on a valve I guess PCV method saves a fraction of weight over the other methods.
 

oexing

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Not much of a chance for weight saving in collets on valves, all place is used up by all types of collets, no different. But last night I checked my Argentinian scrap parts and found the taper in spring caps very different to common collets: Mostly the angle is 8-10 degrees as set on lathe, so 16-20 degrees angle included. But the parts I got look like 25-30 degrees and no old valves still got the wire groove on them, mods in Argentina I guess. One spring cap is brass or bronce, some are alu. What is the standard material for spring caps really ?
In case alu was used in production they could have decided on a wider taper in spring cap for the collets in alu not to get drawn down with time. But even so, no real reason to have an extra wire clip there, a common split collet type with that extra wide taper would do just fine as well. So no idea still about why . . . .
As to weight saving in this place, the alu pushrods I made are just 29 gr compared to solid plain steel originals at 39 gr, 10 gr difference !! No way I´d keep these, also the material is not quite suitable in all alu Vincent engines. You´d like to have some more heat growth in pushrods as well with alu cylinders and heads to maintain same valve play ideally . All you can do with steel is nil play cold. Will be a lot more with hot engine, so it is only one of several reasons for valve clatter.
The 10 mm alu pipes with 2 mm wall require a different assembly as they don´t drop through the adjuster threads: You have the cylinder and loose pushrod shrouds on engine and drop the alu types onto the follower cups. Only then you put the head on top of this and feed pushrods into head recesses while lowerimng the head down. A bit careful action here with wide angle shrouds but no real difficulty to do.
Some time ago I posted photos of the engine case shroud recesses which don´t align with follower cups by at least 1 mm. So I had shroud seal adapters made excentric for clearance for 10 mm alu tubes. Did they never rectify this offset or was this only on early B engines ?
Again, another of many questions about why . . . .

Vic

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bmetcalf

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Cold clearance of nil isn’t the only possibility. For more clearance, use the 28 tpi to know one revolution of the adjuster is approximately .036” and one flat is .006”. Matchy singles are adjusted this way.
 

Gary Gittleson

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But if the cold clearance is more than nil and the engine has stainless pushrods, things will get noisy once warmed up, no?
 

vibrac

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Our experience at Castle Combe when I (yes my fault:() put unhardened push rods in the racer on 3 rockers. They were adjusted perfectly at the start and just wore down in the race, Ben said he could feel the engine loosing its edge (he still won) it occurred over 3 races until we ran out of adjustment. so correct adjustment is very important for performance and unless it happens over a short time (like it did above) it would be easy to not notice.
 

greg brillus

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My single racer was doing similar, but over a longer time........It was the valve collars wearing badly where the rocker fork presses down on it, on both valves........Perhaps a hardening issue, but I will improve the oiling to that area anyway........Cheers.
 
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