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

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Cyborg

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An ET38 Geezus clip installer. Some folks just install them with their thumbs, but I could never figure out how one builds up their thumb strength to that degree….plus most Vincent owners seem to have shops littered with these clips.

Tool consists of a chuck, a piece of 5/16 stock (part A) with a bullnose on one end and a concave taper (to match the taper on the end of the valve) on the other end. Another piece of stock (part B) with a 5/16 hole bored through it. Part B is used to push the ET38 clip onto part A. Part A is held against the end of the valve and then part B is used to push the clip onto the valve. Wish I had figured this out years ago….

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oexing

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VOC Member
That is a silly idea from the start to have alu pushrods without hardened caps on them, same with stainless types, thinking they will "workharden" in use - not so. You want 50 HRC at least on end caps, stainless , carbon steel or alu. So in Vincent case alu is desirable because the rest of engine is alu as well, trying to maintain low valve clearance in hot engine too. Once you got a bit too much clearance you lose all minimal quieting ramps of cams and enjoy the rattle in valve train.
BMW and Horex had alu tubes with steel end caps for long times, never a problem , and they got revved a lot with pushrods ca. 28 cm , while Vincent rods are only 15 cm or so.
In photo 2 at the left are Horex 400 alu top and bottom ends, then BMW alu with looong cap, then BMW stainless - a bit heavy. Some titanium tubes at right, no good, low heat growth !

Vic
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davidd

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VOC Member
Solid aluminum pushrods seem to work well. Pushrods made from 7075 do not work and bend rather easily due to the heat. 2024 aluminum worked well in Benson's Flash and Palmer's Flash.

Tubular Aluminum rods can be bought off the shelf from Smith Brothers, but for some reason, I have the notion that Smith Bros. did not sell outside of North America. The tubular rods cannot be removed through the pushrod adjuster. I always ran stock rods in the racer and never had any serious problems. I had one shorten once and simply replaced the pushrod. That replacement is still in the engine.

David
 

Bill Thomas

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I use standard 10x2 mm alu tubes, even so 10 grams lighter than steel originals. What is squarish ??

Vic
Really strange cams, You have to use radius followers, Polydine Cams ?,
Great lumps welded on the followers, Best ever for a Vincent, No Clacking like the others,
A friend gave them to me many years ago.
 

royrobertson

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VOC Member
Hi, I make my own pushrods are per the drawing attached. These have been used in various other racers over the years, Reg Bolton's and John Renwick's being examples. Also road bikes. They have withstood the abuse of racing with very fierce cam profiles for many years and very rarely need any adjustment. They are also slightly lighter than the originals The lift at my inlets at the valve is 0.465" and exhaust 0.420" so you can see they have a hard time. I used stainless steel shanks as the thermal expansion is good but not as good as aluminium alloy. Silver steel is not as good and titanium is poor. Check the charts.
They also go through the rockers eyes.
Sorry about the quality of the hand drawing.
Roy
 

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royrobertson

Well Known and Active Forum Website User
VOC Member
Sorry guys and girls I obviously made a change from the original drawing sometime as the 3/4" shown is now 1.25". See the actual pushrod and you will be able to see the join.
I put it down to old age.
 

royrobertson

Well Known and Active Forum Website User
VOC Member
Now I remember. My pushrod tubes are alloy and maybe slightly thicker. Anyway there were rub marks where the pushrods touched on the extreme lift so I increased the length of the tapered portion to clear.
Must try to Remember More. Roy
 
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