ET: Engine (Twin) Push rod tubes

davidd

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VOC Member
I have never seen a TT pushrod tube "in the flesh" so don't quite see how how they are adjustable other than the smaller section being able to slide up and down in the crankcase seals? Does the the smaller diameter tube slide in the larger diameter part that screws into the head? If so is there a seal in the larger diameter part. A drawing would help explain the setup if someone has one.

The drawing is very helpful. 609 MPH, page 18.
Capture.PNG

The adaptor becomes part of the head, in effect, and the bottom of the adaptor is angled and flanged to mate with the tube, at an angle, if necessary.

See MPH for the full set of drawings.

David
 

bmetcalf

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When the 2 valve Ducatis were the top models, the go-fast guys got billet reed valve units and the shops would sell the used standard ones fairly cheap.
 

BigEd

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VOC Forum Moderator
The drawing is very helpful. 609 MPH, page 18.
View attachment 38617
The adaptor becomes part of the head, in effect, and the bottom of the adaptor is angled and flanged to mate with the tube, at an angle, if necessary.

See MPH for the full set of drawings.

David
Thanks David. That explains how it works to allow for a different angle and deck height.
 

Marcus Bowden

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VOC Member
The reason that your TT tubes do not have the movement the standard tubes have for alignment is that I only had 1" diameter alloy to make them from and the hole in the nut is too tight a clearance, The real TT PR tubes have a radius at the bottom of the head adaptor and a bigger diameter funnel at the top of the tube under which there should be a conical washer sealing the very thin funnel against the radiused adaptor and a square form under the washer that the nut seats against. I just used an "O" ring grooved into the taper the very dumpy PR tube fitted against. Sorry, my handsome I shall endeavour to make another pair for you and myself when I get suitable material.
bananaman.
 

greg brillus

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The 2 parts that make the stock tubes become difficult to remove from the head is.......If the flange atop the tube is a snug fit in the head, and the lower sealing washer that sits bellow this flange and the gland nut........If you assemble the washer on to the tube, then linish the OD of both on a belt sander or similar, so the assembly slides easily into the head recess.......This makes assembly and future disassembly much easier.. Just quickly on my racer........I am going to make a shroud to sit over the breather inlet in the timing chest to stop excess oil being flung at it from the timing gears........ I will look at some form of reed type valve to reduce the build up of pressure in the cases, and this should stop the leak at the lower pushrod tubes........It is easy to see from this why the lower seals on a twin can easily leak in service with the tiny stock engine breather system........I have double "O" rings on each tube that normally seal with no problems, and the pressure is forcing oil out of them, especially the rear inlet one.
 

vibrac

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I had to turn a small amount off the OD of one new pushrod tube flange as it was catching on the head thread . I also made sure that the push rod nuts ran up into the head. one of the nice shiny chrome ones was a bit stiff I dont have a 1"X20 tpi plug tap (after all only the pushrod tube nuts have that size thread on a Vincent) so I selected an old brass coulored one which went in a treat I also assembled the head with the head nuts finger tight so there was a smigin of movement while the pushrod nuts were being run up. I then brought the head nuts up to 27ft lbs and tighted up the push rod nuts fully I shall bring the headnuts up to 32 today there is a lot to compress with the top hat 600 to 500 conversion plug and two gaskets.
 
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