E: Engine ET104 heavy duty

[Marcus Bowden]

We use to campaign a works Grey Flash LRO 993 with a big port head and it had TT-style pushrod tubes which consisted of a union that screwed into the pushrod holes and was a rounded taper at the bottom, the lower part of the tube was funnel-shaped with thin walls and a gland nut with a floating bevelled washer inside. The nut would be tightened up over the union in the head pulling the tube up through the normal seal which I find very good if they are new and flexible. The beauty of this system is as soon as the gland nut is slackened the head can be lifted as the normal pushrod tubes have to be extracted from the head. Also, the seals can be replaced without lifting the head !
Remove pushrod, slacken gland nut, push tube down into C/case remove the union from head pull up and out the nut and tube leaving seal exposed to be renewed easily.
I will get a set-out photo them with sizes some time, very much more practical.
bananaman

 

[vibrac]

I wanted to use those I have a set however they have a design that tends to be rather more inflexible to cylinder height. The set I had were fine on the racer but when I wanted to use them on a lower compression road bike it was impossible to assemble as the angles prevented threading up while conventional tubes easily accommodated the angle I guess if you had concertina ' bellows' like Dan Smith's short stroke you would be ok
NB I have now searched all my old emails and PM but still can't find where I got those seals from....

 

[Martyn Goodwin]

no matter what type or material the seal is you will never stop leaks if the push-rod tubes are not completely round and free of any scratch or score marks