72 t120 Pushrod Tubes

Motorossi · 2025-09-21T17:37:20-0400

So, I have worked on rebuilding my 72 t120 from the ground up, but ever since the rebuilt, I’ve been struggling with constant oil leaks at the bottom of exhaust push rod tube / tappet location. I took apart the engine and decided to take the pushrod tubes to a machine shop for inspection, and what they found is pretty concerning. Keep in mind, I bought these new from UK. The tops of the rings where they seal, differ in height by about 0.010” to 0.040”, depending on how you measure them, since the tubes are bent so badly. Using an inspection V-block on a calibration-grade flat surface, the machinist compared them side by side. He also mounted them in a lathe, where the wobble was obvious. The wobble is so severe that it wouldn’t even be possible to flatten the sealing surfaces — the cutting tool would break through the tube wall.
It looks like this is a manufacturing defect, and I suspect it’s been the root cause of my leaks since the rebuild. I also wouldn’t be surprised if others are running into the same issue with these tubes.
See pictures and videos for reference. Im trying to show you the range of the gap in the pictures and the wobble in the videos.

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ijmakeadifference · 2025-09-22T03:48:55-0400

It looks like the main issue is the height difference. One side will deck out before the other achieves the correct squash. The out of true can probably be rotated to get a decent fit. I can't tell from the photo if there's enough material at the bottom to grind off. Ideally send them back.

Motorossi · 2025-09-23T12:18:05-0400

There is not enough material. Please check the video.
I would send them back but I'm afraid that most if not all push rod tubes are like that. They are made from welded sheet metal to reduce cost but you end up with this problem. This is inherent to the original ones as well and I believe that this contributes to the infamous triumph tappet leak that has been so common throughout the years.

tridentt150v · 2025-09-22T05:29:18-0400

Not Wassell are they

Motorossi · 2025-09-22T08:56:00-0400

Are you guys able to see the video? If I try to correct the difference in height by facing the top rings, the cutting tool will actually eat through the wall of the tube. It wobbles that much.

StuartMac · 2025-09-22T10:07:49-0400

Hi,

Motorossi said:
tubes are bent so badly
tops of the rings where they seal, differ in height by about 0.010” to 0.040”

Motorossi said:
If I try to correct the difference in height by facing the top rings, the cutting tool will actually eat through the wall of the tube. It wobbles that much.

Not intending just to be blunt but ... why bother?

Seems a good definition of "polishing a turd"?

Motorossi said:
bought these new from UK.

Again, why? Buying from GB seems to be some sort of Holy Grail but, I assure you, we can get crap just as easily - difference between buyer in GB and buyer elsewhere in the world is we have fairly tough consumer protection legislation, buyer outside GB doesn't, so guess who gets the crap from unscrupulous British retailers?

Otoh, US has some good retailers and at least one good wholesaler (Coventry Spares in MA), Coventry Spares answer the 'phone; while they won't sell direct, they will tell you the dealers they supply. Seems crazy to me to pay p&p, President Trump's tariff, US Customs fees, for crap from another country when good parts are likely available in the US?

Hth?

Regards,

DMadigan · 2025-09-22T11:13:36-0400

Adjustable

Rancidpegwoman · 2025-09-22T11:54:48-0400

Adjustable and high quality

Rancidpegwoman · 2025-09-23T14:48:13-0400

0.01845" Aluminium pushrod tube, 18 thou

0.01095" Steel pushrod tube, 11 thou

0.00885" barrels, 9thou

Calculated for 6" tube with 250f degree temperature rise.

2 thou extra crush with steel 9 thou extra crush with alloy.

I would fit the high quality alloy tubes and set the cold O ring crush to around 22-24 thou.
when hot it should be app 31 32 thou crush On the O rings Perfect.👌
the steel ones are an unkown quality, I have seen so many where the top ring is not brazed on square to the tube.

Regards
Peg.

jimmymc · 2025-09-24T05:22:55-0400

Rancidpegwoman said:
......... I have seen so many where the top ring is not brazed on square to the tube.
Regards
Peg.

The first time I lifted the head on my 2nd T140, this is what I found

jimmymc · 2025-09-24T13:12:35-0400

It did, it was the bottom that was leaking

tridentt150v · 2025-09-24T22:54:08-0400

I like that they had a second go at it and still couldn't get it right. And that braze job.....very professional 👀

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72 t120 Pushrod Tubes

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