Sprint jackshaft replacement.

[GrahamFountain]

Having looked at the state of the water pump drive gear, I have to ask if it's possible to replace the Sprint's jackshaft with the engine in the car?

Graham

[xvivalve]

I believe it is possible by lifting one side of the engine slightly and removing one of the radiator grilles, but have never done it in situ myself.

[GrahamFountain]

I was wondering if it might be possible with the rad out? I don't mind doing that, just can't lift the block easily.

Graham

[Mad Mart]

I've done it, many years ago. You do need to remove the rad, the rh grille and the engine mountings and wedge the block over to the right. It should come out through the right hand grille iirc.

[GrahamFountain]

Thanks. At least it sounds easisr than pulling the block.

Graham

[trackerjack]

Yes it can be done as stated, however the shaft has wrecked the gear probably because the jackshaft has worn its fit in the block (there is no bearing) and allowed it to move off centre. Sadly this causes the cam to be starved of oil as oil passes through this fit on its way to the cam.

[GrahamFountain]

The good thing about pessimism is that you're never disappointed; however, whilst it mayn't comfort Job in such fullness of measure, as the rad's got to come out to pull the engine anyway, I might as well take a look at the jackshaft while it's accesible - just on the off chance the engine can stay in. The glass might be two times over specified, after all.

Graham

[Jon Tilson]

Yes I did one a couple of years ago.

Its not too bad and comes out through the grill with the rad out and engine mounts loosened. Check for wear on the keeper plate.
Not an easy part to find now though...

Jonners

[GrahamFountain]

Thanks, Jon, I'll remember the tip about the keeper plate. However, I'm hoping its the pump that's caused the trouble, not the jackshaft side. Now I've looked at it, the old pump is clearly in a very bad shape. Still, won't know till it's out, and that's going to have to wait for other things. Hope it does.

Graham

[trackerjack]

A few years ago there were some bad pump shafts being supplied that were not hard enough and mashed up however I have several good ones here if needed.
It was said at the time that if the shaft had "Zephyr" stamped on it that it was a good un.
I have only come across one worn jackshaft bore in a dozen or so rebuilds.
Fingers crossed.

[xvivalve]

Well, yes, of course the radiator comes out; you'd struggle to undo the timing gear with it in the way, let alone withdraw the shaft!

[Graham.Fountain]

It's hard to see the jackshaft gears down the pump hole, but they were very shiny, and there's a lot of backlash with a good pump fitted, so I think they're fairly buggerd. Question is, of the dozens of engines where the jackshaft bore wasn't worn, how many had jackshafts with worn gears - especially if the water pump was Fouled Up, Completely Knackered, or Entirely Destroyed - there's an acyronym in there somwhere. I've only needed one replacement jackshaft out of about 4 engine rebuilds, but the bore on that was fine.

Graham

[trackerjack]

Back when Dinosaurs ruled the planet I met an engineer who was involved in manufacturing Sprint engines and he told me that they (BL) had a lot of trouble lining up the jackshaft and that if you were unlucky you might get one that the back bore was not in line with the front!
Well I bought his clutch that he swore would never wear out and was used in the competition cars and guess what? I did towing and track days for 12 years and that clutch was still going strong........so he was not a liar.

[xvivalve]

Put your finger down the pump hole to see how sharp the teeth are; if in good order they have a flat on the apex but if worn they can be razor sharp

[80Sprint]

Hope you don't find what I did on the last block...