Twincam Jackshaft wanted

[JonB]

Hi

On examining my Twink's jackshaft, I found one of the teeth missing on the gear that drives the fuel pump. Hurm. I think it is still usable, but I'd rather not. So, has anyone got a spare jackshaft lying around?

Thanks
JonB

[rgh0]

I presume you mean the gear that drives the oil pump and distributor. The fuel pump actuating lever is moved by a lobe.

cheers
Rohan

[512BB]

And just make sure that if you are offered a jackshaft Jon, that it is the correct one for a twin cam, with the right oil porting. When I went to look out a j/s for my current engine build, the first 2 I picked out were wrong, incorrect porting slots. Trouble is, I have had them so long, I cannot remember who I got them from, to wrap them round their heads, in a friendly kind of way.

Leslie

[JonB]

I presume you mean the gear that drives the oil pump and distributor. The fuel pump actuating lever is moved by a lobe.

cheers
Rohan

Yeah oil pump, what was I thinking? Cheers!

@Les : that’s worrying.. I’ll stay sharp. Like I was when I bought the car

So, I thought this shaft was basically a camshaft off a standard 105E engine. That not entirely true?

[512BB]

No, its only resemblance to a camshaft is that it is made of a metal and has a few lobes.

Post a picture of the sprocket end to see if it is a correct shaft Jon.

Leslie

[jono]

If you get stuck QED do new ones at £105 + VAT

[JonB]

No, its only resemblance to a camshaft is that it is made of a metal and has a few lobes.

Post a picture of the sprocket end to see if it is a correct shaft Jon.

Leslie

Errr… sorry, but I think you’re mistaken, Les.

My jackshaft is a 119E camshaft, as reused in the TC application by Lotus. It has multiple cam lobes which would have driven overhead rockers in the original application, and a helical gear to drive the distributor and oil pump. Exactly the same as the jackshaft shown on p.111 in Miles Wilkin’s Twin Cam book. And we know the likelihood that this engine has been dismantled is slim. The wear I’m seeing is, I think, consistent with an engine that’s done the recorded mileage from new.

The QED jackshaft has no lobes for driving pushrods and rockers, because it’s manufactured from scratch, rather than reused like the jackshaft originally fitted.

I’m wondering why it was laid up all those years ago. So far I’ve found nothing in the engine, apart from the jackshaft gear missing a tooth, and a brand new oil pump. I think the pump and shaft damage are related. Any thoughts?

[types26/36]

The Lotus jackshaft is a Ford pre XFlow camshaft with a couple of additions.
The Lotus one has a spacer fitted on the front with a longer dowel to line up the chain sprocket.
The other modification is that it has four slots in the front bearing journal as opposed to the Ford jackshaft which only has one slot, this is to increase the oil flow to the head and cams.

[512BB]

'The Lotus jackshaft is a Ford pre XFlow camshaft with a couple of additions.
The Lotus one has a spacer fitted on the front with a longer dowel to line up the chain sprocket.
The other modification is that it has three slots in the front bearing journal as opposed to the Ford jackshaft which only has one slot'

So, as I said, the jackshaft is Lotus specific, no matter what it started out life as. See pic in my engine build thread. Are you posting a picture of your j/s Jon?

Fyi, a NOS correct jackshaft was offered on ebay last year. I wanted it for my NOS Big Valve engine that I have tucked away. Unfortunately I did not bid enough and it sold for £132. Was right miffed. Used correct j/shafts usually sell for around £60 now.

Leslie

[JonB]

Ok.

The cam lobes are clearly evident. Compare with the jackshaft shown in Wilkins, it is exactly the same.

Closeup of the gear damage.

109E marking clearly visible

Anyway, origins notwithstanding, it seems that QED is my next stop. This shaft does work (turns dizzy & oil pump), but I’m uneasy about the missing tooth.

[512BB]

'I’m uneasy about the missing tooth'

I would be too, but would not use, which is a shame, as the bearing surfaces are in great condition. You have a model boat anchor there. The bad news is, it was the correct j/s.

Leslie

[promotor]

Ok.

The cam lobes are clearly evident. Compare with the jackshaft shown in Wilkins, it is exactly the same.

IMG_4433.jpeg

IMG_4434.jpeg

IMG_4436.jpeg

Anyway, origins notwithstanding, it seems that QED is my next stop. This shaft does work (turns dizzy & oil pump), but I’m uneasy about the missing tooth.

Jon,

I've modified used Anglia / Cortina etc camshafts to use as Lotus jackshafts - an extra three oil slots need cutting into the front bearing surface to give a total of four slots, and then you just remove the spacer plate and dowel from the old jackshaft and fit to the replacement.
Starting with a camshaft that is in good condition in terms of the bearing surfaces, skew gear for the oil pump and distributor and an unworn lobe for the fuel pump plus machining may well be a good alternative if you can't find a good used jackshaft.

The last jackshaft I had from QED had just the one slot and a continuous annular(?) groove around the bearing journal to give a constant supply plus an additional pulse of oil every revolution.

Cheers.
Al

[jono]

shortened one on Ebay now at £20 BIN.

...but it's in someone's basket so be quick

[2cams70]

The last jackshaft I bought from QED was bent. Whilst it rotated fine in the bearings the clearance between it and the thrust plate was inconsistent around the circumference. It may have just been a one off but the OEM original parts are most often best. BDA jackshafts had the annular groove standard but they also had an oil restrictor orifice in the block gallery.

[JonB]

shortened one on Ebay now at £20 BIN.

...but it's in someone's basket so be quick

I don't think that will run the fuel pump. The lobe on mine is after the middle bearing jornal.