The Triumph Dolomite Club - Discussion Forum

Turns out that I have a problem with what is now the spare vacuum unit. It looks like it's been bashed or dropped. And while it still works, it means the arm goes too far into the distributor, which then has to be rotated so the screws holding it down are at one end or other of the adjustment slots, depending on how I engage the gears. I may have a go at pulling it back into shape, but as it works, with some issues, I'd like to have another spare in case.

Anyway, I was wondering if anyone knows if the 45D unit fits the 44D? From the pictures on ebay, they look similar at least.

Graham

As far as I understand it, the vacuum advance will be setup different for each engine and car. So the unit may well fit but it would have the wrong advance profile for your car.

I could be wrong about that but that is my understanding of how it works.

I've got some spares, both original and new ones on the shelf, that you're welcome to. Pm me your address and I'll post them to you.
Mark.

cleverusername wrote: ↑Sun May 31, 2020 10:38 am As far as I understand it, the vacuum advance will be setup different for each engine and car. So the unit may well fit but it would have the wrong advance profile for your car.

I could be wrong about that but that is my understanding of how it works.

Given the variation in profile across the 3 different types of 44D4 and that it only affects timing off load on the overrun, to reduce emissions, I doubt it's critical enough to worry about - I've only blown pistons on the sprint from pinking when running on 2 star by mistake, and when the static advance had slipped to something like 30 BTDC. And even that big an advance only did for the piston lands going up Kidstones from Kettlewell to Aysgarth - it's not like Hardknott, but it's still bare steep.

Graham

Looking closely at the vacuum unit that causes the dizzy to be set at one end of the slot or other, it is stamped 54429200, but its poorly stamped and the E in LUCAS ENGLAND is back to front (upside down).

Are there bad copies out there?

Graham

I got the two 45D4 vacuum units (thanks Mark) today.
The obvious differences are that the 54429200 vacuum unit from the 44D4 is bent up at the end that fits to the pin on the underside of the contact breaker plate; the hole in the old style 54424752 45D4 unit is smaller; and the arm on the new type is quite a bit (about 5mm) shorter than either the two old ones. However, that new style one has a hole the same size as the 54429200, and despite not being raised up at the end, fits well enough. I did check at full suck, the breaker plate doesn't hit its end stop first.

But, I got which of the two 44d4 vacuum units I have that has a longer arm the wrong way around, and it's the one that puts the mounting screws in the right place that's longer by about 2mm. So, it's likely that if I drill the hole on the 54424752 to the size of that on the 54429200, it will also have the screws where I don't want. But the new style one may be so much shorter, that it's a full tooth out on the drive, and be back in about the right place.

The other thing is that, if I put the offset in so as to minimize how that shortens the arm, and lean on enlarging the hole so it moves or drill a new one further away from the diaphragm end, that may lengthen it enough to make the position about right.

So, if mark's not wanting it back, I will modify it and try both it and the new style to see if either is a viable solution to replacing a faulty Sprint vacuum unit.

Graham

Keep hold of them. They're no use to me anymore, without a dolly. People on this forum have been so very helpful to me, it's just the start of my unloading parts.
Mark.

marko wrote: ↑Fri Jun 05, 2020 11:05 pm Keep hold of them. They're no use to me anymore, without a dolly. People on this forum have been so very helpful to me, it's just the start of my unloading parts.
Mark.

Thanks Mark, I'll look at modifying the oldun tomorrow.
Graham