ROG100

The roller arm and new tensioner is the straw that broke the camels back.

heinrich

Yessir it is.

ROG100

I will recommend we stick with the original setup and do a visual/tension check every 12 months.
Thanks for all the wonderful advise.

worf928

PET shows the same tensioner part number for 85, 86 and 87 USA motors? 928 105 066 00.

so why is the tensioner different?

Garth S

The same tensioner will work, as will the center cover; however, the S4 carrier arm is needed for the revised mounting of the idler when switching to the S4 type pump as noted in my previous post.
The cover issue comes into play if the cross brace is added .... otherwise, no change.

I've thought of drilling & tapping the head of a pivot bolt and making a cross brace to the old style pump - just haven't bothered yet .... will do it first on some poor unsuspecting 928'er who wants a hand with a TB ...

marton

Should not; as somebody else posted - all the gears & rollers are in the same vertical plane - if not in the same vertical plane, then the TB would not run straight.

Marton

heinrich

OK

For the '85 Euro I did this on, what I listed is correct but that is, granted, a 16V. The US 85/86 pumps have no boss for the little brace but I can't say for sure if that is on the S4 plane or not. I am pretty sure that the hole of the S4 arm (that you need Rog) and that of the 85/86 are different I/D's because the S4 bolt and the 85/86 boss are different O/D's. Garth can you confirm/deny?

So, Rog, I'm sorry, looks like you need an updated roller but NOT a tensioner, because the tensioner and arm are already in the same plane. Let's let Garth confirm. About the arm, we need to make sure the I/D of it is good for S4 pump.

Garth S

HH, it is a real schmozzle of parts - but I see your point; maybe this will unschmozzle some of it .

From the better close up attached, the 'S4' set up on the left is compared to the early generation 32V ( and some of the last 16v).
All pivot studs and bolts are of the same 12mm diameter - and both use the same bushings in their respective arms: the stud has 38mm of working length for the bushings as compared to the 28mm distance of the bolt. With the latter, there is also the 6mm thickness of the underlying spacer .... plus the height of the water pump boss. The boss is absent on the S4 gen. pump. These features are combined to set the large tensioner roller in the vertical plane of the TB & drive components.
It is the presence or absence of the pump boss that dictates which carrier arm and idler roller to choose .... for the pumps are otherwise identical [ the last gen pumps have additional reinforcing ribs cast in as well as additional tapped holes for the cross brace - but are dimensionally identical].

Anyway, the pic says it better than I
The idler rollers are almost identical, but the S4 version shell has a #6905 bearing pressed in vs the # 6004 used for the early 32v.

worf928

Garth? I don't suppose you have any images of the different water pumps? That would complete the picture.

Bill Ball

Yeah, the same question came to my mind. Garth has already pulled a lot of part rabbits out of his hat.

worf928

Surely Garth isn't out of Rabbits? Say it ain't so Garth

Garth S

Put two rabbits together ..... and wait a few days ..... should be 'wots of wabbits' in the near future.
Hummm - I've got a S4 pump here, no 16V pump - but maybe some pics: Actually, I think Roger previously posted excellent pump pics back when a hacked uprebuilt pump would not allow the cross brace to fit.

H2

Interesting topic...good start for an article on "How To" update your early car's Idler Roller and Cam belt System to S4 standards....

I wonder if there's any market for an update kit?

Harvey

ROG100

Once all the parts are recieved I will post pictures and try to show everything side by side.
Last part to arrive is the roller carrier arm. Coming from Germany.
Roger

ROG100

Attached is a list of the old & new part numbers showing what needs to be changed.

I just modified the file with an update on the idler roller number