SD8 alternator adapter question

[airguy]

I got my SD8 alternator and tried to mount it up on the vacant vacuum pump pad on my IO360 tonight, and ran into a problem. The adaptor currently on the vacuum pump pad is (as close as I can measure it) 1 3/8" deep, and the SD8 will not seat fully on it, it appears that the adaptor need to be about 1 1/2" deep. Does this adaptor come in various thicknesses? I have been unable to find what I'm looking for online, and I have confirmed that the gear is indeed fully seated (the adaptor block itself would stand proud if it wasn't) and the adaptor block is firm against the engine block. Here is a pic showing how it fits up, the gap is right at 1/8".

[SMO]

Greg, the adapter on my 540 is 1.25" - just went out and measured it - and the SD8 fits fine. not sure if there are any differences with a 360.

[Walt]

I have mounted a few of these on O-360's and never encountered a problem. As far as I'm aware, there is only one size spacer/adapter available.

[chaskuss]

Greg,
Judging by the gap, I suspect that the gear on your SD8 is not meshing into it's drive gear. Try rotating the gear one half tooth and try again. While you have it back off, measure the distance from the end of the gear to the gasket mating surface on the SD8's housing.
I have an SD8 in a box. I can measure mine so that you can compare them.
Charlie

[airguy]

I have confirmed that the gear is meshed inside the accessory case (otherwise the adapter will not sit flush against the case) and the SD8 is meshed with the gear splines but the end of the shaft of the gear sits out proud past the end of the adapter by about 1/8", and it needs to be flush or slightly recessed for the SD8 to mate up. Does that gear shaft come in different lengths? It looks for all the world to me like that gear shaft is about .150" too long. If I cut it down it will still make up to the oil seal, I'm just reluctant to start cutting a good engine gear if there is another way. With the gear meshed inside the drive case and the adaptor seated on the case, the spline shaft of the gear sits a full 1/8" proud of the open end of the adaptor. I have enough room on the spline shaft to trim it 3/16" or 1/4" and still seal up on the oil ring.

The SD8 is bottoming out fully in the splines, it's the gear shaft that is too long (or the adaptor is too short).

[DaAV8R]

Someone else had a similar problem with their mags not seating properly not long ago and they had the wrong gear installed in the accessory case. You might check the deck height to the drive gear and compare to another engine.

[airguy]

Originally Posted by DaAV8R

Someone else had a similar problem with their mags not seating properly not long ago and they had the wrong gear installed in the accessory case. You might check the deck height to the drive gear and compare to another engine.

That's what I suspect is the issue here - the gear total length on mine is 3 1/16", and I think it should be about a 1/4" shorter.

[mahlon_r]

4 cylinder and 6 cylinder vac pump adapters and gears are different lengths. But will fit in each other. I suspect you have mismatched installed.
Good Luck,
Mahlon

[airguy]

Originally Posted by mahlon_r

4 cylinder and 6 cylinder vac pump adapters and gears are different lengths. But will fit in each other. I suspect you have mismatched installed.
Good Luck,
Mahlon

Mahlon - what is the cheaper fix? Short gear or long adapter?

[mahlon_r]

see pm...
Good Luck,
Mahlon