Crank Trigger guidance

[jonesb930]

So I am starting to make some forward progress on my project and need some guidance on installing a crank trigger on my 1976 930/50 motor. I currently have the factory trigger as well as the mount to use the flywheel that Patrick Motorsports sells. I plan on using the upgraded scavenge pump from Clewitt with the cam sync sensor as well.


Below is a photo with the mount installation location. My question is, how do I best locate it and make the necessary mounting holes. Does anyone have a process that they can share? Any suggestions would be appreciated.

[flightlead404]

On my engine (1986) those bosses were cast in already. The only thing I had to do was use an angle grinder to make a hole in the transmission bell housing.

[onboost]

Originally Posted by jonesb930

So I am starting to make some forward progress on my project and need some guidance on installing a crank trigger on my 1976 930/50 motor. I currently have the factory trigger as well as the mount to use the flywheel that Patrick Motorsports sells. I plan on using the upgraded scavenge pump from Clewitt with the cam sync sensor as well.


My question is, how do I best locate it and make the necessary mounting holes. Does anyone have a process that they can share? Any suggestions would be appreciated.

Originally Posted by flightlead404

On my engine (1986) those bosses were cast in already. The only thing I had to do was use an angle grinder to make a hole in the transmission bell housing.

The 1986 case being a later (3.2/3.3) unit, the boss and holes are already in place given that G50 Carrera trans was coming for the 87-model year, and of course the G50/50 for the turbo in 89.

I'm actually surprised that the bosses were even there on the 1976 case but assume it's part of case strengthening. I would think maybe someone could trace a pattern that you could use as a template to mark and drill.

Curious, doe this/your motor still have the 6 bolt 2.7 crank found in the earlier turbos or has it been modified/swapped?

[Speedy Squirrel]

I think you misunderstood. They are not present on the 76 3.0 cases.

[jonesb930]

I have this cross posted in the engine rebuild forum as well. Here is a picture of what I am working with. I have the mount and trigger sensor already.

[onboost]

Originally Posted by Speedy Squirrel

I think you misunderstood. They are not present on the 76 3.0 cases.

Originally Posted by jonesb930

Here is a picture of what I am working with. I have the mount and trigger sensor already.

Yes, this is more in line with what I was thinking for an earlier case. That being said, have you reached-out to Turbokraft? If anyone has a solution it would probably be them.

[jonesb930]

After some thinking I believe the safest, easiest proven route would be to just buy the Clewitt kit and put it on the crank pully. I was already considering their serpentine belt setup so what's a few more dollars to just add it there and be done with it. I had the mount and sensor from a box of stuff I ended up with but maybe I can just list them for someone else to use eventually.

[TurboKraft]

Hi,

We are not fans of trigger wheels on crank pulleys, and sensors near the heat of a turbocharger. BTDT, and we consider it a last resort.

All the crankcases had flywheel sensor mounting bosses incorporated starting in 1984 when the case was shared with the Carrera 3.2L. So what to do for the earlier cars?

1982 930
Here's an early EFI conversion running an AEM Series-2. It likes a 12-tooth timing pattern. No problem -- machine the factory flywheel.



Then drill & tap the bell housing for a hall-effect sensor, inline with the flywheel.
You could use a high speed mag sensor, too, it depends on what your EFI system likes.





Easy.

==============================

Now, we usually update the crankcase for a factory sensor mount.
And machine the flywheel for the factory 60-2 trigger pattern, exactly the same angles (for guys using original DME) and utilize a factory high-speed mag sensor.

Here's a 1984-89 case:



Here's a 1978-79 case that's been updated.
Our fabricator made it emulate the factory design, but really, you could do it way simpler: drill and tap the existing flange for M6x1.0mm bolts in the factory positions, and use a pair of aluminum spacer tubes or a block of the appropriate thickness to get the correct sensor bracket offset. The correct offset is when the center of the sensor is in the center of the tooth of the flywheel.
Don't forget to notch the transmission register ring.

We have a template for doing this in the workshop, and one of these days we'll have it as a shippable DIY kit...

[jonesb930]

Chris,

Thank you for this! I already have a brand new factory sensor and bracket. I was thinking I could make a spacer, I have plenty of scrap aluminum and a mill. but don't have a good way to locate the mounting position. There is a reason the factory put it there. I suppose I need to order my Flywheel soon.

[TurboKraft]

Exact positioning will only matter if you are using a factory DME.
Using an aftermarket, the exact position won't matter, just get the sensor gap correct.

[jonesb930]

Chris,

I am finally back on this project. I was sidetracked working on my son's WRX for a while. Can you tell me what the gap should be? I did source a flywheel from Patric Motorsports from your recomendation.

Bill