Distributor thrust washers - more than one?

[Gordon Watkins]

Is there a reason why there would be 2 thrust washers underneath the distributor drive gear, the ones that notoriously fall into the third piece? I've not seen mention of more than one but mine had 2 and I'm wondering why.

[David Jones]

I used to shim the distributor drive gear to a gap of 20 thou and eliminate the tension spring on race engines for F Vee. Maybe a previous owner was using the same trick?

[Tim Berardelli]

I shim every motor I build to have .010 lift on the distributer drive gear. With the stock shim, a rebuilt distributer with the correct internal shims and lift, it's not unusual to see as much as .040 lift, due to wear on the surface of the timing cover that the OEM shim contacts. This vertical lift creates gross timing changes that alter the engines timing-advancing and retarding the timing while the engine is in operation.

[Gordon Watkins]

Thanks for the informative responses.

The 2 shims under my 031 distributor drive measure .031 each, while the single shim under my BR18 is .050. Both have springs.

[David Jones]

Gordon, as you obviously have the 3rd piece off the case you can check the vertical free play of the drive shaft with the distributor installed. As Tim said if the play is excessive then add shims till it is in the 10 thou area. I could have easily been remembering the wrong number when I quoted 20 thou but I do remember seeing some larger numbers especially when re using VW cases for Vee race engines. By the way the shims are the same for VW and Porsche engines.

[Gordon Watkins]

The 3rd piece with the 031 is now mounted but the BR18 is not. I'm unclear how to check vertical free play. Is it described in the shop manual?

[Jim Liberty]

You could always contact John Jenkins here in So. Cal. He is an expert on distributors. I never do a motor without one of his rebuilds. .................Jim.

[David Jones]

Assemble everything and bolt the distributor down but leave the spring out between the drive shaft and distributor then measure the free vertical play and shim to 10 thou but no less.

[Gordon Watkins]

Got it. Thanks David.

[Gordon Watkins]

PS: Is it possible to check it through the fuel pump hole if the 3rd piece is mounted?

[Paul Lima]

Paul Christensen covered this subject in great detail in the Registry Vol 37, #4 if you are interested in the details.

[Gordon Watkins]

Great article with excellent photos. Makes sense now. Thanks Paul. I'll also go back and read Craig's book again. I won't be removing my just-installed 3rd piece on my 912/SC engine, especially since it was fairly recently rebuilt, but I will be sure and check free play on my yet-to-be installed 1600S cover.

I'm curious how many folks pre install the distributor before mounting the 3rd piece, as the Maestro suggests? Seems like alignment with the crank gear would be tricky. I used the nerve-wracking, slide 'em down the screwdriver method for the shims then installed the drive gear by lowering it with a magnet while guiding it with my finger through the fuel pump opening. Forgot the spring until I awoke in the middle of the night with that "oh s#&t" realization.