Shims for a distributor

[AndyBill402]

I'm installing an aftermarket intake and a Pertronix distributor in my 383 Stroker. How would I know if I needed to shim the distributor?

[wallaby]

I found this on the subject:

 

Excessive Distributor Gear Wear on Chevrolet:

Problems with irregular distributor gear wear can be caused by the distributor being "bottomed" out on the oil pump or cam walk. This problem can be easily prevented if the proper precautions are used. First, we will cover the problem with "bottoming" the distributor. Bottoming of the distributor usually occurs when engine work such as the block, heads and intake have been milled. This will allow the distributor to sit farther down in the engine. The best method for checking the distributor to find out if it is bottomed, drop the distributor in the engine with no gasket. Also, make sure the cap and rotor have been removed for this test. Firmly hold the distributor against the intake with one hand and with the other, pull on the top plate of the main shaft. Very Important! Make sure you grab the top plate where the weights and center cam are riding. Do Not grab the reluctor (the part the rotor attaches to) because this part has up and down movement at all times. By grabbing the top plate you are checking for any up and down play in the shaft. If the shaft has up and down movement, you are now ready to install the distributor permanantly by adding the gasket and installing your hold-down clamp. If there is no up and down movement in the shaft, then the distributor is bottomed on the oil pump. You will need to add a nylon distributor shim of correct thickness until the up and down play is achieved. Nylon distributor shims are available from Performance Distributors in thicknesses of .030", .060" and .100". When the correct shim has been determined, add the gasket and proceed with the final installation. Always use a gasket with the shims. Warning! Do not stack gaskets in an attempt to raise the distributor height on the intake. Gaskets will compress and the distributor will eventually bottom out. Always use a shim when necessary.

[John Burns]

I used the nylon shims and they leaked badly. I ended up stacking the gaskets. Maybe a steel shim would be better- not sure where to get one.

 

Also - make sure you don't over-shim! It can pull the distributor out of the oil pump shaft... no oil pressure... boom.

[AndyBill402]

Wallaby and JRB,

Great reply. Thanks a bunch. That explains it very clearly. The first thing I'm going to do is check whether or not the distributor is sitting too low. I also have the nylon shims, but if I have to use them I'm afraid they'll start leaking. Maybe a little non-hardening sealant would help. Thanks again.