chengny
Full Access Member
- Joined
- Feb 22, 2012
- Posts
- 4,084
- Reaction score
- 1,026
- Location
- NH
- First Name
- Jerry
- Truck Year
- 1986
- Truck Model
- K3500
- Engine Size
- 350/5.7
Here are a couple of images showing how the brass fitting needs to be indexed. The centerline of the threaded bores is at a 45 degree angle to the fore/aft axis of the truck. It has to be lined up very close (if not exactly) to this angle, otherwise you will have trouble installing the sender for the gauge indication . I have tried many different configurations and the stock set-up is really the only one that works.
The problem (as you found out) is to find a sweet spot where the fitting is threaded tightly into the block and the bores are at 45's. Overapplication of thread sealant is an issue too, the casing/nipple of the variable resistance sender (bell shaped one) requires a clean connection to ground for proper gauge function. The path to ground is through the threads on the nipple.
Your idea of extending the nipple sounds good at first, but the clearance between the bell and the underside of the distributor is extremely limited. I tried this modification and soon found out it was not worth the effort.
I have found that the best thing to do is use the OEM configuration. If the angle of the fitting is out of spec when you feel that it is tight enough to prevent leaks (but you don't want to back it out and make it too loose) increase the depth/diameter of the tapped hole in the block. If it's tight but still needs to come more in the CW direction, pull it out and run a 1/4" NPT tap down the bore. Try it again. Needs more? Run the tap deeper - it will eventually be tight and properly indexed.
The problem (as you found out) is to find a sweet spot where the fitting is threaded tightly into the block and the bores are at 45's. Overapplication of thread sealant is an issue too, the casing/nipple of the variable resistance sender (bell shaped one) requires a clean connection to ground for proper gauge function. The path to ground is through the threads on the nipple.
Your idea of extending the nipple sounds good at first, but the clearance between the bell and the underside of the distributor is extremely limited. I tried this modification and soon found out it was not worth the effort.
I have found that the best thing to do is use the OEM configuration. If the angle of the fitting is out of spec when you feel that it is tight enough to prevent leaks (but you don't want to back it out and make it too loose) increase the depth/diameter of the tapped hole in the block. If it's tight but still needs to come more in the CW direction, pull it out and run a 1/4" NPT tap down the bore. Try it again. Needs more? Run the tap deeper - it will eventually be tight and properly indexed.
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