HEI/ Manifold Issue

[Jon87V20]

I just bought a 79' Sierra Grande and replaced everything on the top end since it was factory when I bought it. I have an Edelbrock RPM Air Gap for a manifold. After installing everything I noticed that the diaphram for the vacuum advance on my HEI has a clearance issue with one of the runners on the manifold i.e. it runs into it when trying to advance the timing. Has anyone else ever run into this situation and if so what did you do to resolve it? Any advice helps, thanks.

[VileZambonie]

Your distributor is off a tooth.

[Jon87V20]

I don't understand. The distributor will only drop in completely flush in two positions, one being 180 from the other. If I turn it 180 from where it is now it won't run. The distributor its self is sitting flush the way down against the surface as it's supposed to right now. It's just timing adjustment. I can only advance it so far before the diaphram runs into the manifold runner. Hopefully that makes sense.

[Stewart G Griffin]

Your distributor is off a tooth.

(If i could sort of steal the post for a sec, because actually i think my question is related)

Let's say it is off by one tooth.  If we assume there is no interference or that the distributor body (longer shaft) was taller, then wouldn't the engine run fine with no problems as long as we turn the distributor body to comphensate for the rotor being one tooth out of "normal position?"

[Jon87V20]

I'm not sure on that one because then you're potentially messing around valve timing. Perhaps you could. My problem is the distributor can't be just a tooth off because it can only drop in two different ways, either it works or it doesn't.

[78 Chevyrado]

Jon79k15:  to clear the interference just bump the dist a tooth in the direction away from the interference. and try to set the timing.  if no go, try another tooth.   As long as the cap is in the right relative position to the distributor body, it's all good.

The reson the dist will only drop in in two positions is because you'll have to adjust the oil pump shaft to line it up.  Look at the tip end of the dist when its out, it has a hole in the end below the gear that a shaft down in the engine fits into.  That shaft runs the oil pump off the dist.  You'll have to turn that shaft a bit with a long screwdriver to make it line up with the dist when you reposition it.  This is a common problem when putting in a new dist or rebuilding an engine.   Look down the hole the dist. came out of and you'll see the shaft down in there and you'll see how it mates up to the distibutor.

(If i could sort of steal the post for a sec, because actually i think my question is related)

Let's say it is off by one tooth.  If we assume there is no interference or that the distributor body (longer shaft) was taller, then wouldn't the engine run fine with no problems as long as we turn the distributor body to comphensate for the rotor being one tooth out of "normal position?"

Yeah that would work fine.  The only reason you couldn't would be if the power and tach wiring (to the cap) wouldn't reach the cap in the new position.

[eventhorizon66]

Dang-it Chevyrado!  I spent the last 3 min typing and you beat me to it.

[Captkaos]

Actually you can move it over a tooth an drop it in and just bump the motor over and the distributor will drop down when it lines back up with the pump shaft.
Some people feel more comfortable if there is someone holding it , but it will drop.

[Jon87V20]

Thank you, I will give it a try.