Engine Timing Problems

[wjbarker85]

Howdy all,

Let me preface with the fact that I was having a hot start problem and decided to check my timing. I dont have a dial-back timing light, but I would guess that my initial reading was around 20 degrees (and yes I did unplug the vacuum advance). I adjusted the timing down to 10 degrees and called it a day. The good news is that my hat start issue is gone. The bad news, something is wrong with my advance.

With the vacuum hooked up at idle, i am reading about 16 degrees of advance. If I run the engine up to about 2000 rpms, my timing drops to about 8 degrees of advance. I get a reading of around 20 inches of vacuum at idle and higher rpms and I am running the vacuum advance from the tree on my intake.

My engine is an 80s era chevy 350 with an edelbrock performer 600 carb and a performer intake but otherwise stock.

What could cause this? Other than the hot start issue, my truck ran great before I touched the distributer. Now it has no power and seems to run rougher than normal. I did try a search for something similar, but no results seemed to match these conditions.

Jeremy

[rsandusky]

I see this is your first post. Welcome 

When you adjusted the timing what was the rpm's of the motor?
If it was more than 500-600 rpm's you may have been reading timing with the weights of the mechanical advance working too.

In which case your timing is probably retarded now.

[wjbarker85]

My idle rpm is around 600-700. I see what your saying but how could that cause the timing to retard at higher rpms?

[1979C20]

Because at higher rpms, the timing advance weights in the distibutor activate, advancing the timing. So when you put a timing light on it, the timing is already advanced some. Therefore, its not an accurate reading. So, when the timing advance weights are not activated, it retards the timing since you no longer have that advance.

[1979C20]

Also, if your air/fuel mixture is lean or rich, it can cause problems. Check your plugs and see how theyre burning. Where was the timing mark before you adjusted it, with the vacuum advance unhooked and plugged? Try timing it to 8° BTDC and see how it runs.

[wjbarker85]

Solved.

Thanks for the suggestions. It turns out the top end of the distributor was worn out. Bought a new one and problem solved.

I should have realized that I had an underlying problem when I first checked the timing.