I have a proform HEI distributor with the lightest springs installed. I don't think it came with stop bushings because the mechanical advance goes up until about 4400 RPM. Is this normal? How do I set the total timing in this case? I set it to 38* at 3000 RPM but that puts the initial timing at 20* at 700 RPM. The engine is a L82 350 with full length headers, true dual exhaust, stock heads and a Edelbrock performer RPM intake.

 

Is your vacuum advance adjustable? My Accel HEI performance replacement distributor came with adjustable vacuum advance. I'm not sure on how to set it but there may be a Lars-authored paper under the 'Other' link above (Tech Tips) that may help you in your quest. Post updates!

Figured I'd save you the trouble:

This is for non-HEI but some may be helpful:
https://www.corvetteforum.com/techti...=109&TopicID=3

This is about the vacuum advance units:
https://www.corvetteforum.com/techti...=115&TopicID=3

 

I disconnected the vacuum advance when setting the timing.

 

Hello,
There may be some bushings that are missing that will limit the amount of movement that the weights have when they are spinning. The springs regulate how fast they move to the full out position which is how the full timing before 3000-3500 rpm setting comes from. The bushings should limit the amount of timing that they will contribute to.
The vac advance unit is on top of this timing, and is what will get you to the 52 - 54degrees total.

Check to see if there are any bushings missing that limit the travel of the weights.

kdf

 

Well it looks like I may have purchased another bad item from a forum member. I think this distributor is hanging up. I have the lightest springs in and it still takes over 4000 RPM's for full advance. Is there anyway to fix this problem?

 

Captainmorgan,
There was a thread a couple of weeks ago about a distributor problem that was related to some of the screws in or around the advance plate. During a rebuild someone used screws that were too long and hitting something within the distributor, or the advance mechanism preventing it from achieving a good timing setting. Because of the rotation of the distributor, this would not happen all the time at the same location.

I know that this is not the problem that you are having, but it may be of a similar issue with your distributor. There may be something internal that is either binding, or preventing the proper movement of your weight system.

With the lightest springs you are not achieving full 36 degrees until approx 4000 rpm. That would make you think then that the springs are not weak enough to allow for more travel earlier in the RPM curve.
One thing that I did with my distributor was to make a matrix of springs, timing settings and RPM values. It takes a long time to do, but in the end I had some type of reference to what was really going on.

Something like this.
Spring1 Spring 2 RPM Timing
silver none 2200 36degrees
silver silver 2400 36 degrees
bronze none 2200 36 degrees
bronze bronze 2800 36 degrees.

This may not be the answer you are looking for, but is all I can offer.

kdf

 

I noticed that you tested with out a spring on one side. Can you run without springs on an HEI distributor?

 

In every spring/weight recurve kit I have seen the weights have always been lighter than my stock ones. I eventually pulled some giant super heavy weights out of an older Buick distributor. I had to drill the holes larger and do some custom grinding to get them to work right but now my timing is just right. It was about a three beer job

 

On Lars paper he states that you cannot run the HEI unit without springs.


Remove your distributor cap and rotor. Remove the 2 centrifugal advance springs. Install the rotor and the cap (without the springs). Disconnect the vacuum advance. NOTE: This procedure cannot be used on the HEI ignition systems. Removal of the springs will cause an artificially over-advanced condition that will never be achieved with the springs in place. You can use the basic technique described in this paper with the HEI units (setting timing up to 36 degrees), but to check total timing, you must install a set of soft springs. You cannot remove the springs altogether.

I read on another paper somewhere that it may be possible to run without 1 spring. One reason to take out the springs was so that you did not have to look down an engine running at 4000 rpm, with the fan blades spinning, and trying to determine total timing. By taking out the springs the rpms will be fairly low in achieving the same result.

kdf