HEI distributor tuning problem
 

I switched to a HEI dist. About a month or so ago and I can't seem to tune out the tapping at the 50-55ish speed. I have played with different base timing settings. I have tried a different vacuum advance module? and even went to the heaviest springs in the distributor.
I'm thinking maybe the distributor is just bad?
The motor (350) does have some kind of performance cam in it, maybe that's effecting it? (Vacuum)

Any thoughts?

Thanks!
Joe
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Re: HEI distributor tuning problem
 

Joe, What does tapping mean? Lee

Re: HEI distributor tuning problem
 

what does it do without vacuum advance connected? Still ping?

Also since it has a performance cam, did it get head work too....compression?

Re: HEI distributor tuning problem
 

Valves tapping?
I thought I was having some other noise problem but after reading about another member with same symptoms it dawned on me what it was.
If I disconnect the vacuum advance and cap the port it doesn't make the noise, it just goes to 5 MPG...
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Re: HEI distributor tuning problem
 

Compression is 180, give or take a lb or two at all 8 cylinders.
I haven't tried high octane, but if it needed higher octane it would ping a lot more often... I would think anyways...
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Re: HEI distributor tuning problem
 

I'm taking it that it did not do this with the other distributor? Did you do any maint (assure the shaft and weights were free, etc) to the HEI? Is the gear orientated correctly? Is the advanced stop in tact? Is the shaft end play excessive?

Re: HEI distributor tuning problem
 

I know it may be a redundant question, but before you put the distributor in did you take cylinder one to TDC? It really sounds like you are still out of time a bit something like about 12-16 degrees. I ran into this once.

Re: HEI distributor tuning problem
 

did you verify the initial timing was set properly with the advance disconnected?

Re: HEI distributor tuning problem
 

To be honest I don't know if it did the same thing with the other distributor, because I also changed the exhaust to a quieter one because I couldn't hear crap over the other one. In fact you can barely hear the noise with the quiet exhaust.
The hei is new and seems fine. Shaft fit good, no excessive play.
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Re: HEI distributor tuning problem
 

Yes I did the initial timing with the advance unplugged and I capped the port.

Yes on the tdc question.
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Re: HEI distributor tuning problem
 

As Lee H mentioned if it was a used HEI.

The last used one I got the grease was so dried out it was preventing the mechanical weights from springing back. They would move but sort of stiff.

Check carefully for vacuum leaks and with a "dial back" timing light check regular and total timing. If you don't have one, rent one or borrow one. It's easier to see total timing with one of those.

As far as using higher octane, it's more expensive but one tankful would let you know if that's your problem. .

Re: HEI distributor tuning problem
 

If you have a timing light with dial up advance on it, start the truck with timing light connected and vacuum disconnected and plugged.

Bring the RPM up with the light on the timing mark. You should see it moving advanced. If it doesn't check weights and springs. If it does and still only goes 5 MPH, pull the module.

Re: HEI distributor tuning problem
 

Just a thought but did you mark the Harmonic Balancer when you brought it to TDC?Occassionally the rubber in a HB will allow the outer ring to slip,giving a false reading of timing.

Re: HEI distributor tuning problem
 

Thanks for all the help!

Sounds like I need to get one of these dial up timing lights.
Longhorn70, you misread my post on 5 mpg when vacuum advance is disconnected, gas mileage suffers greatly when the advance isn't connected.

There is a notch/groove in the HB and it matched up during tdc, I have added the timing tape to that.


Since I have the heavy springs, which are supposed to hold the advance from fully advancing until 3,200 rpms, maybe its the weights? Because basically its going into full advance too soon, thus causing the tapping? Am I understanding this correctly?

Thanks!

Re: HEI distributor tuning problem
 

That's the way it should work. A dial back timing light would let you know for sure. Be sure and read the directions on how to use it.

The tapping descripton is still a little confusing to me. When the engine is too advanced the noise I usually hear sounds like a pinging or rattling chains sound. A tapping sound is normally a loose rocker, piston slap or something not tight.

Re: HEI distributor tuning problem
 

If you have a new HEI, chances are you have an adjustable vacuum advance can. To set the vacuum advance you need a 3/32 inch allen wrench. The adjustment screw is located inside the can, down the vacuum line port. You start by setting the vacuum advance to 0 degrees by turning the screw all the way in until it is lightly seated. Then unsrew it to the desired amount of vacuum advance. On my Accel vacuum can, each turn out equates to something like 2 to 3 degrees of vacuum advance. If your HEI did not come with the vacuum advance curve and adjustment directions, you can go online and find these for the Accel units. By adjusting the vacuum advance, you can possibly remove the detonation without messing with your initial timing or mechanical advance.

Re: HEI distributor tuning problem
 

Yep been there done that even tried another vacuum advance just to rule that out.
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Re: HEI distributor tuning problem
 

I gotta quit inhaling gas fumes.........

Another thought, too "hot" a spark plug could do this too. When this happens you will see whitish flakey deposits on the plugs. Or white/grey build up on the center electrode if I remember correctly.

For grins, have you tried octane booster to find out if it is ping or detonation?

Re: HEI distributor tuning problem
 

I just have regular ol spark plugs in it. I didn't go up in heat size or anything.
I'm fairly positive on detonation. It actually makes kind of a tic tic tic sound. Another bit of info, once its good and warmed up, as in after driving 20 miles or so, it doesn't seem to make the noise anymore. I thought maybe its a oil issue, as in oil is thick then thins out once hot. HOWEVER, when its making the noise, all I have to do is pull over, unplug the advance, cap the port and away I go with no noise. So it can't be a oil issue.

Re: HEI distributor tuning problem
 

What brand distributor is this?
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Re: HEI distributor tuning problem
 

I have the same exact problem! That tapping noise happens when you are sort of maintaining that 50-55 mph? If you still have the links to where other people had this problem and feel like PMing them to me it would be appreciated it. I haven't tried to fix it since it only happens at that one speed.

Re: HEI distributor tuning problem
 

The distributor is from Skip White Performance, the last distributor you'll ever buy! I researched it on here before I bought it. I couldn't find anyone with a bad one. Found post bashing them, because they're so cheap (pricewise) but overall quality looks great, billet shaft, decent parts, etc etc and warranty to, they will swap it, I already talked to them. Just worried the result will be the same since I tried a different advance can and springs.

PM sent

Re: HEI distributor tuning problem
 

This is weird....Usually detonation INCREASES with increased engine temp. Yours seems to be going against that.

Most people install colder heat range plugs in mildly built engines is to alleviate detonation caused by increased head temperatures. I have colder plugs in the Olds engine in my truck and that has helped me get rid of ping.

I have a Skip White 6503 on the Olds. I haven't had pinging problems with it either. That distributor has performed well for me.

Could you be running too lean while cold and when it warms up all is good? Like the heat riser isn't there/working or the choke pulls off too soon?

Please post the solution to the issue when you find it.....I gotta know.

Re: HEI distributor tuning problem
 

subscribed!

Re: HEI distributor tuning problem
 

big difference in quality from something like a shippy chinese and a real quality unit like msd pertronix


THE BITTERNESS OF POOR QUALITY REMANINS LONG AFTER THE SWEETNESS OF LOW PRICE IS FERGOTTEN