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Discussion Starter · #1 · (Edited)
I got my motor built and decided to upgrade dist. to a summit unit with the higher coil/module. Anyways what should my initial timing be set at with this head. I had a guy set it to total timing of 36* and it pings. Now I could back off and drive it and keep doing this til it stops, but realistically is there a number. Seems like the timing is way advanced. The vac. module is almost touching the intake. The guy is a good good mechanic, but he does not know about the vortec heads. He runs dart sportsmans and other stuff.

I know with this head you are supposed to run less timing. Also, should I have the vac advanced hooked up to a vaccum source or not
 

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The vac advance should be connected to a full time manifold vacuum source. Disconnect and plug it only when setting the timing. Back off the timing 2 degree`s at a time until the pinging stops is usally all I do. I don`t think there`s a number since every engine is different.
 

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Carlos9 said:
I got my motor built and decided to upgrade dist. to a summit unit with the higher coil/module. Anyways what should my initial timing be set at with this head. I had a guy set it to total timing of 36* and it pings. Now I could back off and drive it and keep doing this til it stops, but realistically is there a number. Seems like the timing is way advanced. The vac. module is almost touching the intake. The guy is a good good mechanic, but he does not know about the vortec heads. He runs dart sportsmans and other stuff.

I know with this head you are supposed to run less timing. Also, should I have the vac advanced hooked up to a vaccum source or not
Vortec heads do not need as much total mechanical timing due to the design. They work very well with the Total Mechanical Timing set in the 32-34 degree range. The timing is checked and set with the vacuum advance dis-connected from the vacuum cannister and plugged off. Re-connect after setting the timing.

I prefer, use and recommend using full manifold vacuum source for the vacuum advance.
 

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Discussion Starter · #4 ·
Yeah, I was told I needed to drive the 87 octane out and replace with 91. We have only 87, 89, and 91 in ca. I've been told that this will solve it. One way to find out is to put some octane booster in it now.. to see what happens. I have to barely drive it or not put a load on it so it doesn't ping. If that does not help, then I'll have to back the timing down a notch.

F-Bird '88 Vac or no vac source to the vac. module. I had it connected without a vac source. We switched it to a vac source off the carb. I was told to put it back the way it was also (may be adding too much vaccum connected) to see what happens. I keep getting told you want a non metered vac source. What's the deal I bought a summit distributor.
 

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Discussion Starter · #5 ·
I called summit tech today and they did not know believe it or not. There is an adjustment inside the vaccum module that you are supposed to use a 3/32 allen wrench for. I turned the timing down a bit because it still seemed to high for vortecs (36*). Before I moved it down, I did put 91 octane.. and it helped a lot, but the pinging was not higher in the rpm band. It seemed ok.. but I went ahead and moved it anyway because it still heard pinging.

Now to the distributor.. I'm about to send this thing back to summit. With my old HEI when I floored it, it would shift the truck and get on with business and be at 90 withing seconds. Now when I hit it.. the truck dies. Should I adjust the thing inside the vaccum adcance. I never had a distrubutor like this before.. so kind of puzzled. Also, I am stil confused as to if I'm supposed to have vaccum to the vac module or not. It seemed to run better with the old dist.

I also put headers.. and I was thinking it would be louder.. it is quieter. This thing is really breathing too good if that's a possibility. A friend mentioned I needed to fatten it up now with headers.
 

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Carlos9 said:
I called summit tech today and they did not know believe it or not. There is an adjustment inside the vaccum module that you are supposed to use a 3/32 allen wrench for. I turned the timing down a bit because it still seemed to high for vortecs (36*). Before I moved it down, I did put 91 octane.. and it helped a lot, but the pinging was not higher in the rpm band. It seemed ok.. but I went ahead and moved it anyway because it still heard pinging.

Now to the distributor.. I'm about to send this thing back to summit. With my old HEI when I floored it, it would shift the truck and get on with business and be at 90 withing seconds. Now when I hit it.. the truck dies. Should I adjust the thing inside the vaccum adcance. I never had a distrubutor like this before.. so kind of puzzled. Also, I am stil confused as to if I'm supposed to have vaccum to the vac module or not. It seemed to run better with the old dist.

I also put headers.. and I was thinking it would be louder.. it is quieter. This thing is really breathing too good if that's a possibility. A friend mentioned I needed to fatten it up now with headers.
WHOA! STOP! You are getting ahead of yourself! BEFORE you fool with the adjustable vacuum advance you need to set the mechanical timing. Dis-connect the vacuum hose from the vacuum cannister and plug the end of the hose. Start your engine and let it get to operating temperature. Increase the engine RPM to between 2500 and 3000 RPM. Check the timing. Set the total mechanical timing to 32-34 degrees BTDC (this number is because you are running Vortec heads) and lock the distributor down. Re-check the timing to be sure that it hasn't moved when you tightened down the clamp. Re-connect the vacuum advance hose. Use a full vacuum port for the source. The engine idle RPM will increase. Adjust the engine idle RPM to between 650 and 750 RPM when in DRIVE. It will be slightly higher in PARK. Road test your vehicle. When going up a slight incline in HIGH gear at about 35 MPH you should not have any pinging. If you do, drop the total mechanical timing down 2 degrees and road test again.

You should not have to adjust the vacuum advance cannister at all for your engine combo.

More than likely there is nothing wrong with the distributor you got from Summit. The problem is with the timing and /or possibly the carb accelerator pump adjustment. I mention this because you stated that the engine dies when you "hit it".
 

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Discussion Starter · #7 ·
Not only does it die, but it does not act like the beast it used to when I nail it. It used to downshift, then get going. Now it never downshifts.. just goes slowly... :( til 90mph now. It used to take at least 3 seconds.. now it's taking 8-10 secs to get up to 90 and it's not opening up like it used to. My tranny also started slipping after I added headers. I think the additional 15hp supposedly sent it over the top. Thanks for the information. I will take to my guy today and say do this. Not sure where my timing is at now.. but it was at 36* and i knocked it down about a qtr.
 

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Carlos9 said:
It used to downshift, then get going. Now it never downshifts.. just goes slowly My tranny also started slipping after I added headers. I think the additional 15hp supposedly sent it over the top.
Assuming you have a 350 trans; is the vacuum line to the modulator valve still connected?

Is the kickdown cable connected to the carb and is it adjusted correctly?

I doubt you gained 15 HP from a header and distributor swap; but even if you did, it should not have "sent your trans over the top". Is the trans fluid level correct?

Forgot to mention this but ALL timing info I have posted is for a non-computer controlled distributor and using a carburetor for fuel intake. The timing info does not apply to computer controlled ignition or fuel injected systems.

Back to the timing. 36 degrees BTDC for Total Mechanical Timing with no vacuum advance present when the timing is being checked or adjusted is usually too far advanced when running Vortec heads.

Drop the timing to 32-34 degrees BTDC and after setting the timing re-connect the vacuum advance hose and use a full manifold vacuum source.

Total Mechanical Timing should be "all in" between 2500-3000 RPM. If it isn't, then the centrifugal weight return springs will have to be swapped out to yield the results. Usually on a GM style HEI distributor, using one light and one medium return spring will get you in the ballpark.
 
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