[West Coast GTO]

I just replaced the Davis HEI dizzy ( what a piece of excrement) with one from Summit and fired it up today. Beautiful! The Davis unit has had stripped module securing threads, module electrical connections loose/ bent at pick-up side and has gone thru three modules since new.
What is not visibly beautiful but interesting is now the advance is set at 40 degrees BTDC ( vacuum advance unplugged and capped) with 14 inches of vacuum at idle with the engine running strong. No hint of knocking at acceleration or hard starting/ cranking. If I add the 24 degrees vacuum advance , that bring it to 64 degrees all in at 3000 rpm.
Did I simply plug the dizzy one tooth off when re-installing?
Any thoughts or suggestions?

[Sun Tuned]

Where was this DUI sourced from?
Directly from Performance Distributors or from Summit?

They don’t use 24 crank degrees vacuum advance units.
Not sure how that got on there.

Blowing modules comes from several issues…
1. Bad or about to die ignition coil
2. Welding on the car…mufflers???
3. Jump boxes or jump starting other cars
4. Bad/missing engine ground straps

[Goatracer1]

Also low voltage to the dist. can cause short module life. Lower voltage raises the amperage required by the module increasing the temp.

[chuckies76ta]

What is your initial timing set at.? You need to setup up your initial timing, then setup your mechanical timing all in usually by about 2800-3000 rpm. You can then add vacuum timing to your liking through a vacuum can and connected either ported or manifold vacuum.
Mechanical timing is done with the advance weights by the usage of selected springs and selective bushings.

[Kenth]

Are you checking timing at the correct ignition cable?
#1 is the front cylinder drivers side.

Does the Summit unit use the correct parts for a Pontiac V8, coil, polepiece etc.?

FWIW

[Joe's Garage]

Before you do anything else, make sure that the mark actually indicates TDC.

It's REALLY common for the outer ring to slip on older, original balancers.

[chuckies76ta]

This also^^. TDC #1 compression stroke. You can drop the distributor in where ever you like as long as your gonna fire the #1 plug. Most of us will usually set Dist in so #1 is on driver side though.

[West Coast GTO]

OK. Dizzy came new from Performance Distributors and was set with mechanical advance at 24 from their factory. That new Davis unit had a stripped screw at one location holding in the module, one of the pole wires to module loose and barely making contact with the module and that module lasted for four starts of the car, then needed to be replaced. Coil new with the Davis dizzy, no welding on car, no jumping other cars, and all of the ground straps intact and tight.
Engine was rebuilt 3 years ago including cam, timing chain, damper,crank, rods, pistons, rebuilt aluminum heads and intake with a Cliff built Quadrajet. Initial timing was set at 20 BTDC and ran 13 inches vacuum at 800 rpm and the engine really liked that timing. With the new dizzy, I ran a 12 gauge with from fuse box directly to dizzy, eliminating the 6AL control box and coil. Timing uses #1 cylinder ( drivers front) and vacuum module on dizzy points to drivers side. Yes, Summit unit uses correct pole/module set up for Pontiac and that new unit was partially dis-assembeld/ re-assembeled prior to install. Also, I changed the springs from the Davis unit to the new Summit unit to replicate the Davis vacuum setting and verified with a vacuum pump prior to install.

[chuckies76ta]

Ok so you said initial 20 btdc. Now on new distributor what is mechanical advance? Hopefully not 24 deg as that means you’ll have 42 deg total. Do you actually know how to set initial and mechanical timing on distributor?

[steve25]

I am assuming you have a degreed balancer or a accurate timing tape on your balancer?

[West Coast GTO]

I have a new TDC degreed balancer with the engine rebuild. Yes, the new dizzy has 24 degrees advance, just like the Davis unit had and initial mechanical timing NOW is at 40 degrees BTDC without the vacuum advance for a total of 64 degrees all in.. Yes, I do know how to set the mechanical and vacuum advance as well as degreeing the cam at engine rebuild. Timing was set using a Craftsman adjustable timing light.
One thing I did not mention: When the car died with the Davis unit, I was at 65 mph and the engine died cold with a thump. Car had to be flat bed towed home where I determined the coil was bad and the module was below specs. neither of those components would have caused the thump when the car died. I might assume that the new timing chain MIGHT have skipped a tooth but I can't confirm that unless I pull the front cover/ water pump assembly.

[Sun Tuned]

Well with 20 initial he’s running 44 total with the DUI, plus they likely set it up with a 15 degree vac canister, so that’ll park another 15 and put that at 59.


Why running the timing in outer space? Must be pretty radical setup?

Now the Summit distributor, who knows , but I’ll guarantee it had even more vac adv on it than the DUI did.i know what vac can Perf Dist sends 90% of them out the door with. But now we’ve started swapping stuff back and forth between the two and now it’s a smorgasboard of stuff mixed together.

Question: why didn’t you call them and tell them you had a warranty issue? They’ve got a nice warranty on the stuff and would’ve taken care of it.

If you thought theirs was a piece of junk… wait till you run that summit heap for 6 months…if it makes it that long.

About the only thing I could add here is this…
While we’re modifying brand new stuff, might oughta look into the grease Summit hasn’t packed in the top of the grease well to lube the top bushing.

I’m quite sure you’re gonna need it.

[Schurkey]

Originally Posted by West Coast GTO

the new dizzy has 24 degrees advance

How do you know this? How was it verified? WHICH "advance"? Some coincidence: 24 degrees centrifugal advance, 24 degrees vacuum advance.

Originally Posted by West Coast GTO

initial mechanical timing NOW is at 40 degrees BTDC without the vacuum advance for a total of 64 degrees all in.

Seems unreasonably high--as in the engine shouldn't be running right with 40 degrees initial. WHY are you setting it that high?

OTOH, 40 degrees total advance could be 16 initial, plus 24 centrifugal. Then add in whatever your vacuum advance supplies for a theoretical maximum of 64 degrees. I have the sense that you don't know spark-advance terminology. What you're calling "initial" is in fact "total" and with 24 degrees of vacuum, you're at 64--which is high, but not absolutely insane. Trim the REAL initial to ~8--12, and get a different vacuum can, or restrict the travel of the can you have from 24 to 10--15 ish. (See attachments.)

Originally Posted by West Coast GTO

Timing was set using a Craftsman adjustable timing light.

That's suspicious right there.

Originally Posted by West Coast GTO

I might assume that the new timing chain MIGHT have skipped a tooth but I can't confirm that unless I pull the front cover/ water pump assembly.

Crank the engine with a TRUSTWORTHY timing light attached. If the initial timing is way off from where you set it previously, the chain may have jumped. If it's about the same as what you set it to previously, the chain didn't jump.

The chances of the chain jumping on a relatively new timing set are approximately zero.

[Schurkey]

Originally Posted by West Coast GTO

Initial timing was set at 20 BTDC and ran 13 inches vacuum at 800 rpm and the engine really liked that timing.

Fairly pathetic vacuum given the amount of advance and the RPM. Radical cam?

Originally Posted by West Coast GTO

Summit unit uses correct pole/module set up for Pontiac

I'd love to see a photo of the pickup coil and ignition coil color codes. My guess is that you've got Chevy/Cadillac "Yellow" color-code parts. (Which would make little or no difference except perhaps during cranking.) There's no difference in the modules--just the coils.

Originally Posted by West Coast GTO

I changed the springs from the Davis unit to the new Summit unit to replicate the Davis vacuum setting and verified with a vacuum pump prior to install.

What "springs" are those? The only (accessible) springs in a Delco distributor are for the CENTRIFUGAL weights; that has NOTHING to do with the vacuum advance. You'd need to swap the weights, center-piece AND the springs to get the same centrifugal curve. The springs control how fast the curve comes in--but not the shape of the curve.

There's a spring in the vacuum advance canister, but you'd have to essentially destroy the canisters to get the spring out of one and put it in another, and "good luck" getting the thing back together again.

[West Coast GTO]

So, some months later:
Following advice from Lee;
Quote:
Originally Posted by West Coast GTO View Post
The Proform dizzy really likes 40 degrees at idle after warm up at the crank with vacuum disconnected. I choked it down to 30 degrees and the vacuum number off the carb went down to 12 inches. Car will run and start easily but you can feel it wants more advance.

"I've seen that scenario multiple times, all when the timing chain is off one-tooth."
I removed the pulleys, damper, timing cover and timing gear set and replaced with a .005 under unit from Butler ( I already had the new Rollmaster purchased BEFORE the machine shop line bored the block and I didn't take that into account when i installed the standard size timing chain set, my bad).
All back together now and still, the Pro Form dizzy still likes 32 degrees at idle after warm up with vacuum disconnected. I installed heavy mechanical advance springs from a MSD kit and left the vacuum advance out of the circuit ( that adds another 10 degrees at 3000 rpm. )
I did order a ready to run TSP distributor from Butler to convert back from the HEI Pro Form.

[steve25]

The proform Dizzy likes 40 at warm idle!

This statement is insane and makes no sence!

[West Coast GTO]

Exactly. At idle with vacuum disconnected and engine warm, this engine runs great. If I choke it down to 32 degrees BTDC, it does not run as well but still runs strong. After connecting the vacuum advance can, it advances to 50 BTDC at 3000 rpm. I corrected the timing chain issue, re-degreed the cam ( 108 per cam card) and even tried repositioning the dizzy on the cam by one tooth ( engine would not start and tried back firing)

[Barrier Blue]

Which TSP distributor did you buy from Butler, and how do you like it? I’ve been considering getting the TSP-JM7704 model.

[West Coast GTO]

I bought the ready to run unit with tach lead( black cap). Interestingly enough, the photos and descriptions show a set vacuum can but this one has an adjustable vacuum can. Price fit and size are great. I installed the coils sideways and am having trouble with crank/ run at start up. I will put the coil in the original position( vertical) and run it again.

Originally Posted by Barrier Blue

Which TSP distributor did you buy from Butler, and how do you like it? I’ve been considering getting the TSP-JM7704 model.

[Schurkey]

Originally Posted by West Coast GTO

I installed the coils sideways and am having trouble with crank/ run at start up. I will put the coil in the original position( vertical) and run it again.

Coil position makes ZERO difference.

Epoxy-embedded coils, or oil-filled canister coils...makes NO difference what position they're mounted in.