Distributor restoration - Pontiac GTO Forum
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post #1 of 18 (permalink) Old 09-26-2019, 04:25 PM Thread Starter
 
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Distributor restoration

I have a timing issue with my '67 GTO 400. It runs best with the base timing at 39* BTDC at idle. No pinging but overheats quickly. Not sure why it won't run if I set the base timing down in the 8* range. I'd like to have my distributor tested but can't find anyone locally that has a distributor testing machine. I went to 4 different restoration shops & talked to 4 different mechanics and they all told to to can the stock distributor and put in an MSD electronic distributor. I'd rather not.

I've found several distributor restoration shops searching online. Has anyone had any experience with a distributor restoration shop? Any recommendations?
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post #2 of 18 (permalink) Old 09-26-2019, 05:21 PM
 
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Originally Posted by NDExpat View Post
I have a timing issue with my '67 GTO 400. It runs best with the base timing at 39* BTDC at idle. No pinging but overheats quickly. Not sure why it won't run if I set the base timing down in the 8* range. I'd like to have my distributor tested but can't find anyone locally that has a distributor testing machine. I went to 4 different restoration shops & talked to 4 different mechanics and they all told to to can the stock distributor and put in an MSD electronic distributor. I'd rather not.

I've found several distributor restoration shops searching online. Has anyone had any experience with a distributor restoration shop? Any recommendations?
Gotta be something wrong. With the vac advance unhooked & hose plugged, (You DID have your vac adv unhooked, right ?) it should idle OK at somewhere near 10° or a little more. Back in the old days, I set my 455 bracket engines at 13° initial. Some like as much as 18° or even 20°.

I'm guessing that if your timing light is accurate, the outer section of your balancer may have slipped.

Think about this. Most engines run best at 4000 or more rpm, with aprox 32-36°. But, if you have 39° at idle, that would put your total advance , at 4000 rpm +, about 50°, if your centrifugal only adds 10-11°. And most dist are set up to have more than 10°. I've read of some that set theirs up with 12° initial & 24° centrifugal, so they'll have 36° total mechanical. Then, for street cruising, they also run a vac advance to add a little more at low rpm cruise conditions.

You mentioned overheating quickly. It is commonly posted that low advance can cause overheating. So, maybe even tho your timing light is showing 39°, your ACTUAL timing is MUCH lower.

What does your timing advance to, as you get to 3000 rpm ? 4000 ?

Opinions about how a timing curve should be set up varies all over the map.

Pontiac Street Performance - Initial Timing Question

https://www.gtoforum.com/f170/timing...ontiac-125953/

https://www.gtoforum.com/f12/70-455-...timing-110929/

"...Has anyone had any experience with a distributor restoration shop?..."

I recently bought a Cardone rebuilt factory HEI. Probably not high quality. But it was cheap. Paid $80 on Ebay. Guessing that most commercial dist shops would charge 2 or 3 times as much, to rebuild one. I replaced the module, which was a GM #466 , with a Pertronix D72000 rev limiter module. Also added a screw to make a positive centrifugal advance stop. Haven't installed it in the car yet.

https://www.amazon.com/Cardone-30-18.../dp/B000C46K9Y

Cardone also sells rebuilt point dist. Can get 25% online discount code for Advance. Have used it several times.

https://shop.advanceautoparts.com/p/...1851/3850048-P
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Last edited by bigD; 09-26-2019 at 06:44 PM.
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post #3 of 18 (permalink) Old 09-26-2019, 07:11 PM
 
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bigD covered it. If the engine is running hot, it typically means the timing is retarded. Pontiac distributors turn Counter Clockwise.

First thing to verify as bigD stated is the timing gun. Can you borrow a buddy's timing light to verify?

Next is the harmonic balancer. If stock, it will be the 2-piece balancer. Is it possible you have the 1-piece 1968 and up balancer on it? In either case, if original, the outer ring can slip as age deteriorates the rubber bond that holds the outer ring to the inner ring.

The 2 years are different with the '67 being smaller and has a matching timing cover. Enclosed pics of the 2-pc & 1-pc balancer, and '67 timing cover and 1968 & up cover. A mismatch of balancer-to-cover will give wrong readings.

If the timing marks on the cam were off some, and not properly aligned, this could affect the timing marks. Has a new chain and gears been installed lately?

You should not need to swap out the distributor, I don't think that is the answer at this time.
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post #4 of 18 (permalink) Old 09-26-2019, 09:21 PM Thread Starter
 
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Vac advance was plugged off when I tested it. I tried 2 different timing lights and also brought it to a restoration shop where they also tested it. That mechanic said don't believe the timing light with an old distributor. Throw it away and install an MSD. He's also the one that said it was running fine, but I didn't even make it 5 miles from their shop driving 25-30 MPH before my engine temp went to 230 & I had to pull over & let it cool down.

One of the first things I did was replace the harmonic dampener with a new Kaufman Engineering dampener. I also have a new Kaufman Engineering timing cover (my old timing cover didn't survive removal during the engine rebuild). I also have a Flow Kooler high volume water pump & new Desert Cooler aluminum radiator. The fan blows my rubber fender covers off if I try to run the engine with them on the car, so the fan seems to be OK, too.

I had the engine rebuilt by a machine shop experienced with Pontiacs. The owner used to circle track race Pontiacs. He installed a 68 grind cam from Ames Performance. I'm fairly confident he installed the cam correctly.

I pulled the timing cover off to check the timing marks on the crank & cam. Before I pulled the timing cover off I put a compression tester in cylinder #1 & bumped the starter until I got compression. Then I hand rolled the engine until the timing mark on the dampener pointed to 0 on the timing tab. Pulled off the timing cover & the marks on the crank & cam were both @ 12 o'clock.

In addition to overheating there's a flat spot under acceleration in the mid range (probably around 2500-3000 RPM, no tach so I'm guessing). Aforementioned mechanic said my carburetor rebuild done by Cliff Ruggles was a crappy job. Needless to say, I won't be back there as he has no credibility in my opinion. He also told my to toss my Quadrajet & install a Holly Sniper EFI.

I rebuilt the distributor as per Lars Tuning Tips post in this forum, but without actually putting it on a test machine I have no idea how the distributor is acting. I'd like to find someone that can verify that the distributor is actually OK. I've tried indexing the distributor moving it 1 tooth each way from where I had it and the engine still wants to run at 39 deg BTDC regardless of where the distributor is.

I'm kind of at a loss as to what to do next, other than pulling the engine again and having someone else tear it all down & put it back together again.
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post #5 of 18 (permalink) Old 09-27-2019, 08:29 AM
 
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ND sound sounds like a great engine, here is what I would do first. Do what BigD suggested, buy a rebuilt Pontiac distributor at your local auto parts, they are usually Cardone about $60...they have new points and condenser. You can keep those or swap in your Petronix etc.

Get a curve kit for it about 10 bucks, and get a this Vacumn can,

Standard Motor Parts SMP VC 181....rock auto has it,.....O’Reilly auto Parts calls it a BWD V375.

Email Lars and get one of his vacumn correctors, it comes with instructions and that in it will limit Vac advance to 10 degrees.

Try a silver and bronze spring to start. You can use the curve kit weights if they seem to move the distributor less than the ones that came with it. Just by feel on the bench to start with, or use the original weights just to begin.

Drop it in, plug the vac set it to 10 or 12 base, now start it up and with your timing light read max advance,...say it is 38, now you know your
“Centrifigal”......emphasize “Centrifigal” .......advance number....

That is your second most important number....the first being your total advance number...base + Centrifigal. Your total needs to be 36 for all this tuning.

Now add the vac advance...that will give you ten more at idle. In this discussion 10base + 10 vac = 20* idle timing. You likely need more than that, radical cams can take much more at idle, 28*or 30* say.....with 10 coming from vac advance. Not unusual to have 18* base with 10* vac
For 28* at idle......and then 18* CENTRIFUGAL.......for 36 total.

You drop the centrifugal by using a bushing on the points distributor that comes with your curve kit. It will drop the centrifigal timing 3* to 6*

So you may be able to get 18 or even lower Centrifigal, but you don’t have to start out with thar necessarily, you can put the bushing on at any time and adjust accordingly.

ND you say what you base was set at, you say 39*.....was that 39* base?...and Centrifigal never advances? Are there springs on those weights? Or badly stretched weights and they are going all the way out at idle.......

I think you are running hot because your timing is so far advanced and inefficient and your mixtures are all then messed up when you rev it up.

So if you want to try some of this it may help you get it running where it should, it may “like” 39* at “idle “ but it “hates” it everywhere else, ......so that can’t work.

I still see guys do this, they want to turn up their base idle timing real high, they say they tune it by ear, sounds smoother, they have no idea what the centrifigal timing is and they then turn the total timing way up........way past 36 and the detonation zone.....if you don’t know the centrifigal advance you cannot properly set the base timing....no matter how “smooth” it sounds......


A rebuilt distributor will make your setup easier, and you can deal with the one you have later. Recondition it or not.....

Good luck, pretty clear you know this stuff and have done a lot already, I think you are close, you may wind up with 30* at idle and a real smooth engine all throughout the range.
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post #6 of 18 (permalink) Old 09-27-2019, 10:08 AM
 
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Sorry ND,

I just saw that photo of the Cardone HEI you are running....

So let me make the corrections

I would change that vac can to a Standard Motor parts SMP VC 302
O’ Reilly calls it a BWD V482.....you will not need a vacumn corrector. Disregard the point distributor Vac can and curve kit and corrector...I mentioned earlier.

This HEI can will pull 10 degrees and at pretty low vac..you can try an HEI curve kit but those weights may be the same.

Other than that the notes I gave you are the same....you need to find out what the centrifigal advance is in that distributor....

Google this article .......”How to optimize the centrifigal advance in Pontiacs”, by Rocky Rotella.

and you can check the centrifigal advance on the bench......go from there.
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post #7 of 18 (permalink) Old 09-28-2019, 01:58 PM
 
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I hate to mention this, but my 68 400 low compression with a cam and all MSD ignition runs the same way. Don't know exact base timing but it's about 2 inches btdc off the stock scale on the cover.

I've ignored base timing and advance the timing until it pings or the starter strains to turn the motor. Well I couldn't get mine to ping EVER but I did find the point where the starter strained and then retarded the timing to stop that.

Full timing is about 52 degrees. I still have a low speed lurching that I have to deal with. just replaced my valve oil seals and smoking has stopped.
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post #8 of 18 (permalink) Old 09-28-2019, 02:02 PM
 
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Forgot to mention that my 8563 MSD distributor has NO vacuum advance nor will it accept one.
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post #9 of 18 (permalink) Old 09-28-2019, 02:33 PM
 
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"...I just saw that photo of the Cardone HEI you are running..."


Those pics are mine. I have no idea what dist the OP has.
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post #10 of 18 (permalink) Old 09-28-2019, 02:39 PM
 
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Thanks BigD........I thought I was having Deja vu..all over again...when I looked at that thread link I thought I missed his photos.....

Asleep at the wheel I was.....anyway, now ND has the tips for points and HEI distributor, ....either one!
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