Engine Running on when Timed Correctly - Team Camaro Tech
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post #1 of 11 (permalink) Old Apr 29th, 04, 04:12 PM Thread Starter
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Help!

I'm just finishing up a front clip off resto of my '68 Coupe/327/lumpy cam/Holley 4bbl. The only changes I have made to the engine during the resto are:
(1)upgrading to Pertronix IgnitorII/Flame
Thrower Coil/Low Resistence Wires/Header Plugs.
(2)rebuilding the Holley.

Before the resto, she liked to be timed at 3 degrees BTDC. Now if I set her at that, she runs great but will not shut down when I turn off the ignition. She only shuts off if set at 4 degrees ATDC and doesn't run as well at that setting.

I was very careful when reinstalling the distributor with the Ignitor and have checked the rotor to make sure it's pointed in the right direction. I did put in a new ignition switch before all of this after I thought the old one was shot. Could this "new" one be the problem or should I look at other angles. I also have had problems setting the automatic choke, could this be the culprit? What kind of timing change should I expect with the Pertronix unit?

Someone set me straight, if I had any hair left, I'd be pulling it out!

Thanks in advance,
Dan

68 Std.Cpe./327/Saginaw 4spd./10 bolt 3.08(all numbers match)
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post #2 of 11 (permalink) Old Apr 29th, 04, 05:28 PM
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Have you confirmed that the timing point is aligned with top dead center? It is common for the dampner and pointer to be mismatched. Also the dampner ring can slip If so your 3BTDC or 4ATDC may really be off by 10s of degrees. I don't know too many engines that will run at 3BTDC.

Dave
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post #3 of 11 (permalink) Old Apr 29th, 04, 06:54 PM Thread Starter
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Did I mention the fact that this engine sat for a few years while I did the resto! There was a full tank of gas in the tank (of which I added Sta-Bil a few times) and I was pretty diligent at squirting oil into the spark plug holes every once in awhile. Could old gas cause this dieseling problem?

dnult-
I will check for TDC alignment tomorrow and mark the dampener across the front to see if it slips.

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post #4 of 11 (permalink) Old Apr 30th, 04, 01:08 AM
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Fresh fuel certainly wouldn't hurt. And a good romp on the street would be good.

Years of oiling the cylinders would definitely create some carbon deposits in the combustion chamber. These deposits remain hot and ignite the air/fuel charge without spark, hence, dieseling.

Once you get the car on the road, pour in a car of fuel cleaner to help remove the carbon in the combustion chamber.

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post #5 of 11 (permalink) Old Apr 30th, 04, 09:31 AM Thread Starter
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Well, it's always an adventure!

First off, I noticed that when I put the new distributor cap on, I had the right firing order but each wire was rotated counterclockwise two positions from where it should be. After correcting that, I needed to rotate the rotor a few clicks until I could get the car started.

Then I took dnult's advice and checked for TDC markings after taking out the #1 plug and cranking until I could feel the piston at the top. He was right! My dampener mark was off by about 10 degrees! I ended up setting the timing at 2BTDC (in reality more like 12BTDC).

It still diesel's a bit but if I shut it off in gear and let out the clutch, it shuts right off. I agree with Everet#2390 that it's probably the old gas (which is about used up) and all the carbon build up. I'll add new gas and put some Seafoam into it when it hits the road (no front sheet metal on it yet).

My next question is, shouldn't the timing mark jump around with the vac advance hooked up and running at idle? I don't get measurable vac pressure out of the carb outlet at idle and I get 10Hg at 2,000 rpm. I know I have a heavy cam which is probably causing this but since I don't have idling problems is it anything to worry about?

Thanks for all the help, this a great site!

Dan

68 Std.Cpe./327/Saginaw 4spd./10 bolt 3.08(all numbers match)
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post #6 of 11 (permalink) Old Apr 30th, 04, 09:44 AM
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Sounds like you're using ported vacuum for the distributor. Try using manifold vac from the port in front on the carb baseplate.

Also turn down the idle screw on the carb, my guess is that's your problem.

With manifold vac, the idle should go up, so I'd say re-adjust the curb idle down and mixture screws for highest vac..

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post #7 of 11 (permalink) Old Apr 30th, 04, 02:57 PM
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I agree with Don. Manifold vacuum for the advance, reduce the idle, and possibly take out a few degrees of base timing and it should run much better.

Dave
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post #8 of 11 (permalink) Old May 1st, 04, 03:23 PM Thread Starter
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OK guys, next chapter in this saga--

I hooked up the vac advance to manifold pressure, and no change! I tested the vac pressure coming from the manifold port and it was 7Hg @ 700 RPM. When checking the timing with the vac hose hooked up to the distributor, the timing mark did not move around. Am I right in assuming that the vac cannister is shot?

I do appreciate the help!

Dan

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post #9 of 11 (permalink) Old May 2nd, 04, 04:14 AM
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You can use a vacuum pump to test the canister. It should hold vacuum when you pump it. However, if your timing is already advanced far enough, you may not see any difference with the canister connected. Next time you pull off dist cap, also inspect the condition of the weights and springs....make sure all is moving smoothly...If your advance is all in too soon, you may want to try a different set of springs.
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post #10 of 11 (permalink) Old May 2nd, 04, 07:00 AM
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As for your run-on problem you are having to open the throttle blades too much. This can be caused by the sec throttle blades not being adjusted correctly but is usually the pri throttle adjustment controled by the idle adjustment screw.

To test what I'm saying, set your initial timing to 12 degs btdc (what ever your pointer says to really be at 12 degs btdc) with the vacuum adv disconnected and plug the source. Then turn the idle screw until the idle comes down to about 600-700 rpm. Now adjust your idle mixture for highest idle or most vacuum if you have a vacuum guage. Idle may go up so re-adjust using the idle adjustment. You engine should start and shut off fine now... If you still have run-on you need to pull the carb and adjust the sec throttle blades. The adjustment screw is accessable from the bottom of the base plate. Back off the screw until the blades are closed and then turn the screw until it just makes contact and then go 1/2 turn from there.

Unless you really have a radical cam you should have more than 7" of vacuum at idle (700rpm) The above adjustments should get you more if it can be gotten. 7" may not be enough to activate your vacuum canister. If that's all you're getting at idle raise the rpm to say 1500 and check your timing and your vacuum. Now hook up the vacuum canister to the manifold source and check your timing again. If you don't see a change in timing now the canister isn't working...

...Dennis

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post #11 of 11 (permalink) Old May 2nd, 04, 05:29 PM Thread Starter
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Well I went to shut the car down after warming it up and before making any adjustments and, Voila!, it shut down right away on the first time. I can only guess it was due to the fresh gas I added the other day.

With that solved, I went on to the "vac" issue. Adjusting the idle mix did not get me any more vac at idle. I bumped up the idle to 1,500 like DjD suggested and I was getting almost 20 Hg. But the timing didn't change with or without the vac hose hooked up to the distributor. I'll pop a new vac can in it as soon as I can and update.
Thanks for all the help, I'm learning quite a bit here!

Dan

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