C2- 67 timing idle question? -I give up!

[Glenn Ochs]

I have a 1967 coupe with 327/300,auto,air. Completely stock except pertronix ignition. The car will simply not idle properly and will die when put into gear. The carb is a brand new Holley 3810(original type). Spark plugs are new. I have pretty much tried it all but I think I have a timing adjustment problem or maybe a vacuum leak or some thing I really don't understand.

I do know when I set the timing,I disconnect the vacuum advance and set it to 6BTDC/700RPM as per the book. When I reconnect the vacuum advance, the idle races to 1500RPM and the timing is 30 degrees advanced. By the time I get the idle to operating range the car will hardly run and will die when put in gear.At this point the timing is quite retarded. The only mark on the advance can is "B1" if that means anything.

I really don't know if any of this is relative, but I truely need input on whether it could be something to follow.Or any other direction you may have. This car has not run properly since I got it last year. Any direction will be appreciated. Thank you in advance for your input. The next step is to sell the thing and buy a C5.

[Duke W.]

Re: C2- 67 timing idle question? -I give up!

B1 is the correct vacuum can - 0@8" 16 deg. @ 16".

I suspect the vacuum can signal port is not providing full manifold vacuum at idle. Is it a CA model with AIR? They have ported vacuum advance and a very different centrifugal curve. Verify from the dist. no. and carb. no. what you have.

If a 49 state version disconnect and set the initial timing at no more than 500 RPM. Reconnect the vacuum can and set the idle back to about 500. Now read the total idle timing. It should be 6 + 16 = 22. If it still shows just 6 degrees remove the vacuum hose and see if it has vacuum. If not you have ported vacuum advacne and either a CA model or the wrong carb or the vacuum advance signal line is not connected to the correct source.

Assuming it shows about 22 degrees in the above test, firmly set the parking brake, CHOCK AT LEAST TWO WHEELS, and place the gear lever in drive. Having a helper hold the service brake is even a safer way to do this. Carefully turn the idle screw to achieve about 475 RPM in drive. If it will idle stabily at 450 go for it.

Duke

[Duke W.]

PS

Once you have set the initial timing a 6, reconnected the vacuum advance, set the idle speed at about 500, and verified that the TOTAL idle timing is about 22 go through the idle mixture setting procedure in your '67 CSM.

Go through the idle mixture procedure again at the idle speed in drive. If the speed changes, reset it to your target and go through the idle mixture procedure again. Keep interating until there is no change.

Duke

[Glenn Ochs]

Re: PS

Duke ... The way you explain it is the way I thought it should work. When I re-connect the vacuum after setting timing to 6BTDC the idle flys way up and timing goes to 30Degrees. By the time I get it back down to proper idle the timing is well below TDC and running poorly. The 6+16 degree method just does not bear out in this case.

The car is not an A.I.R. equipped car. This condition was there before I put the new carb on. It was the original carb prior. Any ideas are extremely welcome. Glenn

[Joe L.]

Re: C2- 67 timing idle question? -I give up!

Glen------

Since the engine was rebuilt, has it ever run properly? If not, I suspect that you have some sort of internal engine problem. First, though, I'd check to be absolutely sure that the distributor has been installed properly and is not "a tooth off". Get the engine at the engine at the POSITIVELY KNOWN #1 cylinder firing position and, at that position, make sure that the distributor rotor contact points to the #1 cylinder position on the cap. Then, make sure that all of the other plug wires are installed correctly on the cap according to engine firing order.

If the engine does have an internal problem, I'd say that it's most likely that the timing gears were not aligned properly when the engine was assembled. Another possibility is an incorrect valve adjustment.

[Patrick H.]

Re: C2- 67 timing idle question? -I give up!

Duke,

A question,

Should the vacuum reading at idle change when he puts the car into gear? In other words, is it possible that his vacuum level dips when his auto trans is engaged and load is placed on the engine, thus making him lose advance and killing the engine? I suppose it would depend if vacuum cans give a "linear" curve.

Patrick

[Glenn Ochs]

Re: C2- 67 timing idle question? -I give up!

Joe... I really don't know when or if the engine was rebuilt. I have not gotten to checking the physical distributor timing persay,but I will tommorow. I can say "without the advance hooked up" and the timing properly set(6BTDC), the engine runs like a dream and will idle at 500RPM in gear like nobodys business. Thank you for your input I'll check it out. Glenn

[Duke W.]

Re: PS

Something doesn't make sense here. The timing should never drop below the initial setting. If you disconnect the vacuum can and set the idle to about 500 then set the initial timing and then reconnect the vacuum can, an increase in speed due to the additional advance is normal and the centrifugal will also begin to deploy by 1500, so more than 22 degrees would be normal.

Three suggestions - verify that what kind of vacuum advance signal you have - ported or full and measure both the vacuum and centrifugal curves against spec. What is the dist. number? Just because it doesn't have AIR now doesn't mean that it didn't have it originally. Do you know for sure the initial delivery state?

Duke

[Patrick H.]

Re: PS

"The timing should never drop below the initial setting."

Generally, yes, but I have a thought. Feel free to correct me if I'm wrong.

Let's say that at 500rpm, his advance springs are already so loose that his weights have started to advance his timing. He doesn't know that, of course. He then sets his timing (although notes it jumps a little), reconnects the can, and readjusts everything. As the now-connected can and distributor are operating the idle speed is brought down, the timing checked, and it has dropped below the initial setting.

Why do I venture this guess? Because it happened to me. I could never figure out my timing problem until my distributor was placed on a distributor machine and the curve mapped out. Once I knew that I had "never seen" base timing and at 600-700 rpm was getting some centrifugal advance already kicking in, it all made much more sense. The distributor was recurved, and has done very well since then.

Just my $0.02.

Patrick

[Glenn Ochs]

Re: PS

Duke...I concurr wholeheartedly about not making sense.
The car is definately not a CA car as I have the tank sticker and it is of east coast origin. I am fairly certain that the timing goes below zero when I attempt to adjust the idle to operating speed with the vacuum advance connected. The distributor is the original by number and build date. It does have the "pertronix ignition system",could this be the culprit? I really wanted to go back to the points system when I got the car. Do you think this would be something to try?

I realy don't know what to do to measure advance curves but I can find someone that does.
Thanks again Glenn

[Joe L.]

Re: C2- 67 timing idle question? -I give up!

Glen-----

If the engine runs like you say "without the advance hooked up", then I don't think that you have a problem with either of the things that I mentioned previously. However, by the term "without the advance hooked up" are you referring to the VACUUM ADVANCE or the CENTRIFUGAL ADVANCE or BOTH?

It's hard to imagine that just about ANY failure mode of a vacuum advance could create the problem that you've described. If the diaphragm failed in the advance pot, then you would have the same thing as NO vacuum advance. At FULL deflection of the pot, it only produces 8 distributor degrees of advance. So, even if "stuck" at full deflection, I don't see how this would account for your problem and it's VERY unlikley that happened, anyway.

Centrifugal advance is another matter. You should have only 1 or 2 degrees of centrifugal advance in at idle, so it should show no significant effect at idle. Improper installation of the centrifugal advance parts or incorrect parts could cause all manner of problems, though, as the engine speed is increased.

There is supposed to be a small, plastic "collar" on the vacuum advance rod end which limits the travel of the rod. Is yours in place?

[Joe L.]

Re: PS

Glen-----

I'd definitely recommend going back to a points installation until you have this problem sorted out. It's possible that the Pertronix unit is bad, WAS INSTALLED INCORRECTLY, or something else in the distributor was "goofed up" as part of the Pertronix installation. ALL VERY POSSIBLE scenarios. I should have suggested this previously.

[Wayne W.]

Re: Wait a Minute

Read between the lines here. He is trying to set the idle by turning back the distributor and not by adjusting the Idle stop and mixture screws on the carb.

[Glenn Ochs]

Re: C2- 67 timing idle question? -I give up!

Joe .... Sorry about that, I mean without the "vacuum advance" hooked up and the line plugged. The distributor rotor can be turned by hand a few degrees and it will spring back, so I assume the centrifigal advance is operational. I will have to look tommorow for the nylon collar you mention on the vacuum advance. Does it go over the turned up end of the advance inside the distributor? Thanks again Glenn

[Glenn Ochs]

Re: Wait a Minute

Wayne ... Not doing what you suggest. Very easy to read that into this though. It is one weird circumstance. I have timed many a Chevy in my days but never with this type of result. I'm leaning more and more on a Pertronix issue. Glenn