[WINGNUT]

I think I'm getting closer to getting my '72 tuned in better.

Before I was setting the timing with the vacuum advance connected, this time I disconnected the advance and set the timing to 14, then reconnected it. Man, does it run better. I gunned it hard and it never backfired, and it actually wants to rev now. Is this the correct method for properly setting the timing? Also what is the proper screw settings for the fuel/air mixture? I had them set WAY out, like 6 or 7 turns. Is the proper setting 3 or 4 turns?

And I also figured out how to set the dwell with my meter. I was hooking up to the plus side of the wire instead of the negative. So the dwell is now set at 30.

["QUICK-SILVER"]

You are right on the timing, it sets with the vacuum unhooked.
The number of turns on the mixture screws is just to get you close, there is no exact number. Run them in till the engine starts to chug down. Then back them out till it smoothes up. For an automatic I give them an extra 1/2 turn.
Make sure it's not idled too high when you set the mixture screws.

I was wondering about your dwell meter when you said how many wires there was where you was hooking it up. Thats why I noted the difference between the + & -.

[Schurkey]

Idle mixture screws should be set for maximum idle vacuum with the engine fully warm--and then turned about 1/8--1/4 turn lean. The final lean adjustment will DRAMATICALLY cut pollution, but make almost no difference in idle quality.

You could adjust for maximum idle RPM--but the vacuum gauge will be easier to "read".

Of course, when you're done, you'd re-adjust the idle speed to spec--and then have another go at the idle mix.

The two (primary) screws should be very close to the same number of turns out. If not, you've likely got internal carb problems. (blocked air bleeds, for instance.)

Most carbs will not have secondary idle mix screws.

[WINGNUT]

On the tuning label on the radiator support it states that the timing should be set with the vehicle in drive and with someone holding the brakes with the vacuum advance disconnected. I figure I'll try this tomorrow to see what it does. Because it almost seems like it wants to run even more advanced....but not by a whole lot.

["QUICK-SILVER"]

The engine idles down when you put it in gear and the centrifical advance reduces timing advance. You can check this with your timing light. The lable is for basic tune up. Engines have different personallities, tune it to make you and it happy.
I like adjusting the carburetor with everything hooked up (vacuum advance and air filter), idling in gear. Setting in traffic is more important than setting in a parking lot.

[66GTO Jim]

One other basic that I didin't see mentioned. When you disconnect the vacuum line from the distributor to set the timing, you need to plug the carb end of the vacuum hose.

Jim

[WINGNUT]

Originally Posted by 66GTO Jim

One other basic that I didin't see mentioned. When you disconnect the vacuum line from the distributor to set the timing, you need to plug the carb end of the vacuum hose.

Jim

I tuned it again tonight with the vacuum advance disconnected but I didn't plug the hose, so I should probably do it again. I had my brother put it in drive and I adjusted it to 14* BTDC, which is at the end of the scale. Is this TOO far advanced?

What will happen if the vehicle is too far advanced in the timing?

I did take it for a spin tonight, I just got back. It ran great. I can break the tires loose from a rolling stop now, I couldn't do that before. The idle is fantastic as well.

The only thing that is unusual now, is that whenever I floor it, the rear squats down and it scoots up to 80 mph like it should, and then it kinda levels out.....almost like there is a governor on it somewhere; or could it be fuel starvation? Other than that, everything else is normal.

["QUICK-SILVER"]

If your having no cranking problem or valve ping, timing is not too high at all. It could probably stand some more 16*, 18*, starter will grunt and valves will ping when you have gone too far.
Check timing again in park with vacuum advance unhooked. Rev the engine and see how far the centrifical advance is moving, it may not be advancing enough. It should move a couple of inches off the timing tab. If it's not, that's probably why it feels like engine has govenors.
If it was starving for gas, it should fall on its face instead of leveling off.

[WINGNUT]

I will check it again tomorrow. After revving the engine in Park, the centrifugal advance should move off the mark and then go back to 14*? -which is where I have it set now.

If it is not advancing enough in the higher RPMs how do I adjust for this? Should I plug the vacuum advance while re-checking as well?

["QUICK-SILVER"]

Originally Posted by WINGNUT

I will check it again tomorrow. After revving the engine in Park, the centrifugal advance should move off the mark and then go back to 14*? -which is where I have it set now.

If it is not advancing enough in the higher RPMs how do I adjust for this? Should I plug the vacuum advance while re-checking as well?

Exactly, With the vacuum advance unhooked it should move about two inches off the mark when you rev it and return to original setting at idle.
The spring loaded weights under the rotor button work the centrifical advance.
A few things can go wrong with the centrifical advance, springs break or wear out and let the button advance all the time, sometimes they just get stuck, rusty or galded.
The weights can be rebuilt. If it's stuck you may need another distributor, if it can't be freed up.
See if it's working first and we'll go from there.
Vacuum advance works at idle and cruise. It doesn't work at WOT.

[WINGNUT]

I just checked the centrifugal timing. I disconnected the vac. advance and put the light on it. I had my brother rev it a few times and the timing mark went way advanced by about 2 - 2.5 inches and then returned to normal. So I guess its working.

Could it be something else? I can give out more symptoms as to what the car does...maybe it will help to pin point something.

The car itself is VERY fumy, almost overpowering. I am just assuming that it has something to do with the lead additive I use. I know that most cars of the era have that smell to them because of the lead. Maybe I am using too much of the additive.

It puffs out some bluish/blackish smoke after it settles down to idle after a rev. But thats the only time it does this.

Thats all I can think of so far, other than that, its running good. I'm hoping its nothing internal. The car has 91,000 miles on it and has never had a rebuild.

["QUICK-SILVER"]

Puffing a little smoke after backing down from a rev? If it quits doing that I'd be worried.
Try setting the timing a little higher sometime and see what happens. Look at the tab and see how much distance it would take to raise it another 4* or so. It might wake it up a little more. If the starter grunts and the valves ping you've gone to far.
I have set them with the mark 1/2 or 3/4" off the plate, to get all the goody out of them.

[WINGNUT]

So the puffing smoke is normal? I was worried it could be something wrong internally. I just brought the timing back down to 12*. I haven't test driven it yet, I might do that tonight. I had it running in the driveway earlier and I stopped it after it warmed up a bit. I tried to start it about 10 minutes later and the starter sounded like it was stressing a little, like it was pausing while it was cranking; almost like a drained battery. But then it started. So I would take that as being a starter 'grunt', so I bumped it back 2*. I'll try that and see what happens.

[WINGNUT]

Well, I just got back from a test run, and it seems just a tad bit more sluggish with the timing set at 12*. So next time I get a chance I'll try it back at 14*. I set it back because it seemed like the started was struggling a bit to start. Plus, its still doing the same thing, when punched hard it will take off strong, and then around 80 mph it just goes blah, and it doesn't want to rev or go any faster. I have never encountered this before so I don't know what it could be. Of course its only a Tomco remanufactured carb, so I might be expecting too much from it.

["QUICK-SILVER"]

blah, That does sound like it's starving for fuel.

[WINGNUT]

It is possible that Tomco gave me the wrong CFM Q-jet. Upon hard acceleration, the rear of the car squats down and starts off strong and gains speed, but it reaches a point quickly where it will refuse to rev higher anymore and the car itself stops charging forward. I'm wondering if maybe there is a mechanical governor on the thing somewhere. I think some Q-jets had this, the lower CFM ones that is.

["QUICK-SILVER"]

No such thing as govenors on quads. Check how far the back air flap will open. While you are holding it open, have some one mash the gas inside the car. Look down the back of the carb and make sure the throttle blades are standing straight up.

Just make sure you are getting full throttle travel and not just under the hood.

If the back air valve doesn't open very far, it is one of the smaller CFM quads.
If you like the way the car runs with this carb, the back half can be modified to open up more.

[lust4speed]

Distributors vary from one to another. Some have very limited advance and you can really jack up the initial, and then others have so much mechanical advance that you have to really limit the initial advance. Best test is to always listen for pinging, and regardless of where you "think" the initial advance should be - back it down until you never hear detonation. The massive variances in distributors is why the posts above tell you to advance it more. You are after total advance between 32 and 36 degrees depending on how your engine tolerates it. If you have the distributor degreed on a machine then you can pick an initial advance number and know where the top is going to fall - or if you have a reliable dial-back timing light you can set for maximum timing and let the initial fall where ever it may.

You have been lucky at this point in the engine has just went soft on you and didn't let you know you had exceeded its limitations by the "rod through the pan" warning. You didn't state whether you had a tach so I don't know whether you are simply exceeding the breathing (heads, exhaust, cam, and manifold) limitations of your setup or if it might be point bounce cutting power.

What have you done to the engine, and what RPM does it drop off?

[WINGNUT]

Originally Posted by QUICK-SILVER

No such thing as govenors on quads. Check how far the back air flap will open. While you are holding it open, have some one mash the gas inside the car. Look down the back of the carb and make sure the throttle blades are standing straight up.

Just make sure you are getting full throttle travel and not just under the hood.

If the back air valve doesn't open very far, it is one of the smaller CFM quads.
If you like the way the car runs with this carb, the back half can be modified to open up more.

I'll check for this the next time I'm free from work, it might be a few days though. I'll post my findings.

[WINGNUT]

Originally Posted by lust4speed

Distributors vary from one to another. Some have very limited advance and you can really jack up the initial, and then others have so much mechanical advance that you have to really limit the initial advance. Best test is to always listen for pinging, and regardless of where you "think" the initial advance should be - back it down until you never hear detonation. The massive variances in distributors is why the posts above tell you to advance it more. You are after total advance between 32 and 36 degrees depending on how your engine tolerates it. If you have the distributor degreed on a machine then you can pick an initial advance number and know where the top is going to fall - or if you have a reliable dial-back timing light you can set for maximum timing and let the initial fall where ever it may.

You have been lucky at this point in the engine has just went soft on you and didn't let you know you had exceeded its limitations by the "rod through the pan" warning. You didn't state whether you had a tach so I don't know whether you are simply exceeding the breathing (heads, exhaust, cam, and manifold) limitations of your setup or if it might be point bounce cutting power.

What have you done to the engine, and what RPM does it drop off?

The engine is a 400 with 91,000 miles on it, it has never been torn apart. It's all original. The car doesn't have a tach, so I'm not sure what RPMs this occurs at. It's at the top end though. I have the dwell set at 30 with my meter (is this also known as the total advance and the initial advance is set with the light?)

I have heard that Pontiacs like to run with a bit of advance. Instead of setting the timing with the timing gun at around 12* or 14* degrees, I should try to set the total advance (points) around 32-36 with my engine analyzer? Maybe I was setting the wrong advance ahead.

I do have a timing light with the timing dial on it, I am not familiar with how to use it though. Right now I'm using a non-adjustable timing light. What purpose does the adjustable timing light have, and what is the proper way to use it. I bought it a couple years ago, its about time I learned how to use it.

BTW, thanks to all who have helped me to try and get this problem solved. I'm further ahead now with my tuning skills than what I was before.