New Distributor Vacuum Advance Issue--any ideas??

[matts70]

Timing chain test OK

OK. I tested the timing chain and it's not a problem.

The method used: turned the crank by hand clockwise and noted the rotor turning. Marked the crankshaft pulley. Began turning the crank counter-clockwise until the rotor started to turn, then stopped. Measured the degree the crank turned before the rotor moved.

Total movement, or slack, was 5*. From what I've read elsewhere, this is good.

I can try Viperwolf's test next, unless it essentially indicates the same thing. Any suggestions? I'll keep trying.

 

[broncnaz]

Also inspect your harmonic balancer if the rubber is cracked between the hub and outer ring it could have slipped and is causing a false reading. Might be a good idea to replace before the balancer comes apart if the rubber is cracked/

 

[matts70]

I suggest you set the timing correctly and then find the real problem. That's why you should check the position of the rotor. You should also check the slop in the timing chain. Something is very wrong and it isn't the distributor.

I set the timing at 12* instead of 8* because it won't run at 8. Shut it down and hand-turned the crank to 12*. Pulled the distributor cap and the rotor was dead on the wire to cylinder #1.

I checked the timing chain and have 5 or 6 degrees of slack, so the chain isn't the problem either.

I also checked the vacuum diaphragm on the distributor to see if it might be leaking. It's holding its seal.

 

[Viperwolf1]

You've eliminated valve and ignition timing problems. Start looking for vac leaks or carb idle misadjustments.

 

[DirtDonk]

When I take it down to 8 BTC, it's on the verge of dying.

Start looking for... or carb idle misadjustments.

Yeah Matt. When the engine started to die at 8° did you re-adjust the carb's idle speed screw?
It's all one big symbiotic relationship. You change the timing, it changes the idle speed. You re-adjust the idle speed, it changes the idle/air mixture. You change the idle/air mixture, you have to re-adjust the idle speed. When you do that, you may have changed your base timing again.
And if you have points still, when you adjust the gap, it changed the timing. and on and on and on...
So you have to do "all of the above" multiple times until you achieve a balance.
And are at last one with the engine grasshoppa!

Have fun.

Paul

 

[matts70]

You've eliminated valve and ignition timing problems. Start looking for vac leaks or carb idle misadjustments.

Checked for vacuum leaks--I'm good there. Readjusted the idle on the carb--that's good.

I played around some more. I set the idle at 10* with all vacuum plugged. This is the point at which the vacuum gauge is at 18" and is right on the border between the Normal Timing/Late Timing indication on the gauge. It doesn't run so hot at this setting, but it runs. Once set, I connected the distributor's vacuum canister to full manifold vacuum to try something different and it idled MUCH better. But, timing jumped to 36*. When I'd hit 3500 RPM, the exhaust would start to backfire a little bit. Next, I adjusted the vacuum canister (on the dizzy--turned the allen screw inside the vacuum port) until the engine stopped backfiring when it was run at 4200 RPM. This changed the full vacuum timing at idle to 24*. At 3500 RPM, advance is around 57*.

I realize full manifold vacuum is different from ported vacuum, but this is the best thing I can figure out at the moment to get everything running as good as possible.

Any other thoughts or ideas what might be going on definitely are welcome!

 

[DirtDonk]

Did you ever verify that the alignment of the timing marks with the pointer on the engine. AND that they were right on at TDC on cylinder #1 based on the old finger-over-the-sparkplug-hole test?
That's such a common issue with older engines, especially with Fords that have had multiple PO's, that it's always worth verifying. If only for your own peace of mind when checking stuff, so you can know that the foundation of your engine is dialed-in.

Paul

 

[matts70]

Yeah Matt. When the engine started to die at 8° did you re-adjust the carb's idle speed screw?
It's all one big symbiotic relationship. You change the timing, it changes the idle speed. You re-adjust the idle speed, it changes the idle/air mixture. You change the idle/air mixture, you have to re-adjust the idle speed. When you do that, you may have changed your base timing again.
And if you have points still, when you adjust the gap, it changed the timing. and on and on and on...
So you have to do "all of the above" multiple times until you achieve a balance.
And are at last one with the engine grasshoppa!

Have fun.

Paul

Thanks, Paul. This morning I readjusted the idle mixture screws on the carb at 10* at idle and all vacuum plugged. They didn't really change from where they were beforehand. That's when I tried full manifold vacuum (see my post above). The points were replaced with a Pertronix Ignitor.

 

[DirtDonk]

Yeah, I caught your post just after I hit send. I see you're on the quest, just haven't reached Bronco-Nirvana yet.

I forgot to add, when all else fails and the world is crumbling around you, a bullet down a carb venturi does wonders!

Paul

 

[Viperwolf1]

What do the spark plugs look like?

 

[matts70]

What do the spark plugs look like?

Plugs look great. I had them off yesterday in the middle of all this. Light brown coloration and clean.

 

[broncnaz]

Well that says your not to lean. I say your timing marks on the balancer are off somewhere.

 

[matts70]

Well that says your not to lean. I say your timing marks on the balancer are off somewhere.

Is that possible given the following: when #1 piston was at TDC, zero on the damper is right at the timing indicator. When I timed it to 12*, stopped the engine, and cranked it by hand to the 12* mark--it was dead on the #1 wire post on the dizzy cap.

I recently installed the Performer intake, carb, and distributor, but it was exactly the same way before all that with the stock intake and carb on it. I found this out last summer when the stock 2 bbl was leaking and needed to be rebuilt. When I reinstalled the carb (it was still set at the previous timing point) the timing was out of whack then. Meaning, when I tried to set timing the way you're supposed to--no vacuum connections anywhere and low idle--it ran poorly anywhere in the vicinity of 8-12*. The motor was rebuilt several years ago and it ran fine up until that carb problem, so I never even looked at the timing during that whole period. When it was rebuilt, it was connected to full manifold vacuum (I didn't realize any of this until recently). It ran fine ONLY when run off the manifold, or a high initial advance timing (around 36*) if the ported vacuum was used--which is what I tried after installing the rebuilt carb.

So, I am somewhat surprised with all the changes and checking, this motor still doesn't like to run off ported vacuum at 8* or 10* BTDC. I can deal with it running the way it is, but it definitely is a much greater hassle trying to tune it in and there's a big part of me that really wants to know what is going on.

 

[broncnaz]

Well just wanted to make sure your balancer was ok. As they can slip over time. Its really hard to say as the piston will stay at TDC for a few degrees the time chain has slop of a few degrees and other things like the carnk key way or cam dowl pin can be off a few degrees it all can add up.
Do you know what parts were used during the rebuild?
What type of timing light do you have? standard or adjustable type? If Adjustable I might suspect that its bad.

I still think you have a vacuum leak somewhere. Which is causing a poor running engine at low timing settings and possibly a lean condition at higher speed when the engine falls on its face. Or you could just have a lean condtion in both the idle curcuit and at high speed but its good at medium cruise.

Does the engine run smoothly at all engine speeds? You might also try noting how much vacuum the engine pulls when normally driving on flat ground.

 

[matts70]

Well just wanted to make sure your balancer was ok. As they can slip over time. Its really hard to say as the piston will stay at TDC for a few degrees the time chain has slop of a few degrees and other things like the carnk key way or cam dowl pin can be off a few degrees it all can add up.
Do you know what parts were used during the rebuild?
What type of timing light do you have? standard or adjustable type? If Adjustable I might suspect that its bad.

I still think you have a vacuum leak somewhere. Which is causing a poor running engine at low timing settings and possibly a lean condition at higher speed when the engine falls on its face. Or you could just have a lean condtion in both the idle curcuit and at high speed but its good at medium cruise.

Does the engine run smoothly at all engine speeds? You might also try noting how much vacuum the engine pulls when normally driving on flat ground.

• I don't know what parts he used to rebuild it, but it's highly likely the rebuild parts came from Napa--that's where this guy got the rest of his parts to repair things.
• The timing light is a newer Snap-on digital from the neighbor. It was re-calibrated not that long ago.
• I sprayed everything on and around the intake and carb with carb cleaner--no leaks anywhere.
• Engine runs smooth at all speeds, but when it's on the road, it is sluggish. It's missing some torque, or get-up-and-go, when you mash the accelerator. It's a slow and steady acceleration instead of a jump.

I've got two things left to try.
1) I found this article recently and I'm going to follow these steps carefully when I get a chance.
http://www.fordmuscle.com/archives/2000/03/timing/index.shtml
2) Connect the vacuum gauge inside the vehicle when it's running on the road.

 

[Viperwolf1]

You could have a vac leak on the bottom of the intake ports or maybe the pcv valve is stuck open.

 

[blubuckaroo]

IS it possible you clipped the timing light to the #5 cylinder instead of #1?
Passenger side front. I've been there.

Amen to that!
It's hard to un-lern Chevy!

 

[matts70]

You could have a vac leak on the bottom of the intake ports or maybe the pcv valve is stuck open.

Hmm, how would I check for a vac leak on the bottom of the intake ports? What does that mean exactly too?

The PCV valve is brand new. New hose leading to the carb.

 

[Viperwolf1]

Intake gasket not sealing on the bottom edge of the intake port, sucking air from the crankcase. I don't know that there is an easy way to diagnose it other than pulling the intake off. Maybe try to seal everything off (pcv, vent, dipstick) and then see if theres vac being created inside with the engine idling.

 

[broncnaz]

As I believe someone mentioned have you tried putting the points back in? or checked for a full 12 volts going to the pertronix igintion?