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Discussion Starter #1
Daughters problem turned out to be engine related. What she thought was tranny slipping was really engine surging. It would have been nice to find that out b4 I pulled the valve body! Next time, I will drive the car first!

Her setup: 289, 2V 2100, petronix, 51K miles.
Engine setup for 10BTDC, engine pulls 21 INHG vacuum at idle. Idle adjustments out 1.25 turns. Engine stall test passes, (full throttle with brake on). PCV valve checks good. Just pass idle, the engine starts to surge, doesn't want to rev freely. A little more throttle and you can hear the engine RPM changing with steady throttle. Vacuum gauge goes up to about 22 INHG then starts jumping about 1 INHG at bad spot. Engine getting about 10 deg spark advance with just mechanical. With vacuum, it goes off the marks. On the road, you can feel the car surging. I tried pulling each plug wire, engine drops RPM each time. Then I started thinking bad coil but that should have showed up durring stall test with missing and roughness. I pulled carb top and float level checks right on at 27/32" wet.
Flat cam? I am aware that I did not brake the cam in right.
Any other brain storms, or farts in the case of older VMFrs.
ty
Eric
 

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Easy things first.I could be wrong but 1 1/4 turns doesn't sound like a lot.Have you tried backing them out any further?The air bleeds could be dirty,try short blasts of carb cleaner through the orifices while it's running.Most likely the vacuum advance has been replaced with a generic replacement,sometimes these have way more advance than the original did and could very easily be your problem.Try driving it with the vacuum advance disconnected,but make sure the mechanical advance isn't sticking.Just twist the rotor and if there's any resistance it will be obvious.I've seen many of these rust stuck on the shaft.One last thing,the high vacuum reading doesn't mean there can't be an air leak.I've cured similar problems by coating the carburetor base gaskets with white grease.It swells the gasket and makes it seal much better.I'll be up for a while if you're still working on it,let me know what you find...
 

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I think you hit the nail on the head. Especially with the vacuum diaphram and too much advance.

Just like to throw my $.02 in, the bores for the throttle shaft might be worn excessively, leaning out the fuel mixture even more.
 

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Discussion Starter #4
Hiyas
More info for you. The distributor was blue printed to stock specs about 35k ago. That doesn't mean it couldn't have some mechanical sticking on the advance. Koger's Distributor did the work in March of '99. Specs call for 11 degrees mechanical and thats what I saw. Vacuum calls for 9 deg and thats looks pretty good too so lets rule out distrib problems?
The carb is spotless as it was rebuilt about 5k ago. I agree with vacuum leak, I just gotta find it!
 

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I have had this problem too with a new vacuum advance.. I also couldn't advance it to about 7 degrees pre-advance. With no pre-advanve it didn't surge(popping/hesitating) anymore but the engine acted a little weak. I put some shims in the vacuum advance to make the spring a little tighter so i could advance it again..

Maybe i bought the wrong advancer or is it normal that it needs to be shimmed??

Thanks in advance
Richard
"The Netherlands"
 

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How much initial spark advance(vacuum advance plugged,idling)does it have?Stock cams don't like a lot of timing.Advanced more than 2-3 degrees over the factory spec can be misleading,it will sometimes increase throttle response but reduce part throttle torque and the engine will feel somewhat lazy.The symptoms you describe are worse than this but you may have two or three small things working against you.I would make sure the initial timing is set at 5-6 degrees,no more until the problem is absolutely diagnosed.Next,check the fuel filter,it could be a simple fuel delivery problem.It most likely is a vacuum problem but the other things I mentioned can contribute to the condition and make it more difficult to diagnose.One last thought,make sure the idle speed is no more than 550 when you check the initial timing,any higher than that the mechanical advance could be moving and give you a false reading.Let us know what you find....
 

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You were dead on.Many replacement vacuum advances have way too much travel,and I've had so many jobs come to me after someone retarded the timing to make it run.Carbureted engines with mechanical distributors haven't been manufactured for many years now,and simple tuning on them is becoming a lost technology.I guess twenty years from now,people will stumble onto this site and have no idea what we're even making reference to....
 

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Discussion Starter #8
Great suggestions, keep them comming. I checked the fuel delivery by running the engine sans carb top right after I checked float level. Float level was steady and I saw good gas flow into float seat. I picked up a new coil, just for grins. I don't have hope that it will fix anything. the spark looked weak when I checked for dead cylinders.
I'm still betting on vacuum leak but I don't think it was at the carb. The previous carb had a bad base and its symptoms were erractic idle and low vacuum. I will check timing again and see if a little retard helps.
ty
Eric
 

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I'm sure you're checking all potential vacuum sources,but don't forget the modulator.Block it off at the manifold and try it.I'll give it some more thought and get back with you later.You can send an e-mail if you like,I can answer you quicker that way.I have a lot of paperwork to do and can't monitor the site as much as I'd like to today..
 
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