I Advance the timing its hard to start I retard it and it stumbles

[treihesse]

I bought this truck and since I have owned It I can not get this thing to run right. It right on the edge. If I have the timing advanced alot it runs good but the engine turns over hard. If I retard it the truck will idle good but stumbles when driving. Should I replace the Dist? I think the vacum advance is not working. I need to get emissions done soon and I need this truck 100%. Please any input. Im 99.9% sure the carb is dead on but I could be wrong. Do Dist. go bad and when they do How do they go bad??

 

[broncnaz]

If you get a stumble when the timing is retarded then that pretty much points to the carb or a vacuum leak. While vacuum advance canisters do go bad they usually dont make that big of a differance and shouldnt cause a stumble if not working. While I hate to see you throw money at parts that may not help you a rebuilt dist is only about $50(at least they were a few years ago) from autozone and they usually have a lifetime guarantee.
When your timing is retarded was does it read at the crank? Also when advanced whats the reading? You could also have a dist that doesnt give enough mechanical advance due to the heavy stock springs which will hurt driveability but still shouldnt create a stumble. I'd still lean towards it being more carb related than iginition.

 

[Viperwolf1]

You can test the vac advance by hooking up/unhooking full manifold vac while watching timing with a timing light. Vac cans are available if it is bad. The only reason to replace the dizzy is if the bushings are worn. This would cause timing to jump back and forth very much like a stretched timing chain would.

 

[treihesse]

where are the bushings

 

[Broncobowsher]

Please detail the stumble a little better. During tip in, steady idle, steady cruise, heavy throttle, transition from cruise to accel?

It could be a fuel delivery issue that you were masking with overadvancing the ignition.

 

[treihesse]

stumble in start up and when shifting

 

[treihesse]

the trick has a checker elec fuel pump but it seems to be working fine. os there anyone on denver who can give me a hand with this or has a shop

 

[broncnaz]

Bushings are inside the dist the shaft is centered by them worn bushings are not as big a issue in a electronic dist as they are with points type dists if they are worn badly then the trigger points on the shaft will usually start rubbing the magnetic pickup they you will have a problem.
Stumble during shift usually points to either having to much or not enough of a accelerator pump shot. Not sure how you get a stumble on startup? Do you mean it stumbles on take off? When you just start pushing the throttle. That also points to accelerator pump or a vaccum leak.
Doubt itys fuel pump related as it would feel as its running out of gas when driving.

 

[treihesse]

The pump was rebuilt and It does it on all three of the setting do I need a smaller shot of gas?? Can you do this

 

[broncnaz]

First you can check to see if its getting to much gas with the engine running open the throttle quick if you see black smoke come out the exhuast it has too much of a shot. No smoke not enough it may be better to do this while driving have someomne watch your exhaust. You need a different sized squirter which is located just under the choke plate they usually have numbers stamped on them you'll have to get a bigger or smaller one depending on your need. Edelbrock sells a kit with 3 different sized squirters to cover all the bases.

 

[treihesse]

Which one would you run?? I just want this crap done with ya know

 

[treihesse]

Im going to buy a vacum tester as well how do I check for a vacum leak

 

[broncnaz]

Very hard to say which one I'd run without knowing if it needs more or less of a shot and not knowing what you currently have. But usually a bigger squirter is needed in my experiance. I have 2 1406 carbs that I got from the pick and pull(one was in a engine fire other just old) they both have different sized squirters and I havent put either on a engine yet I only have one that is engine ready so I cant really say what has worked for me.
Use a can of carb cleaner and spray around the base of the carb or any other area that could be leaking if the engine speeds up you have found your leak.

 

[treihesse]

and a leak like that can cause that much damage>??

 

[treihesse]

stumble on start off??

 

[COBlu77]

Im going to buy a vacum tester as well how do I check for a vacum leak

There are several (probably safer) ways, but I'd use a can of brake cleaner (evaporates quickly and doesn't leave a residue) and spray it around the base of the carb, along the edges of the intake manifold, any vacuum trees or connections. If spraying a certain place makes it idle faster, you have a vacuum leak there. BE CAREFUL DO IT OUTSIDE AND HAVE A FIRE EXTINGUISHER HANDY (caution there for Ward and any other fire fighters).

If you have factory power brakes with the factory vacuum booster, it's a good candidate for an internal vacuum leak. You can tell if it's the vacuum booster, if it stumbles when you have your foot on the brake at a light.

It sounds to me like it's a vacuum leak or a carb issue and changing the timing is only exagerating the issue. It could be many things from your description, but I'd start with looking for a vacuum leak and go from there. You didn't say what type of carb, but idle mixture, jetting, or a bad/wrong accelerator pump are the next place I'd look.

I'm in Arvada and happy to help when it warms up a little. I have a vacuum gauge, timing light etc. Get your Bronco club going and we'll start it off with a tuning session.

 

[treihesse]

I will be sending out emails in Jan. to set up a date for the club. Also I have a Edelbrock 1406 I rebuilt it and put a stage 3 lean jetts in it. I am buying a new dist. because: The balancer shows TDC and the #1 piston is at the top of its stroke so when I try and set timing at 12 degrees or so it bogs down on start off. I think the dist has something broken in it. Maybe its a vacum leak on the vacum tree but the dist need to be replaced so Im starting there. what kind of gaskets are people using on the card the thick rubber ones??

 

[broncnaz]

and a leak like that can cause that much damage>??

Usually not it just causes a lean condition but if the engine is too lean you could burn a piston or valve.