I'm in over my head

[MustangPaul]

As I said, I'm in over my head.

Here goes. My car (66 GT, 289 4V) has a surge that is especially present at around 55 MPH. This is annoying, so I thought I'd try to fix it. I follow Pony Carbs suggestions and rotate the distributor until the car idles the fastest. I turn it until it can't go any further due to the thermostat housing. Still surges.

About the same time, my present carb started acting up. No problem. I have an extra 4V that was rebuilt by Pony Carb a few years back. I pull the problem carb--gunked up--and put on the new one. I can't believe what a difference it makes. As for that, I'm feeling good about myself.

Anyway, the surging gets worse. I replace the distrib cap--mine was a bit worn--and the plugs as my previous carb was running a bit rich. No difference.

I remember reading that surging can be caused by a overly lean carb setting. I richen the carb settings a bit (1/2 turn in small incriments) and no luck.

So, I give in, get a timing light, a get a pal to teach me to use it. We have the car set at about 6.5-7 degrees, but still surges.

Ok, here's the questions.

A) What is your car timed at? What is too much timing?
B) What in the devil can cause this surging? I'm pulling my hair out in big chunks, and I don't have much to spare!

I realize that I went about this in a goofy way, but timing and carbs is not my strong point. (Yeah, I know. That's obvious!)

Any and all ideas appreciated!

Thanks for reading.

--P

 

[pabear89]

The surge can be from a number of things.
from carb being starved for fuel to a vac leak in the dist advance.
I set my timing as far advanced as possiable short of having a ping.
book calls for 6btdc and it is running at about 14.
But that is what it likes the best.

can you give a better discription of this surge?


PB

 

[Jonstantine]

i assume these are holley carbs? or autolite or something

i would guess fuel starvation
is your fuel pump good and your fuel filter clean

changing the idle screws should not really have an affect on your cruise
you'll need to change the jets to richen up the mixture

 

[MustangPaul]

The surge is noticeable between 45-55 mostly. About a 200 RPM drop back and forth, but only under steady speed. When you stomp on it, it takes off like a rocket. Hold steady at 50 and you feel it.

It also seems to be worse when the car is cold or just fired up.

Does that make sense? It is just so (&*#&(# frustrating as we are having beautiful weather here--not too hot yet--and I'm having to take my gutless, yet dependable, 93 Toyota truck to work.

--P

 

[MustangPaul]

It is an Autolite 4100. Whoops forgot that. I'm running a cheap inline filter before the standard filter on the 66. (Sometimes the gas down here is not so good) I can easily swap out both. The fuel pump is about 2.5 years old.

I didn't know about the mixture vs. jets issue. I know better than to crack open a carb, though.

 

[pabear89]

The surge is noticeable between 45-55 mostly. About a 200 RPM drop back and forth, but only under steady speed. When you stomp on it, it takes off like a rocket. Hold steady at 50 and you feel it.

It also seems to be worse when the car is cold or just fired up.

Does that make sense? It is just so (&*#&(# frustrating as we are having beautiful weather here--not too hot yet--and I'm having to take my gutless, yet dependable, 93 Toyota truck to work.

--P

If your running a vac advance dist, check the vac dash pot for leaks or improper adjustment.

PB

 

[Ozsum67]

The spring under the points plate in the distributor are weak and allow the timing to advance too much at a high rpm. Disconnect the vacumm hose to the dist and plug it and see if it still does it. If it doesn't...... bingo.

 

[brianj5600]

Lean conditions are worse when the engine is cold, so I agree check for vacuum leaks. If that is fruitless, try a jet change.

 

[MustangPaul]

If your running a vac advance dist, check the vac dash pot for leaks or improper adjustment.

PB

PB--Stupid question, but how do I do this?

 

[jesserose17]

Just pull the distributor advance hose from carb and suck on it, if you see the plate is moving - it's good. Also, if you have vacuum pump, you can test it to see if it will hold the vacuum - if it doesn't, replace it.

 

[67GTA-FB429]

how old are the fuel filters?

 

[dodgestang]

If your running a vac advance dist, check the vac dash pot for leaks or improper adjustment.

PB

Totally agree...it sounds like your timing advance 'is dancing'. Know anyone with a spare Dizzy you can 'borrow' for some simple diagnostics. Put in a dif dizzy if the problem goes away you know what to repair/replace.

 

[Ozsum67]

Like I said before, just disable the vac advance and it will stop if that is the culprit. No need to swap out distributors just yet.

 

[pabear89]

Now the 20 bucks for a vacume pump would show if it works or not.
even allow you to run the engine and check with light.

Darn thing I thought I would never use.

Something with timless Wisdom.

PB

 

[Ozsum67]

Now the 20 bucks for a vacume pump would show if it works or not.
even allow you to run the engine and check with light.

Darn thing I thought I would never use.

Something with timless Wisdom.

PB

Mine would cut out at around 3000 rpm. By disabling the vac advance, it allowed me to run it untill the new dist arrived. It runs fine without it, just not as good a performance.

 

[MustangPaul]

When I get home from work, I'm going to pull the hose off of the advance and plug it. I'll post how it behaves and get y'all's feedback.

It's good to have all of this wisdom in one place!

 

[MustangPaul]

Update

Ok all. Sorry I'm tardy in getting back to you. Spent yesterday taking care of my wife after outpatient surgery. We're all home and well. Now, back to the car while my son and wife are both asleep.

Pulled off the distributor vaccuum advance hose today and ran the car. No real difference in the behavior. The surge comes on a tad bit earlier and stays a tad bit later, but is still there.

Have new plug wires and a fuel filter on the bench waiting to go in. Going to replace the vaccuum hose to the distrib. on the off chance that is the problem.

Recap:

• Timing at 6.5-7 degrees
• New Plugs
• New Dist. Cap
• Plug wires to go in
• Fuel filter to go in
• Fuel pump about 2 years old

Any other thoughts other than bringing out the timing light? I have a Mustang Club Picnic this weekend and if we show up in the wife's diesel Jetta, I'll be used for humor.

Thanks

--Paul

 

[jesserose17]

Have you checked the points dwell? I don't remember the spec's... since I have Pertronix.

 

[MustangPaul]

Have you checked the points dwell? I don't remember the spec's... since I have Pertronix.

Jesserose, we're running the same.

Since my son woke up, I'm back. (He's on my lap trying to bang on the keyboard.)

New events.

Put in a new fuel filter on the carb. When I started to loosen it from the carb, it began to hiss as if it was a bottle of coke being opened. I tightened it back and took the line off of the filter. It shot gas all over. There shouldn't be that much pressure, right? I'm ditching the initial filter and going back to just one on the carb.

While I'm sopping up the gas on my engine I notice that my dist is almost touching the thermostat housing timedat 6.5 degrees. I believe that PB said he was running over 10--there is no way I could get the dizzy there. Whatcha think? Wrong tooth?

How big a pain is it to restick a distributor?

--Paul

 

[Ozsum67]

Jesserose, we're running the same.

Since my son woke up, I'm back. (He's on my lap trying to bang on the keyboard.)

New events.

Put in a new fuel filter on the carb. When I started to loosen it from the carb, it began to hiss as if it was a bottle of coke being opened. I tightened it back and took the line off of the filter. It shot gas all over. There shouldn't be that much pressure, right? I'm ditching the initial filter and going back to just one on the carb.

While I'm sopping up the gas on my engine I notice that my dist is almost touching the thermostat housing timedat 6.5 degrees. I believe that PB said he was running over 10--there is no way I could get the dizzy there. Whatcha think? Wrong tooth?

How big a pain is it to restick a distributor?

--Paul

I find my best performance with my timing at 12 DBTDC. I could go farther, so I'd say you have it in the wrong tooth. It's not that hard to restick it. It might be posible that the cam itself is worn out and the timing is just flucuating. If the fuel pump was on a "push" stroke, you may find the line under pressure.