71 Javelin Surging problem at full throttle.

[ekafrawy]

I installed a new Holley Carb on my 71 Javelin 360, a few weeks back, and it runs ok, but when i stomp on the gas, it surges, and doesn't accelerate smoothly. But if I press the gas abut 3/4 the way down, it pulls pretty hard.

The carb is a 4bbl 650 Holley, and the only adjustments I made to it is the idle. The timming is set at about 5* advanced. The car is completely stock other than that, and only has 35,000 miles on it.
I did replace the plugs, wires, cap/rotor, air filter, and fuel filter.

it was also doing this before i replaced the stock carb. So i thought getting a new carb would help.

Any ideas?

[donsjave]

I installed a new Holley Carb on my 71 Javelin 360, a few weeks back, and it runs ok, but when i stomp on the gas, it surges, and doesn't accelerate smoothly. But if I press the gas abut 3/4 the way down, it pulls pretty hard.

The carb is a 4bbl 650 Holley, and the only adjustments I made to it is the idle. The timming is set at about 5* advanced. The car is completely stock other than that, and only has 35,000 miles on it.
I did replace the plugs, wires, cap/rotor, air filter, and fuel filter.

it was also doing this before i replaced the stock carb. So i thought getting a new carb would help.

Any ideas?
This is just an idea and take it for what it's worth. Try checking the vacum advance on the distributor. Both the vacum advance and the mechanical advance. What it sounds like is the advance curve either isn't there or it's not working at all.
I had a similiar problem many years ago with an Oldsmobile Cutlass which was doing the same thing.After struggling with it for a year I finally found a HEI distributor for it and all of the suden it ran like it should have.
Total advance should be around 24 degrees (give or take about 4 degrees) and it should be oblivious with the use of a timing light and speeding up the idle to about 2000 RPM. You should not see the timing mark when idling this fast. Note: Most factory (AMC) set for the distributor is about 28 degrees total advance about 3800 RPM. I re-curved my distributor to get full advance at about 2200 RPM. It runs great and haven't had any problems thus far with the dist set this way.

[ekafrawy]

Donsjave,
Thanks for the post. I too think that the main cause of the surging at full throttle has to do with the distributor. This is what i have as for timming.

The base timming is at 3degrees advanced. Anything lower and it doesnt idle very well at all. I have a timming light, so to test the advance, all I have to do is increase the rpms to about 2500 and see if the timming mark moves down or not. (Down meaning more advance). My car doesn't have a tach, so i will have to estimate where 2500 rpm is. How do i tell if the vacuum advance is bad or if it is the mechanical advance.


Do you have a new distributor in your car? If so, is it difficult to wire to a stock igniton system?

Thanks,

Eric

[donsjave]

Donsjave,
Thanks for the post. I too think that the main cause of the surging at full throttle has to do with the distributor. This is what i have as for timming.

The base timming is at 3degrees advanced. Anything lower and it doesnt idle very well at all. I have a timming light, so to test the advance, all I have to do is increase the rpms to about 2500 and see if the timming mark moves down or not. (Down meaning more advance). My car doesn't have a tach, so i will have to estimate where 2500 rpm is. How do i tell if the vacuum advance is bad or if it is the mechanical advance.


Do you have a new distributor in your car? If so, is it difficult to wire to a stock igniton system?

Thanks,

Eric
Since I live in high attitude (over 5280 feet) in the Denver, Colorado area here's what I did:

I set the timing at about 10 degrees advance. For the 71 Model year AMC, factory setting should be 5 degrees advanced. My 71 Javelin engine tag so stated this and at sea level it would run fine. At attitude I had to re-adjust the timing to 10-12 degrees advanced. 71 dampners do not read above 10 so I kind of guessed where 12 was. Anyway, it settled in at 10 and I was not going to quibble with it.
When I put in my 401 in last year, I went ahead and installed a MSD distributor. This was a simple drop in unit that still is available. This distributor did not require a box to run it. It is a simple hook up of three wires 2 wires go to the negative and positive sides of the coil and one goes to ground on the engine block. If you want a box, this is option that this distributor can be hooked to, but again it is not a requirement.
The dist can be wired to the stock coil you already have or you can spring for the MSD Blaster coil (I went with the MSD Coil). The stock coil will put out about 20,000 volts where the Blaster Coil is capable of 50,000 volts (at least that is what the box said).
The easiest way for me to tell if the advance is working is put the car on high idle and check the timing. High idle will give you around 2000 RPM. The springs on the dist are normally the stock springs that came on the engine originally. What I did on mine is to change the springs to one heavy and one light. Some people prefer dual light springs while others want to keep it as close to stock performance as possible.
If you want I can see if I still have the stock numbers for the MSD. Just let me know if this will work for you.

[ekafrawy]

Thanks for the info. If I could get the number for that distributor that would be great. I may just go that route.