1973 challenger 440 - dies when in drive or reverse

[josephqatarcarguy]

Why not measure the vacuum? My power brakes work with 7" of vacuum. If you have another car that runs run a hose to that and try it. I would also play with the timing before I bought a new carb, just because in the end I think that is your fix.

i will , the carb is leaking fuel bad to get that sorted first with the timing

 

[josephqatarcarguy]

Yes that needs to tested. I had a 68 Dart no PB it stopped OK, my only street car no PB. You might go that if needed?

ill add a vacuum reservoir , that should sort it out?

 

[super-bee_ski]

think its an aggressive cam and creating less vacuum.......

I agree, as I hear the more data you provide.

 

[josephqatarcarguy]

I agree, as I hear the more data you provide.

heres a vid of her idling at 1100k rpm

 

[josephqatarcarguy]

Lads I can turn the idle screws all the way in with no effect... is it cause she's idling at 1.1 k rpms ?

 

[4406bbl]

No it is because the front throttle blades are open too far usually. You are going to struggle until you get the timing right, as in find top dead center, give it 18 degrees initial, limit the mechanical advance to 20 degrees, and add idle air somewhere else by the way that cam sounds. It may need more. A new carb will not fix this unless you get one with adjustable idle air. Spend a few days online in threads about big cams and idle.

 

[josephqatarcarguy]

No it is because the front throttle blades are open too far usually. You are going to struggle until you get the timing right, as in find top dead center, give it 18 degrees initial, limit the mechanical advance to 20 degrees, and add idle air somewhere else by the way that cam sounds. It may need more. A new carb will not fix this unless you get one with adjustable idle air. Spend a few days online in threads about big cams and idle.

Thanks mate , any quick fixes u can point out ?

 

[4406bbl]

Nothing quick sorry. What I do is the ignition first, as much initial timing as the starter will take. I then get it to idle with the front blades closed, I do this by making a vacuum leak at the pcv valve port of the carburetor, starting with about a 3/16" restriction and move up or down from there. A piece of 3/8" hose with different size holes drilled in it that are plugged with different size bolts will get you in the ballpark, trying one restriction at a time. You want the primary throttle blades almost closed, like 1/4-1/2 turn off the stop, and once the restriction is the right size it will idle and the mixture screws will work like magic. The only quick fix is maybe they were using a vacuum advance can to add timing at idle and it has failed....I doubt it as what you have sounds like it has 5-8" of vacuum in gear. You really need to read up on how to get a strong idle with long duration cams. Tons of info out there. More timing, and more air with the primaries closed is what you need, because of the cam.

 

[josephqatarcarguy]

Timing advance kit bought
Here a pic of the engine bay

 

[josephqatarcarguy]

Hey guys , bought an msd advance spring and bushing kit , pulled the distributor and found it had a red bushing on it which limits the mech advance to 28 ? Hence I could not put much initial on her , anyways I replaced it with a black bushing- 18 max mechanical advance so I can set Initial timing around 18 ? Should give me a total of 36 ? Also timing is at 15 Initial now and I only get 7-8hg vacuum at idle- got her to idle at 850 rpm now

 

[4406bbl]

Is that 7-8" at idle in gear, or park?

 

[josephqatarcarguy]

Is that 7-8" at idle in gear, or park?

In park , shoots right up under throttle, will try bumping timing upto 18 ?

 

[4406bbl]

Yes you could try 18-20 if you only have 18 in the distributor. You will be limited by the starters ability to start the car, and detonation at some point.
The low vacuum is difficult to deal with with an auto trans with a stock torque converter, as it likes to die when put in gear, you will need lots of timing to get the throttle closed at idle, and maybe a bit more idle fuel. Do you have a vacuum advance can on that distributor?

 

[Outsider]

Plug the vacuum lines to the brakes and dist for testing and recheck vac. Change anything that is drawing vac down.

I have 10" of vac w/ a 240deg cam @ .050" lift which pretty much requires a 4k converter and gears in 4s to run well. 7-8" of vac in Park seems very low unless you have a really big cam, in which case you would have to have the valve train to match, ie. adjustable rockers, converter, rear gears, etc.

In other words, keep looking for vacuum leaks. Perhaps a compression check and leak down check.

 

[josephqatarcarguy]

Is that 7-8" at idle in gear, or park?

I need to back out the main idle screw and not the air / fuel mixture screws for them to have an impact ?

 

[josephqatarcarguy]

Once I bump down the idle screwas i increasetiming?

 

[josephqatarcarguy]

Yes you could try 18-20 if you only have 18 in the distributor. You will be limited by the starters ability to start the car, and detonation at some point.
The low vacuum is difficult to deal with with an auto trans with a stock torque converter, as it likes to die when put in gear, you will need lots of timing to get the throttle closed at idle, and maybe a bit more idle fuel. Do you have a vacuum advance can on that distributor?

No , no vacuum advance

 

[4406bbl]

As you increase timing the idle rpm should go up allowing you to close the curb idle screw/ primary throttle blades down, and then see if the mixture screws start to respond. Do not go past 38 degrees total timing at 3000 rpm, no matter what it is at idle.

 

[josephqatarcarguy]

As you increase timing the idle rpm should go up allowing you to close the curb idle screw/ primary throttle blades down, and then see if the mixture screws start to respond. Do not go past 38 degrees total timing at 3000 rpm, no matter what it is at idle.

Took it to a know garage here , the guy said a fitech efi system would solve the problem, is this true ?

 

[4406bbl]

I can't say he is wrong, electronic on the fly adjustability is real nice and saves a ton of time. I have been happy with fi systems I have used.