67 Coronet - 440 Stumbles when in gear

[Schober Motorsports]

Hey guys!

Well I just got my Coronet out to the track for the first time after repainting it and rebuilding the engine, plus all the issues I've had to put up with and it just continues!

Started the car up, warmed it up to 180... When I'm in Park or Neutral, I can hit the throttle and I have perfect response, engine doesn't backfire, or stumble or anything...

Now when I have it in gear and I slam on it, it'll stumble real bad and then die out. If I'm easy on the throttle it'll go, but I just can't hammer it...

Carburetor has been rebuilt and I am at 12 degrees before TDC on initial timing. I got the 6T MSD Box w/ Master Blaster Coil. Its a 440, got a 700cfm Holley Double Pumper on there, Hughes "Whiplash" Cam [.518 Lift], 2500 Stall Converter, and a Cheetah Manual Valve Body installed. I was thinking maybe it was low on trans fluid, because I know that engines do strange things when it's low... But it was right where it needed to be...

All advice is welcome!

Thanks, Craig

 

[67 coronet]

first thing is to check if you accelerator pump is adjusted correctally.

 

[tpodwdog]

ok...you guys might think im crazy....but...just last week i put new plug wires on my car....383....i was SOOOOOOOOOOO careful as to NOT SWITCH any of them.....well,,,,being that nobody can stay the hell out of my barn when im in there with the car...i got distracted and switchd #2 and #6 wires....i didnt notice anything was wrong UNTIL i went to drive it....because it idled nice and revved as it should and acted like nothing was wrong.

when i went to drive it...it spit....sputtered...choked and puked. ALL BECAUSE I ACCIDENTALLY SWITCHED 2 WIRES.. its very easily done!

check your firing order !

 

[Schober Motorsports]

ok...you guys might think im crazy....but...just last week i put new plug wires on my car....383....i was SOOOOOOOOOOO careful as to NOT SWITCH any of them.....well,,,,being that nobody can stay the hell out of my barn when im in there with the car...i got distracted and switchd #2 and #6 wires....i didnt notice anything was wrong UNTIL i went to drive it....because it idled nice and revved as it should and acted like nothing was wrong.

when i went to drive it...it spit....sputtered...choked and puked. ALL BECAUSE I ACCIDENTALLY SWITCHED 2 WIRES.. its very easily done!

check your firing order !

I will, I'd rather it be something dumb like that then something majorly wrong with the engine!!!

Escuse me while i go lose my mind :icon_eyes:

 

[midnightrider1818]

Hey guys!

Well I just got my Coronet out to the track for the first time after repainting it and rebuilding the engine, plus all the issues I've had to put up with and it just continues!

Started the car up, warmed it up to 180... When I'm in Park or Neutral, I can hit the throttle and I have perfect response, engine doesn't backfire, or stumble or anything...

Now when I have it in gear and I slam on it, it'll stumble real bad and then die out. If I'm easy on the throttle it'll go, but I just can't hammer it...

Carburetor has been rebuilt and I am at 12 degrees before TDC on initial timing. I got the 6T MSD Box w/ Master Blaster Coil. Its a 440, got a 700cfm Holley Double Pumper on there, Hughes "Whiplash" Cam [.518 Lift], 2500 Stall Converter, and a Cheetah Manual Valve Body installed. I was thinking maybe it was low on trans fluid, because I know that engines do strange things when it's low... But it was right where it needed to be...

All advice is welcome!

Thanks, Craig

fuel pump push rod is worn down. change that and i bet your problem will be fixed

 

[66 coronet]

Try one size stronger on the secondary spring, sounds like your secondarys may be coming in too quick.

 

[Schober Motorsports]

fuel pump push rod is worn down. change that and i bet your problem will be fixed

I got a electric fuel pump w/ a regulator in the car, running at 7 psi

Instead of changing springs and all that, would it be better to get a mechanical distributor instead of a vacuum one? It really won't see the street too much and its mostly going to be used for drag racing. Also where can I get springs for this thing???

 

[Garys1969RR]

Try advancing the cam 2 deg, longer headers, and maybe a good dual plane like the RPM Perfprmer. What intake are you running now? It looks like a single plane of some type. Those are great for higher end power, but a good dual plane will work better off the line. Also maybe run as much initial advance as your engine will tolerate. Like 16 to 20. Max of 36 deg at 3000 RPM. Good luck, and you need to enhance low end torque.

 

[67 coronet]

in the pics it looks like your dist vacuum is running under your intake for some reason.it should hook strait to the vacuum connection on the pass side of the carb,in the meetering block,with nothing else hooked to it.also,did you set initial timming with the vacuum advance disconnected?you should have to get it right.

 

[Garys1969RR]

To me the vac advance tube appears to be kinked, but may just be the pic. Try 67 s suggestion and run it directly to the carb vac advance hook up.

 

[Garys1969RR]

I think ign timing has alot to do with your issue. I run 15 to 20 degrees initial advance, and my 440 has real good low end response. Just experiment with timing , thats the easiest. So you can eliminate that as a problem area.

 

[Schober Motorsports]

Thats what I'm going to try first, was going to replace the plugs and throw a new wire set while I was at it, mine are all messed up

Also, its just a rubber hose that is going into the carburetor for the vacuum advance, its in the right spot and I know it isn't plugged, You guys are talking about the port that is off the metering block right?

Intake is a TM7, like ya said I believe it is a single plane intake.

 

[Schober Motorsports]

Hey guys,

Put a new set of wires on it and new plugs without any change...

Noticed when I was testing it that my back pumper wasn't really spraying like it should
Took that apart and found out that the little rod that holds the check valve in that pump broke...

I might of just found my issue!

Gonna put it all together tomorrow morning and see where it takes me

 

[tpodwdog]

cool...glad ya got it fixxed...thats a beautiful machine by the way !

 

[Schober Motorsports]

Yep that did it, nice to get all that power back!!

tpodwdog - Thanks man!

Thanks guys for the help!