Some 1978 Questions

[Joel T.]

Hi All;

I'm currently finishing up on a makeover of a 1978 Pace Car Replica.. This is not meant to be a show car but rather a fun driver for around the neighborhood and perhaps to the track on a Sunday morning...

The project included swapping out the original (tired and not correct) L-82 for a ZZ383, Edelbrock dual plane intake and a 3124 Holley (service replacement) which I had left over from my L78 efforts.

Everything is back together and running fairly well but I'm dealing with a couple of small issues which I would like to get some thoughts/advice on....

1 - Idle - I can get it to idle down around 900 RPM however if I apply the gas, the idle will drop to perhaps 1200 RPM and sit there until I tap the gas pedal again at which time it will drop to my 900 number.

2 - Stumble - Car idles fine... when I'm driving it I get an initial stumble as the gas pedal is pressed, like a flat spot more or less.. After a second or two, the car will pick up and accelerate. This happens from a standing stop or when running at speed and transitioning from cruise to acceleration mode... I suspect accelerator pump but could use some tips as to process for adjusting (i.e. more or less squirt)

Engine pulls 15" vacuum at idle. I'm running an Accel HEI distributor with a fixed vacuum can full in at 13" (Duke), basic timing is 8 BTC.

Thanks in advance!

Joel

[John H.]

Re: Some 1978 Questions

2 - Stumble - Car idles fine... when I'm driving it I get an initial stumble as the gas pedal is pressed, like a flat spot more or less.. After a second or two, the car will pick up and accelerate. This happens from a standing stop or when running at speed and transitioning from cruise to acceleration mode... I suspect accelerator pump but could use some tips as to process for adjusting (i.e. more or less squirt)

Joel -

Have you done the accelerator pump adjustment exactly as outlined in the Chassis Overhaul Manual? Some folks miss the step where you hold the throttle plates at WOT with the pump operating lever depressed when you make the .015" clearance adjustment. It takes three hands, but when this is done properly, you'll get a shot of fuel from the squirter instantly with the slightest movement of the throttle lever.

[Joel T.]

Re: Some 1978 Questions

Joel -

Have you done the accelerator pump adjustment exactly as outlined in the Chassis Overhaul Manual? Some folks miss the step where you hold the throttle plates at WOT with the pump operating lever depressed when you make the .015" clearance adjustment. It takes three hands, but when this is done properly, you'll get a shot of fuel from the squirter instantly with the slightest movement of the throttle lever.

John,

Thanks for the response... I do not have the chassis overhaul manual but did some investigation... There was play in the accelerator pump linkage probably due to the fact that the throttle plate was swapped from another carb onto this one. In any event, I adjusted the linkage and all appears well. Once this weather breaks i will be able to do some extended road testing.. I also found a disconnected vacuum hose up by the headlamps... man does this thing have a lot of vacuum hoses. Getting that one back connected has helped the idle, along with a heavier return spring...

Getting closer...

Thanks again!

Joel

[Steven B.]

Re: Some 1978 Questions

Joe, my '77 and '78 have/had all original vacuum hoses. I have found numerous cracks and splits, especially at the engine. Since the '77 is the one I have modified I have replaced many of the hoses and noticed an improvement as you did. A word of caution---I was a little too firm and aggressive removing some of the old hoses and broke some of the 35+ year old plastic connections. I tried cutting some of the hard to remove hoses with a very sharp and thin knife and it worked well as long as I didn't press too hard. Rubber and plastic get pretty brittle under that hot hood over the decades. Have fun with your hot rod! We all need one.

Steve