1970 Roadrunner won't stay running

[Bobby D.]

Sorry for making a new thread but I'm trying to get my 1970 Roadrunner to stay running and I'm a little new to carburetor stuff. I've been here for awhile but haven't started really messing with my car. It has a 383, which will start and stay running, but I have to keep the throttle cracked open. The carburetor is an Edelbrock with a stupid adapter from the spread bore to square bore. The car possibly has a bigger cam and still has points and mechanical fuel pump.(that's the way I bought it) The second I let my hand off the throttle it dies.

 

[Geoff 2]

Need a loooooooooooooooot more info. What is the minimum rpm it will idle at? New carb? Float level adjusted? Do idle mixture screws control idle quality. timing at idle? Etc.

 

[Bobby D.]

Need a loooooooooooooooot more info. What is the minimum rpm it will idle at? New carb? Float level adjusted? Do idle mixture screws control idle quality. timing at idle? Etc.

Thank you for reply. It won't idle. It's not a new carb, it came with the car. I haven't touched the float levels or needle and springs. Idle mixture screws don't do anything, I cleaned the passages. If I keep it running and have the vacuum gauge hooked up, it's about 5 to 10 in. But I don't know what rpm its at. Spark plugs are black and it burns the eyes in the garage while running.

 

[493 Mike]

Check that carb adapter for sealing. Some of those create a huge vacuum leak.
Mike

 

[Bobby D.]

Check that carb adapter for sealing. Some of those create a huge vacuum leak.
Mike

I think your right cause I just never liked the idea of the adapter. Is there a good spread bore carb I can buy that'll fit on, what I think is a factory intake? Just to eliminate that possibility.

 

[493 Mike]

I think your right cause I just never liked the idea of the adapter. Is there a good spread bore carb I can buy that'll fit on, what I think is a factory intake? Just to eliminate that possibility.

If the intake is OEM it will say so cast in the top side. If so, it was from a 400 and designed for a Carter Thermoquad. They were/are very good units. I ran a 650 Holley spread bore years ago on a Chevy small block 400 with good performance. Mopar used Rochester Quadrajets and those are also good carbs.
Mike

 

[turbine68rt]

Verify point gap/dwell setting, check/set timing after that.
What type fuel pump? Is choke opening a sufficient amount after a cold start?

 

[Bobby D.]

Verify point gap/dwell setting, check/set timing after that.
What type fuel pump? Is choke opening a sufficient amount after a cold start?

I have new points and mechanical fuel pump coming. Even when the engine gets hot it will not idle when I let go of the throttle.

 

[turbine68rt]

Do you have a good spare condenser?
With the Edelbrock carbs you may want to keep the pressure around 4-5.5psi.
What is the rating on the new pump?

 

[Geoff 2]

I doubt the carb adapter is the problem [ causing an air leak ].

To test: spray WD40 or similar around the carb gaskets. If rpm changes, you have a leak. Be careful not top spray directly at the throttle shafts because there is a gap there & rpm would change which would be normal.

 

[cosgig]

Do you have a good spare condenser?
With the Edelbrock carbs you may want to keep the pressure around 4-5.5psi.
What is the rating on the new pump?

My thinking exactly. I was advised to change the condenser way back when I owned my 64 Belvedere with a 440. Thing needed constant foot on the pedal, and it was “flaky”. I sort of scoffed, but they’re cheap, and I never had a problem after that. Smooth as silk!

 

[Bobby D.]

Do you have a good spare condenser?
With the Edelbrock carbs you may want to keep the pressure around 4-5.5psi.
What is the rating on the new pump?

I have to go to Summit and buy them. I'm sorry I said they were on the way but I need a day off to drive to Summit. Any suggestions on what to buy?

 

[turbine68rt]

I have to go to Summit and buy them. I'm sorry I said they were on the way but I need a day off to drive to Summit. Any suggestions on what to buy?

The pump or condenser?

 

[Don Frelier]

I'd try advancing the timing.
Mark the distributor with a fine Sharpie in a convenient spot.
Rotate clockwise maybe 1/4" and see if it improves. You can always put it back.

 

[Bobby D.]

The pump or condenser?

Both. I wanna get a good brand pump, points and condenser.

 

[Bobby D.]

I'd try advancing the timing.
Mark the distributor with a fine Sharpie in a convenient spot.
Rotate clockwise maybe 1/4" and see if it improves. You can always put it back.

It tried that and it didn't like either way I turned it.

 

[Geoff 2]

If it starts & stays running, it is NOT the condenser!
What it could be is the points gap has closed up, which happens as the rubbing block wears down. Old worn dists have enough wear in the shaft & bushing such that enough centrifugal force [ cam block is heavy ] is generated to open the points at higher rpms, but not at idle rpms.

Check the points gap.

 

[turbine68rt]

Gap/dwell suggested in post 7. If he is already installing a new set of points, may as well change both while it's apart.

 

[Bobby D.]

If it starts & stays running, it is NOT the condenser!
What it could be is the points gap has closed up, which happens as the rubbing block wears down. Old worn dists have enough wear in the shaft & bushing such that enough centrifugal force [ cam block is heavy ] is generated to open the points at higher rpms, but not at idle rpms.

Check the points gap.

Your right I checked and the points are not adjusted. That's why I want to get points, condenser. And the fuel pump just cause I don't know how old they are. The points won't adjust any further out. What brand would you recommend I buy for all these parts?

 

[pro451bee]

probably limited to what can be found , the napa brand used to be the better quality,