Idles only after slow warmup

[richardgoesfast]

I'm still kinda new to this 1970 383 and haven't gotten it on the road yet. I'm quite sure this car was kept in a garage and only ran seldom, if at all, for a period of maybe 6-10 years before it became mine. I know the previous owner never registered it, so it was not driven. Don't ask me why on that one. . .
Anyway, I've done the usual, drain tank, new plugs, new fuel filter, new fuel (obviously) and I've got it running, so that's good.
Starts right up, but will die unless I start with a high idle (about 1000 I'm guessing) and gradually let the RPM's slow for about 4 minutes. So I slowly let off the gas and at that point it will idle and sounds terrific. If it stalls, I cannot restart it unless I splash a little gas in the carbs. If I let it sit overnight, it will start up.
This sounds to me like a carb that needs a rebuild but what the heck, I thought maybe it could be something simple that I don't know about. It is an original Holley carb it would appear. Any thoughts appreciated.

 

[RonLiv]

I recently went through a lengthy process trying to identify a fuel problem. Mine would start, then run for a while, then quit. The carb was dry. Turns out though it wasn't the Carb, it had been recently rebuilt (by the way I don't think the Holley would be original to your car, probably would have been a Carter AVS in 1970) the fuel lines were clear, but check those for sure, it wasn't the fuel pump as I replaced that and it didn't solve the problem, and it wasn't vapor lock either. Mine was the fuel pump push rod was worn. Not saying this is your problem though. Ethanol is a funny substance and can play havoc on something that has sat for a while.

 

[69hemibeep]

I would start with the carb it set to long.

 

[richardgoesfast]

Thanks. That's what I'm pretty much thinking.

 

[ACME A12]

by the way I don't think the Holley would be original to your car, probably would have been a Carter AVS in 1970

Could have been a Carter or a Holley in 1970 - see below. I think HemiBeep nailed it - sat too long.

Year Engine/Trans Make Style Part #

1970 8 383 S/T Carter BBD 4725
1970 8 383 A/T Carter BBD 4726
1970 8 383 S/T (California) Carter BBD 4727
1970 8 383 A/T (California) Carter BBD 4728
1970 8 383 A/T (Export) Carter BBD 4730
1970 8 383 A/T Carter AVS 4732
1970 8 383 A/T ECS Carter AVS 4734
1970 8 383 A/T Carter AVS 4736
1970 8 383 A/T W/AC Carter BBD 4894
1970 8 383 E.C.S. A/T Holley 4160 4218
1970 8 383 C.A.S. A/T A/C Holley 4160 4369
1970 8 383 E.C.S. S/T Holley 4160 4217
1970 8 383 C.A.S. A/T Holley 4160 4368
1970 8 383 C.A.S. S/T Holley 4160 4367

 

[‘69_Sunfire_RR]

If the Holley on your 383 has an electric choke you may consider checking this. Same if it’s a manual choke, you should ensure it is in proper working order. Choke is essential at start-up, at least with my experience. Same symptoms when I bought my ‘69 a year ago. Somebody previously did not wire the electric choke and instead left it disabled and also fixed the choke blade wide open with a piece of solid copper wire. She wouldn’t idle until warm.

 

[RonLiv]

Could have been a Carter or a Holley in 1970 - see below. I think HemiBeep nailed it - sat too long.

Year Engine/Trans Make Style Part #

1970 8 383 S/T Carter BBD 4725
1970 8 383 A/T Carter BBD 4726
1970 8 383 S/T (California) Carter BBD 4727
1970 8 383 A/T (California) Carter BBD 4728
1970 8 383 A/T (Export) Carter BBD 4730
1970 8 383 A/T Carter AVS 4732
1970 8 383 A/T ECS Carter AVS 4734
1970 8 383 A/T Carter AVS 4736
1970 8 383 A/T W/AC Carter BBD 4894
1970 8 383 E.C.S. A/T Holley 4160 4218
1970 8 383 C.A.S. A/T A/C Holley 4160 4369
1970 8 383 E.C.S. S/T Holley 4160 4217
1970 8 383 C.A.S. A/T Holley 4160 4368
1970 8 383 C.A.S. S/T Holley 4160 4367

Interesting. The chart I typically refer to doesn't show any Holley Carbs for a 383 in 1970. Only 225 & 340. Learn something everyday I suppose.

http://www.mymopar.com/carbguide.htm