64 chevy 327 with rochester 4 barrel carb. starts fine when it's cold but after running for awhile then shut off for short time, it cranks excessively before starting. I think it's a carb problem but not sure. Ideas??

40

Asked by Jun 03, 2017 at 08:01 PM about the 1964 Chevrolet Impala SS

Question type: Maintenance & Repair

Starts fine when it's cold with 1 pump of gas pedal, but after running for awhile
then shut off for short time, it cranks excessively before starting. I think it's a
carb problem but not sure. Ideas??

22 Answers

510

Adjust air and fuel mixture screws all the way in then adjust out 2 full turns and another half on each. Once running. Make sure carburetor plate or carburetor itself isnt sucking air. You can use a spray bottle with water and spray all around the base of carb plate and carb. If still continues. Check float levels and fuel filter at carb

40

Thanks for the quick reply. I will try that and let you know. Thanks

40

OK, mixture adjustment didn't do it. Doesn't appear to be sucking air around the carb. I'll check the filter and float setting tomorrow. If I shut it off & restart right away it pops right off. But if it sits for 10 minutes it has to crank for almost 10 seconds before it starts. I still think there's something in the carb not holding fuel like it should.

510

It's flooding I believe. Needle valves probably not closing off with floats. Sounds like it hot soaks and loads the intake

40

It doesn't seem flooded when it DOES start....unless I pump it a time or 2 while it's cranking.

9,890

IMO your seriously out of timing

69,305

Check your fuel line routing. If it's too close to the hot exhaust manifold you may be having a vapor lock type of condition. Same deal if the heat riser valve on the exhaust manifold is stuck closed. Do you have air-conditioning? If so there may be a fuel return line (to the gas tank) to prevent this sort of problem. GM was using that set up on air-conditioned cars in the late '60s & early '70s. Not sure if they were in '64 but it's worth a look. One other possibility I can think of. On the back of the carburetor there's a small tang that sticks out. It's an air valve that opens up when the carburetor is hot. It's designed to slightly lean out the air/fuel mixture to prevent an overly rich air/fuel mixture on hot start ups. HTH. -Jim

1 of 1 people found this helpful.
40

Timing is set @ 6BTC. No fuel lines too close to exhaust & heat riser is free. I do have AC but no return line to gas tank. I'll check for the tang on the back of the carb.

1 of 1 people found this helpful.
69,305

Sounds good. Thanks for the update! I forget what the proper name of that tang is. It's been awhile. But that's what it's purpose is. I'm assuming the choke plate is fully open when the engine is warm/hot? HTH. -Jim

40

I'm sure I found my problem!! I pulled the top off the carb & WOW. BAD! I had put a kit in it over 20 years ago and then shortly after put it in storage for 20+ years. It was driven very little after the kit but I had no idea time could be such a problem, especially with a carb filter AND inline filter. There was a lot of junk in the bottom so I'm sure some stuff got into places to cause problems. The accelerator pump was in pieces. I'm very surprised it ran at all let alone how good I thought it was running. I plan to put a kit in ASAP and expect that to cure my problems. Thanks to ALL for your suggestions. Case closed... i'm almost sure.

1 of 1 people found this helpful.
69,305

Awesome, glad you found the problem!! Thanks for letting us know! -Jim

40

Does anyone know the correct float setting for a Rochester 4 barrel (not Quadrajet)? The kit I got say 1 17/32". That's where it was set NOW I'm definitely getting too much gas. At first I thought I did something wrong with the kit (and maybe I did), but it sure seems like it;s a float prob. It starts and idles OK until it floods out. The gas is just pouring thru. I going to lower the float level to 1 7/8" & see what happens. I;m open to anything else that may be wrong. The base gasket was definitely wrong so I used the old one thinking that might take care of it but didn't.

40

UPDATE: I set the float level at 1 7/8" and everything got a whole lot better. I hope I'm done with THAT problem and can move on to whatever is next. I'd still like to know the right float setting for a 64 Chevy Impala 327 with a 4 barrel Rochester. I'm pretty sure I didn't have exactly the right kit but other than the base gasket & float level specs,,,,,it worked. Thanks

40

I realize that's a big change but it's at least drive-able now. There's still a problem. With it idling I can see fuel dripping down the rear barrels. That continues after I shut it off + a little in the front. I've had the top of several times and can see no evidence of foreign "stuff". I've even had the carb off and partially disassembled and can see nothing wrong. What am I missing??

40

I think my problem is in the fuel. Hot carb/ boil over. I'm having trouble finding an insulated gasket or spacer. Seems like they're all for Holleys or Quadrajets not Rochester 4 Jet. Any ideas?

69,305

Check rockauto.com, I see a few non-Rochester mounting gaskets listed. HTH. -Jim

40

Thanks

1 of 1 people found this helpful.
69,305

You're welcome. Glad to help. I meant to say non-Quadrajet. Sorry!! -Jim

40

I found a 1/2" space (which is about all I have room for), and am STILL having raw gas dripping in the carb after it's warmed up. It cut out a little on the highway the other day but most of the problem is if it idles a long time and especially after it sits 5 minutes or so. Then it' got raw gas in the bottom of the intake and of course is flooded. I'm having trouble believing it's in the fuel. I'm using unleaded premium (no ethanol listed on the pump) and I added an octane boost additive. I'm going to change the float level a little more and if that doesn't do it I'll try some racing type fuel (about $8 a gal.). It's just strange that none of my buddies with old cars have this problem.

40

After all this it turns out I don;t have a hot carb/boil over fuel problem. A friend loaned me a carb and the drip and slow start (flooding) after sitting 5-10 min was gone. The floats on both carbs are set fairly close to each other but way off from what's called out in the kit and shop manual. There's still something in MY carb causing this drip/flooding problem. I don't know where to look but now I know IT;S IN MY CARB. Thanks for all the input but I;m still stumped.

69,305

Possibly the accelerator pump? Or leaking jets? HTH. -Jim

40

The AC pump is new & I swapped it into the loaner, It's fine, The needle & seat are new and I cleaner & examined the jets. They're fine. Thanks

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