Carter Carburetor Starting issues

[Gerald C.]

Hello,

I have a 300 hp with a Carter. I'm having a hard time starting the car but when it starts, it runs great. The engine will crank for many seconds and then eventually, it will start.

I'm sure the carburetor hasn't been touched in years and the grime on it proves it. I've been told by a carburetor rebuilder that the gas in the bowl evaporates/boils out thus the need for the fuel pump to fill the bowls before it will start. The rebuilder said that since the car runs great after it starts, I don't need to rebuild the carburetor. I started the car today (after many cranks) and it ran well. A few hours later, while still in the garage, I had a hard time starting the car. But once it's started and then I shut it off, it will fire up right away! I've never had that issue before in my other cars. Another opinion is that the carburetor is leaking into the intake manifold and it needs to be rebuilt.

Any other thoughts about what's going on with this Carter?

Questions?

Thanks

[Duke W.]

Re: Carter Carburetor Starting issues

While the engine is idling remove the air cleaner cover. Then shut down the engine and carefully inspect the venturi discharge nozzles that fuel is not dribbling out of them. If so the float level is too high. Use a good flashlight and magnifying glass.

The biggest issue with the AFB is the choke system. The vacuum break piston gets dirty (especially if using the junky oil wetted foam air filter) and sticky keeping the choke from fully closing when cold.

You can remove the choke system from the carb for disassembly and cleaning, but keep in mind that there is a tiny O-ring between the choke housing and main body that seals the vacuum passage junction for the clean air system, and it should be replaced with a new one.

Zip kits should have one, but maybe some don't.

Duke

[Gerald C.]

Re: Carter Carburetor Starting issues

Thanks Duke. I'll check it out in the morning.

[Timothy B.]

Re: Carter Carburetor Starting issues

Does the choke close fully when cold cranking?

If you are so inclined just overhaul the carburetor and make sure all the adjustments are set properly, you can eliminate many things by insuring the carburetor is clean inside and adjusted. Fuel pump pressure is also something that can play havoc on these carburetors.

[Richard G.]

Re: Carter Carburetor Starting issues

Mine starts fine if it has been run in the last few days.
Extended cranking if it has been setting. I also only use non-ethanol fuel.
Great tip from Duke, I will pull the foam filter and put it back in the plastic bag (where it belongs) and go to the paper filter.
I did get the booby prize when the judge got oil on his hands at the regional. It was his joke but I received no deductions on the filter.
I did have a clean towel to offer him.
You didn't mention if the choke closes when the motor is cold?

[Gerald C.]

Re: Carter Carburetor Starting issues

Well, I started with the simplest fix first. I tighten the choke a bit to make sure the carburetor butterfly closes tightly. On the cold start, the car started very quickly. I did it twice today on a cold engine and was pleasantly surprised with the result.

I'll try it again in the morning. Quick question....what should the car idle at under the fast idle and then on the normal idle after the car is warm?

Thanks

[Duke W.]

Re: Carter Carburetor Starting issues

The fast idle is set with the engine fully warmed up. You should also check that the choke vacuum break and other adjustments are set to spec. All this is in the 1963 Corvette Shop Manual or the '64 or '65 Supplements for your year.

On a cold start the idle should stabilize within a few seconds to about 200-300 RPM below what you set it at hot.

A fully warmed up 327/300 with a manual transmission should idle in neutral butter smooth, 500 @ 18-19" Hg.

Duke

[Timothy B.]

Re: Carter Carburetor Starting issues

I have always had a difficult time getting the 300hp engine to idle at 500rpm as the manual states, maybe the fuel today burns different without lead. If you disconnect the vacuum advance that will do it or reduce the PCV air but I will settle with a slightly higher idle to have both connected.
.

[Duke W.]

Re: Carter Carburetor Starting issues

You may not have an OE camshaft. As I said previously an OE 300 HP cam (or a McCagh Special camshaft) should idle butter smooth, 500 @ 18-19". If your engine is not at least within about 1" of this range you either have a higher overlap cam or some mechanical problem, and if the installed VAC does not meet the "Two-Inch Rule that just adds to the misery.

Duke

[Timothy B.]

Re: Carter Carburetor Starting issues

Everything original, 929 camshaft, 201 V/A can etc., I wonder how many of these 300hp cars out there idle at 500rpm. Maybe some other posters can comment on their hot idle speed, if I port the V/A it will idle there fine and power off real nice but that's not what I want to do so I run the idle at approx 650.

I can't comment on the fuel differences but I really believe the old leaded fuel required a slightly larger throttle blade opening and it's most noticeable in this situation with the 300hp engine. The unleaded fuel must be a little different, I remember that old Amoco gold premium ran great in my chevelle SS but Crown leaded gas made it act like I felt on some mornings after a late night...

[Gerald C.]

Re: Carter Carburetor Starting issues

Update: I closed the choke up a bit and left a little opening in the "butterfly". The car starts very quickly now on three different occasions. So far so good.

Thanks

[Duke W.]

Re: Carter Carburetor Starting issues

Everything original, 929 camshaft, 201 V/A can etc., I wonder how many of these 300hp cars out there idle at 500rpm. Maybe some other posters can comment on their hot idle speed, if I port the V/A it will idle there fine and power off real nice but that's not what I want to do so I run the idle at approx 650.

I can't comment on the fuel differences but I really believe the old leaded fuel required a slightly larger throttle blade opening and it's most noticeable in this situation with the 300hp engine. The unleaded fuel must be a little different, I remember that old Amoco gold premium ran great in my chevelle SS but Crown leaded gas made it act like I felt on some mornings after a late night...

It's not the fuel!!! I've dealt with too many of these over the last 60 years to not know them like the back of my hand, both with the OE camshaft and McCagh Special camshaft that I designed for 300 HP engines with massaged heads.

Measure vacuum at whatever idle speed you use plus at 500 and report the results... xx "Hg at yyy RPM.

Also, have you checked that the 201 15 VAC meets spec and is attached to a full time vacuum advance source

Duke

[Duke W.]

Re: Carter Carburetor Starting issues

If everything is in proper working order and properly adjusted the choke should fully close at room temperature and below when you push the throttle to the floor to add a pump shot and set the choke.

When the engine fires the CHOKE VACUUM BREAK will open the choke valve slightly if it is properly adjusted.

All this is in the 1963 Corvette Shop manual and the '64 and '65 Supplements for those years.

Do you have the proper shop manuals and have you read the AFB sections and specs in the back of the manuals?

Duke

[Timothy B.]

Re: Carter Carburetor Starting issues

It's not the fuel!!! I've dealt with too many of these over the last 60 years to not know them like the back of my hand, both with the OE camshaft and McCagh Special camshaft that I designed for 300 HP engines with massaged heads.

Measure vacuum at whatever idle speed you use plus at 500 and report the results... xx "Hg at yyy RPM.

Also, have you checked that the 201 15 VAC meets spec and is attached to a full time vacuum advance source

Duke

The 1963 300hp engine idles around 600-650 with approx 19" vacuum and my 67 300hp W/Holley is the same, they motor off fine at that setting. If I close the Holley blades further I can get approx 550 RPM idle but it's not enough air through the primary blades, butter smooth is just a bit higher at 650.

I may just be a bad mechanic but I can't help but wonder how many of these 300hp cars idle at 500 RPM butter smooth.