secondary only flooding in Holley 3811 carb

[William F.]

After starting my '67 L36 with correct almost new Holley 3811 carb after a heat soak of about an hour, fuel floods out the booster-discharge nozzles and to some degree the bowl vent on the secondary side only. After some stumbling while driving about a mile, things clear up. When I stop and look into carb with engine idleing after driving, there is no more flooding. I have not seen any fuel dripping from nozzles while car is sitting but hot, only happens after starting after a heat soak. I think possibilities are high fuel pressure or floats too high even though they are set to specs(internally adjustable only on a 3811). I favor floats too high for circumstances since I would think there would be constant flooding and on primaries as well as secondary if fuel pressure was at fault. I have blocked the under carb heat slot holes and insulated the fuel line from pump to carb with no avail. Don't want to get back into the distillation curve theories, but would like to know others thoughts on a practical solution before I do something. I'm favoring empirically lowering the secondary float a bit.
Thanks in advance

[Stephen L.]

Re: secondary only flooding in Holley 3811 carb

Lower the floats.....

[William F.]

Re: secondary only flooding in Holley 3811 carb

Thanks for reply, Steve.
Is lowering the float the concensus of everyone else the reason I have only gotten this one suggestion so far?

[Stephen L.]

Re: secondary only flooding in Holley 3811 carb

While you have it apart, you might want to replace the inlet needle and seat as an insurance measure.......

[Steve G.]

Re: secondary only flooding in Holley 3811 carb

I'd say it's a pretty safe bet to say that you have a high fuel level in that bowl.

As far as what's causing it, it's unlikely that high pump pressure is the culprit. It's not very common with a stock mechanical pump and the other bowl isn't exhibiting signs of a problem. However, it only takes a moment to put your gauge on the line and check the pressure to rule it out.

Once the pump is out of the question you've pretty much determined it's an internal carb problem. Rather than simply lowering the float level and guessing at where the fuel level will be, I would be more inclined to find out why a correct float setting is giving you a high fuel level.

To that end I would probably suspect the float and/or the needle and seat. For the cost and time involved the most practical solution is to replace both. Then set the new float to spec and test.

Steve

[William F.]

Re: secondary only flooding in Holley 3811 carb

Always try to give a followup. I lowered the secondary float about 1/16" from where it was and no more flooding after heat soak. Seems to have enough fuel in bowl since I experience no miss or lean pop when doing a pull to close to redline.

[Steve G.]

Re: secondary only flooding in Holley 3811 carb

You fixed the symptom, but did you fix the problem? If a correct float adjustment was giving you an incorrect fuel level you may be just postponing the problem. If the cause of the inaccurate fuel level was a float losing buoyancy, requiring a lower setting to achieve a correct fuel level, in all probability it will continue to lose buoyancy and the fuel level will creep up again.

Steve

[Timothy B.]

Re: secondary only flooding in Holley 3811 carb

If it 's a 4160 Holley with a secondary metering plate my money is on the metering plate gasket if you changed it while you were in there.

These plates are cheap and can bend out of flat and the gaskets are thin.

[William F.]

Re: secondary only flooding in Holley 3811 carb

I see everybody's points, but: 1. I didn't mess with the metering plate. 2. Yes, on another brand new carb, I had the same problem and after checking fuel pressure, etc, found out that float had a pin hole. This time, I shook the float, and didn't hear any fuel sloshing inside it. 3. If it's something other than just a previously high float level, shouldn't problem return? Wouldn't excess fuel overfill the bowl and cause return of flooding? And remember, this flooding is only for a minute or so after startup after an hour or so heat soak. I'll keep an eye on it.
I disagree about most fuel pumps not having excessive pressure. Seems that many of the replacement pumps do have excessive pressure.