Vapor lock 6-pack question/solution

[6PK2GOBEE]

I had vapor lock problems on my A12 Bee and solved it...

 

[72RoadrunnerGTX]

The ¼” fuel/vapor return line running back to the fuel tank from the fuel pump vapor separator? Liquid fuel found in this line is to be expected. An obstruction that couldn’t be cleared by fuel pump pressure would render the fuel pump vapor separator ineffective however. There is a constant flow of fuel and/or fuel vapor returning to the tank in that line while in operation as designed.

 

[6PK2GOBEE]

The ¼” fuel/vapor return line running back to the fuel tank from the fuel pump vapor separator? Liquid fuel found in this line is to be expected. An obstruction that couldn’t be cleared by fuel pump pressure would render the fuel pump vapor separator ineffective however. There is a constant flow of fuel and/or fuel vapor returning to the tank in that line while in operation as designed.

...is that better now?

 

[72RoadrunnerGTX]

If there is no heat induced fuel boiling taking place in the incoming fuel line, there will be no vapor to separate, what is returned to the fuel tank is then liquid fuel. It’s a return line, not vapor only return line.

Returns vapor and fuel to the tank at a constraint rate as determined by the orifice in the fuel separator while in operation. It is intended for there to be liquid fuel in this line, there is no reason to blow this fuel out as described.

It's always been described in the factor docs as a "return line", not a vapor only return line.

Note to self; always “quote” the posts I’m responding to, in the event the posts disappear or are edited, the responses will then make sense to others.

 

[440 PHIXX]

I had vapor lock problems on my A12 Bee and solved it after I discovered the vapor return line was full of raw fuel. Blew it out with air and that ended the problem.
That line is to vent vapor and if it can’t get through vapor builds up in the fuel system/carb.
Once you set the vapor return line up make sure it is clear.
Seems everybody wants to hang an electric fuel pump which is not the way to solve the problem. The mechanical pump actually does a better job handling fuel pressure and vapor.
Type of fuel: I “make” good old Sunoco 260 by adding 1qt Cam2 purple 110 racing gas to each gallon of Sunoco unleaded no ethanol 91 octane.
The result is ~.4grams per gallon of lead which is plenty to lube the valve seats and a 5 point bump in the octane number. I run this in both my A12 bee(10:5-1CR, Isky 280H cam, 906 heads) and my Daytona(stock 440 HP 10:1-1CR, 906 heads, stock cam)
You can gain a couple more octane points by a 3:1 ratio mix.
Been doing this for the better part of 40 years now! No issues they run like they should and the exhaust smells “right” just like with the old 260!
Don’t use Ethanol gas it boils at a lower temperature.

The DC manual recommended the electric pump with the mechanical pump to alleviate high RPM starvation. It also eliminates vapor lock.

 

[crazyron]

That vent on the center carb should be hooked to the breather cap as shown in this pic. I've seen a lot of them not hooked to anything at all.

View attachment 1286422

it does not go to the breather it goes to the air cleaner you don't want to put gas in your engine you don't want to hook it up to anything that has positive or negative pressure I know this because I called Holly

 

[crazyron]

That vent on the center carb should be hooked to the breather cap as shown in this pic. I've seen a lot of them not hooked to anything at all.

View attachment 1286422

it doesn't go there you'll be sending fuel into your motor you never hook it up to any vacuum source whether it be positive or negative the that that tube goes to the air cleaner there's a nipple on it for how I know this I spoke to Holly about it

 

[72RoadrunnerGTX]

it doesn't go there you'll be sending fuel into your motor you never hook it up to any vacuum source whether it be positive or negative the that that tube goes to the air cleaner there's a nipple on it for how I know this I spoke to Holly about it

Not correct, perhaps you should have a looked at the factory service manuals from ’70-71, relating to the Evaporation Control System, it's function and the correct information on the fuel bowl vent valve hose routing.

Called Holley? Did you ask them why the current re-issues of the ’71 center carbs (list 4670) are shipped with this correct sized 3/8" hose, at the correct length, to connect the bowl vent valve nipple to the correct ’70-71 3-nipple breather, if that's not where it goes?

 

[Sixpactogo]

it does not go to the breather it goes to the air cleaner you don't want to put gas in your engine you don't want to hook it up to anything that has positive or negative pressure I know this because I called Holly

Your comment doesn't make any sense. If you have gas in that bowl vent, you have bigger problems. It is vapors not fuel. Plus, if you did have fuel there, why would you want it going into your air cleaner? Either Holley gave you bad info or you miss understood it.