Vapor Lock Solution?

[meadowbrook]

Hi all.

 

I was in a cruise this past Saturday and during the parade, sure enough, my car vapor locked and I had to wait 10 min to restart.

 

I am convinced it is lack of fuel from heat and I have the stock heat shield above the fuel pump and part of the fuel line to the carb insulated.

 

I was reading that some 70's cars like the Fiat X1/9 and the Datsun 280 ZX Turbo had an actual fan that blew over the carb and later the injector rail to prevent vapor lock.  

 

I was wondering if anyone had tried to add a little fan to blow over the carb and/ or the fuel pump. In my case it would need to be a 6 volt one.

[deathbound]

I must be lucky. In the 6+ years I've owned my car, never had it stall or not start when hot. No heat shields or insulated fuels lines. Maybe it's because I run an electric fuel pump? Removed the mechanical pump and replaced with a block off plate.

[knuckleharley]

Hi all.

 

I was in a cruise this past Saturday and during the parade, sure enough, my car vapor locked and I had to wait 10 min to restart.

 

I am convinced it is lack of fuel from heat and I have the stock heat shield above the fuel pump and part of the fuel line to the carb insulated.

 

I was reading that some 70's cars like the Fiat X1/9 and the Datsun 280 ZX Turbo had an actual fan that blew over the carb and later the injector rail to prevent vapor lock.  

 

I was wondering if anyone had tried to add a little fan to blow over the carb and/ or the fuel pump. In my case it would need to be a 6 volt one.

I'd be more than a little worried about a underhood fan "fanning the flames" if it caught fire under the hood.

 

Have you considered trying an aluminum or special plastic insulator/spacer between the intake and the carb?

[knuckleharley]

I must be lucky. In the 6+ years I've owned my car, never had it stall or not start when hot. No heat shields or insulated fuels lines. Maybe it's because I run an electric fuel pump? Removed the mechanical pump and replaced with a block off plate.

I'd say it is more true than maybe.

 

These old inline engines have a tendency to boil away all the gas in the float bowl and be hard to start,even if they don't vapor lock and just shut down while driving at slow speeds. Your electric fuel pump instantly replaces any fuel that is boiled away.

 

I am guessing this is not such a big problem for guys running multi-carb intakes where the intake doesn't bolt to the exhaust. The Edmunds are one example.

 

Guys running split exhausts don't usually have that problem either,unless they just welded an outlet into the original exhaust,and didn't really split it.

Edited June 14, 2016 by knuckleharley

[desoto1939]

some of the old timers would use the old style wooden clip-on clothes pin and attach them to the fuel line. They have said that this worked back then so I guess it should still work now.  They need to be the wooden style not the Plastic clip-on clothesline pins.

 

Rich Hartung

[greg g]

Is your heat raiser operational? How many parades do you go to? Where is your float set? Is the out put volume of your fuel pump up to spec? Is your needle and seat valve functioning properly? Where is your timing set? Do you have any air leaks in the line from the fuel pump back to the tank? Is your tank properly vented? I would look at those things before investing in clothes pins.

[Jeff Balazs]

Is your heat raiser operational? How many parades do you go to? Where is your float set? Is the out put volume of your fuel pump up to spec? Is your needle and seat valve functioning properly? Where is your timing set? Do you have any air leaks in the line from the fuel pump back to the tank? Is your tank properly vented? I would look at those things before investing in clothes pins.

too funny!

[Captain Neon]

I used to do 20 parades in a summer with my bone stock '46 more door and it never vapour locked on me once.  However, even after almost 10 years, I will probably never do another parade again.

[James_Douglas]

In 15 years running the big Desoto I have never had it vapor lock.

 

In my case, I have done the following:

 

1. I have a pass through electric fuel pump I use when starting the car.  I never run it while driving it unless it is a really hot day >100F and I am stuck in traffic or parade. 

 

2. I source a NOS/NORS asbestos thick carburetor gasket.  It helps keep the heat away from the carb.

 

3. I have a large Fram HPG-1 fuel filter in front of the passenger side radiator diaphragm.   I run the line from the rear through the diaphragm to the filter, then back through the diaphragm to the fuel pump. 

 

4. I run the shield on the pump. My pumps are all rebuilt by Terrell Machine.

 

5. From the pump to the carburetor I have fuel line heat shield.  You get it at any speed shop.

 

On this car, I do not have the heat baffle in the exhaust manifold so in theory, the intake and the carb should be too hot.  In practice, I have never had a problem.

 

James  

[Labrauer]

I wrapped my fuel line in exhaust wrap from the fuel pump all the way up to the carburetor and ran the fuel line as far away from the exhaust manifold and pipes as I could. Never had a problem. I also wrapped the two exhaust pipes from the manifold all the way under the cars floor board about three feet. You can get this stuff in about any car parts store but one thing to remember is that it sometimes makes you itch if you wrap in a short sleeve shirt.

[meadowbrook]

Love all the responses, this is a truly great forum.

 

I always brag that my Dodge has the original engine and original left head light at shows.

 

So on the vapor lock, just one more question, it sounds like the fuel line section between the tank and pump is the one that would cause the vapor lock, no? If the fuel is vaporizing after the pump, it would still be pumped to the bowl.

Since the line going to the pump in my car runs at the chassis level until it connects to the pump (through a rubber hose), it is all below the level of the manifold's heat.

 

From the pump, it rises to the carb and goes near the manifold. I routed it as far from the manifold as possible but there is not much room since the heater box is on the other side.

 

So maybe it is indeed percolation @ the carb. I have seen 2 things that may also indicate this.

 

1- The cast iron carb base is always looking wet.

2- Once after driving, I noticed fuel leaking from somewhere on the carb then it stopped.

 

I rebuild the carb and was very fastidious about it (OCD) and aside from when it vapor locks I notice no leaks and it runs beautifully, I average 17 MPG and once on the open road with OD on and averaging 50MPH I got 22 MPG. Not bad for a 65 year old engine.

[greg g]

Wet carb base and fuel near throttle shaft, usually confirms percolation. Adjust your float level by about 2/32nds lower than factory. This will usually address the problem without effecting driveability assuming your fuel pump is delivering proper pressure and volume.

[50 coupe]

Anyone have a photo of their heat shield under that float bowl. Curious as to design and how you attached it.

[greg g]

I believe there is a template for making a home made shield in the downloads area of this website.

[mopar_earl]

I've seen new reproduction heat shields on eBay if you prefer store bought.

Earl

[Don Coatney]

Anyone have a photo of their heat shield under that float bowl. Curious as to design and how you attached it.

 

 

I believe there is a template for making a home made shield in the downloads area of this website.

 

I've seen new reproduction heat shields on eBay if you prefer store bought.

Earl

I believe the poster is looking for an under the carburetor heat shield not one for the fuel pump. I believe forum member Jeff Balazs designed and made one.

[Jeff Balazs]

I believe the poster is looking for an under the carburetor heat shield not one for the fuel pump. I believe forum member Jeff Balazs designed and made one.

I did. I will try and find a photo of it. It is pretty simple and is just held in place on top of the manifold with a couple pieces of bailing wire.

All anything like this has to do is help with deflecting heat away from the float chamber. I can say I have not had any issues with the dreaded hot start problem since fitting it.

 

Jeff

[50 coupe]

I did. I will try and find a photo of it. It is pretty simple and is just held in place on top of the manifold with a couple pieces of bailing wire.

All anything like this has to do is help with deflecting heat away from the float chamber. I can say I have not had any issues with the dreaded hot start problem since fitting it.

 

Jeff

Yes, thanks Jeff. I have an electric fuel pump and the fuel line is routed to the fender side of the carb but having the hot start issue after driving for a bit. Sitting @ 10 minutes or so resolves it, that is why I think it may be the fuel bowl getting too hot.

Thanks

[DonaldSmith]

Here's a photo of my carburetor heat shield:

 

[desoto1939]

Here's a photo of my carburetor heat shield:

 

carburetor 2014 heat shield.JPG

Don in your picture of the heat shieled I can see the battery cables and they look as if they are from a 12 volt battery and not your typical 6volt heavy gauge 0 or 00 large battery cable. Am I correct on the size of the cable that you are using?

 

Rich Hartung

Desoto1939@aol.com

[Plymouthy Adams]

I recall Donald at one time had two sixer's in series....that is the why of the battery location passenger fender....does not answer gauge of wire though..

[st63]

The fellow who owned my 1950 P-20 before me had constant problems with the carb getting hot and percolating, until he installed a phenolic spacer and heat shield under the carb base.   I found that the heat riser in the manifold had frozen in the open position.  I replaced the manifold with one with a working heat riser, but left the spacer and heat shield in place just in case. No problems since. 

[DonaldSmith]

So, desoto 1939, you discovered my auxiliary battery!  Plymouthy Adams recalls correctly. 

 

The main battery, by the left fender, has the thick cables.  The auxiliary battery, by the right fender, powers my pusher fan and electronic gadgets, so it doesn't need the heavy cables. . 

 

(One problem is that I have to charge the auxiliary battery occasionally, and if I'm ever in a long parade, the pusher fan will start drawing down the auxiliary battery.   Never satisfied, I have a 6 volt pusher fan on the way from Speedway. That would make the auxiliary battery too klunky for powering just a GPS and some cell phones.)  

 

(I started looking into a 12 volt mini alternator, and how to mount it to the right of the engine, and how to arrange a pulley and fan belt, but then I thought, I should have gone with a 6 volt pusher fan to begin with, so that's now the plan.  A portable power pack can take care of GPSs and stuff.)  

Edited August 9, 2016 by DonaldSmith

[50 coupe]

Here's a photo of my carburetor heat shield:

 

carburetor 2014 heat shield.JPG

Beautiful. Thanks Don!! Gives me a good idea of size and location, especially knowing that it worked for you. Thanks again for the help.

[DonaldSmith]

Here's a prettier view of my carburetor heat shield, and my professionally rebuilt carburetor:  

(The black piping is my PCV system.)

(The transmission wires were wrong; the trans wouldn't upshift.)