Hey, guys, I have an inline 300 with a header. Carb sits right above it. I've tried a heat shield, but still get hard hot starts with several carbs.

I really don't want to wrap the headers, and would rather not use the efi exh manifolds to stop the problem. I love the look of the headers. Was thinking of drilling 1 1/2"--2" holes in a line, right above the header on that side, and using a scoop turned to open at firewall side to prevent water entering. That would allow heat to escape. What do you think? Would that work?

 

I don't remember what carb you have, but you might see about a phenolic spacer. That would help isolate the carb from the intake manifold and the heat it absorbs from the exhaust being right next to it.


Summit has 2 and 4 barrel, just adjust the search parameters


http://www.summitracing.com/search/p...9%2B4294916476


Or make your own


https://www.interstateplastics.com/P...ss=0.750&qty=1

 

I did some research on this, and our problem is that with our new gasoline, the hydrocarbin is different (shorter probably) The reason for this was there hasn't been a carburetor installed on a new car from the factory since ~1990 and before. There was a decision that we could make this lower carbon fuel for less $ and it wouldn't matter since everything now has a sealed fuel system and EFI. This was a good idea across the board, make a product cost less, waste less, and easier. The down fall was that the new fuel isn't stable like the fuel of 20+ years ago. It evaporates at lower temps, it evaporates faster, and it theoretically doesn't matter today with new fuel injection systems, evap control systems, and the diminishing number of carburetors. We try everything to keep the fuel cooler, spacers, aluminum components, and it usually is barely enough. I don't think the fuel is getting hotter than it did when these trucks were new, but rather the fuel is evaporating before it has a chance to get hot. This in itself is our problem. I have just learned to live with it, park with my hood in the shade where possible, run lower thermostats, shut the ac off before I park to allow some cooler air to pullover the engine, It helps, but this problem is the way it is, unless you want to go buy av gas, it is leaded and 110 octane, and it will fix your problem, but it is a little harder to get and more expensive.

 

It might be worth it to find out what components are missing from modern fuel that lend it to being less stable and more prone to vapor lock. Probably a fancy distillate like iso-pentane or xylene or whatever. Maybe a trip to the hardware store is all that's necessary, I dunno.

 

Well, it might help. I am not sure what would help the situation, but I have a real adventure, as I am at 6000' above sea level and surrounded by mountains, so stuff boils really easily around here!

 

You've tried clothespins? Is it only a problem with carburetor, or is it a classic vapor lock situation in the fuel line?

 

Mine won't vapor lock, I run an electric fuel pump back at the tanks, so it just boils out of the carb, then I have to crank and crank to clear the fumes then get a restart. Vapor locking was an issue for me if I run the old mechanical pumps, but with a pusher, everything is fixed because the lines are pressurized all the way from the tank, much like modern fuel injection.

 

Ah, that's the deal. So you're reasonably certain that old-school fuel is immune to this problem?

 

you might also try to use non ethanol fuel it boil at a lower temp and destroys carb parts

 

I wouldn't say old fuel is immune, just more stable. less apt to boil. A gas station owner mentioned to me at one point that winter fuel was more stable than summer fuel, due to additives, deicers, and lubricants for the cold pumps. Can't verify truth in this, and the problem of boiling gas is not even an issue for me in winter time. I wonder though because in my area fuel goes up in price in the summer months and down in winter months, I would think that fuel with additives would be more expensive than without, and this evidence does NOT support the theory, but non the less I guess I should wait until about the second week in February and buy 20 gallons then wait till about june and burn it and see if I can notice a difference. I doubt I will ever do this though.

 

I had hard hot start and vapor lock in hot weather on a '47 PW. Same basic problem. An electric fuel pump on the frame rail solved it. The gas will still boil out of the carb with hot soak... the little electric pump pushes fresh gas in so it re-starts.

I set mine up with a check valve that lets the engine driven pump pull fuel by itself through the check valve and put the electric pump on a toggle switch for use when needed.

 

This has turned into quite an interesting thread. Thanks for all the great info, guys. After speaking to other I6 forum members, I believe the root of my problem is the Header. No doubt the new fuel is a major contributor too. Those two are acting together.

Other members with I6's don't complain unless they have a header. But I love the look of the header and don't want to get rid of it. I was wondering if adding a scoop right above the carb to vent the heat would help. Maybe one about 6" wide and about 36" long, with the inlet facing the windshield? Would that be enough of a vent? Would rain get in? I'd hate to do it and have the problem persist.

What I have done in past: I've tried three diff carb types, a heat shield, a phenolic spacer and aluminum spacer. The carbs have been Autolite 4100, Summit, and Quadrajet. They all run great until the hot start time comes.

One point not covered concerning the Ethinol: I had to cut back on my advance when the ethinol got added to the gas.

 

I'm having the same issues. Stuck at a McDonalds in Goodland Kansas. Earlier today I had the same problem. Took the line off from fuel pump to see if any fuel was being pumped, then cranked it, and nothing. I poured gas down the carb, would run till gas ran out. I blew on the lines into the tanks, and didn't seem to be obstructed. Replaced the inline fuel filter on the frame rail. Finally got it started, drove about 60 miles, stopped to fill up, got about 20 miles and started it again. Bucking and lurching like it's starved for fuel, but has a full tank. I even switched ICMs thinking maybe that was the issue. Any ideas anyone?