Vaping

Arctoad · July 19, 2019, 02:45:00 PM

I need some advice on "Vapor lock". When I rebuilt my carbs I opted not to block the heat risers and now I'm wondering what the best way to alleviate the effects..
I should give my side effects first.
The car immediately starts when it hasn't been used for a length of time, probably an hour or so.
It is only after I've driven the car for a while, depending on the out side temperature, that if I shut the car off it takes quit a few cranks of the engine to start again.
Performance while running is really not effected, It does run better in cooler temperatures how ever.
Anyone?

70 Challenger Lover · July 19, 2019, 03:52:34 PM

I'd install a 1/2 phenolic block under the carb to help. Won't cure the issue completely but it helps a lot. Basically, when you shut it off, heat soaks up into the carb and boils off the fuel in the bowl. It spills into the manifold and floods it for a while until it eventually all evaporates. The bowl of course empties out. When you restart it, best to not touch the accelerator while cranking so the engine can clear out the excess faster. With today's ethanol, the boiling point of fuel is much lower making this issue more problematic than ever.

They make a sleeve to cover the fuel line and I've been wondering if they help a lot. Maybe someone here has tried one and can offer their opinion.

Brads70 · July 19, 2019, 03:58:50 PM

I run an electric fuel pump with a regulator mounted in the engine bay that has a return line, so cool fuel is always being circulated. I also used firesleeve on all the fuel lines that were near exhaust. Also running a coolcarb plate. http://www.coolcarb.com/order-products.html
I see they do have this warning....
WARNING
This product is not recommended for the use on:
1. Intakes with heat crossovers and EGR values in the intake.
2. Straight 4-6-8 cylinder motors where the exhaust and intake overlap.
3. Some castiron intakes have had an issue also
REASON: The polycore is an excellent insulation but it cannot take the extreme heat
that the exhaust creates. This causes it to get soft or melt.

Arctoad · July 21, 2019, 06:08:22 AM

Thanks for the reply guys, I'll try the Phenolic spacer for now, I'm not sure if I want to go full on Electric fuel pump yet, although I bet it has some very good performance effects for these motors.

70 Challenger Lover · July 21, 2019, 01:20:00 PM

I have the same thing going on in a barracuda I just picked up with a 318. Runs cool but hard to restart after shutting it off after 20-30 minutes. I sent my carb out for rebuild and I'm going to reinstall with the block. My next step will be the wrap on the fuel line and if I have to, block the heat crossover last. Hate to do that because the thing starts and warms up so well with it's original configuration. I considered the cool carb plate but the warning about not being suitable for heat crossover stopped me. In my case, I can live with it being a mild problem but not like it is now. I've done the 1/2" block on my other cars and it works reasonably well.

Katfish · July 21, 2019, 03:26:41 PM

Edelbrock makes a nice insulating gasket. Several to choose from, worked well for me.

https://www.summitracing.com/parts/edl-9266?seid=srese1&gclid=EAIaIQobChMItJrO5YbH4wIVxJ6zCh3Ibg9fEAQYAiABEgKW5vD_BwE

GoodysGotaCuda · July 21, 2019, 06:31:06 PM

I have the edelbrock phenolic spacer on my carb and a Carter low pressure electric fuel pump [no regulator].

It's cured all of my hot start and long-sit starting issues completely. [On my Warlock]

70 Challenger Lover · July 21, 2019, 06:45:42 PM

How quiet is that fuel pump? I assume is gets mounted by the gas tank and pushes rather than pulls?

Every time I think of electric fuel pumps, I think of the one my dad's old dodge van had. Worked great but noisy as hell. Used to bug me to no end.

GoodysGotaCuda · July 21, 2019, 08:01:38 PM

Quote from: 70 Challenger Lover on July 21, 2019, 06:45:42 PM
How quiet is that fuel pump? I assume is gets mounted by the gas tank and pushes rather than pulls?

Every time I think of electric fuel pumps, I think of the one my dad's old dodge van had. Worked great but noisy as hell. Used to bug me to no end.

It's up near the factory mechanical fuel pump, cant hear it at all with the engine running, and the exhaust is quiet.

Sent from my iPhone using Tapatalk

70/6chall · July 21, 2019, 10:34:50 PM

A Slant6 E-body like mine, with the carb sitting over top of the exhaust, will experience Vapor-Lok, as you refer to. In SoCal during triple digit times of the year this really frustrated me. Then I had to go and increase the already existing problem by adding a set of steel tube Hooker headers. Nothing adds more heat to the engine bay than headers. Then set the carb and fuel line over this set-up, aargh!
To circumvent the problem I had a custom heat shield made out of 1/8" T6 aluminum. It completely covers the intake runners and under the carb with thick thermal carb gaskets above and below shield.
This helps divert the rising heat in deflection out from under the carb. I also gained a plenum increase with a 5/8th lift under the carb. I experience less vaporization of The fuel charge now on extremely hot days. By adding a power bulge hood on a Slant6 powered car this puts my 14x3 open element air cleaner right in line with the scoop opening on the drivers side of hood. So a cool air charge to the carb instead of heated under hood air. Win,Win for me. Had the heat shield polished looks nice.
Thanks, Al

73440 · July 22, 2019, 04:01:30 AM

Had the hard start when hot problem.
Added the wooden carb spacer and also used the DEI sleeving on the fuel line from the manual fuel pump to the carb.
Have not had the hot start problem since.

Arctoad · July 22, 2019, 07:14:51 AM

I took my car to work yesterday, about 40 min drive at 70 mph just humming along. Ran great in the cool morning. It sat out in the direct sun the whole day which was around 30 degrees C for you Northern folk. When leaving at 4:00 pm it didn't want to start.. I have never had this problem being stored in the shop all of the time when not in use. After many attempts of cranking and affirming that I had ignition, It finally started pulling fuel.
I think I will try wrapping my fuel lines for starters and work in from there.

70 Challenger Lover · July 22, 2019, 11:18:28 AM

Quote from: Arctoad on July 22, 2019, 07:14:51 AM
I took my car to work yesterday, about 40 min drive at 70 mph just humming along. Ran great in the cool morning. It sat out in the direct sun the whole day which was around 30 degrees C for you Northern folk. When leaving at 4:00 pm it didn't want to start.. I have never had this problem being stored in the shop all of the time when not in use. After many attempts of cranking and affirming that I had ignition, It finally started pulling fuel.
I think I will try wrapping my fuel lines for starters and work in from there.

All the ethanol in today's fuel lowers the boiling point. After you shut it off, the built up engine heat soaks the carb and the fuel in the bowl boils. At first it spills over into the intake creating a flooded condition. Eventually, that evaporates away. The bowls of the carb percolate away to nothing leaving them mostly empty. That's why you have to crank it a while to fill them again. Ethanol has many downsides and this is one of them. An electric fuel pump would fill the bowl back up before you started cranking but I'd like to prevent it from happening at all if the carb can be properly insulated. Intake heat crossovers and headers make that harder. Insulation on the fuel line probably would help since a bare steel line would pick up heat before the fuel even made it to the carb.

YellowThumper · July 22, 2019, 11:52:13 AM

Bottom line with todays fuel and original carb setups. The fuel boils away after all is shut down. This leads to the "flood" in the intake and empty bowls. Would suspect the same thing is happening within the feed line. Same premise as coffee makers percolating. Hard starting becomes the norm. Post pump line and carb have to be refilled.
Same as Brad noted. I have electric pump with return line for eventual EFI. I am still on carb for now. Bonus effect is it eliminated the hard start issue completely. Because new fuel is primed prior to cranking and hot stagnant fuel is returned to tank.

Arctoad · July 23, 2019, 05:08:08 AM

Thanks everyone for the great info, I'm sure this topic helps everyone that owns pre EFI vehicles.