Vapor Lock Opinions

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Moparmarcus

Moparmarcus

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Recently finished my 360build. Edelbrock intake and carb, therefore susceptible to heat soak and she vapor locks quite easily. What resolution do you guys think is better, plywood or phenolic spacer?
 
Personally I think the phenolic is better at blocking the heat.
I gotta tell ya though, that a return system for the fuel is going to help that a lot more than just the spacer.
It keeps the fuel circulating instead of sitting in the line getting hot.
 
Trailbeast is a car god. :prayer:


My addition is, if that's an aluminum intake that should help too, dick with timing a little bit, see if you can adjust it out.
 
I had this problem ~20 years ago and mentioned my solution in the other thread. I built an 1/8" thick aluminum heat shield that fit under the carb and was the length and width of the intake manifold. Any heat radiating up off the engine hit the shield and was either deflected or radiated into the air before it could get to the carb.

Going this route meant no hole in the hood since it only moved the carb up that 1/8" plus one more carb base gasket.

A return system is a good plan. Keep in mind that you will want the return 'T' as close to the carb as you can get it because the length of fuel plumbing between the 'T' and the carb is semi-stagnant (as compared to the rest of the system) and will try to boil the fuel.
I would use a TBI EFI electric fuel pump and place a by-passing type fuel pressure regulator as close to the carb as you can get it. This will also raise the fuel pressure in the supply line. Like coolant, fuel's boiling point goes up with pressure, so the more pressure that there is, the harder it is to boil the fuel and boiled fuel is really what "vapor lock" is.
 
PoisonDart74 said:
Trailbeast is a car god. :prayer:


My addition is, if that's an aluminum intake that should help too, dick with timing a little bit, see if you can adjust it out.
Click to expand...


Let's not get carried away there, as even a blind squirrel finds a nut once in awhile. :D
 
Like this, only bigger and not as notched:
 

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Best thing I did before I went to EFI was and electric pump in the back, a vapor return system with a Wix 33040 / 33041 filter, and a carb spacer
 
With my old engine 360, edelbrock torquer manifold and edelbrock 625 carb, it would vapor lock all the time, truly was frustrating, the new motor I have edelbrock clone airgap, 1" edelbrock phenolic spacer and edelbrock carb, still only using mechanical fuel pump, and it has not ever vapor locked in 2 summers, and we've had hot summers too, many times over 90 never had an issue, so IMO you only need the spacer and trailbeast is correct get the Phenolic, although it might be that I went from a single plane manifold to a dual plane too, not sure..
 
Why don't you use a carb gasket like this? It is 5/16" thick so it is a good heat insulator, and has "spacers" in the holes to keep the clamp load solid and not warp/break the ears off of your base plate of the carburetor. It also keeps the dual plane split all the way to the carburetor so the throttle response is not compromised on a "true dual plane" application:


BASE GASKET
PART #: 108-18

Features
Fit Holley Model 4010™, Model 4150™ and Model 4160™
1 3/4" Throttle Bore
5/16" Thick


http://www.holley.com/108-18.asp

View attachment Carb Gask Holley 108-18 lg.jpg
 
krazykuda said:
Why don't you use a carb gasket like this? It is 5/16" thick so it is a good heat insulator, and has "spacers" in the holes to keep the clamp load solid and not warp/break the ears off of your base plate of the carburetor. It also keeps the dual plane split all the way to the carburetor so the throttle response is not compromised on a "true dual plane" application:


BASE GASKET
PART #: 108-18

Features
Fit Holley Model 4010™, Model 4150™ and Model 4160™
1 3/4" Throttle Bore
5/16" Thick


http://www.holley.com/108-18.asp

View attachment 1714709756
Click to expand...

I tried that on my car and it helped but didn't cure it.
 
I did too, with the same results. The plate that I made similar to above cured it.
 
TrailBeast said:
Personally I think the phenolic is better at blocking the heat.
I gotta tell ya though, that a return system for the fuel is going to help that a lot more than just the spacer.
It keeps the fuel circulating instead of sitting in the line getting hot.
Click to expand...
ABSOLUTELY...best advice..went thru that crap with my 360 ramchgr....fuel return and circulation...trust me these words of advice can save you $$$ and your sanity not to mention lots of labor/parts changing
 
Thanks guys! I had always thought the plywood was a better thermal barrier but according to this site ( http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html ) I found they are essentially the same. Have also found some very intriguing alleged fixes elsewhere such as:

A metal hanger in the fuel line between the filter and the carb. Based on the premise that a vapor cannot form against an object. Even if true it won't help if my problem is in the bowls.

A clothespin on the fuel line. This allegedly acts as a heat sink.

Ultimately, I will probably go with a phenolic spacer, an inline electric pump and a return line but I thought these were interesting enough to share.
 
krazykuda said:
Why don't you use a carb gasket like this? It is 5/16" thick so it is a good heat insulator, and has "spacers" in the holes to keep the clamp load solid and not warp/break the ears off of your base plate of the carburetor. It also keeps the dual plane split all the way to the carburetor so the throttle response is not compromised on a "true dual plane" application:


BASE GASKET
PART #: 108-18

Features
Fit Holley Model 4010™, Model 4150™ and Model 4160™
1 3/4" Throttle Bore
5/16" Thick


http://www.holley.com/108-18.asp

View attachment 1714709756
Click to expand...




I have used those on my 383 before, I'm actually just going looking for a spacer right now. I do have a dual plane intake, so you are right, that is one more consideration.
 
Also route the supply line away from heat sources as much as possible. You can even insulate it too.
 
Bad Sport said:
Also route the supply line away from heat sources as much as possible. You can even insulate it too.
Click to expand...


I did reroute from the mechanical pump under the alternator over to the inner fender and straight to the carb. I had planned on picking up some insulation tonight, but I don't have high expextations. Having zero improvement so far, I'm guessing it's boiling in the bowls.

Couple more questions though.


I have never purchased an electric pump before and I see a broad range of gph choices. What range should I be in for a 600cfm carb (EB 1406)? Or more importantly what is the criteria for choosing the proper gph? Is there any concern of fuel sneaking through the carb circuit before the float closes the needle due to overpressurization?
 
One other note: Plywood spacers can and do disintigrate and peices of wood end up in the intake.
 
With any electric pump worth considering for your need a regulator will be required. More pressure will do a lot more for you in preventing localized boiling, than will insulation. Neither will help with boiling in the fuel bowls. Airflow, insulating spacer or plate, and not buying cheep fuel are about all that you can do to prevent that. The plate that I built stopped the boiling in the bowls during operation. After a hot shut-down the bowls were always dry and I never found a way to stop that. The best that I could do was to not buy cheep fuels as they seemed to be more prone to this than better fuels. ARCO gasoline was the flat-out worst for this in my experience then, no idea what its like now.
 
I can attest to an aluminum heat-shield as a good solution particularly to fuel boiling... i've used both that and a phenolic spacer and they both work well. The heat shield is nice because it's super thin which helps with hood clearance whereas a spacer can give you a little extra power from bigger plenum
 
If you have headers, you need to insulate the fuel line on the frame. Makes a big difference!

Other then that, fuel return system is the best plan.
 
I'm going to keep hammering on this, raise the fuel pressure in the supply line and use a by-passing type FPR!
 
A vapor return line is the best route either from a fuel filter or vapor separator like hemi and 440 6bbl cars had with a 1/4" return to the tank.
 
69hemibeep said:
A vapor return line is the best route either from a fuel filter or vapor separator like hemi and 440 6bbl cars had with a 1/4" return to the tank.
Click to expand...

Just curious and not to hijack but why did just those cars come with a vapor-return system and not the rest of them?
 
MOPEkidD-3 said:
Just curious and not to hijack but why did just those cars come with a vapor-return system and not the rest of them?
Click to expand...
I also believe the 440 4bbl cars got this treatment also, probably under hood heat and performance. I was surprised to see my 3/8 sending unit for my valiant had the return port on it so its getting the treatment. I had two 401 jeeps that on long hard full throttle hill climbs would run out of gas(vapor lock) and after adding the return the problem went away.
 
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