Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: old blue 75 on May 22, 2020, 12:25:54 PM
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I read some where lately that the e10/15 fuel will vapor lock in
carburetors when used with a mechanical fuel pump.
Is there any truth to this?
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Carburetors are vented to atmosphere and cannot be "vaporlocked".
Vapor lock occurs in fuel lines heated by being too cloose to hot engine parts or exhaust system.
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Correct.
Another big problem I see is "rotten" or porous rubber fuel lines sucking air instead of fuel. This is ALWAYS mistaken for "vapor lock" and easily fixed with a couple of pieces of rubber hose and some good hose clamps.
I would also warn folks reading this to ALWAYS run solid fuel lines on the pressure side of the fuel pump. I'll bet 1 in 3 set-ups I see have had the factory steel line cut for one reason or another and a piece of rubber hose installed with a couple of clamps on it. That's bad enough but folks NEVER put a "bulge" in the metal lines to keep the rubber hoses from slipping off.
That entire deal is a DISASTER waiting to happen!.......
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This is a 1986 chevy truck that is currently all apart.
It will have new duel tanks and lines.
I would like to keep the mechanical fuel pump but if it will cause
problems I may change to a electric in line.
But I am not sure if a inline will draw from the far side tank.
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Does any one know what electric fuel pumps can have fuel pulled thru by a mechanical pump.
My thought is to put a electric pump in line but only use it when needed.
I was thinking of using this mechanical pump. https://www.summitracing.com/parts/ado-41216/make/chevrolet/model/camaro/year/1982/submodel/z28 (https://www.summitracing.com/parts/ado-41216/make/chevrolet/model/camaro/year/1982/submodel/z28)
And maybe a pump like this for inline. https://www.summitracing.com/parts/hly-12-427 (https://www.summitracing.com/parts/hly-12-427)
My thought is to wire the pump to a momentary switch for priming, and a full throttle switch
for high demand.
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I have read reviews that this pump will do it. Airtex E8090
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The only way I was able to get a handle on vapor issues was to install a return system to the tank.
I used the wix return style filter 33041 up near the carb with the return to the tank and eliminated the vapor issue.
I then removed this filter and installed a return style mechanical pump utilizing the return system and this did not work, vapor problem came right back.
I installed a fitting inline up near the carb and used a .060 restriction in the return just like is in the return style filter and low and behold no more vapor issues.
i currently have a rubber return line coming from the fitting which I intend to replace with a metal line near the engine.
In my case the fuel problem was in the line from the pump to the carb. I also rerouted the line at one point and did not help.
Not to mention using an aftermarket mechanical pump that puts out to much pressure causes other issues.
Never have I tried an electric pump.
This is my experience and worked for me.
1974 K5 350
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My thought is to wire the pump to a momentary switch for priming, and a full throttle switch
for high demand.
The tank switch is a momentary switch already, yoi can probably piggy back off the power at tue switching valve. then just hold LH and/or RH tank switch for x seconds to prime with electric pump.
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Have a question on thread sealing. I am plumbing a system like this.
The only way I was able to get a handle on vapor issues was to install a return system to the tank.
I used the wix return style filter 33041 up near the carb with the return to the tank and eliminated the vapor issue.
I then removed this filter and installed a return style mechanical pump utilizing the return system and this did not work, vapor problem came right back.
I installed a fitting inline up near the carb and used a .060 restriction in the return just like is in the return style filter and low and behold no more vapor issues.
i currently have a rubber return line coming from the fitting which I intend to replace with a metal line near the engine.
In my case the fuel problem was in the line from the pump to the carb. I also rerouted the line at one point and did not help.
Not to mention using an aftermarket mechanical pump that puts out to much pressure causes other issues.
Never have I tried an electric pump.
This is my experience and worked for me.
1974 K5 350
That being said what sealant can be used on pipe thread for gas?
Will this work?
https://www.fedprobrands.com/products/pipe-thread-sealants/gasoila-e-seal-thread-sealant.html
Or this?
https://www.permatex.com/products/gasketing/gasket-sealants/permatex-aviation-form-a-gasket-no-3-sealant-liquid/
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I use permatex high performance thread sealant
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^Ditto^.