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Engine compartment heat

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Engine compartment heat

Post by csmck on Sun Jul 09, 2017 1:04 pm

Is/has anyone suffering/ed from engine compartment heat causing fuel system vapor locking? How did you solve the problem

After driving on a hot day and shutting down, the engine compartment temp goes through the roof essentially boiling the fuel line dry. Makes

I'm running a chevy sbc engine with edelbrock 600cfm carb with 1/4 spacer between the manifold, a mild cam and a 4 core griffin radiator. Driving temps are normal range. I've taken to opening the hood after driving to give the engine heat a greater chance to escape and cool down faster.

I'm looking at adding a header blanket insulation, insulate the fuel line, and spark plugs.

Currently running the faux louvered hood, and would love to find someone to convert it to actual working louvers.

Charles


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Re: Engine compartment heat

Post by Hotrod on Sun Jul 09, 2017 10:13 pm

Make sure your fuel line isn't close to the exhaust.  The insulation will help, but much better not to get it too close to begin with. Unfortunately, there isn't much room to work with and moving the line may not be possible.

If the problem can't be solved with insulation, you may have to resort to a return type fuel supply.  GM used mechanical return fuel pumps to combat vapor lock.  That may help you, but you would have to install a return line all the way back to the tank.  Just about any car or truck from the 80's should have that type of pump.  The downside to the mech system is that when you shut the engine off the fuel can still boil because it's  not moving and cause hard starting problems.

You could also go to an electric pump.  It should be as close to the tank as you can get it and below the bottom of the tank.  This helps because the fuel in the line stays under pressure (instead of suction with a mech pump) and slightly raises the boiling point of the fuel.  Plus you have the advantage of the pump pressuring the lines when the key is turned on.  I use electric pumps on all my hot rods because I can prime the carb before I start the engine.  My cars usually sit  for long periods and the fuel can evaporate.  Running the electric pump a few seconds will fill the float bowl up and prevent unnecessary grinding on the starter.

The best system would be an electric pump in or near the tank  combined with a bypass regulator under the hood.  The pump will circulate fuel through the regulator and back to the tank as soon as it's turned on.  This will fill the lines back up quickly even if the fuel does boil off.  

With any return type system (mech or electric), the fuel will stay cooler because it is constantly being circulated back to the tank and never stays in one place long enough to pick up much heat.  Except for the line from the mech pump or regulator to the carb.
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Re: Engine compartment heat

Post by csmck on Tue Jul 25, 2017 7:20 pm

Thanks for the electric pump advice. I'm researching electric pump options; think I'll go with Edelbrock to match the carb.

Also having a local custom shop quote a vented hood.

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Re: Engine compartment heat

Post by Hotrod on Tue Jul 25, 2017 8:42 pm

One thing about the Edelbrock carbs is that they don't like fuel pressures above 5 PSI. I believe this is in the tuning manual that comes with the carb.

I usually run a regulator on them no matter what type of pump I'm using. They will suffer from flooding if the pressure is too high. I've had very good luck with the cheaper Holley brand regulators.
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Re: Engine compartment heat

Post by csmck on Fri Dec 29, 2017 1:18 pm

Has anyone tried/considered converting the hood louvers to actually work?

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Hood

Post by DrJ on Sat Dec 30, 2017 8:48 am

My MX (SBC motor) has had the same issues and Hotrods advice regarding electric fuel pumps would likely solve the issue. I intend to plumb one in this Spring although with a slightly different approach. I had a electric priming circuit in the aircraft I built. Essentially I used a 12v Facet electric fuel pump to pressurize the system. The engine had a mechanical pump as well, lots of redundancy designed into aircraft engines. The boost pump was only used to start the engine and on takeoff and landing approaches. The primer was an electric solenoid valve actuated by a push button in the cockpit. You would switch on the pump, push the primer button for a few seconds and start the engine. Once running you would switch off the Facet pump and run off the mechanical until taking the active runway. Facet pumps are cheep, 50-60 bucks, put out up to 5psi, are self priming, and capable of lifting fuel about 12" if necessary plus no return line. I would omit the whole priming valve thing and simply plumb the pump into the existing fuel line at the tank. To facilitate a hot start (where I experience my start problems) I would flip the switch on for a few seconds, start the engine and flip it off. I'll post my success/failure on this when the ice age comes to an end up here.
Regarding the hood I had ambitions of addressing the louvers as well. With a little internet searching I found companies that sell louver sections in various dimensions and metal gauges. I envisioned carefully cutting out a 12" section of the existing fake louver and creating a slightly sunken perimeter lip that the new metal section could drop into. Would rivet nut plates to the lip so that the metal louvers could be screwed in place and replaced if necessary. You could either retain the remaining fake section of cut them down flush to the hood as this whole process would likely require fiberglass refinishing and painting anyway.
As it turns out I will be starting a new car project this Spring so once I solve the hot start issue, I will probably be putting my Healey up for sale. I'll leave the louver issue to the next enthusiast.

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Re: Engine compartment heat

Post by David V. on Sat Dec 30, 2017 9:23 am

Sad to hear you'll be leaving our little site DrJ Crying or Very sad
Your contributions were always much appreciated, and cool insight into the aeronautical world!
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Firewall Foward

Post by DrJ on Sat Dec 30, 2017 10:26 am

No worries David, I plan to continue to enjoy this site you created going forward. It is a fine environment you have assembled and it has attracted a great group of automotive hobbyists. I have, and hope to continue to learn from this group as fellowship should have no restrictions such as make and model. The vapor lock issue we have been discussing will very likely come up in the new project. Solutions for it and many other "complications" usually apply throughout the hobby.

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Re: Engine compartment heat

Post by David V. on Sat Dec 30, 2017 11:41 am

That's great to hear! Always feel free to post any of your other endeavours in the "off-topic" section, that's why it's there. Pretty fun to see we have members from all walks of life who all contribute in their own way. You'll always be welcome here!

David
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Re: Engine compartment heat

Post by panasoffkee on Tue Feb 27, 2018 10:03 pm

Clothes pens on the fuel line. Louvered hood !, wrap exaust, Retard the timing, High volume fuel pump.
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Re: Engine compartment heat

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