Resolving Heat Soak

1 Resolving Heat SoakWe would like to take some time to share with you some of the answers to the common questions we receive on our Technical Support hotline.

After driving my vehicle for a period of time, and after shutting off the engine I sometimes encounter a hard to start situation (engine cranks over several times before starting) and it usually occurs within a window of 15 minutes to one hour. What can I do to resolve this situation?

Chances are you are experiencing heat soak, compounded by today’s blended fuels. Following are some things to keep in mind in an attempt to alleviate this situation.

  • Ensure that your fuel line is routed away from your exhaust and or block. This will help alleviate excessive fuel temperature in the supply line that can directly relate to pressure building in the line resulting in the needle and seat being overridden by the pressure causing a flooding condition.
  • Remember, heat rises and when the vehicle’s engine is turned off, the rising heat can easily penetrate the carburetor and cause the fuel in the float bowls to expand and eventually boil or percolate.

If hood clearance permits (air-cleaner top to the underside of the hood) then consider installing a heat insulator gasket between the carburetor and the intake manifold. This will create an effective barrier between the hot intake and the carburetor. Here are a few tips when selecting a heat insulator spacer.

  • Aluminum spacers offer little if any protection against heat soak.
  • Wood fiber laminate, black phenolic plastic and heat insulator gaskets provide great insulation.
  • If hood clearance is limited, the following three part numbers are recommended.
  • #9265 open design best suited for single plane intakes (.320” thick)
  • #9266 best suited for dual plane intakes (.320” thick)
  • #9267 best suited for dual quad intakes with 4-hole style carb pad quantity of two (.125” thick)

For additional heat insulators in sizes from 1/2” – 2.00” please visit this link on our website.

Got a technical question? If so, you can rely on our Technical Support Department for the right answer. The Edelbrock Tech staff is here Monday through Friday, 7 am – 5 pm PST to answer all your questions. You can reach them by phone at 1-800-416-8628 or you can visit our Tech Center for a complete listing of installation instructions, videos and FAQ’s .

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20 Responses to “Resolving Heat Soak”

  1. jake simmons says:

    Keep up the good work guys!! Just bought a new carb and intake manifold and the icrease in performance is amazing.

  2. chris romanchuk says:

    hi nice tech tip ,. works well trans adapt offers 1/2″ laminate type . i have a question about a 1813 thunder series avs carb i purchased in 2007 . the issue i am having is i have a 1968 charger with a 383 engine stroked to 500 cu in. – carb charts recommend 760 cfm . thats why i purchased this model carb and size . i have moved the throttle accelerator pump lever rod to the closet one to carb body . also purchased your three larger accelerator pump squirter nozzles . placed the biggest one on .043 . car boggs under fast heavy acceleration only !!!! , i ground off the accelerator brass nozzle tips to get to larger pipe size . a little less stumble . i then drilled one more hole in the accelerator pump lever arm to get more accelerator piston stroke . 95% fixed . is there any way to get a larger accelerator pump capacity displacement ? holley carbs have larger capacity bolt on accelerator reserviors 50cc and multiple accelerator pump cam options !!! i am wondering why a high tech performance company such as edelbrock did not increase the diameter of the accelerator pump piston/chamber when making this improved carter afb carb . a duel carb set up would defintely correct my concern by i purchased this carb to keep my engine looking stock a read all the good reviews . i can not be the only person with this type of problem from this carb 1813 . got any solutions ? if not you should ad a disclaimer so that some with a large cube engine will not waste $500 dollars purchasing this carb and linkage kits to make it work . thank for reading this / chris romanchuk

  3. admin says:

    I forwarded your question to Dave Stinson of our tech dept. Please call him and he will take care of you.

    Tech Line Only: 800-416-8628

    Hours: Monday-Friday 8:00 am-12:30, 1:30-5:00 pm PST, weekdays

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  6. [...] has posted up a very interesting tech tip that helps drivers of carbureted vehicles figure out what is causing an issue where the car might [...]

  7. [...] has posted up a very interesting tech tip that helps drivers of carbureted vehicles figure out what is causing an issue where the car might [...]

  8. [...] has posted up a very interesting tech tip that helps drivers of carbureted vehicles figure out what is causing an issue where the car might [...]

  9. Dave says:

    I have an 83 GMC truck that I bought that has a 350 in it with a performer intake and an edelbrock performer carb on it. This carb has an aluminum spacer under it, I think it is 2 inch thick. I am having the heat issue causing percolation of the gas in the carb. I bought a 9266 insulator to install, but I don’t know that it is a good idea to have the spacer and insulator between the carb and intake. I know that the right thing to do is buy an insulating spacer, but I would like to try and make this work to save cash. Is this possible, and if so, do they sell mounting studs long enough to accomodate this application?

  10. admin says:

    The 2.00″ Aluminum spacer is doing little to nothing to resolve this
    condition, as the alloy absorbs and dissipate heat at a fast rate, and
    said heat penetrates the carburetors main body, in which can compound
    the percolation difficulties you are encountering.

    We would recommend one of our heat insulator spacers available in the
    following part numbers and thicknesses:

    #9266 (5/6″ thick)

    #8725 (1/2″ thick, wood/fiber laminated construction)

    #8711 (1.00″ thick, 4-hole design, phenolic black plastic)

    #8713 (2.00″ thick, 4-hole design, phenolic black plastic)

    The answer another question you have regarding the carburetor studs.
    All of the heat insulator gaskets and spacers come with longer studs to
    accommodate the thickness of the gasket/spacer.

    NOTE: Today’s oxygenated Ethanol based fuel is mostly to blame for this

  11. TIM says:

    800 edelbrock carb would I still have heat soak with this combo

  12. ken hodge says:

    i installed a new Edelbrock carburetor and dual plain intake and after my car reaches 170 to 190 degrees it want to flood at idle and hard to start when shut off.

  13. Gary G. Foster says:

    Just installed a SBC 383 / 425 HP with Edelbrock dual four low profile manifold and 2 1401 carbs. As you can imagine it runs rich. It is also very hard to start especially after it’s been running. What would be an ideal starting point for jets and other settings? I might also mention that it originally started fairly good but I had it backfire a couple times. Could this have caused my hot start issue? I’m sure it most likely didn’t help!! :(

  14. admin says:


    I have forwarded this to our tech department and they would love to assist you. Can you please call our toll free tech line at 800-416-8628 and ask to speak with Dave Stinson.

  15. [...] Are you running any kind of thermal break gasket or spacer under the carb to keep the fuel from boiling out of the carb from the heat soak? Edelblog | Edelbrock Tech Tips – Resolving Heat Soak [...]

  16. Jeff says:

    I have an edelbrock 8867 carb and am having heat soak issues. What model heat insulator P/N shall I use with my edelbrock intake on my Jeep V8 304? I have space between my air clearner and my hood.

  17. admin says:

    I would recommend our #8723 wood-fiber laminated 4-hole spacer, it is ½” thick and serves well to insulate the carburetor from the hot intake manifold.

  18. austin says:

    I have a Edelbrock top end kit 2022, with a edelbrock carb 1405. on a 350, I have a lot of space under the hood of my 66 chevy truck. I am experience the same hard starting issues when the engine is hot. What would be the best spacer for me to get?

  19. admin says:

    I would recommend the #8723 (1/2” wood fiber laminated spacer) unit is supplied with the longer carburetor studs and gaskets

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