Back fire when cold? Edelbrock carb - Chevelle Tech
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post #1 of 20 (permalink) Old Nov 12th, 19, 8:10 PM Thread Starter
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Back fire when cold? Edelbrock carb

It don't get cold much in the south but when it does my engine will back fire through the carb at anything more than half throttle and start to stall, and when I say cold I mean about 10 minutes of idling and 180 temp out of the thermostat. The problem goes away after heating the engine more. The choke is working properly, went though many guides and videos. I'm thinking I need to go more rich but looking at the plugs and intake it looks like im running to rich, if that makes sense? Thinking of getting rid of the eddy carb, I cut my teeth on quads so maybe I'm expecting to much out of it? Any suggestions or advice?

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post #2 of 20 (permalink) Old Nov 12th, 19, 9:05 PM
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Re: Back fire when cold? Edelbrock carb

I have ran the edelbrock carbs for many years and ran Carter AFB's before that and Q jets and Holleys.

The absolute worst has been some of the newer ones like sold in the last 6 years.
The issue I have found is Float issue.

Seems an off road needle and seat will allow the float in some carbs to not seat the needle and run rich.
The float will move up as the fuel level rises. Just like normal.
BUT the float arm on some floats will rest against the steel baffle that is above the float before the needl shuts off.

Other times the floats are bent wrong.
Could have happened in shipping as I have seen Fedex and others toss packages like a football.

I have ran the old style Edelbrock RPM intake and single plane Strip dominator and Iron and aluminum Q jet intakes and have ran many spacers and some intakes were ported.
Now with that said all of them ran fine .. no lean popping etc.

The Edelbrock RPM air gap gave me fith with 2 different carbs an Edelbrock and my 750 Double pumper.
Took a long time to get heat into the runners before it would act right.
15 minutes of driving usually.

I pulled it off and stuck the old style RPM back on and no issues and I was able to pull a lot of fuel out of it.

It might make more on a dyno at full throttle but driving around on my SBC it was not a good experience.

I have ran the 12" tall tunnel-ram with 2 edelbrock 600's and it ran great also.

I have no idea what intake you have or what timing curve you have either.

Could be the timing.
I run 18 minimum timing at idle and sometimes 22 at idle.

In the winter time I can screw my idle mix screws out 3/4 more and it makes it happy.. usually have them 2.5 turns out on my Edelbrocks for warm weather .

Clean the plugs and you may need hotter plugs or hotter coil etc.
I have seen weak coils blacken the plugs and make the engine run like poop.
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post #3 of 20 (permalink) Old Nov 12th, 19, 11:29 PM
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Re: Back fire when cold? Edelbrock carb

likely the cold incoming air is freezing the gasoline in the carb air horn, venturi effect,high pressure to low pressure, one of the reasons heated air from the exhaust was directed into the air cleaner in later years.
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post #4 of 20 (permalink) Old Nov 13th, 19, 8:47 AM Thread Starter
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Re: Back fire when cold? Edelbrock carb

Quote:
Originally Posted by LeoP View Post
likely the cold incoming air is freezing the gasoline in the carb air horn, venturi effect,high pressure to low pressure, one of the reasons heated air from the exhaust was directed into the air cleaner in later years.
Thanks Leo, I read into it and that seems to be exactly whats happening, the insulated fuel line and wood carb spacer isn't helping the situation either.
Here's the article I read if anyone else is curious.

https://www.hemmings.com/blog/article/carburetor-icing/
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post #5 of 20 (permalink) Old Nov 13th, 19, 5:19 PM
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Re: Back fire when cold? Edelbrock carb

Are the heat passages in the heads and intake manifold open, or blocked off?
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post #6 of 20 (permalink) Old Nov 13th, 19, 8:56 PM Thread Starter
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Re: Back fire when cold? Edelbrock carb

Quote:
Originally Posted by Dave Ray View Post
Are the heat passages in the heads and intake manifold open, or blocked off?
They are blocked and it's an edelbrock rpm intake with endura shine for some reason (car is a rat at best). It was something done by the guy I bought it from, I usually don't stray to far from stock but I'm working with what I got, hence the learning curve.
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post #7 of 20 (permalink) Old Nov 14th, 19, 9:59 AM
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Re: Back fire when cold? Edelbrock carb

You want that intake heat closed off with todays fuel..

Just run a manual choke and set it to were it runs nice until it warms up. It will become second nature were to set the cable..
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post #8 of 20 (permalink) Old Nov 14th, 19, 10:25 AM
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Re: Back fire when cold? Edelbrock carb

Rame,

How long have you had the car ? Is this a new "issue" or has it always done it ?

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post #9 of 20 (permalink) Old Nov 14th, 19, 3:32 PM Thread Starter
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Re: Back fire when cold? Edelbrock carb

Quote:
Originally Posted by BillK View Post
Rame,

How long have you had the car ? Is this a new "issue" or has it always done it ?
Been about 4 years now, it only happens when it's about 50 degrees or lower and that doesn't happen too much in my area.

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post #10 of 20 (permalink) Old Nov 14th, 19, 4:20 PM
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Re: Back fire when cold? Edelbrock carb

What is the timing set at


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post #11 of 20 (permalink) Old Nov 14th, 19, 10:56 PM
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Re: Back fire when cold? Edelbrock carb

Yes, what are the timing parameters?

I NEVER completely block off the heat cross over passages on street engines. I do restrict them by adding one each, 1/4 inch hole in the block off plate for one side, and 1/8 hole in the other one.

Completely blocking off heat passages makes for serious problems, especially in things like the stupidity of trying to run an "Air Gap" disaster on the street. Instead of the exhaust heat, even in the small transfer volumes of it I use, water heating under the carb and plenum is the best way to do it, can be shut off for drag racing, used for street use.
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post #12 of 20 (permalink) Old Nov 15th, 19, 10:38 AM Thread Starter
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Re: Back fire when cold? Edelbrock carb

I need to check it again but the timing is 35 all in at 2500 if I recall right. It has vac advance, hei distributor, CS XE262H-10 cam, eddy 1406 carb with rpm intake, hedman full length headers. Other than that it's fairly stock idle in park is 1000 rpm, always had problems getting it to run on cold days.

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post #13 of 20 (permalink) Old Nov 15th, 19, 10:43 AM Thread Starter
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Re: Back fire when cold? Edelbrock carb

Quote:
Originally Posted by hydro462 View Post
You want that intake heat closed off with todays fuel..

Just run a manual choke and set it to were it runs nice until it warms up. It will become second nature were to set the cable..
I tried that about a year ago with that same thought but it didn't help.

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post #14 of 20 (permalink) Old Nov 15th, 19, 5:42 PM
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Re: Back fire when cold? Edelbrock carb

Please outline these parameters for timing, if you would:

INITIAL timing, with vacuum advance hose disconnected and plugged
Mechanical advance degrees, this specification, added to the INITIAL, will give the total advance (INITIAL and mechanical degrees)
VACUUM ADVANCE degrees of timing the unit will add
What source is the vacuum advance working on, ported, or full manifold vacuum?

What we are attempting to do is form a set of specifications the tmiing is working from

NO OFFENSE INTENDED, but, "36" really doesn't tell us anything.
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post #15 of 20 (permalink) Old Nov 15th, 19, 6:21 PM
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Re: Back fire when cold? Edelbrock carb

What octane fuel you running? Higher octane fuel burns slower by nature and can cause problems during cooler operating conditions.If the car runs good when warmed up, try changing your fuel grade to a lower octane. Easy and cheap thing to try. If you live up in my part of the country, there are specific warm and cold weather blend fuels. Generally speaking, octane level requirements drop in colder conditions. Cooler intake charge helps to deter detonation.
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