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Edelbrock question

Hi, me again. :slight_smile:



I have two different 350’s with Edelbrock carbs on them. Both fire up nicely at the turn of the key, but once they are warm and are shut off, they both need to be cranked for a while with my foot on the pedal just a bit before they will fire up again. The chokes are open fully after three minutes.



Both are orange blocks with no computerized equipment whatsoever except one with standard HEI ignition and the other with MSD. Both are on non-EGR Holley Street Performer intakes, and both are rebuilt blocks with religious oil changes and maintenance.



I plumbed both of these with rubber gas line and have done all I can think of to be sure there are no leaks at either end.



Any ideas what is the problem or is this an Edelbrock trait?

You could experemint with small timing changes. Re-wire to give max cranking speed. B+ busing at the starter causes voltage drops. Have the engine scoped to see if the secondary ignition is working optimaly. Play around with plug gap,heat range and type may get you somewhere.

I would concentrate on maxing out cranking speed.

I use a Edelbrock performer on my 330 hp small-block with HEI,all I have to do is jingle the keys and it starts. So long crank times are not a characteristic of the Edelbrock performer carb series. I am not familar with your intake.

I agree with dinking around with the timing changes but what about the possibility of vapor lock?
Holding the throttle open a bit could be a sign of clearing out a flooded condition.

Do these carbs have base gaskets only under them or do they have 1/4" thick insulator blocks, etc.?
If the former, then vapor lock is a possibility; especially if the climate where you’re at is warm this time of year.

With the engine warmed up completely, shut it off, remove the air-cleaner completely and look down the carb throat with a bright flashlight. Do you see any dripping or just vapor in the carb? Now open the throttle wide and pear all the way down into the manifold. Hold it open for 30 seconds while you look for any signs of fuel leakage into the engine. There should be NONE.

Todays gasoline is high vapor pressure stuff, designed for modern fuel injected engines with sealed fuel systems. When used in a carburetor, especially a heated carburetor, it will easily boil in the carbs float chamber, percolating down into the engine flooding it. This is not the carbs fault. Sometimes it helps to install a fuel filter with a tank return built in. This will drop fuel line pressure to zero when the engine is turned off, preventing the carb from filling itself from the pressurized fuel line even though the engine is off…

I never had that problem but you might try opening up the idle mixture screws a little. I guess that the engine isn’t getting enough fuel through those ports for it to start.

Hmmm, ok. I’m glad to hear this is not an “Edelbrock thing”. It really would be nice to get it so I can just bump the key in classic Chevy style.

I have timing set at 12 BTDC and a crane adjustable vacuum can on each to remove any ping under part throttle. I know this is not stock. I’m assuming you mean try backing the timing off a tad for better results?

It’s a Holley Steet Dominator intake. My appoligies. I was going from memory and well, you know… It’s a low rise, single plane, aluminum intake… non-EGR.

Neither carb has a 1/4" spacer under it, just the skinny one (1/32")that came with it, so heat could easily be a problem as neither has a windage tray either. Is a mere 1/4 really effective for this? I note most Rochesters come with 1/4 spacers.

I have seen aftermarket 1" spacers as well, but read they would negatively affect the low-end performance, and wouldn’t be possible in my Malibu. It would go in the truck though. These are daily drivers here. Worth it or nah fuggedit and go with a 1/4"?

Oldschool, I can’t say I understand what you mean with “B+ bussing at the starter”. Are you suggesting wiring in a remote solenoid?

B+ busing, What it is ,GM likes to use the big terminal on the starter as a “bus” point,that is a power distribution point. It makes for more than necessary connections and voltage drops. We only have a little over 12V to start with so loosing a little here a little there adds up.

There are techniques that move the bus point off that hot solenoid up onto the fenderwell. You bridge the starter solenoid so the only time power goes down there its to engage the solenoid and turn the starter.

Basicaly just techniques to reduce the number of connections and reduce voltage drops.

How many amps is your starter pulling? How is the cranking speed? could it be better? Would shimning your starter help out? Ever get the dreaded “click” and nothing else when you turn the key? Reducing voltage drops helps these thing tremendously.

You made this post while I was answering the others. I’m leaning towards the vapor lock - boiling gas theory, at this point.

I do have in inline gas filter down by the fuel pump. It’s one of those 2" can types. It is close to the block (1 1/2"). Would the gas boil in the filter and line and force it’s way past the needle etc… resulting in flooding?

Thanks for the excellent description. I know just by listening to it that it needs to be shimmed. Just something I have been putting off, really. The cranking speed seems to be ok, but I’m sure shimming it would help, and if I don’t do it sooner or later I can kiss the starter good-bye.

I’ll have a look at the wiring harness to see when I’m down there, but I recall it being pretty simple. Just the one main wire to the main lead, and a few “feeders” to power the solenoid. I have no idea how many amps my starter pulls. It is stock.

The Edelbrock carburetors look very much like they’re based on, if not exact copies of, the old Carter AFB carburetors of the 60’s, pre-Quadrajet. If that’s the case, the behavior you’re seeing is certainly not normal for them. They would fire an angine as soon as you got near the car with the key.

You’ve said that the choke is fully open in three minutes, and apparently that’s when the engines get hard to start. Do they get any easier to start after they’ve been run for, say, 30 minutes and shut down for 4 or 5 minutes? Completely off choke in 3 minutes seems a little soon to me, unless it isn’t at all cold where you are.

It sounds more and more like a vapor lock problem to me considering the only gasket is a simple base gasket. I would never consider running a carburetor with today’s gasoline without a thick gasket (called an insulator for a reason) under it.

That aluminum intake pulls heat out of the cylinder heads and transfers it directly into the carburetor. Since an engine becomes hotter for a short time after it’s shut off this surge causes the gas in the float chamber to boil and overflow through the discharge tubes.

This was a chronic problem on Subaru carburetors back in the 80s. The carbs had a glass window in the side of the float chambers and one could actually look in there and see the gasoline boiling just like a coffee pot about 5 minutes after the engine was shut down. Nissan and Toyota carbs also had sight glasses and the same thing could be viewed with those.

I had a 78 Ford Granada at one time and it was also prone to vapor lock until I changed the steel fuel line to rubber and installed a thick insulator under the carburetor.

Those 1’ thick spacers will not hurt anything. Matter of fact, they can improve the low end torque a little bit.

Have these both always had this problem, or is it recent? If they always have had it, and you do the checks others mention, then I’m inclined to go with the vapor lock idea. I spent lots of time on this with carb cars (long story) and your symptoms match. Besides the insulating gasket, you can also check if the fuel line is running by the exhaust manifold/pipes or other hot areas. You’d be amazed at the places I’ve seen fuel lines! I also agree with OK, a 1" spacer should help, not hurt, bottom end (very slightly).

This is one good thing about fuel injection - the higher pressures in the fuel lines has largely eliminated vapor lock.

Yes, that can happen…Some fuel pumps (most) have a check-valve to prevent reverse flow back to the tank. As fuel in your filter heats up, pressure builds up which can overcome the needle valve. Also available are small fuel-pressure regulators which mount right on the carburetor fuel inlet and are adjustable. They can solve a lot of problems…

Yes, they have always had the problem. Once I can, I’ll be putting spacers on the both of them as I’m convinced it’s vapor lock as well.

Man, this board sure can flush out a problem! Thanks again, all

Heres a little trick that used to work for me, lower the float about an extra 1/8".