Boiling Fuel & Carb Spacers etc.

[Clois Harlan]

I think I finally have the carbs dialed in with the hopefully proper jets etc. However, after a good RPM test I find that the engine does not want to start after I shut everything down. If I wait a few minutes it fires right up. I was talking to Jay Nordstrom last night who suggested I was boiling the fuel and the cure would be to put a spacer between the carbs and the manifold. I have the spacers and can do this if I take the short metal velocity stacks off each carb and let the filters rest directly on the carbs.

Clearance becomes a problem if I leave the stacks on and use the spacers. Any thoughts or suggestions on this?

Clois

[Mr.Fixit]

I doubt it is a boiling fuel in the carbs issue. Does the engine crank over kinda slowly after the good RPM test?

[Clois Harlan]

No, engine cranks normal. Timing is set at about 9 deg. Using Autolite 3924 plugs gap set at .050. timing is all in by about 3350 RPM. Idle set at 850 RPM. Runnig 93 octane pump gas. 10.5 : 1 compression.

[Mr.Fixit]

SO it cranks over at a normal speed, but doesn't seem to spark off?

If you give a little throttle mash before starting, do the accellerator pumps squirt fuel?

Doesn't smell too rich or anything does it?

[Clois Harlan]

I will give it a little squirt and it will just spin like crazy. Or I will hold the throtle to the floor and same thing. The accel pumps are working fine I can see the fuel squirt.

It is almost like it is not getting any fire.

[Nantucket427]

I want to hear Mr. Fixit's reply ?

but I can't wait to add my two cents about spacers.
I purchased the spacers from Summit because I think I needed them but I have been reluctant to put them on because the are really made of wood. I have had a backfire thru the carbs from time to time. Fire and fuel and wood don't mix. The metal spacer will conduct the heat almost as well as the manifold.

Now I will shut up and let Mr. Fixit continue.

[Mr.Fixit]

Well, you have cranking speed, and you have fuel. That makes me wonder about the spark. What kind of ignition do you have? Is it possible that the ballast resistor bypass wire is not bypassing he ballast reisitor to the coil during cranking? Just guessing now. But I would wonder about the spark now, since the cranking speed and fuel both seem to be fine. Lay a sparkplug wire on top of a valvecover and see if you get a good spark snapping.

Nantucket, the wood spacers are called "phenolic" and are good. They will not catch on fire. It's either that type, or the sandwich stack of aluminum plates and gaskets as a heat spacer. I prefer the phenolic type. If you ever do catch the top of your carb on fire due to a backfire or such, just crank the engine over and start it, the fire will get sucked into the motor and go out.

[BB427]

If the motor starts fine as long as it is cold I doubt it is an electrical issue. I think you were on the right track in the first place. The motor sounds flooded with fuel. Do you have an electric or mechanical fuel pump? If you have an electric pump shut the fuel off and let the motor run out and die on its own. Then turn the pump back on and start the engine. If it starts OK then you know what the issue is and you can adress it. You can also remove the carb after a few minutes and see if there is fuel laying in the manifold after shotdown.

Brent

[Clois Harlan]

Last night I ran some tests and found my timing had slipped to about 6 degrees so I re timed the engine. Also, I pulled the tops off my carbs and re checked the floats. My front carbs floats were approx 1/8 to 1/16 inch too low so I reset those. At the same time I installed three gaskets under each carb.

I took the Cobra out to a long deserted stretch of road along the canal for a rpm test. Again she performed like a stripped A$$ Ape and then we brought her home and rechecked timing - OK and shut her down normally. I waited less than a minute and refired her up. Perfect. Made a quick run around the block at normal speed and back to the house. Shut it down and wait about 3 - 4 minutes. Fired right up. Since I changed several things I am not sure what the problem was. I'll see how it does tonight.

Clois

[flipper35]

BB427, I had a distributor that went bad. Everything was good cold, but as soon as the reluctor got hot it didn't sart or idle well.

Fixit, I got to try the old keep cranking thing when I replaced the dist and it backfired up through the carb. I had one hand cranking the starter and the other rotating the dist to get it timed close enough to start. It was a long few seconds.

[Mr.Fixit]

Originally posted by flipper35


BB427, I had a distributor that went bad. Everything was good cold, but as soon as the reluctor got hot it didn't sart or idle well.

Fixit, I got to try the old keep cranking thing when I replaced the dist and it backfired up through the carb. I had one hand cranking the starter and the other rotating the dist to get it timed close enough to start. It was a long few seconds.

I did something like that when I was 16. Trying to start my freshly rebuilt 396 (my first engine rebuild) and it kept backfiring through the carb. In a fit of 16 year old genius, I looked down through the carb while cranking it to see if fuel was flowing, and it was. Flowing straight up in a vapor cloud, around my head, on fire. I lost my eyebrows and looked a little funny for a while.

[decooney]

...Just some other input that I experienced on my FE. I had the exact same warm/host start issue a while back with my new motor. Would not start easily once warm. After several checks, and chasing it around looking for something complicated, it turned out to be something very simple. I had previously played with my idle mixture screws just a bit and they were just a tad lean. I set them back to 1/8" out on each and wallah! Tuned it from there. I didn't think something small like this would make that much of a difference, but it did. Cured, never had a problem since.