Jvette73

Its a list#1850 600cfm with electric choke conversion as well as secondary metering block conversion kit making it a 4150 series carb. The carb has worked great since day 1 untill now. Heres the problem: Yesterday morn when trying to start it, found that the engine was flooded. Once the engine and plugs were dried the engine started and ran fine all day with a # of shutdowns and restarts. This morn again it wouldnt start due to being flooded. Im thinking that there must be an internal problem with the carb that is allowing the gas to leak down out of the bowl or bowls into the engine overnite. Im familiar with working on Holley carbs but have never encountered this type of problem with them. Can anyone offer me any insight as to the possible cause of this leakdown before go in to tear it down ? I doubt its the floats because that would also cause a problem when the engine is running. Once its running its fine all day. Its leaking down overnite I believe. I mean really flooded bad. Spark plug insulators filled with gas on removal.

I do plan to change my oil when I get the flooding condition corrected.

Any help on this matter is greatly appreciated.

devveldogg

found this on the Holley web site, could be what your are experiencing, http://www.holley.com/HiOctn/TechSer...o/Trblsht.html


QUESTION After I shut my car off and come back out the next morning there is gas on the throttle shaft and puddled on the intake. What causes this?

ANSWER This is usually caused by percolation. This is when the engine is shut off and the engine temperature rises it causes the fuel to boil in the bowl and leak out of the boosters. There are a couple of things you can do to cure this one is make sure the fuel level is not too high. You can also lower the fuel level about 1/8" below the sight plug hole and this will cure it sometimes. The heat from the engine will rise into the carburetor sometimes and will cause the fuel to boil. Installing a phenolic heat spacer between the carburetor and the intake or a heat shield can cure this. These parts will prevent heat from getting to the carburetor and boiling the fuel.

Chuck Harmon

Sounds to me like it's the inlet seal. Pressure in your fuel line eventually discharges all the fuel between the pump and and the carb into your engine. A slow leak may take many hours to accomplish. If you parked for less than an hour, maybe not enough fuel to make it hard to start, also the dry cylinders are warm and easily started.

I don't think percolation would be a problem when starting an engine that is stone cold.

Chuck

Paul 75 L82

I would take it apart and check the floats anyway. Make sure everything is tight and then see how it does. I had a float stick on my 4160 on my 73 Z-28.

Jvette73

Thanks everyone, these all seem like possible causes of the problem. I will say the motor has always run relativly cool and perculation is unlikely but its worth looking in to. Ill check the floats for stickage and see if the level is not too high. I will also check the inlet seals to see if they're tight and sealing good. I can imagine that if they are leaking that the pressurized gas could come in and overflow the bowl into the engine. But am I correct in asuming that that would not actually empty the bowl? There is a ton of gas being dumped in the engine it seems. Im also gonna open the choke adjustment wide open to rule out flooding due to choke flap not opening on initial startup.

I saw a post on the fuel bowl leaking down to empty on this forum before. I remember someone giving a specific thing that could cause it. Hopeing to get that pointed out again. Ill check the archives to see if I can find it.

Anyone else got any other sugestions?

Jvette73

Fuel level is fine. Its just below the sight holes where it should be. Cant find any obvious problems with the carb after all. Looking into ignition problems now. I think all the gas is getting dumped during cranking while trying to start the engine with a very poor spark. With the choke flap closed on a cold engine, I guess it doesnt take too long to load it up with gas if it doesnt start right away. Hooked my timing light up to the ignition wire and cranked the engine and looked for the flash of the light. No flash. Then hooked my timing light up to a wire on my truck and cranked. good flashing there. So the light is working. The ignition on the vette is so weak it wont light the timing light. Pulled the coil wire from the dist and stuck a screwdriver into the end and held it close to ground to check for spark. It wouldnt spark untill I got 1/4" away from ground. Sounds pretty weak huh? Im gonna yank the pertronix and slap the points back in and replace the coil. Ill post back with results.

norvalwilhelm

I run dual holley 850's and run into this same problem. I would let it sit and it would flood. I ended up removing the sight plugs right after getting home and putting the car in the garage. Then I would monitor the float level. Check it every hour or so and again in the morning. I found one of the levels would go down. You could see the float itself settling in the bowl. I tried everything thinking it was a leaking gasket. I finally borrowed another metering block from my son and found the block was the problem. I remachined the gasket surfaces on the block but to no avail. I ended up replacing the metering block and problem solved.

Jvette73

Thanks norval, im gonna snug up the bowl screws too and see if it helps. The carb is new this year. I am on to some ignition probs as well. I think its actually weak or no spark causing the starting probs. Might be the dreaded pertronix causing the prob. If it is the pertronix its my fault maybe. I could have fried it by leaving the key in the on position without the engine running for several hours. Also got into a tither with my better half last week. I stole the coil wire so she couldnt take the car. :jester . She cranked and cranked till the battery went dead. I most likely caused these probs myself.

norvalwilhelm

My carbs were brand new. This was last summer. It turned out that the metering block had an internal leak. The speed shop gave me on from another old carb and it worked fine. Just because the carb is new doesn't mean there is not a casting flaw. Tightening the float screws will not help. A loose float bowl will leak to the outside. Power valve leaks also do not count with overnight floading, just idle.

Jvette73

Turned out to be a bad IgnitorII. I put the old Pertronix original Ignitor back in and she fired up instantly. Thanks again for the replies.