Spark Plug / Carb Issue on 602 - Ideas needed

[dluna11w]

I race once a week. For the first 3 laps, my motor will miss and cut out like crazy. After that, it doesn't skip a beat for the rest of the night. Our track only allows 2 classes of cars to hot lap each week, so if I am not in that group, I am going to have a miss the first 3 laps of the heat race. The only thing that fixes this issue is a new set of plugs before the race.

My assumption is that when I fire up the car on Sunday to unload/wash, it is fouling the plugs with excess fuel. Then on Saturday when it burns it all off (after 3 laps), the car runs fine.

I make certain it is at operating temperature before I go out for hot laps. I've tried not washing the car to see if moisture is an issue. I've tried pulling the plugs on Sunday after washing, spraying them with brake parts cleaner, and blowing them clean and dry with air nozzle. I changed the power valves per carb builder request as well.

What can I do to fix this besides buying a new set of plugs every week?

[grtforever]

We were having a similar problem with our 604, if we didn't put fresh plugs in after heat race it would stumble and miss off the corner.

[50j]

Could be that you need a better carburetor or it's out of adjustment.

[swaybar]

Carb jetted too rich or spark plug heat range too cold?

[rubbinsracin]

Our 602 does this also. We have a good crate carb and all. Does it especially when its a little more nippy out. We just open the gap on the plug up to like 42 and put some carb cleaner right into the carb on start up and its fine after a few minutes. Another thing we have done is set the idle a little higher like around 1800 and let it warm up a little then back it down and it gets better.

[dirtrace09]

Are you on gas or e85? what type of carb and what fuel pressure do you have?

[dynoman14]

What is your current plug number and what is the gap?

What dizzy, ignition box, wires???

Are you getting water in the gas tank, carb or ignition?

Do you have an Ionization hole drilled in your distributor cap?

Will wait for your answers.

[dluna11w]

Carb is a 650 holley done by Kenetic Performance in New York. I am running 110 race gas.

The spark plugs are NGK R-5724-8.

The distributor is bone stock as it came from Chevrolet. I did drill a hole in the bottom to run the wire in for my rev limiter. Wires were brand new at the beginning of the season from JR Motorsports.

I don't have an Ionization hole, nor do I know what that is.

I don't believe it is fuel in the tank or lines because I am extremely careful when washing the car. I have also tried not washing it at all and it does the exact same thing. Cut out for the first 3 laps of hot laps and runs like a top the rest of the night.

I am replacing valve springs and plugs for this weekend so I am sure it will not cut out this weekend, but next weekend it will be back to it again.

[swaybar]

Carb is a 650 holley done by Kenetic Performance in New York. I am running 110 race gas.

The spark plugs are NGK R-5724-8.

The distributor is bone stock as it came from Chevrolet. I did drill a hole in the bottom to run the wire in for my rev limiter. Wires were brand new at the beginning of the season from JR Motorsports.

I don't have an Ionization hole, nor do I know what that is.

I don't believe it is fuel in the tank or lines because I am extremely careful when washing the car. I have also tried not washing it at all and it does the exact same thing. Cut out for the first 3 laps of hot laps and runs like a top the rest of the night.

I am replacing valve springs and plugs for this weekend so I am sure it will not cut out this weekend, but next weekend it will be back to it again.

My opinion, those plugs are too cold for the 602. Go with an NGK TR-5 or the AC Delco plug in the crate owner's manual.

[50j]

I agree, and if you dyno you'd be surprised by the difference in plugs.

[dynoman14]

You might be condensing moisture in the Dizzy or the carb when you wash it. Even though you don't spray water in the part when you cover it the temp difference could be causing condensate to build up in either or both and 2-3 laps required to get it gone.

How long do you warm up your engine to get it to operating temps on oil and water before racing???

Or do you do this??? Might need to.

Ionization hole is a 1/4-3/8" hole drilled into the top of the cap to relieve pressure build up from Ionization of air in the cap. This can cause significant power loss and ignition problems. If you run for a long time like this you can compromise the ignition module and all the contact points in the cap.

If you look at a high dollar MSD cap you will see a little black bump in them, that is the cover for the Ion hole.