22r #4 Plug Gas Seepage

[Deagle]

This is a professional stock rebuilt '84 22r carburetor engine by a reputable engine rebuilder. New Weber Carb 32-36 mm progressive installed. All new vacumn hoses. New spark plugs and wires (both toyota oem replacement). THe engine only has about three hours of running time. Smooth running at idle and higher rpm. Timing set at 8 degrees tdc.

Problem/Symptoms: At operating temperature, the #4 spark plug seeps gas at the seat of the plug. Spark plug threads are wet when plug is removed. #1, #2, #3 plugs seats are good, no seepage. THe wetness is a gas/carbon liquid (not water - radiator levels are normal) Oil pressure and water temperature normal. Occasional puffs of black smoke on quick accelerate and deccelerate.

Actions taken: Replaced #4 with new plug. Swapped #1 plug with #4 plug. Tightened plug to ensure proper seating. Inspected and deburred, as required, the spark plug seat. Problem nor corrected.

I was told by the rebuilder that the ring on the spark plug is to seal for compression only. Also, that this is not a problem and is to soon to know if there is a problem. Rebuilder does not think there is a problem.

I was thinking hairline crack at the seat. However, I would expect no gas mixture seepage since gas mixture would be burned up at plug spark.

Any Ideas ... Thanks

[Brian R.]

See if you can get the rebuilder to check it out with a borescope. Might find a defect around the plug or in the combustion chamber.

Is it easy to start after it has sat overnight? If you have to crank it more than normal, maybe the carburetor has a leak in the bowl. Do you have another working carburetor to try?

Very strange.

[Deagle]

Originally Posted by Brian R.

See if you can get the rebuilder to check it out with a borescope. Might find a defect around the plug or in the combustion chamber.

Is it easy to start after it has sat overnight? If you have to crank it more than normal, maybe the carburetor has a leak in the bowl. Do you have another working carburetor to try?

Very strange.

Brian
Thanks for your interest. I asked the rebuilder how "we" would approach this since my interest is to fix the problem and not place blame. He suggested I drive the vehicle for 1000 miles plus to break in the engine. And he states again there "probably" is not a problem and to wait and see after the break in period. I sensed from the rebuilder that he wasn't about to do anything about it. He did ask to keep him posted. This is not to promising unless I can show cause.

Driving the vehicle concerns me in that gas seepage out of the #4 and near the header creates a somewhat dangerous situation. And at this moment, the vehicle is not in a condition to be driven. Only the engine has been installed into a restored chassis. The truck cab is not mounted and temporarily set on the chassis for the purpose of testing/running the engine.

Everytime that I have started the engine, within hours, the next day, or several days after; one 360 degree turn of the crank and it starts right up. No starting problem at all whether it is a cold start or a start after normal operating temperatures.

I don't have another carburetor for this.

I will contact Weber tech support direct to be sure that there is not a float adjustment problem. And I will test the fuel pressure (electric fuel pump).

I am approaching this as if there is a problem until I can get data to support otherwise.

Any other thoughts ... thanks

[SigmaProjects]

Have you checked all the components in your ignition system? Are the spark plug wires bad? Or the distributor cap, rotor or the entire assembly?

[Deagle]

Originally Posted by SigmaProjects

Have you checked all the components in your ignition system? Are the spark plug wires bad? Or the distributor cap, rotor or the entire assembly?

Hello SigmaProjects? Curious ... are you familiar with the DMAIC process?

OK Two anomolies in work
1. Gas Seepage
It appears after further lab environment testing that the rebuilder has installed a "helicoil" in the #4 plug hole. Consequently, the spark plug is not seating completely (the helicoil does not allow for a proper seal between the spark plug compression ring and the cylinder head seat)

DOES ANYONE HAVE EXPERIENCES WITH HELICOILS INSTALLED IN CYLINDER HEADS TO REPAIR STRIPPED SPARK PLUG THREADS?

2. Wet #4 Spark Plug
Since #4 plug is wet and there is seepage about the #4 plug, it appears the #4 plug seat anomoly has to be fixed first. Then on to the wet plug.

I have new plug wires and plugs. And I have inspected the dist cap and rotor. It is a good point you bring up. I will replace the cap and rotor just to be sure, "cheap insurance at half the cost".