Is there a way to richen the mixture when the motor is cold? I know nothing at all about EFI.

 

i guess so, there's a temp send for that purpose too, you can also get issues if running with a cold thermostat like 160 F because the coolant doesn't reach the temperature it is supposed to work with.

 

Sounds like it is lean at idle as Tech advised. Are you able to see the AFR or no? If yes, then that will be the proof in the pudding. Also, it would make sense that your problem would be in one of the corners if it is indeed lean.

I'm sure you TBI chip burner can increase the fuel at idle. Hopefully that is the problem - good luck.

 

Thank you for the input, i'm just curious, if a lean condition even if something very minor like in my case because it's a matter of minutes or even seconds can damage the spark plugs or make them acting crazy?

 

I would contact Howell efi about your problem.

 

I'm curious of how long we're talking about before it starts to run smooth. Does your Howell system have computer controlled ignition or is it mechanical?

 

You could try putting a little propane into the intake air stream to see if it smooths out. This will effectively richen the mixture. Do you have a way to look at fuel trims and stuff like that with this system.
The more information you can come up with the easier it will be to troubleshoot

 

This is a common problem with the NKG BPR6EFS in an aluminum head seemingly worse with a cool climate but not exclusive to that. I presume your using this plug for header clearance. A plug, if not actually visably fouled, has developed a conductive coating, probably nearly clear, on the projecting insulator that bleeds the high voltage to ground without jumping to the ground strap so no spark and a missfire results. As the plug heats up the condition sometimes corrects itself. A new plug solves the problem till it too develops the conduction to ground coating again.

The BPR6EFS is one heat range colder than the Champion RN12YC. You can shop for an NKG BPR5 heat range which would actually be closer to the Champion in real heat range.

Other things you can do is to increase the operating temp of the engine aluminum heads lose heat pretty fast so you can run the coolant temp up to 200 to 210 degrees F which will heat the plugs up more and keep them cleaner. There is quite a bit more forgivness with a hot plug in an aluminum head because of how fast these heads pull heat so a hotter range plug over your 30% performance cycle shouldn't be a problem. If it is you can expirement with coolant operating temps against plug heat ranges.

The addition of a Capacitive Discharge ignition can help by hitting the plug with a sharp square wave form at a higher voltage so there is no sine wave ramp up time for voltage bleeding down the insulator to take place. A multi-spark is also quite beneficial at the low RPMs you sight operating at most of the time. Other things you can play with is low resistance metal core high voltage wires and or non resistor spark plugs. You may also want to individually ground each head and the distributor to insure that there are solid low resistance ground paths specific to the job at hand rather than trusing that current is flowing through various structural fasteners many of which are well pasted with sealers on a Chevy to prevent external coolant and oil leakage paths.

Mixture ratios can be a problem TBI has the same equitable mixture distributon problems cylinder to cylinder that carbs have. So some are running richer that others. Overly rich cylinders run cooler thus are more prone to foul out their plugs. This again is a problem that is better controlled with a CD ignition. Or you can get a cylinder that is so lean you can't get it to fire at all. In which case the entire engine has to see a richer mixture to get the leanest one rich enough to fire.

A big help is getting the engine warmed up sooner, a great aid in this is an engine oil to coolant heat exchanger. The coolant comes up to temp faster than the oil while the colder oil slows the coolant in reaching operating temperature. By using an oil to coolant heat exchanger the time/driving distance it takes to get the motor to an even temp is easily cut in half.

While the plugs are out do a wet compression test just make sure that none are so low as not to fire. If this is a sold lifter cam it is also worth pulling the valve covers to inspect how much valve movement there is to see if a lobe and lifter is not wiped out, killing cylinder temperature and fouling the plug.

Bogie

 

Thank you for the response, so much appreciated.
I've ordered today a new set of hotter plugs, NGK BPR5EFS, hope these will perform better, i like the idea of the oil cooler, the only reason i didn't put an external one (i know this kind wouldn't add any benefit to cure my problem), is because my engine has a fairly low oil pressure when warm 5-7 PSI with a
5w50 Mobil 1 and an oil cooler i'm pretty confident may cause the pressure drop even more unless i will get a low pressure drop one and with the less amount of elbows and hoses...
I know GM made in the past a sorta of heat exchanger oil/coolant coupled to the oil filter housing, i'm wondering if there's the chance to get one of them...

 

You issue is most likely a mixture problem not a spark plug problem.