Spark Plug Mystery
 

My truck has a new (less than 300 miles) 350/260 crate motor. Just about everything on it's new. The mechanical fuel pump was putting out way too much pressure for the Edelbrock carb, so I know the plugs got fuel fouled. I've got a good pressure regulator on it now, and put a new set of plugs the other day; I'm running the "shorty" Accels, since access is limited with long tube headers. On the driver's side, sure enough, cylinders 1, 3, 5 and 7 were pretty black and sooty, but, on the passenger side, only 4 and 8 were. The plugs in 2 and 6 had almost white ceramics still.

Timing was at 12 degrees with full manifold vacuum, nowt reset up to 16 degrees. The truck runs good (for what it is), with no odd noises, no oil use, no water use, no missing, no smoke. I would think if I had 2 dead cylinders, I'd certainly feel it, so I'm stumped. Thoughts?

Jerry

Re: Spark Plug Mystery
 

At what idle rpm did you set your timing?

Re: Spark Plug Mystery
 

Originally, and this time, about 750 in park, vacuum disconnected and plugged...

Re: Spark Plug Mystery
 

No problem there!
What's your fuel pressure?
What intake?

Re: Spark Plug Mystery
 

Rock solid at 5.25 pounds on the pressure, with a factory (not performance) fuel pump. For an intake, I have the Edelbrock EPS, with the Edelbrock AVS 650, and a 3/8" composite spacer, feeding out to Hedman 1 5/8" long tubes. Also, the fuel line is 3/8", from the tank to the carb.

Not sure if it matters, but the truck runs cold as my first wife's heart. I made the mistake of using a 160 thermostat, and it never, ever gets beyond that, even with everything - fan, water pump, etc., being new, but pure stock.

Re: Spark Plug Mystery
 

I would replace the 160 with a 195 thermostat. That is what stock SBC have been designed for since the 60's.

Assuming this is a daily driver type of truck, I would just follow the break in procedures for the next several hundred miles and not worry too much about it. Things are still seating and fitting to each other. As long as it runs smooth and idles smooth, let it break in before trying to fine tune it.

Re: Spark Plug Mystery
 

Have you looked in the carb at idle.
Could be dribbling a little fuel out of one or both boosters.
Eddy carbs are not only sensitive to pressure, they're touchy about float level too.