TheSamba.com :: View topic - Motor running hot. Spark plugs 1,3 are black, 2,4 are white.

Fri Jun 13, 2025 12:34 pm

Hi all

I recently bought a 62' and haven't been able to drive it more than a couple miles due to the engine getting hot. I've been researching and found that a lean motor run can run hot so I pulled the sparks plugs to see what they look like. Cylinders 1 & 3 are black, while cylinders 2 & 4 are white. I'm hoping someone can tell me why they are different and what they indicate? I'm new to engines with dual carbs, or a single carb for that matter, so I'm learning as I go.

I do have a little background on what is in the motor from the previous owner. The paperwork says it has a 1914cc engine in it with a scat counter weighted crank, Engle 120 cam, 042 big valve heads, dual Kadron 40mm carbs, and A1 Sidewinder exhaust.

Any advice would be greatly appreciated, it's a fun car to work on, just wish I could drive it a little more.

Fri Jun 13, 2025 3:42 pm

Sure about those plug numbers? A bit odd to have one cylinder on each side running rich while the other runs lean.

Check to see if all the valves are adjusted properly (.006" with engine stone cold). Also check to see that you're getting a good strong spark at each plug wire (with wire removed from connector, spark should be bluish in color and be able to jump 1/8" to ground while motor cranks over). Check the points for pitting and correct gap (.016"). Check the ignition timing with a strobe (28°-32° BTDC max advance @ 3500 RPM). While doing that, notice if you're getting spark scatter (timing mark jumps around erratically under strobe), which could mean excessive runout in the distributor shaft. Check the inside of the distributor cap and the rotor for worn contacts, cracks or carbon traces. Lastly, see that the carburetors are adjusted & properly balanced side-to-side and check for vacuum leaks where the intake manifolds meet the heads. Are the two manifolds connected by a balance hose running behind the shroud? If so, check it for cracks and/or leaks.

Ideally, all the plugs in a well-tuned motor should look something like this.