Spark plug diagnosis?

**Mark Ferrari** · 01-10-08, 04:32 AM

I need some advice on the color of the plugs from my road engine. The engine is a std 302 Windsor from an Aussie 90's AU series Ford Falcon with Motec M800 and 4 barrel fuel injection. Also 4 into 1 exhaust with cats and no crossover. The fuel map is an emission map to get the car registered, so is not perfect, but I don't understand why the plugs from the end cylinders (1,4,5,8) are blacker than the middle cylinders. The individual cylinder trims are within ~6% of each other (up to 3000RPM and no differences after that) and don't correlate with the color of the plugs. Is this a sign of different temperatures between cylinders and is this a normal state of affairs for the Windsor V8? Or is this a sign of a cooling problem? The only other change to the engine is a valve in the water line from the rear of the inlet manifold. This was put in after reading posts on this forum a couple of months ago. However, this valve may not do much as the engine is not tilted like most because the engine mounts have been lowered and moved forwards. I have found though that having this valve wide open lowers the engine temp by ~5 degrees Celsius. Could this cause uneven cylinder cooling?
The car is to be dynoed next week to improve the mapping and has wide band lambdas in both exhausts, but will not indicate individual cylinder lambdas. So I am keen to know if I have a problem before the dyno day.

Andrew E · 01-10-08, 05:13 AM

Hi Mark,

The RF compliant map for the 302 setup is certainly not ideal and most RF owners have struggled to get their car to run well with that map. I wouldnt be too concerned at this stage, but get the thing sorted out on the dyno, there shouldnt be IMHO the need to individually trim cylinders once the map is corrected for your engine. It is interesting that no two 302 engines loaded with the compliant map although supposedly the same have ran the same, most very poorly. The sooner you can get your own map sorted probably the better and then time to make any judgements on the plug senarios? I have the rear water line to the rear of the engine but no valve, happy with engine temps. Good luck with the dyno hope it resolves issues for you.
Andrew