Spark plug colour test on a 5.7 Litre Votec engine

[Black as]

Hi Guys
I had a chance over the weekend to do a spark plug test on my 5.7 litre Vortec engine running a 4 barrel Rochester, engine has done 20 hours total and in both cases the plugs remained the same colour. One test was done at 2800 rpm and the other was done at 4500 rpm. My thoughts are it's a little lean side and from the reading I've done my thoughts are is to increase the size of the jets in the primary only and leave the secondaries alone, what do you guys think, see the attached photo Also while out on the water I then went to WOT and the RPM's went to 5200 rpm so I backed off, also what are you thoughts on this as well.

 

[Bifflefan]

Re: Spark plug colour test on a 5.7 Litre Votec engine

You really cant get a good look in a picture.
99% of performing the test is time duration and how you ran the test. To get an accurate test, you would need to use a new set of plugs, run the engine at a sustained RPM for say 5 mins, and shut off the ignition when running at that RPM, pull the plugs and replace them or at least inspect them so you can see what it was doing right then.
Then you need to inspect them with a magnifying glass, and know what you are looking for.
I dont know how long you ran it, but they look fine in the picture. If you are not running warm or getting an detonation, I would leave it alone.
Vortec engines are very good at swirling the mixture and getting a clean burn.

 

[Silvertip]

Re: Spark plug colour test on a 5.7 Litre Votec engine

5200 rpm is a bit over the upper end of the recommended RPM band. If you made this run alone but you normally carry a heavier load, then do nothing. If you spend most of your time alone, then step up a number on prop pitch.