Just noticed only 7 of the pri tubes have turned yellow blue. Pri tube #2 is still chrome like new. Compression is #230 & engine idles @ 15" vacume (226/240 @.050). Any ideas ? ick.
Get a thermal lazer temp gun, those will tell you a lot. See how much cooler the tube is from the others? What intake are you using?
Usually this happens because some cylinders are burning hotter than others. This is alluded to above when John asked about what intake you are using. Many people would be surprised to see how far off the air/fuel mixture is from cylinder to cylinder. I use an 02 sensor in each header collector and then an temp sensor in each cylinder. I know it sounds overkill but at least I know if I have a hot cylinder.
Distribution issues typically, but also it can be related to anything that is related to the engines ability to draw fuel and compress it. That's the valvetrain, heads, intake ports and position, piston rings, ect ect. It's not uncommon, and typically nothing to worry about, but make sure it's not cold, that could be an indication of a problem. If you have a dual plane intake, notably an Edebrock performer or B4B, then this condition is normal, and I am surprised this is only showing up on one cylinder. Distribution is much better with the single plane stuff, but still not perfect. JW
Thanks for the replies,I am running the stock iron intake ,checked the plugs & they have a very light gray tan , engine has not run much more than cam break-in & tuning. I am updateing to new lifters (leak down problems) with the Poston lifters bought in 1990 LOL & SP-1 intake manifold. ick.
I'm surprised you have ANY color on the porcelains with that little run time. Sure the mixture isn't over-rich anywhere in the fuel curve?
You and i both know that the only way to read plugs is from a full throttle blast without deceleration.
Forget about plug color, if your using pump fuel.. Only race gas will allow evaluation of plug coloring. JW
Running HCR PLUS SUNOCO fuel @114 leaded. Update just installed new hydro lifters # 1405 from T/A, SP1 intake manifold & AED 950 HO carb. Replaced fuel lines with Areoquip Socketless hose & fittings from the fuel pump to carb -6AN. This Skylark still has it's stock 3/8'' line from the tank to fuel pump. I'm thinking it should be borderline for this combo , est. 425-450 hp. ? Engine combo 462 - 10.1 cr - 260cfm in. 190cfm ex. (70) iron heads - SP-1 intake - 950 carb - T/A timing cover & oil mods to block passages - 226/240/113/ .505-485 lift - 1 7/8'' headers.
