93 383 LT1 ported heads, 1.6 RR, Hot Cam
Received new chip from popular guy here in forums. Thanks for everyones input. No more surge at stop sign/Light. No more up and down Idle when I start the care cold in the morning. Can anybody you tell me about this. Concerned: Prior to new chip I had Ford 21#-(I didnt know) and Street and Performance chip. I took a heat gun and this is what I got. Front engine drivers side: 222, 307,303, 252, Front engine Passenger side 220, 310, 379, 358. Had problems with idle at stop sign ect-down-up even. Now with 30# ford injectors and new Chip. Every thing is wonderful only: Front engine drivers side: 235, 364, 354, 328 and Front engine Passenger side: 257, 407 460, 430. It is the same exact pattern only hotter. coincidence? What would cause this? This is from the heat gun about 2-3" away from head on header approx 8-10" away. Could this be the ECM. Is it safe to drive with these temps. The car rocks! Coolant temp is 205 degrees at most.

Thanks

 

I don't know, but I want your car!

 

Thanks!

You guys are great! I have had alot of problems and really apreciate everyones help!

 

More fuel from the larger injectors could be cause for the temp increase. What did the new chip do for ignition timing? Was their a change from the prior chip?

 

New chip guy must have done something to timng because engine runs great. when I initially posted the idle problem everyone said it was the timing yet someone else was telling me the injectors were clogged and had to be cleaned and that would cure the problem. Puzzled at the pattern of the cylinder that were hotter then are still hotter now?

 

FWIW, my header temps as measured with a heat gun vary a lot too. The car runs great though in all other regards.

 

But as high as 466. Could this be spark plug related?

 

Member SloRvette has/had individual EGT sensors mounted in
each of his primaries and may have logged results.

If you PM him, perhaps he can offer some knowledge from
his experience.

.

 

I have done the same with my headers for temps.
Yours are withen reason.
My 1,2,7,8 are 300+
The center cylinders are 600+

It is not your plugs. I went through this and researched as well as spoke to many knowledgable engine builders. They all said temps are based on many things but power has a significant effect on raising temps of headers. And not to worry, my temps were not out extreme and to enjoy the car.

 

The temp differences has to do with the air fuel mixture in the individual cylinders. The pulse width is the same for all of the cylinders, the injectors are new and balanced (?), but the intake manifold doesn't admit the same amount of air to all the cylinders. The end cylinders tend to run rich. This is not unusual and I wouldn't let it cost you any sleep, but you could pull the manifold base and experiment with porting in different individual runners to see if you cam make them more equal.

RACE ON!!!

 

What about the coating thickness?

 

Typical LT1 header temps with coated headers (uncoated sometimes in excess of 600 deg). Because of the reverse flow, the front cyl on both sides are always the coolest. They get hit with the water straight out the radiator. If the tune is set up so it idles in closed loop the A/F isnt the cause of the increase temps, unless the before results where skewed because it was rich and past its limits (fuel trim) to lean it out to stoich.
In other words, if it was idling at stoich before, which it sounds like it may not have been, and its idling at stoich now, then the logical answer would be its because of a timing change.
But, it sounds and looks like it was probably on the rich side before.
Tip: When you shoot the temp gun, take readings at different places on the tubes. Why? Because they register hotter on the outside of the bends, as opposed to on the straight parts of the tubes. So, if you're shooting one tube on a straight piece, and another on a bend, the bend is always going to be hotter.
It been my exp that the center cyls run hotter header temps just because they're right next to each other. Been that way on SBCs as long as they've been around. LS1s tend to be alot more uniform. Same for big blocks. Why? Because they have equally spaced exhaust ports.
BTW BEAUTIFUL 66. Few more years and thats retirement money!!!! Heck its retirement money now!

 

I wasn't addressing the before and after readings, just the cylinder variations, which, as you noted prevailed before AND after. I wasn't talking about a big variation in the a/f mixture. Just a small amount caused by the manifold air flow. Also, I am assuming that the cylinders DO average out to stoichiometric and that the O2 reads that. The cool, reverse, water flow, and the exhaust port layout can easily be factors, too.

RACE ON!!!

 

Thanks Guys-Your expert opinion make me feel better. I was prior chasing the cause of my lose of 1 quart of oil per 300 miles on my newly rebulit 383. As it turned out, the builder did replace the Total Seal no gap rings. He said he didnt even rehon. the cylinders looked great. He just put Speed Pro Moly Plasma in its place and I have been happy ever since.