What The EGT !

For nearly a year, I have had a strange acting #4 EGT reading, that's repeatable on my 6A.

ENGINE
O320 DIA, FP prop, GRT EIS 4000, 1019TT, 467 SMOH (previous owner found corrosion on cam and had engine OH at 552hrs.) , Slick Mags, <100 hrs since OH, all SBs completed,
Slick Start, <100 hrs on TEMPEST plugs, 11 years on Slick harness, 11 yrs since new intake and exhaust gaskets.

Symptoms
After a normal engine start, warm up and mag check, Immediately after takeoff, #4 EGT is 200 degrees LOWER/COOLER than all others, spread alarm initiated.

HERE'S THE ODD thing.... I can reduce power by 100 RPM (2350 to 2250), and the EGT comes up within 5 seconds, in line with the others, and all is good. There is no roughness, or other symptoms than this.
The remainder of the flight EGTS are all ideal, responds appropriately to leaning, and at let down all respond as expected. I have verified my #4 is indeed #4, I have used a heat gun on all probe areas,
and get expected rise, in the same time span, per the EIS. Here is a picture in cruise....to me, these numbers are all pretty darn good. I am clueless what this is telling me, but dang tired of it happening
and no longer want to ignore. I have flown about 100 hours a year over the past 3 years of ownership.

Forgot to attach to original post

Pic of cruise engine stats

I assume that the throttle condition with the EGT imbalance is WOT. If so, it is common for carb'ed Lycomings to have very poor fuel distribution. Many find it very bad at WOT, but if they pull the throttle back a bit from WOT that things even out nicely. Sounds similar to your case. The 200 drop is either overly rich or lean.

Larry

Yes

Yes, WOT Larry .... Thanks

Building on Larry's thought... Maybe try a WOT climb after stabilizing in cruise for a bit. See if the EGT responds as it does on departure? If so, that would support the poor fuel distribution hypothesis.

Well I’ll be....

Rob..... I did the Savvy Induction leak test yesterday..... yep, from level flight 4500’ climbing slowly to 5000 ( where M Busch recommends one performs the test), about 30 seconds into WOT mixture RICH.... EGT Span alarm goes off ! Wow, just WOW ! Thanks guys....wish I could buy you both a beer . Thanks, I’m gonna move on and enjoy my RV. It is what it is. Outstanding group here at VAF !!!

BH1166 said:

Rob..... I did the Savvy Induction leak test yesterday..... yep, from level flight 4500’ climbing slowly to 5000 ( where M Busch recommends one performs the test), about 30 seconds into WOT mixture RICH.... EGT Span alarm goes off ! Wow, just WOW ! Thanks guys....wish I could buy you both a beer . Thanks, I’m gonna move on and enjoy my RV. It is what it is. Outstanding group here at VAF !!!

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You can't get to a point where you know everything in life. You just have to know who to ask.

Indeed Greg

I’ve been happy at not knowing everything, but surrounded myself with others that usually do . Happy with this new piece of knowledge!