6 Pack header temp

[Big Sugar]

Hey folks, while recently baselining the carbs (promax 6 pack ) we got the engine to level out and maintain 15" of vacuum at 900 rpm, exhaust fumes were good ..no burning eyes and tapping the accelerator pump brought the idel up so we felt the carbs were good, Im about 1/2 a turn out on all my idle mixture screws on all carbs. We did a laser temp check on the header tubes at the heads, and noticed the 7 and 8 header tubes run about 100* cooler ? Around 360* where as the centre header tubes range from 450-550*on cylinders 3,4,5,6 and  425* on cylinders 1,2.   
   Question is ......are exhaust port temps that are cooler richer at idle ? Or leaner ? (No .....we did not pull plugs simply cause we like our skin )

      1          Will the left idle screws adjust temp nominally on the left side of the engine ? And same for right ?

      2          What is acceptible range in temp for the header tubes to be in at idle ?

      3           What is max temp at at the header exhaust  ports idle ?

      4           Previous to my cam swap the 7/8 cylinders were always rich.



All good question im sure....hoping for good answers LOL

Vacuum in gear D was about 13 at idle.   Timing during the carb tuning was 16* initial and 34 in at 3100+
My timing holds initial till about 22* then climbes in 2 - 3 * per 200 rpm up to 3100+

We readjusted timing after we finished up too 18* initial and 36 total all in again at around 31~3200

No pinging on 94 octain. Engine feels good.

Engine is a
    .30 over 10.5 -1 compression 440 with ported 452 heads mopar stamped rockers, promax 6 pac TTI 1 7/8 headers.  A lunati 603030 hydrolic cam (268/276------.493/.513)

Would upgrading to a 1.6 or  a true 1.5 ratio rocker draw a worthwhile improvement over the stamped rockers
Again the heads have been fully ported. (Money and time well spent ?)


Ron

[jlatessa]

I would assume the two center cylinder ports are going to show higher temps
because of their proximity to each other, i.e. less cool head material to absorb
their heat versus the end ports.

Sound reasonable?

Joe

[Big Sugar]

I would assume the two center cylinder ports are going to show higher temps
because of their proximity to each other, i.e. less cool head material to absorb
their heat versus the end ports.

Sound reasonable?

Joe

Makes sense,

I pulled the #7/8 plugs and they were a little lean so i back out the idle mixture screws on the rear carb a 1/4 turn, the centre plugs were spot on and #1/2 were just a tad light so I gave them a slight turn out  on the front carb as well. the centre i left alone, as the plugs looked great on all 4. Gonna do a plug Chop tomorrow to see what they look like after a high RPM blast and power kill.


Ron

[firefighter3931]

As Joe mentioned above ; the two center tubes will show higher temps due to their proximity (to each other) and radiant heat. The back 2bbl carb is probably a bit rich which is why you are seeing slightly cooler temps on those two tubes.

I'd say that your observed primary tube surface temps as within the normal range from what i've seen....nothing to worry about other than dialing in the idle mixture on the back carb. 

Keep at it Ron....getting closer ! 



Ron