408, Small or Big Block? Need EGT Info

[70DusterBob]

You're rich at cruise.

Aim for 12.8 or 13 at cruise? I have a jet kit and bleed kit. I can get any mix I know to aim for.

 

[70DusterBob]

I gotta get busy with stuff. I'll check back this evening.

 

[mygasser]

So just keep the AFR around 12.5 to 13, maybe 13.5 outside? Never 14, back off throttle at 13.8 and add fuel? What are the outside parameters of the AFR reading?

that all sounds reasonable to me.

 

[Ricks70Duster340]

Big block pictures below....
View attachment 1715741452 View attachment 1715741453 View attachment 1715741454

Ooh, love that thermoquad!

 

[justinp61]

Aim for 12.8 or 13 at cruise? I have a jet kit and bleed kit. I can get any mix I know to aim for.

Mine is in the low 14's at cruise.

 

[flyfish]

EGT 12.5 ish 15 spike
I researched this as I will be running nitrous which can quickly spike egt
Keep a close eye on timing

Brooks, that would be AFR (Air Fuel Ratio), not EGT (Exhaust Gas Temperature).

To the OP, like have others said, you are better off looking a AFR than EGT for tuning. Tune it with the AFR and you won't have to worry about the EGT.

And a total side note, if you If you don't get on the motor soon its going to be a pooch ("have not taken it above 3000 RPM")....just sayin....There have been studies of identical engines that are broke in and babied v.s. the "hammer down" approach, and the latter make more HP. All of my engines I do the hammer down approach, and they run quite well.

And yet another side note: My AFR's with e85 look so very difference than gas...I run mine at 0.77 lambda at WOT.