Dyno Question, Richer or leaner with Dyno headers?
 

If you tune your engine on Dyno headers, will it get richer or leaner when you install wet manifolds??

Sorry, I meant to post this in the Technical section, my bad.

It'll richen up considerably with a wet manifold vs. a dry header.

X2

x3 It will also usually shift your curve a little lower too.

Ok super good news, Had my engine tuned on the dyno on dyno headers over the winter, did some end of the year checks and pulled the plugs, and they were VERY black (better that than the other way).

100% agree on the curve, we did make two pulls with the SM manifold (obviously wet) and it moved the power down about ~200 rpm and dropped 20+ horsepower, but we were unable to measure the A/F ratio with them since I had it done at an automotive facility (free, so I can't complain).

Running 88/94 jets on a Holley 850 80443 DP, ideas on what to do??? Left it pretty conservative with dyno headers only down from a 96 on the secondary. Made 539 through the SM manifolds.

Not knowing what all you have in your motor it is hard to say. The best way to do it is put in a A/F gauge and rock on.

You asked and you shall recieve:

Gen V 502 Converted to roller with scorpion roller rockers and valvetrain to match (springs, etc.)
Basicaly stock bottom end with block shaved .010 to remove corrosion on the face
088 Heads port matched to intake and cleaned up, shaved .010
With the above two, compression is about 9.25, up from 8.75.
Marine Kinetics Cam mild duration, lots of lift
Edelbrock Air gap intake
Holley 850 80443 one jet size down on secondary 88/94 (stock was 88/96)
DUI distributor at full advance set to 34 degrees
SM Manifolds with standard risers

On dyno headers left it pretty conservative at just under 13:1.

Back to this, the motor is out for the winter and I have to time to mess with this stuff. I developed a transom seal leak and am having it repaired Good news is no rot) -- any idea what to do here? I was thinking about just dropping one jet size on the primary and secondary? Thoughts? I'm at 88/94 for jet size now.

While you have it out, put some O2 bungs in the exhaust and check it in the boat in the spring. Then, there is no guessing. Anything shy of that is just guessing. This way you will be certain of where and how much jet you need to pull out.
Eddie