[chewingum]

Got Holley truck avenger 770 with vac secondaries on a 383. I swapped cams to get about 1000 more RPM than I had before. I was running #74 jets (came that way from the factory) and last night I rejetted up 3 sizes to #77's. Think that was a good move? I know everyone says to look at the plugs to tell, but it doesnt see WOT all the time, trying to tune for maximum HP.

Any rules of thumb to go by with jetting?

 

[GMCTruxrule]

I would use a vacuum gauge.

 

[florida4x4]

so get out there and do a WOT blast. cut the ignition so you can read the plugs.

 

[chewingum]

I would use a vacuum gauge.

For what? Pulls 4 inches at idle, before the cam swap it was pulling 17.

 

[just4cuz]

Yea no shit, did that once with a 307, called Eldelbrock help line...duh.
Too much cam for the motor, no vacuum, hell I knew more than he did.
Need more compression for the vacuum to come up or go back to a smaller cam.

 

[Grumpy_old_fart]

to dial it in to perfection, you need a wideband O2 sensor.

Make sure the fuel pump and fuel system is up to snuff.

running out of fuel is not a good thing.