Bog at 3000 rpm at WOT

[Seff]

'72 Olds 350, HR-kit rebuilt '77 Q-jet. Runs well, except when going to WOT - at that point, it bogs when it reaches 3000-3500 RPM, falling ~1000 RPM before it picks up again. Happens from a standstill, and when going from 55 to 80 MPH with no change.

Currently the power piston rod is in the inner hole. Or am I looking at secondaries opening too soon/too late? The choke pull-off works well and doesn't leak.

Thanks, Mark.

[ejowrench]

One thing you can do if you want to know if you have a problem in the secondaries or the primaries, temporarily [and carefully] lock the secondaries closed so you are only operating on the primaries. Good luck and keep us informed....


Once you dial-in the secondaries  on a Q-Jet, you may find you need better rear tires!

[Cliff Ruggles]

Choke pull-off release time and spring tension on the secondary airflaps play a role here.  How quick is the pull-off, and how much spring tension?....Cliff

[Seff]

I'll get back to both of you with info on all of that. Right now a slack timing chain job has the engine halfway apart.

I CAN tell you that it's the factory pull-off. Do you suspect it's a lean or a rich condition I'm experiencing upon WOT?

[Cliff Ruggles]

In most cases a "bog" going to full throttle is a lean condition, as it takes a heap-ton of fuel to flood out an engine enough to cause a "bog".  In most cases overly rich results in no real noticeable issues going to or at WOT, just not ideal power output.....Cliff

[Seff]

Gotcha.

I tightened the secondary air valve spring an 8th of a turn at it helped, so another 8th of a turn will be attempted.