Air Valves Not Opening

[Dogmeister]

Was at the chassis dyno with a friend the other day, and the secondary air valves on his stock 400 1967 GTO automatic would not open. We saw immediately that the lockout was not disengaging with the choke off. It was obvious also that the air valve dashpot was not allowing the air valves to open at WOT. When we shut the engine down, the dashpot released as I would expect. Unfortunately, we were unable to fix either issue due to time constraints.

The lockout is an easy fix, but what would prevent the dashpot from releasing at WOT? If the lock out is fixed is there enough 'pull' on the airvalves to overcome the dashpot?

The '67 manual says the dashpot seats at more than 5-6" vacuum and unseats at less than 5-6". I suppose checking the manifold vacuum is in order?

[Cliff Ruggles]

The choke pull-off opens at heavy and WOT and would not have prevented the air flaps from opening unless there were problems with the linkage.

If you shut down the engine and observe the choke pull-off release, then push down on the air flaps and they open easily then it will be working correctly on the dyno or on the street when you go to full throttle.....Cliff

[Dogmeister]

The problem was the pulloff was not opening at WOT, and there did not appear to be any issue with the linkage. I'll let you know what happens when we're able to take a look at it.

[Cliff Ruggles]

Assuming vacuum to the pull-off was falling of to close to zero at WOT the pull-off would release and allow the secondary flaps to open, but it may take a few seconds depending on how big the restriction in the inlet to it is.......Cliff

[Dogmeister]

We got his secondaries operating. Looks like the choke rod was not adjusted properly and not hitting the lockout tang like it was supposed to. Now he's saying it seems to bog down some right before shifting into the next gear. Not like it dies, just loses some revs. I suggested backing off his air valve spring 1/8 turn, but is there something else that could be causing this?

[Cliff Ruggles]

Sucking the bowl low or empty.

Could be fuel delivery or the N/S assembly is too small for the power level, or a little of both.......Cliff