How could I verify when/whether secondaries open?

[Honolulu]

I know I can bench test the vacuum unit diaphragms, but how to verify this when on the road?

This would, hopefully, tell me that both secondaries open at the same time, and the same amount. Call it carb synchronization, level 2. I've been through the no-linkage idle speed synch, the connected-linage idle synch, and the 2500-rpm synch. Still have some considerable stumbling at higher rpms.

I know the dwell is okay and timing is correct, that leaves carbs as the culprit, or does it?

Hm this might be easier with Weber 32/36 having mechanical secondaries, wouldn't it? Then I'd know that they open, but still wonder if they were opening in synch.

[velocewest]

As I've been told, the vacuum secondaries will not open without a load on the engine. That's why you cannot get them to open by revving in the driveway.

Your options would seem to be, rent some dyno time, or rig up some mirrors/small video camera/bribe a stupid friend to ride under the hood...

[Honolulu]

but I don't have any stupid friends that would fit under the hood. Big and stupid, yes.

Was hoping someone could think up a rig to assess this.

[Arde]

but I don't have any stupid friends that would fit under the hood. Big and stupid, yes.


Big and stupid? Used them as a dyno to put a load on the engine :)

Now seriously, would lack of synch of secondaries explain the stumbling? If so I may need to borrow your friends soon.

[velocewest]

In all seriousness, renting dyno time would be the best choice. You can have someone else "drive" while you watch the carbs and futz with the adjustments.