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1964 Olds 98 394 with the stock 4 barrel. I'm doing a tune up. Noticed that the secondary butterflies don't open at all with the throttle linkage at full open. Primaries are open all the way normal operation. They are freely moving if I stick my fingers in there and open them up, but the linkage doesn't move them at all. I'm in book #1 of the service manuals, but I can't seem to find any info on the operation of the linkage for the secondaries at WOT. Not sure if something is stuck or just gummed up. I'm not versed in 4 barrel carbs all that well yet so any help would be appreciated if you've run into this problem before.
Others can provide more definitive info. The secondary's only open under acceleration or WOT vacuum load - that is, going down the road. They are not opened by of the linkage.
The thing you are looking at is NOT the secondary throttle blades. It is a auxiliary air valve that is above the throttle blades. The auxiliary air valve only opens in response to the airflow needs of the engine. Moving the linkage will not open it. Revving the engine in park will not generate enough airflow either. I suggest you read the carburetor section of the Chassis Service Manual, which describes this system.
Others can provide more definitive info. The secondary's only open under acceleration or WOT vacuum load - that is, going down the road. They are not opened by of the linkage.
Sorry, but that is not correct. The secondary throttle blades on a 4GC are mechanically operated by the throttle linkage. The auxiliary air valve is only opened by the airflow needs of the engine. The OP cannot even see the secondary throttle blades when looking down into the carb - the auxiliary air valve is above them.
Okay, I'll take a closer look at it next time I'm out there. I'm reading that it needs at least 9" hg to open those. Guess I need to get the vacuum gauge out and see what its pulling......thanks for the explination
Okay, I'll take a closer look at it next time I'm out there. I'm reading that it needs at least 9" hg to open those. Guess I need to get the vacuum gauge out and see what its pulling......thanks for the explination
I don't know what you are reading, but engine vacuum does NOT open the auxiliary air valve. It is the mass of the air being pulled through the secondaries that opens those valve. A vacuum gauge will tell you nothing. Is there some problem you are trying to diagnose? If not, you are creating a "problem" where none exists. The carb sounds like it is operating as designed.
