Ever see something like this before?
August 10th, 2012, 11:18 AM
#1
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Join Date: Jan 2009
Location: Chicago suburbs
Posts: 211
Ever see something like this before?
Just curious. Anybody see this before, and what the heck does it do?
http://www.ebay.com/itm/GM-Rochester...a#ht_914wt_952
http://www.ebay.com/itm/GM-Rochester...a#ht_914wt_952
August 10th, 2012, 11:41 AM
#2
Seasoned beater pilot.
Join Date: Jan 2007
Location: Chicago
Posts: 5,468
Fixed your link.
Looks to me like a similar concept to a coolant system thermostat. You run it to a vacuum port, and once the engine gets hot, the mini thermostat opens up a valve for a planned vacuum leak in the system to raise RPM.
I need the opposite of this for my car Hahaha. Since the crossovers are plugged, I need high idle on start up, and low idle when hot
Looks to me like a similar concept to a coolant system thermostat. You run it to a vacuum port, and once the engine gets hot, the mini thermostat opens up a valve for a planned vacuum leak in the system to raise RPM.
I need the opposite of this for my car Hahaha. Since the crossovers are plugged, I need high idle on start up, and low idle when hot
August 10th, 2012, 11:43 AM
#3
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
Never seen one that wasn't built in to a QuadraJet, but it opens when the engine is hot (such as idling in traffic on a hot day) to lean out the mixture a bit, as older carbs tended to run rich if they got too hot.
- Eric
- Eric
August 10th, 2012, 05:01 PM
#4
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 48,237
It's called a Hot Idle Compensator and it works exactly as described above. Some carbs have them built in (look at the rear of a Qjet float bowl casting, between the two secondary ports). In the early 1960s there were retrofit units as shown here. My 62 had one on the original carb.
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