WS6 Berlinetta

I just rebuilt and installed a Q-Jet out of an '82 caddy. It's the black smoker I posted about before. I found some weird stuff with this carb. It has 2 extra fuel pickup tubes on the air horn which I found out were for the "High Speed Fuel Feed" near the choke. The air valves also open all the way without binding like my last 2 Q-jets I can feel the difference with this carb. Anyone know of any other hidden features to look for when picking up a junkyard carb? I noticed that I might beable to install an old "Hot Idle Compensator" valve into a CCC Q-Jet since all the bosses are there just waiting to be drilled and tapped, would there be a point to this? I know the ECM can compensate but I'd like to try this if there is some benefit.

Thanks
R

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'84 360ci WS6 Berlinetta
Fastest Berl In Cali
WWW.SDFB.ORG

Damon

The hot idle compensator MIGHT have some benefit under the cramped hood of an FBody. If you already run a 160* stat, don't run in hot weather and/or have some place for the hot underhood air to exit (cowl induction hood, for instance) you won't ever need it. But if you don't you might see some benefit. Basically it just speeds up the idle a smidge (100 RPMs) when it gets really hot (over 150* or so) and slightly leans the mixture (which the ECM doesn't need any help with). But since you got the carb running so good already why mess with it?

The high speed fuel feed is a pure emissions crutch. It basically draws fuel stright from the fuel bowl when velocity through the primaries reaches a certain point (like above about 30% throttle, 2500 RPMs). I'm really suprised that feature is included in a CC Qjet since the O2 sensor and M/C solenoid should be more than adequate to hold a constant A/F ratio at various throttle positions/RPM ranges WITHOUT the help of an old-school crutch like this. If you get a chance try to blow through the tubes. They might be blocked off, in which case you can just eliminate them. The discharge holes are near the top rear corners of the choke horn. Very mysterious.

Your carb's full secondary air valve opening without binding is what I've been talking about for a long time VS. stock LG-4 and L-69 carbs. The tension spring on the Chevy carb starts to bind once you get past 75* of air valve opening. Your caddy carb has the "good" air valve shaft that allows full 85-90* opening without binding the spring up. The geometry of the shaft is just slightly different from the LG-4/L-69 shaft and it makes all the difference. Hold onto that shaft- you can swap it into other QJets down the road.

WS6 Berlinetta

I like to experiment with things I'm learning about. I'm not going to do the hot Idle comp on the carb I've got on right now but I want to try it on another one so I can switch them back if I messup or if it doesn't work. Does the valve do anything at part throttle?

I have to move the short accelerator pump to the caddy carb I think that might be part of my slight bog problem then tune the air valves and secondary rods. Even with the bog I feel alot more power with this carb compared to my previous carb before the TPS went bad. I guess it's the air valve shaft I was never quite sure about the whole shaft argument until I was showing my friend what I was doing with the screws and I noticed more resistance at the point where it stopped stock. I guess that big caddy needed more power to get going.

Thanks

R

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'84 360ci WS6 Berlinetta
Fastest Berl In Cali
WWW.SDFB.ORG

Damon

The valve works all the time, regardless of throttle position. It's a bi-metal temperature sensitive spring that opens the valve. It's like a temerature-sensitive vacuum leak. It doesn't leak much air past so it's main effect is at idle and very slight throttle opening.