Car is a 1965 Chevy II. Mostly stock 327 (200 deg cam, perf intake, headers), w/ a PG (yuk!), and 3.08 gears. Convertr stalls at ~1800 rpm.

Carb is from a 1980 305. Jets are 71 w/ a 42 prim metering rod, DR sec rods, and H hanger. Carb was just rebuild w/ float at 1/4". Fuel pump is a new Carter 6900 mechanical unit. Air door is set at 3/4 turn. Vaccum can is "2-3 sec" unit.

Here is the scenario:

Mashing the gas off idle gives no hesitations or stumble. Car begins to pull strong, but revs slow, due to a 1.82 1st gear and 3.08's. When it gets to about 3000-3500 rpm, it feels like it goes "flat". At 4000 rpm, it starts to pull again like someine flipped a switch, and pulls until 5000-5200, where the small cam and heads give up.

What is going on here? It did not do this with the previous carb, which was a 1850-3 Holley. Could it be that the DR's are too rich on initial opening? Could it be that the vaccum can is not "damping" the initial secondary opening?

Remember, 40 mph is like 3000-3500 rpm in first gear, so the engine spends a lot of time at WOT under 3000 rpm accelerating the car to 35-40 mph. This is a bit different than most A3/A4/manual trans combinations.

Help! What should I do?

 

BTTT

 

You're vacuum secondaries are set too tight. It's taking a great amount of vacuum pressure to open the secondary flap (plate), and at 4000 RPM.... this is where the engine is finally getting it to open, feeding it a rush of more air etc.. (thus more power only at this particular RPM)....

Loosen the the secondary plate a 1/4 of a turn for at first, then give it a test drive. If it's still holding back until a later RPM..... loosen it somemore. Keep loosening until you start to 'bog' a little, then you know you loosened too much, so tighten it back up a drop til the bogging stops.

If the quadrajet came off of a stock 305/350, and you're putting it on a mod motor (even if it's basic mods).... resetting the secondary plate is a MUST!!!

 

I don't think that's it, but I guess it would be worth backing off tension completely to see what happens.

I have played with many Q-jets, and it seems that all of the ones I have used before have always liked A/V tension to be between 1/2 and 1 turn. I have never tried taking this one below 1/2 turn.

 

You're leaning out as the AV opens. Get a lower-letter hanger like a "B" to pull the secondary rods out of the secondary jets more, relative to AV opening.

 

You think that is the problem? I'll try a "B" hanger and see what happens.

Thanks!

 

The other possibility is that the AV hanger cam is worn. It's the plastic thing that lifts the hanger as the AV opens. Check that, and if it doesn't appear to pull the hanger/rods up smoothly, replacement may be in order. They are available here http://www.carbs.net/cams.asp , p/n 85-104.