i have a 71 BB with a lars-erated qjet.. the other night i decided to put the pedal to the metal and though it responded quite respectably, i didn't feel the secondaries open. brought it home and adjusted the throttle cable as tight as i could... next time out, floored it again and no secondaries. it worked as it should when i first installed it but i don't floor it everytime i drive it. before i started fiddling with it i wanted to hear what you guys thought i might check... thanks

 

Darn, I forget what it's called, but the upper plate on the secondairies is vacuum operated. It keeps the secondaires from opening before engine is demanding the extra flow. Check the actuator and the hoses. The air horn plate has a little tab on it, if it gets bent then it won't let the upper plate open, period. Years ago this was a favorite trick of some of my friends, bend the tab a little to see how long it took someone to figure it out.

 

You don't need the engine to be running to see if the secondary throttle blades are opening. Hold the choke open and move the throttle to wide open. You should see the primary linkage move the secondary open on the driver side. You have to hold the choke open because there's a secondary lockout on the secondary throttle shaft that catches a pivot lever that locks out the secondary when the choke is closed.

If you see the secondary open then you have only a couple places to look. Check to ensure that the lockout is releasing when the choke is open. Then check that the pulloff dashpot is functioning by applying vacuum. It should pull in and allow the lockout to the air valve to move through its full range of travel. If the dashpot pulls down, then just manually open the air door to see if it moves freely.

The last thing to check if all the linkages are right is the actual tuning of the air valve opening. Though, if Lars tuned it, I'm sure the secondary is probably right.

Lastly, you should not be able to feel the secondary open. If you do, this is very close to a bog. The secondary should open smoothly and the only perception that its working is that the engine pulls strongly to its redline (or beyond). If it seems to hit a wall at around 4k or so rpm, and is very slow to accelerate beyond that, it could be the air valve is opening too slowly or not at all.

 

good info...well, in fact it does pull strong all the way through the rpm range. but i always expected to get a wot...WOOOTTT!!!! when i floored it...thats what i don't feel. nevertheless by your last paragraph what its doin is what it should...thanks

 

As Bubb Rubb says, get whistle tips for that woooo wooooooo!!

http://ebaumsworld.com/bubbrubbvideo.html

 

HA! Bubba Rubba