Just got the new Edelbrock 850 on. Two problems. 1. Should I see the secondaries open when revving the motor at no load? 2. The idle circuits have no effect on idle. I can totally close them and nothing will happen. Motor is 10:1, Stage 1 ported heads, 413 cam.
If it's an Edelbrock Q-jet, the secondary throttles will open, but it's not likely that the secondary air valve will open like that - the secondary vacuum break won't have time to let off, and unless you're revving to the sky, it won't pull enough air. Can't think of why you'd want to do that, the real test is in driveability. If your idle screws aren't having an effect, you've got a problem. - Is the idle speed screw really backed off enough to get the throttle blades closed? Look down the primary bores while it's idling - any fuel being pulled out of the venturis? If so, the carb's up above the idle circuit, and you need to work it back down into true idle.
The 1910 is the Edelbrock q-jet. Just doing the quick blip on the throttle. Just wanted to know if the secondary air valve (thanks for the name ) should open under that condition. The actual throttle blades for the secondaries are open. The idle speed problem. I think you are correct James that the blades are not closed enough. Problem is the motor will die if I back off the idle screw. It will idle at about 900-1000 out of gear and drop to about 750 in gear as is but I know that there is a problem. Only pulling about 9 to 10 inches of vacuumn. I went from a stock 800 q-jet that had the same problem to the Edelbrock because it is supposed to be designed for bigger cams. Any ideas would be appreciated.
I have the 1910 also, I can see and hear when they open. :TU: You should be able to hear them from inside the car when you stick the go pedal. :3gears:
Getting a Q-jet off of the "off-idle" circuits and back down onto the idle circuit can be a real pain in the neck. To confirm the throttle blades being too far open, if you see fuel coming out of the primary venturis at idle, that's the real giveaway. If not, you might have to shine a flashlight down the primary bores, and see where the throttle blades are. They should be completely closed or just a hair opened. Look for the transition slot openings to be completely above the leading edges of the throttles. If the throttle is opened too far (like we suspect), the throttle will be in the middle of those slots, not below them. Pulling the carb off the engine is the best way to check the throttle position, you can look under the throttle plates directly. I'd suggest setting the idle mixture screws at about 3 full turns out, then try and wean the engine off the idle speed screw. You'll have to go back and forth between the idle mixture and idle speed screws to do this. (One thing to doublecheck before any of this, is that the ignition is good and your timing is right.)
Just did some checking. There is fuel coming out of the venturis. Timing is 18* initial with 32* all in at 2200 rpm. I was just going over the problem with Joe T and we wonder if the cam should be advanced. Especially when the low vacuumn is factored in. Second the secondaries are not opening. The SP-1 that I had cut for a q-jet was not done correctly and does not let the secondaries open. Thanks for the replies.
18* initial? Yow, that seems like a lot... o No: But I'm not familiar with tuning for a big cam like you've got. But you need to get the throttles closed to get it onto the idle circuit. I've heard of guys with big cams having to drill holes in the throttle plates, but again, I'm no expert...keep up posted on your success. :beer
