fwayne

I have a new Holley Street Avenger on a new small block in my '75 that I just got from the shop yesterday. The car was idling at 1,500 rpm when I got it home. I was able to drop the idle to around 1,000 by adjusting the idle screw, but that's as far as it will go. Shouldn't it go lower?

This carb has an electric choke. Is there another idle adjustment on the choke side? Should the choke even matter when the engine's warm?

Any help is appreciated.

TTop Tony

Make sure theres nothing interfering with your secindary linkage. I had a egr block off plate that was holding the secondaries open and causing a high idle. Just a thought. Also it could be running too rich I think that causes a high idle.

fwayne

Thanks for your reply.

I had just gotten the car back from the shop and I figured that they knew what they were doing when they set up the carb. As it was, the idle mixture was set REALLY rich on one side, the distributor was plugged into a non-ported source so that the car had 29 degrees of advance at idle, and electric choke was hooked up to a wire that was never hot.

I wired up the choke, rerouted the distributor vacuum and adjusted the idle mixture and the choke. The car "idles" at around 800 now.

bigvette1

Just happened to be poking around this end of the forum and ran across your post. I have a 770cfm Avenger. It idled at 1500 and drive me nuts and Holley support. Finally, I took a look with a bright light and magnifying glass and the lower secondaries plates were not shut. They were misaligned from the factory. Had to take them out and smooth the edges then reinstall. Resolved the problem.

HeaderDesign.com

When you get a Holley carburetor out the box, you need to make sure it's ready to run. I take it apart to see how it is calibrated and to check the levelness of the floats. Then I check to see that the accelerator pump actuates on the slightest movement of the throttle. Sometimes the cam follower wants to sit on the throttle return spring at idle. It's just pure luck if the pump cam and squirter are right for you. Start lean and work up.

But most importantly, I set both the primary and secondary throttle plates so that 0.040" of the transfer slots are showing. The amount of slot that shows at closed throttle should be between 0.025" and 0.060" or something is wrong. Count the turns out on the primaries to get to 0.060", and then return to 0.040". Set the idle fuel screws to 1 1/2 turns out and fire the engine. Set the curb idle RPM counting the turns.

Once the engine is "warm", adjust the idle fuel screws several turns out to richen the mixture. At this point the mixture is governed by an internal restriction. Then increase the idle speed of the engine, counting the turns, until most of the primary transfer slots are exposed, but no fuel is coming out the mains. Adjust the idle fuel screws in evenly until best mixture is first realized. Now reset to curb idle RPM and adjust idle mixture screws for best lean idle. If you didn't have to adjust the idle fuel screws to find best lean idle you are lucky. Otherwise you need to adjust the secondary throttle plates to expose more or less of the secondary transfer slots. Do it in 1/8 turn increments on the secondary throttle plates.

When you've got it right, both primary and secondary throttle plates will expose the right length of slot, and the idle mixture screw settings will provide best mixture at both curb idle and high idle. This will go a long way toward making accelerator pump tuning easy, and will greatly improve light cruise throttle response, power and economy. Who needs fuel injection?

norvalwilhelm

I agree when you get a holley you have to go through it completely. I even end up remachining alot of gasket surfaces, restricting the idle circuit etc, etc but I NEVER want to see the transfer slots exposed at idle. This is the problem with poor idle caracteristics with big cams. The slots are exposed thus causing the mixture screws to be ineffective.
You are trying to cover up these slots and let the motor idle on strictly the idle circuit. I go to great length with drilling the throttle plates and putting a restrictor in the idle circuit to get the transfer slots covered up. I even put adjustable jets in the transfer slots to lean them out in the transition. I drill and tap 10-32 threads in the main body of the transfer slot passageways and install homemade jets.
From you post you seem to know alot about Holleys but I don't agree with you on this

HeaderDesign.com

Norval,

Sounds like you do alot of carb work with race-type engines. That's probably more fun than street type. I was addressing the 670Avenger as a street type application. I've found that the transfer slots provide an important percentage of the idle fuel on street calibrated carburetors (smooth idle). The PCV also provides an important percentage of air. I set the idle fuel screws at idle RPM, 1500RPM and 2200RPM on a street engine. If the engine doesn't respond to both rich and lean adjustments at these three engine speeds I know I have a problem. I use the secondary transfer slot as a means to adjust the mixture, as well as the idle fuel screws. Plus I just love taking the carburetor on and off the engine to adjust the secondary throttle plates.

norvalwilhelm

It also sounds like you know your carbs. We just seem to disagree with how the transfer slots work.
I strictly set them up for the street. My personal car is a 8-71 blown 460 and I get consistent 12 mpg around town, idles forever without loading up and never, never fouls plugs. After 3 years of running the same plugs they look like new. I do tend to run things lean and use the power valve to richen the mixture at the right moment.
When I get a new car from the local speed shop I spend at least 1 full day remachinig and making my mods. When I trade the carb in for something different in a year or two I get full puchase price back.
I take whatever is takes to cover the transfer slots at idle and get the idle screws out to the 1 1/2 turns. The screws need to be responsive and the idle mixture is screwed up with fuel from the transfer slots.
I am leaving now for the weekend and won't be back until Monday morning so any response by you is not being ignored. I don't have access to a computer in about 20 minutes so have a nice weekend and thanks for not getting upset with our disagreement over the transfer slots.
Nice to be able to disagree and still respect the other persons view.
Have a nice weekend
My blown 460.