The Money Pit

I have been playing around with an idle issue for a year now, not constant,but tweaking here and there.The car runs great, starts easy, turns 7000 rpms when the urge hits,but won't idle in gear for long.

The current set up is this. 406 cubes, 10.1:1 cr, AFR 195 heads,RPM intake,1 5/8" headers into 3 inch duals, 3000 stall,and the cam........ Isky Z-35 with 1.60 rockers. (254@.050,.560 lift Int/Exh 108 LC in at 108)

In neutral or park it idles at 12-1300 with vacuum of 12 inches, In gear 1000 rpms,7-8 inches, and in short order will stall without tapping the gas.In trying to solve this I've tried different timing advance curves,and presently am running 36 degrees locked out.This has given me the best vacuum at idle ever.(Originally I had only 10 inches in park,6 inches in gear with the Vic Jr intake.)

After all this I'm certain it's carb idle calibration,and I have already tried different idle air bleeds, and drilling idle feed restrictors. (The stock holley metering block.)In the procees of tweaking, I bought QFT billet metering blocks, which have screw in idle feed restrictors, and a Proform main body. Neither of which fixed the idle, but both of which will allow for infinate tuning.

The 3310 originally was a two corner idle carb, and from what Quick Fuel tells me, all I need to do to convert to four corner idle is drill the secondary idle ports in the throttle base to match the primary side, and match my idle air bleeds primary to the secondary. The parts are on the way now.(70 idle air bleeds, .035 idle feed restrictors)

Is there anything else I need to look for or modify while the carbs apart?

morganjd

what power valves are in the car? If 6.5 or bigger, try a 4.5. If you have a rich idle, you need to restrict the idle feed restrictors, I put a .015 wire in mine and the results are unreal. You need an air fuel meter to get the correct air fuel ratio at idle, the other alternative is to set your idle mixture screws to obtain the highest vacuum reading and then i have found you lean it out (turn screws in) an 1/8 of a turn, to get an ideal a/f ratio of 13.5 at idle. The idle mixture screws are very sensitive, and can only really be seen with an a/f meter, make both sides are dead equal

The Money Pit

Power valve is a 4.5, and the only way I,ve calibrated at all was with plug reading and a vacuum guage. I found going from the stock 70 primary jets to 74's changed my plugs from bone white to light tan. The idle problem, though very minor, bugs me. I will try to tune this out with carb calibration,as I' sure it can be done.

The same engine with a slightly smaller 240@.050 hydraulic cam idled fine with the same carb. Since the cam change, I've modified timing and jetting to try to accommedate the larger solid cam.At first I had a very rich idle, and ended up drilling the throttle plates with 3/32" holes to allow proper transfer slot exposure. Now the idle is the only problem,but in neutral will easily idle at 12-1300, which isn't that bad for a solid cam that will pull 7000 rpms.

The reason for this post was to find direction on drilling my baseplate to four corner idle.I feel confident I can tune this cam.