oldsmoboogie

In order to get my car to idle i have my timing set to 20 deg int with total being 36. I have a box stock 770cfm street avenger carb with vac sec. I cant understand why its doing this. It seems like its getting too much fuel at idle. Could i need a smaller power valve? Im new to tuning a carb so im trying to figure this out. My combo is 9.5 comp 30 over 455 with ported heads and cam specs are 240,246 with 541,544 lift on 110 lobe sep. Im running a rob mc mech pump and 1 3/4 headers. I have a msd billit dist and msd 6al box. Any direction in where to start is appreciated thanks

oldcutlass

The 770 should be perfect for your car! Is it a 4 corner or 2 corner a/f screw setup. Vacuum secondaries or the mechanical? What is your idle speed? And what are the indications that your running to rich?

oldsmoboogie

Its a vac secondary, at 20 deg int. it will idle at 600 rpm but if i try and back up int timing it wont idle unless you turn the idle screw almost all the way out and then its way rich as you can smell fuel out of the tail pipes and my eyes would burn. I think the question i shouldve asked is what people run for int. timing for a performance engine? What would be the benefits of running less int timing? I can take 3 more degrees of total out of it if that woud help performance. But i still dont understand why i cant get it to idle properly with less int. timing? I havnt been able to road test it yet because of rain so im curious of how much total you guys recomend? Im at 36 now and i can limit that to 33 if necessary. Thanks for any input.

ferndaleflyer

My set up: 30 over 455, flat top pistons, Cam is 523 intake-544 exhaust 108 lobe separation. Timing set at 32 but no advance in dist----I have 20degree retard in my MSD to start. Carb is a home made Holly 800 jetted real lean (I forget what all I did to it) Your problem other than the carb sounds like a vacume leak.....lots of things can be done to a carb to make it act stupid. My car runs 6.60--6.70 in the 1/8 at around 100mph. Also run your idle screws in all the way and back them out 1 turn---see what that does for the idle.

oldcutlass

The 20/36* is fine as long as it does not ping, 18/34* is probably more on the safe side. Either way you'll probably have to limit some vacuum advance if you hook it up. Like mentioned above, turn your a/f mixture screws all the way in until they gently seat, then turn them out 1 full turn each. Set your idle speed to 700-750. With your cam a vacuum gauge probably will not help with setting your carb. Your going to have to give the engine what it wants for a smooth idle.

What manifold are you running? How much vacuum are you pulling? Is the electric choke hooked up?

oldsmoboogie

im running a torquer manifold, no electric choke, and it will pull 7.5 in of vac

70Wcars

Put in a 4.5 power valve. Then follow the above procedures.

Danny

oldcutlass

The Torker manifold is a single plane 2500-6500 rpm range, it's going to run somewhat rich at idle. Did you readjust your a/f mixture screws? Is this for the track or mostly street?

Danny's suggestion would be my next thought.