Well have 85 Z28 with 350 Edelbrock intake and Edlebrock 750. Have my timing set to about 10* BTDC. Also have 270 comp cam in the 350. While adjusting my carb set idle at 850. When setting the idle air mix screws. How do you know when you have hit the sweet spot. So to say. Have carb about 3 1/2 turns out on mixture. With my mild cam and all I just don't know?

 

You need to use a vacuum gauge! Adjust both sides for maximum vacuum, balancing both sides, put the timing back to where it's supposed to be again, then adjust both sides again. You'll probably rock back and forth a few times depending on how bad it is in the first place.

 

I really don't understand by what you mean on maxing out on the vacume guage. When I was turning idel mix screws the vacume didn't drop to much. Just that my curb idel work bog down. At what vacume pressure should I be at? Also does the return spring have to have a certain tension on it? I had to use just a single spring. Seem throttle is smooth. But the curb idel set screw bracket doesn't go all the way back to normal idel. Will stay at about 925rmp. If I tape it back with my hand it will level out to 850 again?

 

Well, first of all you must disconnect the 4-wire harness going into the distributor if it's still comp. controlled, otherwise, disconnect and plug the vacuum advance hose going into the vac. can (on the dizzy).

**) Raise idle speed with the adj. screw on the carb until you get about 2000 rpm or so (exact not important)

You have to get manifold vacuum signal also, not ported. Ported will not vary too much as you adjust, manifold vac. signal will. Any connection at the base of the carb will do, anything up on the body of the carb is ported vacuum.

Normally, you should see about 15-20 # of vac at idle, so adjust each of the idle mix screws until the vacuum goes to the highest point. There will be a point where it starts to come back down. Adjust the other side, until the mix maxes out again. By this time, your idle should be coming down. Recheck your timing to make sure it is where it is supposed to be (mine is 6* BTDC) It will probably be out. Bring it back and go back to **) and redo all steps, until it gets rocked in to where timing stays the same, and vacuum readings are at max. Idle mix is done, so reconnect all your vac. lines, bring back your idle speed to wherever it belongs (600-700 rpm or so) and call it good! (don't forget to lock down the distributor!)

If you take your time, it's not hard and makes a world of difference with drivability!

Hth!!

 

Did the steps stated and seem when I drove the car around. It had some hesitation on the throttle side? Rolled out slow then a big hit of TQ from the engine. Then it'll level out as I go on down the road. When I am coming from out of drive into park the idel goes way back up. Seem that throttle is sticking. When I turn off engine it will desile on. For a sec. If I mess with the throttle had mash it back down to the stop screw or idel screw. It won't continue to run?

 

are all u guys usin timming lights cause i don't have one. also how do u know wut your timing is set at?

 

FatOne: IIRC, dieseling is a symptom of timing, too far advanced I think. You might have the engine that requires 0* TDC instead of 6* BTDC. Check the emissions sticker at the front of the engine compartment to see. There is something radically wrong with that whole timing setup. Did you reconnect all the hoses and wiring? It never fails, usually whenever I'm working on mine, even if I double check, something gets missed!!

89formula#1: Not meaning to be picky, this is a casual board after all, but please write in English! Nine errors in two short sentences is ridiculous! Let me guess, fonix?
Anyway, yes, you should absolutely be using a timing light! The only people I know that don't, are the 2 mechanics I knew in SoCal that have been doing this for about 100 years! They can tune an engine by ear better than most techs with an engine analyzer!
You can even pick up a cheapie at a local auto parts store for a few bucks, but then again, you get what you pay for. Get as good as you can afford!

 

My car only seems to deisel when I drive it around for 30-45 min straight. Shut down and keeps trying to run, spits some gas out of the carb too. When I go to turn it back over it'll make a popping sound from the carb? What gives? Seems if I lift the hood and ram back the throttle cable all the way back down to the idel stop. Then shut down and no deiseling will occure. I have tried many different * on my timing. Thing is no one can tell me the right * to set it at with the mods I have. No little sticker on the hood or anything like that. With the return spring, can I see what tension should be on the carb? Edelbrock 750 Vacume Sec. with manual chock. Also can I clean the throttle cable somehow? It was the stock 305 TPI cable now on the 350 carb setup. I'm really lost with this.

 

l'd like to start out by saying this, just check over the plugs, wires, and distributor cap and rotor to make sure youre operating at the engines full potential. sometimes after being ash-fouled, the carbon on the plugs can tend to glow red and cause detonition after awhile. l can also reccomend changing your plugs, possibly to a heat range or two cooler. although many people may disagree with this method, l've always adjusted all my carbs by simply (depending on carb) closing all adjustment screws, backing them out about 3/4 of a turn, and starting from there. (the motor should be at operating temps when doing this obviously) making small but equal turns, driving the car, and repeating the process. making adjustments as nessecary. you don't nessecarely need to follow this advice, its just my 2 cents.

 

Ahhh, ok!
First, yes to a certain extent, you can clean the cable. The way I've done it (probably not the best method, but it works for me!) is to remove the carb end, spray a lot of WD-40 into the cable jacket, and work the jacket up and down a few times, then turn upside down and spray some more in there. A couple times of this, and most of the crap will be out of there. Let it dry out for a bit. Then I just shoot some white lithium grease, very sparingly up in the jacket and work it around too.

I've also heard that there is a different mount for the throttle cable (TPI vs. carb) where it attaches to the engine. Sounds like maybe the cable is binding when it comes out of the jacket (or before it goes into it around the firewall). Double check to make sure that the cable geometry is straight.

Just more $0.02 (man, you're gonna get rich from this!)

 

Guys I thank you for all the help. With a lot of time on the weekend I think that I've finally have it tuned out pretty well. As far as the throttle cable I think I'm going to order a new one from Lokar. Other than that and my tranny lock up I'm almost done. Once again thanks for all the helpful feed back.