6-port N/A streetport,polish.Full racing beat exhaust,dellorto 48mm sidedraft.Holley Blue fuel pump and Holley adjustable regulator,MSd coils and 2 MSD 6AL's.The problem----------car hard starts and won't restart after it's hot,need,help with carb adjustments[mixture screws] etc.VERY RICH at idle and loads-up after awhile.Idles at 1000RPM,Street-port sounds like a Bridge.Any help Please!

 

My Setup on stock 6 ports.

Needle and seat:
#350

Idle jet holders:
7850.8

Idle jets:
80

Emulsion tubes (main jet holders):
7772.8

Main jets:
230

Pump jets:
90

 

I'll have to remove jets,emulsion tubes,etc to see what sizes they are but,what's the procedure for adjusting the air/fuel mixture screws?Thanks.

 

What do you have your fuel pressure set at? I believe it should be around 3-3.5 psi. Too high can cause the rich condition. 2.5 -3 turns out should get you in the ballpark with mixture screws.

You can download a Webber and Dellorto book from Sgt. Fox's site.
http://foxed.ca/foxed/index.php?page=rx7manual#other

Check out this site also.
http://www.gruntled.com/Dellorto

 

First set your fuel pressure as mentioned above, then takes these next procedures one by one in this order.

Idle mixture procedure, do this before diagnosing the other jets. Fully seat both screws(don't overtighten, just gently seated is a better word), then let them out about 2 turns, turn the car on, and with it running, GENTLY and SLOWLY adjust both, keeping note of how many turns they are from fully seated. I go by 1/8th turn increments on both and wait a few seconds and listen to the car, then take note of the idle. Keep doing this until the idle is at it's highest, once it peaks up then starts dropping again, go back to the peak setting, this is the indication that the mixture is at its absolute optimum (as the atomization causes the fastest idle speed. Also make sure this is a smooth consistent idle. Then play with your throttle return positioning screw to get the idle where you want it. If there is any hesitation in the progression circuit (slowly increasing the throttle under load) it means your idle jets are too lean, if the car drives without sputtering or hesitation, then those jets are good. Next, try a few hard throttle stomps, if it hesitates there, then the pump jets are too lean, once again, if it drives fine, then you're good. Last thing you'll want to test is you main jets by just getting into the higher RPM. If it pulls strong, then the main jets are giving a fairly good mixture. Watch your temp gauge, if it rises after the engine has had prolonged exposure to RPM above 3500(cruise on the highway for a little while at 4000-4500RPM in 4th gear for 10 to 20 minutes,if the gauge is going up (don't let it get past halfway), then your main jets are too lean. The procedures for seeing if it is too rich are less important, but if the richness is proposing a problem, they include looking at the spark plugs, smelling the exhaust, listening for fire(fireballs out of the exhaust are ok when letting off at redline, but doing so while daily means driving the car is too rich), and often flooding. Lastly, if you use my testing to make sure that you're not running to lean, you can take note of what jets got you to pass my test, and buy a few that are richer, and a few that are leaner, then play with jet combos on the dyno for peak power and accurate air-fuel ratios. Hope this helps, and it should point you in the right direction.

 

Thanks Turbo II for your info.I'ved done as you said,but still hard starts and idles brap,brap.brap.I'ved checked the timing and noticed it's WAY ADVANCED.Re-did the timing,set dead-on and the same damn thing.Wiggled the rotor on the dist and noticed there is a 1/4 to 3/8 side to side play WTF.Is this suppose to have any play at all if any?Cause if not,then this will explain the hard starting and brap,brap,brap at idle?Any input please anyone. Thanks.

 

A vacuum leak...

On my YAW Nikki It sounded like the motor was ported like a baby brap hah. Starting eventually got harder and harder. Eventually real hard. Anyways w/the same symptoms your describing, it turned out to be a vacuum leak on my lower manifold. The idle totally smoothed out and starting became waaaay' mucho easier / normal again.

87' That's some explination you gave up there.

 

Thanks 85tIIdevil,i'll check tommorow for a vaccum leak,but does the rotor on the dist suppose to have THAT MUCH side to side play?Everytime i set the timing dead on,upon checking with a light it's WAYYYYYY advanced.

 

I don't know about the distributor but when my car was idling like you described (brap brap on a stock port?) one of my mixture screws had the needle head broken off. It was running that rotor WAY rich on the idle circuit, and I think it would just foul the plugs in that chamber and the engine is idling on one rotor when it makes that sound. Is it also shaking with every "brap"? I suggest inspecting the mixture screw tips. Over tightening them can cause ridges to develop on the needle face ad thus ruin the metering ability of the screw. as far as my needle being broken off, I don't know how the PO did it, but the book I have about Dells says it's not completely uncommon.

 

No vaccum leak found,but changed the distributor and the brap,brap problem solved.Idle mixture screws were removed,cleaned,inspected and re-installed,non broken.Idles smooth at 1000RPM,But still takes a few attemps to start.Idle screws are turned out alot to get it to stay running and not load up and also the idle speed screw is turned all the way in.Although i had set the timing dead-on again,my light is still showing about 5 to 7 degrees advanced.Tried to retard it to get back to factory mark,but it dies.----------------------------
13B 6 port big street port and Polish
MSD Ignition boxs[2]with MSD Blaster Coils
Racing Beat Intake And Dellorto DHLA sidedraft
Full Racing Beat Race header and Exhaust
Holley Blue Fuel pump and Adjustable Regulator
Thanks EVERYONE for all your input,I just need to figure out why my timing is advanced,when it is set to factory specs.

 

If you have to turn your idle mixture screws out that far you probably need to rejet to get a richer (?) mixture. When its jetted right you should only be turning them out 2 - 2.5 turns. This is basically what the tuning book tells us.

 

Okay,does anyone have an enlarged diagram of this dellorto dhla carb showing the different components,jets,etc?this way i know what i'm removing,main,idle jets in order to get this car responding and idling as it should.