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I have bone stock 1980 C3 with quadrajet. I finally got it to idle but it only idles smooth at 900 to 1000 rpm WITHOUT vacuum advance. I can't check timing because harmonic balancer is slipping and got one ordered and it's coming.
Funny thing is car idles smoother at 900 to 1000 rpm without manifold vacuum advance. As soon as I connect vacuum advance to manifold vacuum ( i connected vacuum advance directly into the manifold port, not carb port), it idles rougher.
Manifold vacuum reading at 900 to 1000 rpm is 20 inches of mercury and it's steady.
At the time of this testing, only the PCV line and brake booster line is hooked up on the carb. Everything else is capped on the qjet. When I connect the vacuum advance to the ported vacuum nipple on the carb and rev the engine, it revs fine even beyond 4K. I am using 93 octane fuel. Another question is I am getting full 12 volts on the choke electric connector but when connector is connected to the choke housing blade, at the blade, it only shows 4 volts. Shoudn't the blade also show 12 volts also? Shouid I do ohm testing?
Last edited by riverwabbit703; Dec 4, 2021 at 05:40 PM.
Reason: more info
At 1000 rpm you're likely getting vacuum applied to the dist and the dist is probably advanced too much. Since you can't use a timing light just yet, retard your timing so the rpm drops to around 800 to 850 (if an automatic) or 600-650 (if a manual). You should not have any ported vacuum at that RPM. See how it idles and runs set that way.
Good luck.
At 1000 rpm you're likely getting vacuum applied to the dist and the dist is probably advanced too much. Since you can't use a timing light just yet, retard your timing so the rpm drops to around 800 to 850 (if an automatic) or 600-650 (if a manual). You should not have any ported vacuum at that RPM. See how it idles and runs set that way.
Good luck.
Thanks for the quick reply. I will try to retard timing by twisting the cap may be 1 to 2 mm tomorrow and get the idle down with using distributor. I should not try to get the idle down with the curb idle screw at this time? I should only adjust curb idle screw after idle mixture is set correct? Should I do this is gear since it's automatic?
Thanks for the quick reply. I will try to retard timing by twisting the cap may be 1 to 2 mm tomorrow and get the idle down with using distributor. I should not try to get the idle down with the curb idle screw at this time? Sure, that could be the easiest to try but I recommended trying to adj the timing since applying vacuum makes your engine run worse. In case your engine gets worse you can put it back and concentrate on the carb.
I should only adjust curb idle screw after idle mixture is set correct? Should I do this is gear since it's automatic?
Since it's an automatic I'd leave it in Park & set the idle RPM to 800-850. Normally an SBC can drop 100 -200 RPM once put into gear and the goal is to get the RPM to 600-650 RPM in gear.
With all that said there are some other checks & tests you should do before you start adjusting.
1) Choke. Is the choke opening up all the way? It could be that it's staying at one of the high idle settings. Sometimes an ice cold SBC with a carb can take several minutes to get to normal idle.
IF you decide to try and adjust the idle via the carb idle screw and it doesn't effect or change the idle, your choke may be set too "rich".
IF the idle does drop by adjusting the idle screw don't mess with the timing just yet. Get the RPM down to 800-850 THEN adjust the two idle mixture screws one at a time. Theres an art to that adjustment that a tach or vacuum gauge helps to fine tune.
Good luck.
From: At my Bar drinking and wrenching in Lafayette Colorado
You can't do any carb adjustments until the timing is correctly and properly set. Timing affects carb. Carb does not affect timing. Replace that balancer, do a TDC and timing mark verification, and then set up your timing correctly (including vacuum advance) as outlined in my papers. Only then can you start looking at any carb adjustments, including idle speeds. You cannot set idle speed with timing - that's completely bass ackwards - sure recipe for failure. Don't bother touching the carb until you have all your timing problems properly corrected.
You can't do any carb adjustments until the timing is correctly and properly set. Timing affects carb. Carb does not affect timing. Replace that balancer, do a TDC and timing mark verification, and then set up your timing correctly (including vacuum advance) as outlined in my papers. Only then can you start looking at any carb adjustments, including idle speeds. You cannot set idle speed with timing - that's completely bass ackwards - sure recipe for failure. Don't bother touching the carb until you have all your timing problems properly corrected.
Lars
I would like to add to make sure your vac can is in fact working and not sucking air.....this will cause what you are describing. Also.....on an 80', the idles screws are behind two non-tamper caps that need to be removed before the mixture can be properly set......
Post what you find after you get the new damper on....
I would like to add to make sure your vac can is in fact working and not sucking air.....this will cause what you are describing. Also.....on an 80', the idles screws are behind two non-tamper caps that need to be removed before the mixture can be properly set......
Post what you find after you get the new damper on....
Jebby
yes, I have the damper in hand but can’t install it until I get the rear brake lines installed. Steel line broke and got one ordered. Once arrives I can get the car moved into the garage and get the damper on with the mechanic buddy. Car is parked on incline and it’s getting f ing cold here in Virginia.
From: At my Bar drinking and wrenching in Lafayette Colorado
Make sure you buy/borrow/steal and use the correct balancer removal & installation tool. Don't start or attempt the job without it:
If you have to order/buy the tool, you might want to order and procure a top dead center verification tool while you're at it so you can verify that the timing mark on the new balancer aligns correctly with your timing tab. E-mail me for my "How to Verify TDC" tech paper for tool description, part number, and instructions, and make sure you have a current copy of my "How to Set Timing" paper.
Lars V8FastCars@msn.com
Make sure you buy/borrow/steal and use the correct balancer removal & installation tool. Don't start or attempt the job without it:
If you have to order/buy the tool, you might want to order and procure a top dead center verification tool while you're at it so you can verify that the timing mark on the new balancer aligns correctly with your timing tab. E-mail me for my "How to Verify TDC" tech paper for tool description, part number, and instructions, and make sure you have a current copy of my "How to Set Timing" paper.
Lars V8FastCars@msn.com
I borrowed one of these kits on loan from either advance auto or auto zone when I replaced my damper earlier this year. Basically you buy it and then get reimbursed when you bring it back. I think they allowed 90 days. With that type of timing and the fact that you can't go 5 miles without finding another AA or AZ, you would run your own shop without ever owning any tools. One note, if you go that route, inspect the kit before you take it and have them note any problems like damaged or missing parts. In my case I noted both issues, bent bolts and a missing tip needed to go on the bolt that pushes against the crank.
Make sure you buy/borrow/steal and use the correct balancer removal & installation tool. Don't start or attempt the job without it:
If you have to order/buy the tool, you might want to order and procure a top dead center verification tool while you're at it so you can verify that the timing mark on the new balancer aligns correctly with your timing tab. E-mail me for my "How to Verify TDC" tech paper for tool description, part number, and instructions, and make sure you have a current copy of my "How to Set Timing" paper.
Lars V8FastCars@msn.com
Would this one work? This is only kit they rent at advanced auto. Autozone just has jaw puller around my area.
I heard I would need to bake the balancer for few hours in the oven for easier press fitting?
NO! A few hours? Really? You will ruin the rubber ring….
You should be able to push it on with the tool…..make sure the threads on the tool are lubed with moly…..
If you do heat it….or find it is hard to put on and need to heat it….use a camping hot plate and heat the snout facing down….for about 5-10 minutes….
NO! A few hours? Really? You will ruin the rubber ring….
You should be able to push it on with the tool…..make sure the threads on the tool are lubed with moly…..
If you do heat it….or find it is hard to put on and need to heat it….use a camping hot plate and heat the snout facing down….for about 5-10 minutes….
Jebby
thank god you told me this. Does it have to be moly lube? Are you taking if anti friction lube?
Slickest **** you have…..the idea is to not fight the friction of the threads installing it…..I use moly….best there is….
Jebby
one problem after another. Got the car started, tried to move it up to the garage and car died on my inclined driveway. Thought I ran out of fuel but when engine was cranking, my buddy was able to see fuel being discharged from the nozzle. He took off spark plug cable and placed another spark plug in the plug hole, started the engine we got no spark on first two tries and got 2 sparks on third crank of the motor. Looks like either HEI coil or the pick up coil is bad. Checked ohm reading between tach and bat and it was .05 ohms, got 12 volts but it was late and did not check the ohm readings between the secondary and ground wire. If I end up replacing the HEI coil, should I also replace the 41 year old pick up coil as well?
Replace the whole unit......don't mess with replacing parts that you are unsure is the problem.
Buy this....drop it in and set the timing to 36 total......done. Pre Curved unit specifically for the ZZ crate engines..... https://sdparts.com/i-19924795-chevr...stributor.html
The pickup coil requires the shaft to be pulled out of the distributor....and in 35 years.....I have never seen an HEI coil fail....it is always the carbon button on the bottom of the coil through the cap or the connections to the coil......(both of which you can check before replacing).
Replace the whole unit......don't mess with replacing parts that you are unsure is the problem.
Buy this....drop it in and set the timing to 36 total......done. Pre Curved unit specifically for the ZZ crate engines..... https://sdparts.com/i-19924795-chevr...stributor.html
The pickup coil requires the shaft to be pulled out of the distributor....and in 35 years.....I have never seen an HEI coil fail....it is always the carbon button on the bottom of the coil through the cap or the connections to the coil......(both of which you can check before replacing).
Jebby
Do you know what ohm reading should be on the carbon button to ground connection wire should be when testing? Yeah, if I gotta replace the pickup coil, I might as well just get that distributor you linked.
Do you know what ohm reading should be on the carbon button to ground connection wire should be when testing? Yeah, if I gotta replace the pickup coil, I might as well just get that distributor you linked.
Do not concern with the ohms of the button.....make sure it is intact, that the rotor tangs has good contact, and that the spring is present.
On the GM distributor.....I usually replace the vacuum advance can with an adjustable one.....adjust it for 12 degrees. It gets no better than that.
Do not concern with the ohms of the button.....make sure it is intact, that the rotor tangs has good contact, and that the spring is present.
On the GM distributor.....I usually replace the vacuum advance can with an adjustable one.....adjust it for 12 degrees. It gets no better than that.
Jebby
I took the distributor parts out and it looks like everything looks okay? Pick up coil look little loose on the orange connector next to green one. Is that okay?
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1980 c3 quadrajet and timing question
