Hei Timing And Carb setup Help

[twoskies]

hey

1979 350 with hei and rochester quadrajet, have timing set at 8 advance, secondary choke on carb is unhooked(was already like this) motor starts up on electric choke, primary door opens after a minute or two, motor then has to be set at a high idle or it wants to slowly lope down and die, it does start right back up and you can keep it running by feathering the gas
does run a little rough after choke kicks off

do i need more advance(have seen some setting at up to 16)

or is it possibly a carb issue , setup, or secondary choke that is not hooked up

thanks for any help

[jocko]

Initial advance is likely not your issue, 8 deg is more than sufficient to keep er going. What happens once it's warmed up (if you keep it running long enough by tapping the gas)? Does it eventually settle down and keep running? If you can get it to that point, recommend adjusting idle mixture screws. If you can't keep it running (or maybe try this first when it's not running), you can very carefully count how many turns it takes to seat the idle mixture screws (that way you can at least return to your current setting, depending on what you find when you try this). Approx 1.5-2 turns out from seated should be ball park. If you're close to that, I'd just reset it where it was. If not set to that, try that setting and see what happens. When you say high idle is needed to keep it running, how high? Is the engine up to temp on your temp gauge if your truck has one?

[geezer#99]

Got headers?
Working heat riser?
Stock air cleaner or not?
Got pics of your carb with and without air cleaner on.

[kwmech]

It's winter and it's a carb'd engine. I have the same issue every winter with my 454. Cold blooded with a 4 core radiator...takes about 5-7 miles b4 everything is happy

[twoskies]

hey

thanks for the replies, motor is out of a 1979 el camino, friend said it was a replacement motor, low mileage, dont know for sure, he had it on a stand when i looked at it, was alot warmer, seemed ok then, it did set for a few months inside garage before i got it in truck

no headers, stock dual exhaust kicks out right behind wheels
running an electric choke, i am running 12 volts to it
i do have a old replica cadillac batwing air cleaner on it, runs same with or without
i can set the idle screw in and it will run on its own
i can keep it running with the gas pedal
ill check the idle mixture screws, just bought a carb tool yesterday, mine had the double d screws, never knew there was a screw like that

and ill try to get a couple pictures today

thanks again

[twoskies]

hey

just snapped a few pictures, also found the secondary choke is not hooked up, would this cause idle problems

thanks

[geezer#99]

That’s not a choke!
It’s the secondary air door. It’s spring loaded so it stays shut until needed.
Tap it with your finger and it should pop shut again.
Is the vacuum hose to that back vacuum pot hooked up or blocked off?

[rotten67]

Have you checked for vacuum leaks? How old is the gas in it? Try cleaning or replacing the spark plugs. Are the points ok? Or does it have electronic ignition?

[MySons68C20]

He has the HEI....If it was mine I would pop the carb and at least give it a good cleaning and rebuild so you can rule that out.
Today's ethanol fuel plays havoc with the internals especially if allowed to sit for extended periods.

[randy500]

Looks like your curb idle screw is way in...should be about 1 turn open, it also looks like the secondary lever could be holding them open at idle, pull the secondary lever forward to make sure they are closed.

Base timing should be at least 16 so bump that up.
You have to forget about all the engine stickers saying base timing is 8, etc.
the engine wants 36 degrees at about 2k rpm. that Hei has about 8-10 centrifugal at that rpm and continues to provide advance to about 5k rpm, which is stupid but that's how they are set up.
Base 16
Centrifugal about 10 at 2k, another 8 or so at higher rpm

With 16 base timing your still short a lot of advance.....
Vacuum...only providing advance at high vacuum cruise conditions.

[HO455]

Sounds like you may only need to adjust your fast idle setting. When the engine is cold step on the throttle and " set the choke". This allows the throttle plate to open and the fast idle can to drop so when you release the throttle the throttle butterflies are open slightly. At this point you should see clearance under the idle set screw. If not then the fast idle adjustment is wrong. The carburetor should be holding the higher idle speed without your input. Setting the choke requires the parts to move free as gravity is the power source to move some of the parts.
Here is a link for some choke information and there are some videos out there on how to adjust the fast idle setting on your Qjet.

I recommend you look at the choke's operation first and make sure it is working correctly before adjusting anything else. If the truck runs good when warmed up, then my money is on the choke. You may find the choke mechanism has been assembled incorrectly in the past. Something I have seen many times.

https://www.hemmings.com/magazine/mu...t/2144991.html

Good luck.

[twoskies]

ok
again thanks for all the replies

i reset the timing to 16
adjusted the 2 dd screws to 2 turns out
still has to run fast at idle or it dies

might have found a possible issue(or at least not helping the problem, trying to adjust carb screws with the squeal sucked), alternator started squealing really bad, am going to get a replacement in the morning, also going to get carb filter

thinking about what someone said, pull it and rebuild, kinda leaning that way
ill update tomorrow

[GASoline71]

How is your plug gap? With the HEI, it should be at least .045

Gary

[twoskies]

hey

the plug gap is set at .045,
i have changed the plugs
ac R45TS

thanks
Jeff

[twoskies]

hey
first, Thank You to all that replied,
some i had thought of others i had not

first i double checked my timing, 16 advanced, good

checked my dd carb adjustment screws, 2 turns out worked like a charm,
i did find my brake vacuum had a small leak( fixed)

adjusted idle to very acceptable speed,

i did remove the front vacuum, pretty sure i got it back on the same, even if not, when warm, truck runs good, so if i have to deal with choke issues, i can figure that out

Thanks again and
a very happy new year to all

[AussieinNC]

Are you running a thermostat?

You should have little to no radiator water flow until the thermostat opens...

Running headers you have no divorced choke feed back into the intake manifold heat passage further slowing warm up...

Suggest you look into a rebuilt carb and save the angst of fiddling with the old one...