Argh, engine tuning

[TexasRed]

OK, no, I am still having some problems with my '84. Rebuilt Carb, seems to be a crap load better, good vacuum at idle (or what I believe to be idle). Occasionally it stalls at idle, if I put it in gear, it stalls. If I drive two-footed, it's not too bad and the transmission shifts pretty well. I have not hooked the distributor to manifold vacuum yet. I have an aftermarket tach, I can't seem to hook up the wire to the distributor tach signal, so it's not been hooked up yet. Now my starter makes a weird "whirl" noise but the truck still starts (and keeps running if I keep my foot into it a little bit). I checked #1&2 plugs and they seemed lean. #2 had a few more deposits (perhaps it's burning oil)? But #1 seemed fairly clean. I try to set my timing by driving it and adjusting it a degree or two from pinging. My distributor is an accel, perhaps the springs are too heavy? I didn't change the spring, I assumed it would be a stock build. Any thoughts? I may change the starter this weekend but I don't think this is my problem. Engine is '84 305, quadrajet carb, dual exhaust, 700r4 transmission. Thanks!

[78 BIG TEN]

If you put it in gear and it stalls you need to increase your idle on you carb.

[Captkaos]

The starter doesn't have anything to do with the stalling. 
Is the engine stock?
What is the vacuum at idle?  20 is good with a stock motor. 
What is you base timing set to? 10 degrees is where I would start. 
tach should hook up with just a few connections into the cap, what kind is it?

[DnStClr]

One thing to suspect is a bad torque converter. 2nd, You might have to remove the tranny pan to check for metal shavings in the pan. That would indicate a worn clutch pack or a clutch pack that's not releasing.  Either of these tranny problems will cause the engine to stall when you put it in gear.

[TexasRed]

Ok, well the transmission has been rebuilt (and it's not stock since GM did not offer it in this model in 1984 I don't believe). I have disconnected some vacuum switches that were leaking vacuum under the dash, the transmission shop just used the converter lock up connector from my th350c to connect lockup to my 700r4, so I'm thinking that maybe I *need* those vacuum switches hooked up. Also, it stalls when I put it in reverse, when lockup shouldn't happen.

Well, at 900 rpm, I get about 20 inches of vacuum. Engine is fairly stock, it's got a mild cam, not sure what it is, installed many moons ago and gives it a SLIGHT lope at idle (when the engine was younger, after it was rebuilt .030 over). I figured out the tach thing. .

I don't know my base timing as I usually just set it at a place, drive it and see if I hear pinging and then back off little by little until I don't hear pinging during acceleration.I don't have the timing tab and I guess I could get timing tape. Would an autoparts store  be the place for that as most speedshops have closed down?  One thing I did not do when I installed this new distributor, was to turn the vacuum advance canister with the allen wrench included with it. I assumed it should run pretty well out of the box. . . .

This also may be a case of bad gas. As the gas has been sitting for a few months (I did add stabil but ethanol has a tendency to break apart old dirt and most of our trucks are more than 20 years old). I put it some 93 octane so I could advance the timing a little bit.

Also of some concern is that I cannot idle it down (past 900rpm) with the idle stop screw, is that because maybe I have the mixture screws too rich? It could also be trash holding the metering rods out of the jets? I'm thinking of pulling the air horn on this qjet and checking it out. I had the trash problem with an edelbrock, so maybe it has happened with the qjet too as they both use the same type of enrichment device. There is daylight between the idle stop screw and the linkage.

[Blue 82]

In your first post you said you have not hooked up the vacuum line to the dist.
this should be hooked up

Not being able to idle below 900 is of concern
is the fast idle engaged? (pass side/check linkage)

did you use a new baseplate gasket
not the thin 1/16" gasket
but a 1/4" gasket
this will eliminate most baseplate gasket leaks

If you have an unknown (performance) cam, a 10* baseline will get you in the ballpark
Not hooking up the vac advance will cause it to stall
It should be hooked to the port with the highest vacuum at idle unless you still have the emissions crap
check the timing while hooking this up with a timing light
it should jump another 10* (advanced)

eliminate the easy stuff first
make sure you don't have any vacuum line leaks

[TexasRed]

In your first post you said you have not hooked up the vacuum line to the dist.
this should be hooked up

It is hooked up. To the outlet in the vacuum diagram, so it should be ported vacuum. Some suggest hooking it up to the manifold vacuum (which I have not done).

Not being able to idle below 900 is of concern
is the fast idle engaged? (pass side/check linkage)

I checked the fast idle by screwing it out and it didn't seem to affect it. Also if the idle was 900 rpm, I should be able to put it in gear and not have it stall. . .

did you use a new baseplate gasket
not the thin 1/16" gasket
but a 1/4" gasket
this will eliminate most baseplate gasket leaks

Yup. That's what the carb builder even gave me. I sprayed carb cleaner around the carb and it doesn't seem to affect idle.

eliminate the easy stuff first
make sure you don't have any vacuum line leaks

I've plugged a lot of the vacuum connectors and it seems the only thing that affected the vacuum and rpm was the airpump and heat riser. It seemed to drop the rpm pretty good, as I guess the exhaust is being forced into one pipe? I did notice that one side of the exhaust seemed to be pushing out more than the other. The passenger being the side that's less. My thinking is that an intake leak is what's happening. I wish I had a way of this being definitive. How hard is it to change those? Thanks for all the help and ideas.

[rob1946124]

It could be a problem with the float or needle and seat in the carb. Too much fuel is being pushed into the engine for it to idle. By pressing on the gas petal or adjusting the idle screw on the carb, you are opening the butteryfly's on the carb giving it more air so it will run.

The timing could also be the problem, but it sounds more like the carb. If you are adjusting it by how much it pings while driving, it can be way off during idle. Especially with the vacuum advance unit. It gives you a wider band to adjust the timing through the engines acceleration curve. The advance unit is not factory adjusted... Don't expect it to work right. By the way, the advance unit needs ported vacuum from the carb. Some factory advance units used ported vacuum, some used manifold vacuum... That is where the descrepancy comes in. Might want to put the old advance unit back on until you get the issue resolved, and find out a way to set the timing at idle.

I would check the carb first, and then the timing.

[TexasRed]

Well, I moved from manifold vacuum (I thought I was using ported vacuum but apparently not) to ported vacuum for the distributor. The carb builder said it was probably the idle air bypass which he would be happy to plug. I put together a holley which idled at 600 rpm instead of 800 and I could put in gear. I couldn't get the holley to stop leaking fuel, it wasn't that bad but I'd prefer no leaks to a very slight leak.