stalls when gassed...

[72grande]

Ok, my friend has a 67 289 with a number of problems that are likely all linked, but we're not at all sure. He has added a 600cmf carb, headers/dual exhaust and an MSD ignition.
Now if he tries to launch the car at all harder than with the flow of trafic, it dies almost uncontrolably. This means no camera catching burn outs or any good racing.
The car also seems to never reach full operating tempurarture. It doesnt matter how long you let it idle or how far you drive it, the temurature always reads cold. He's tested the thermostat.
It also seems to be a gas guzzler even beyond what would be expexted of a 25 year old v-8. Like less thatn 15 MPG on the highway.

My gut tells me it all simply has to do with tuning, but we have no idea how to tune it at all. We've located two screws on the carb that look like they adjust somting, but we are hesitant to touch them lest we make the car worse because we're not sure what the two screws really do. Any help is apreciated.

[PKRWUD]

The screws you are talking about are likely the idle mixture screws. To adjust them,
1) Gently turn both mixture screws in until they bottom out.
2) Back them both out 1 1/2 turns.
3) Warm up engine
4) Turn idle speed down as LOW as the engine will maintain.
5) Adjust the screws in two round trips (adjust one side, then the other, then come back to the first side, then go back to the other side) to get the highest RPM.
6) Add an aditional 1/8 turn out for each screw.
7) Reset idle speed to desired level.
8) Shut off engine and check that both screws are the same. If they're not, set both to the average of the two.
9) Restart engine to check idle quality.

As far as having trouble with hard acceleration, this could be several things. What is the timing set at? If he was sitting at a traffic light, and the light changed, and he just floored the gas, what would happen? What about if he was on the freeway and floored it? Lastly, if he were to come to an unexpected panic stop, would the car stall?

Do you have a vacuum gauge? If you can get one, you'll be able to do much better diagnostics and tuning.

As far as the temp goes, is this being confirmed with an aftermarket gauge, or the stock one? What temp did the t-stat open at when your friend checked it?

Take care,
-Chris

[72grande]

Do the screws only change the mixture at idle, or do they set sort of a base point for the mixture throughout the powerband?

I dont know what the ignition timming is set at. Where are the timming marks to chekc that (what I mean is hwere do I point the timming gun?) Do you adjust the timming by just turning the distributor? What would 'spec' be, like 15°BTDC?

The car will just stall completely out if you try to hit it from a stop. And no aceptable amout of clutch slipping will stop it. If your on the highway and you hit, it just goes, no drama. Panic stop, are you kidding me? it has 4 conner drums, theres no such thing as a fast stop.

The temp is just being read by the stock guage, I dont know how he checked the guage buthe said he did.

Thanks so much for your help, you seem to be the resident brain around here. And a mac user too, if you were a girl it might be love.

[MetalHead]

Hey PKRWUD,

The "friend" that 72Grande is talking about is me. Thank you for the mixture tuning instructions. And its true that my car doesn't do well with a hard acceleration. I don't have a vacuum guage and its the stock temp guage as well. Some ideas i have to the cause of this accel. problem is that the cam can't keep up with the carb, and i don't have a choke on the carb yet.

To answer your questions it will stall off the line, it will react on the highway but not very well, rather meagerly. It would probably stall if i came to a panic stop. I'm not really clear on timing or t-stat.

[tinner]

Go to the holley site they have a Q and A section that tells you how to set your acc. pump. That is a common prob when you stall off the line. My 65 had the same prob that fixed it. .......... good luck

[crewzin]

Just off the top of my head it sounds kinda like the accel pump is bad in the carb. Just a though.

[PKRWUD]

You guys are too much! You're going to kill me. Buy a book!

Okay, what kind of carb do you have, and what kind of timing light? Does the timing light have a dial on the end, or does it just hook up and flash?

[72grande]

Get a book? I thought you were a book, with some sort of magical keyboard grafted to it.

[70_Nitrous_Eate]

Well, I'll throw in my $0.02

Have you checked your accelerator pump?

If you don't know how, here's some simple instructions...

1) Remove air cleaner assembly.
2) Shine flashlight down primary throttle bodies
3) Pull on your throttle linkage (go from no throttle to full throttle fairly quickly)
4) You should see a small stream of gas shoot out across the throttle body. If you don't see any gas or only a weak squirt, you need to put in a new accelerator pump. Good news: They're cheap.

[72grande]

We adjusted the idle mixture screws and that really helped. But it still bogs off the line. We went to play with the timming but we couldn't figure out how to adjust it. On my probe one adjust's the timming by literaly turning the distrubutor, but we loosened the only nut we sould see holding the disty down on his car, and th disty wouldnt turn. That left me stumped on adjusting the timming.

Ohh and we did check the acelorator pump, it was fine.

[PKRWUD]

You are correct on how to adjust the timing. Sometimes the distributor get's "stuck", and requires a bit of muscle.

Take care,
-Chris

[72grande]

You were right, it just needed a lil 'convincing' to turn. But I'm not clear on where the marks are to point the gun at. Its one of the simple guns, with just a trigger, no dial. I assume there is some sort of mark on the crank pulley, and someother mark on the block. At least that's how it is on my probe. Where is that second mark on the block? And wahts a good base timming on these engines, like 15°BTC?

[PKRWUD]

Clean the balancer edge with some CRC Brakleen (red can). You'll find that there are degree marks grooved into it's edge. There should be a pointer on the timing cover, passenger side (i believe, the 289 might be on the drivers side, but you'll see it). Clean it also. Get some liquid paper, and mark the tip of the pointer. Then draw a thin line with liquid paper along the 12 degree line on the balancer. Disconnect and plug the vacuum hose at the distributor. Hook up the timing light. Start the engine, and point the timing light at the pointer. Pull the trigger. The white mark on the balancer and the white mark on the pointer should be lined up. If they aren't, loosen the distributor hold down bolt and turn the distributor until the marks are lined up. Tighten the distributor hold down bolt. While the engine is still running, and with the timing light on, snap the throttle. The white line on the balancer should jump a few inches, and then settle back down in line with the pointer. If it does, the mechanical advance inside the distributor is working. Next, reattach the vacuum line to the distributor. With the timing light on, slowly bring the idle up to 2000 rpm. The timing mark on the balancer should slowly move as the engine speed increases. release the throttle to idle again. The mark should drop again. If it does, then your vacuum advance is working properly. Shut off the engine and make sure the distributor is tight. Go for a test drive, and jump on it hard. If it pings at all, you need to retard the base timing (with the vacuum disconnected) by 2 degrees, and try again. Keep doing this until it no longer pings. That's it.

Take care,
-Chris