Pontiac Guru's - HELP!

I have a '67 Poncho wagon, 400/400 combo. Had problems with it stalling, so I swapped out the Carter AFB and installed a new Holley 670 CFM with Edelbrock intake. Car starts and idles great, fantastic throttle response. My problem: it stalls when trying to put into any gear except Neutral...This has a vacuum shift and I installed all new vacuum lines when I did the carb/intake change. Any ideas? Suggestions?

Thanks

 

where is the idle at?

bring it up to 1000 in park and see what it does.

 

This is not Pontiac specific, but i'd like to ask the same as Lux. If you raise the idle "speed" screw a little at a time until it doesn't stall going into gear, does it now bang into gear as if idle is too high now? Also, make note of where the idle "mixture" screws are and go a half turn in or out and see if the motor gets real happy. You may have a bad mix that's just on the edge of being good enough in neutral, but ass in gear. Again, it's sure hard to fix these things remotely like this. Let us know what you find

 

Groucho and Lux,

Thanks for the quick feedback. Factory specs show 600 RPM in gear which is where I have it set now. I'll idle it up and see what happens. If that doesn't work, I'll try the idle mixture screws...don't want to mess with too much at one time.

51FourDoor

 

OK, i'm lost! How can you have it set at 600 RPM in gear, when you say it stalls whenever you put it in gear????

 

OK, sorry for the confusion; started having trouble with it a few weeks ago, factory setting at 600RPM. Installed the new carb and intake, set the timing and it ran for about 10 minutes (warm up time). Set the curb idle during this time at 600RPM, put it back into park, made sure all the tools were out from under the hood etc...(car running at about 1000RPM in park). Go to take it for a test drive and then started having the problem again. I can put it into neutral, no load, but anything else it lurches and stalls.

51FourDoor

 

I don't know what cam/torque converter you've got. But, 1000 RPM no load, and 600 in gear? That's a big span. Unless you've got a big cam, no compression, and a tight converter, i'll say Vacuum leak or timing's way retarded. Again, it's tough to do a virtual diagnosis

 

well?

 

i would check what was said above and check points (dwell)/timing.

 

One thing you can do is head down to a trans shop, tell them you want a 400 high stall converter. If they dont know what you are talking about, go to another shop. It is a 13" stock type converter, but it stalls around 1900-2200, it will act like normal, but it will let you set the idle pretty much anywhere you like. they run between $100 and $150, so they arent expensive. I ran 11s with one in a 3700lb Firebird

Also set your timing between 30 and 34 total, unless you have 670 heads on it, in that case you will need some race gas to ward of detonation. With the 670 heads a 400 will have between 9.8:1 and 10.3:1 compression with a flat top piston. Far too high for a Pontiac on pump gas, even 93 octane. A recurve might help some too.

Do you have the vacuum advance connected? If you have it connected to a vacuum source that sees manifold vacuum, then you are getting full advance at idle. Put a finger over the port you have it hooked to. If you feel vacuum at idle, plug it and use one that has no vacuum at idle, when you open the throttle that one should start to pull your finger. fart if you choose. ok bad pun.

The Qjet is a great carb if its rebuilt properly, but the holley works too. But changing to the holley from the carter will make a difference in how it runs. I am no fan of the Edelbrock carb nor of Carters, but since you have the Holley on it, no problem.

One of the biggest problems with Holleys that most people miss is float level. An engine like a Pontiac that makes plenty of bottom end torque, and consequently has a high vacuum signal, needs a lower float level than a high strung small block with less than 10" hg. I start at the bottom of the sight plug, and then drop the level down another 1/16". Then check to see if the boosters are dripping fuel. If the boosters are dripping fuel then the float is still too high or you have a plugged vent tube. Speaking of vent tubes, make sure the tube on top of the carb isnt restricted, if it is you will have issues, somewhat like you are talking about.

Forget the book and the 600rpm, see if it wants to creep forward with the idle at 800rpm. With a somewhat tired engine, it might not have the ring seal to hold 600rpm anymore. It wont hurt anything to bump it up a bit.

Idle mix screws should be set with a vacuum gauge connected to manifold vacuum. I have found they run best when you turn them down a bit under the highest vacuum reading. It might just be how I have my carbs set, but its how I do it. if nothing else you can tell where it likes it best with the gauge, it gives you a quantifiable number that correlates to where the screw is set.

If the screws have no effect, then the throttle blades are open too far and the transfer slot is exposed, that will make the screws ineffective and will also dump fuel at idle, burning your eyes.

 

Thanks for the feedback and ideas / suggestions. I wasn't able to get to it tonight, but will be back at it tomorrow. I'll walk through the info given and post what happens.

Thanks again for all the info!

51FourDoor

 

I wanted to post an update; had a water leak that I had to work on first...

I tried the adjustments listed; float, idle mixture and ran timing advance as far as I could and then backed it down about 2 degrees at a time. Still same result; dies when I put it in gear.

The only thing I can think of is torque converter is going,(but I can still put it in neutral and it runs) or the modulator is going out. I'm going to talk to a trans shop tomorrow and see if these symptoms sound like trans problems. The thing is, that even with a new carb and intake, I'm still running into the original problem I had...maddening!

Thanks for the suggestions and ideas; stuff I didn't think of on my own.

51FourDoor