hey guys.

I've got an 84 T/A that I put a 350 in. Voodoo Cam (.515in/.530ex), Performer Head, world Sportsman II heads, jet performance products Qjet carb, roller rockers, stock torque converter.

The problem I am having is that in order to keep the car running, I need to have the idle set to around 1100 RPM or so. When I drop it into gear (automatic), the rpms drop to about 700 or so and it flucuates, won't stay steady. If I drop the idle rpm down to about 900, when I put it in gear the rpms drop so far it stalls the car out.

Also, even at 1100, if I put it in reverse, sometimes the car stalls out.

Any ideas why this might be? The guy at the car shop where I had the final checks done says that the idle needs to be high because of the cam. Any truth that? Any ideas on how I can bring the idle down?

 

sounds like you need to have your carb tuned.

 

that is a big cause of your problem right there. that converter is too tight and it's gonna want the car to start moving at 1100rpm. what are the duration numbers on that camshaft? this is an issue i'm facing while i try to slap a car together for my dad to start daily driving. it's got the old 305 outta my car, which has a comp magnum 280H...which really wants ~ 2500rpm stall speed...

you'll also notice that once you do get going the car will want to surge when sitting at a stoplight...this is normally referred to as cam-surge, and can only really be fixed by getting a looser converter.

depending on your budget and intentions for the car, i would call a reputable company and have a converter built for your car's specs...this makes it to where the converter is perfectly matched for your combo/intentions rather than just grabbing an off the shelf converter.

 

Nova...

Man you'r not the first person I've heard mention that I'm going to want a looser or larger stall torque converter. you're just the first persons judgement that I trust.

The cam specs are:
advertized duration is 270/278
Duration at 050 Lift is 219/227
Lobe separation is 112.
.515 Intake lift
.530 Exhaust Lift

I can't say that I've experienced the cam-surge but when I drop the car into gear it does want to "go".

I dont' know that I want a 2400 stall, but maybe a 2000? I've been looking at TCI's models and they all look pretty good. The "Breakaway Converter" is a 2400ish stall and the "Saturday Night special" version is advertized as havng around a 2000 stall. I really want to be able to pull the idle back down to 900ish where it belongs because 1100 is way to high and it shouldn't want to die when I shift into gear. Which do you think would be better?

 

A loose converter would help but i think most of your problems is in the tune.

When i first got my camaro running i had a 305 with a comp xe268. Had a stock coverter and had the same problems you had. I played around with the tuning and goot it to run prety good. Would idle fine and drive fine. But if i stomped it all it would do is bog bad then take off.

 

man, i daily drove a 4000 stall ati 10" converter with lockup so anything under that seems fine to me...the converter took a little to get use to because the tranny "seemed" to slip during regular driving...but man, when you jumped on it, it was ready for business.

fyi, TCI is not a reputable company

i would call either yank, vigalante, fuddle, or maybe ATI...maybe...they made me kinda mad the last time i called them.

 

Where can I look to find a good book or instructions on how to tune the carburetor?

 

the best way is to put it on a dyno and have a professional tune it so they have a constant a/f reading and can set it right so you dont blow it up. but you can search on yahoo or google for how to tune a carb and you should find what you need.

 

your suggestion to him is to PAY A PROFESSIONAL!?!?! no...that's not what this site is here for. we have a whole section JUST for carburetors...ask five7kid and sonix or F-Bird '88 about quadrajet tuning...they have links to a stupid amount of information on tuning qjets.

people have been tuning carbs based on spark plugs long before widebands were even available...that type of equipment is not necessary to tune a carburetor.

 

There is alot you can learn on this site.

There is also alot of books that will tell you all you need to know. Do a search on google for the books. My advice is to get a few and read them all before you start. Alot of the books contradict each other so read a few then do what makes sence to you.

 

Yep paying someone to dyno tune it is the best way. I found a guy around here who charged $85/hr which included unlimited dyno pulls. We did it in an hour and half, which included having to change out the spark plugs. He set my idle mixture, idle, and even changed my jets. I picked up 22whp by just having it tuned. Also sounds like you need a larger torque converter. I have a 2200 stall from Bowtie Overdrives which only cost around $175 for a lock up converter.

 

Intake manifold vacuum leak.

Incorrect spark timing at idle. (incorrect timing tab location)

 

and home boy knows his stuff (f-bird that is)

 

I will check the vacuum this weekend for a leak. (put a vacuum gauge on it anyway). As for the incorrect timing tab location, a possibility that the shop that put the motor together got the wrong one I guess...how would I tell?

 

Find true TDC using a piston stop. adjust the timing tab as nessessary to correct.

 

what dist are you running ? make sure the timing is not falling off when you put in gear..had that happen many times and seem like a carb issue...have somebody drop in gear while you watch the timing..see if it starts backing up...Rob

 

I'm using my original distributor with a new cap, rotor, coil and plug wires. It also has a melonized gear on it to handle the upgrade to my roller cam from the flat tappet I was running in my old engine.

 

Aside from a small problem of breaking a valve spring on the number 8 piston which threw me off for about a month, the car seems to be running better now that the lash is set right. I had the shop double check the valve lash the builder had set the motor too and it seems the guy originally didn't follow the cam card. Talk about crappy. Anyway, been driving it for about a week and a half now and I'm still having the "dies when put in gear" issue. I'm going to have to wait to get my taxes back before I can tune it however, I don't believe the issue is a vacuum leak.

Was repairing the wiring for my fan tonight (fan switch connector melted with new coated headers breaking in), and put a vacuum gauge to the car. With the car in idle at 1100-1200 RPM in park, i'm pulling 12-13 Hg on the gauge. Revving it up in park from about 2000 RPM all the way to 4000, I pull a steady 16 Hg.

Now, there is a little warble on the gauge at idle, it's not perfectly steady but when I rev it up it steadies out. Also, when I let off on the gas or give it gas there is a surge in vacuum which I am going to assume is normal based on how the engine works as an air pump.

It is possible that I put an incorrect timing tab on the motor which is going to throw all of my timing off a tad...though I used directions found here on the board about how to make sure i got the right one. So until I take it to the dyno and have it double/triple checked, I'm going to make the assumption that I've got the right one on there (yes, assuming can be very, very bad for ones health, I know...I'm just really really leery about doing anything timing/piston/engine related without someone who's done it before standing next to me).

That said, what else would cause the car to want to die when it's put in gear? If it's cold, first started, it will die, 2-3 times before I can put it in gear and drive. Reverse is worse than the forward gears.