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Cars > Crazyfast79TA’s Garage > Blog > 1979 Pontiac Trans Am (Blackbird) > Searching for answers


Crazyfast79TA’s Profile Photo


M –51
Bovey, Minnesota
United States


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Searching for answers

By Crazyfast79TA

Filed under: 1979 Pontiac Trans Am (Blackbird)

I was tinkering with my car today after work. The carb just wasn't acting right. I didn't have too much time, but I rigged it so the secondary vacuum pod wasn't restricting them from opening. I took it out for a test drive and tried a couple of burn-outs. It had to work hard for a little bit of squeal and smoke, but that's more than it would do Saturday on the Poker Run. It's still real "punky", but I'm getting the problem narrowed down. I'll try rebuilding the carb first. If that doesn't fix it, I might try a new one. If that doesn't fix it, I'll try a new cam. I don't know what I'd do after that. Hopefully I'll be working on my Nova and too distracted to worry about the Trans Am. Oh well....

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Read comments on this blog post 1 – 5 of 5

ChevroletBuick1’s Profile Photo
Aug 2, 2013 at 3:18 pm
Carburetors are so damn frustrating.
Shaker’s Profile Photo
Aug 2, 2013 at 9:02 am
When I first got my '79, the 403 with .273 gear wouldn't do a burn out. You could hold the brake (with the rear brakes backed completely out of adjustment) and it still wouldn't spin on dry pavement. We rebuilt the carb and it still wouldn't do it so we bumped the timing up considerably and that woke her up! You can hold the brake and 'light them up" as long as you've got rubber left now and I run 295/50s all the way around. Also, the gasoline we buy these days is crap.
Meatball’s Profile Photo
Aug 1, 2013 at 3:37 pm
Hey Crazy. Quadrapukes are actually one of the best carbs on the street...if you know a little about them. First thing to check on one of these: The secondary fuel tubes fall out fairly regularly. Take off the top and make sure they are still in their holes. If not, reinstall and lightly tap them into place with a small brass hammer, if you have one, or anything else...just don't hit too hard or you'll mash the end shut. By the way, if you're new to these, take out the secondary metering rods(small screw on top, between the blades) and remove the rods. Using a small pin punch, or something similar, tap the roll pin that retains the accelerator pump lever in towards the center of the carb..just enough to allow the lever to pivot out of the way(when reinstalling, use a flatblade screwdriver to push it back in). Remove the screw in the choke plate at the right side (remember which way the offset goes) and remove the piece. Now you can remove the top of the carb easily after taking out the rest of the screws. Try not to tear the gasket. There are a variety of secondary metering rods available too. You can richen or lean the secondarys by changing rods but lets assume yours are adequate. If there are 4 brass tubes in the're good to go. Spray a little carb cleaner thru them to be sure they are clear and reassemble. There is a spring that controls how easily the secondarys come in. It is on the shaft at the right side of the carb and is adjustable. We're assuming that the carb is decent otherwise...float not contaminated and sinking....reasonably clean, etc. For performance applications I unhook and discard the green linkage. Adjust the spring tension by loosening the allen-cap screw and turning the adjuster with a regular screwdriver (the cap screw locks the adjustment). You want the blades to require a much lighter pressure than stock to open. If they open too easily, it will bog. If they are too tight, secondary airflow is not correct. Experiment with the adjustment until there is no bog and the car "honks" properly. This adjustment is easily done with the carb still on the car and the engine warm, just be careful not to drop parts in the engine. You may want to remove it just to be able to see better but the secondary adjustment can be done on the car...particularly necessary when making the air-plate adjustment. How much timing you running? Stick or automatic? A lot of guys are bashful in this area. Assuming premium, I like at least 16 initial, 10-12 in the vacuum advance, and 10-12 in the weights, for a total of 36-40. You may have to remove some from the "can" to get this. I put a spot of weld behind the main plate of the vacuum advance which also increases the tension while limiting the amount of timing. You can have the timing drop out quicker when hammering on it too pass etc by increasing the tension on the internal spring this way. Hopefully you won't need to get into this. Even better would be an adjustable vacuum advance, but they cost money and most of us don't have that to spare. Depends on your fuel mostly as to what you can get away with. Sticks can take a bit more. That initial is really important for low end power. I'm assuming you have some experience with this stuff so float level and Idle air adjustment will be done properly. That critter should be able to roast the tires with little problem...unless they're oversize drag radials. Let me know if any of this helps and remember, there are super/stockers with these carb running 10s regularly. The quadrajet is a great all around carb. The small primarys keep airflow fast at lower rpm, for efficiency, and the huge secondarys give plenty of airflow at W.O.T. None of this can replace the wonderful late model electronics that make the newer stuff infinitely adjustable, but I've done a lot of it for 40yrs or more with excellent results. Good luck. Tom
SittinLow’s Profile Photo
Aug 1, 2013 at 9:14 am
Can you do a compression check too? That will tell you if any cylinders have a leak down issue. They should be around 160 psi and all be within 10% of each other. If you don't have a compression tester I have one and could ship it out if you send it back. Easy to use just screw it into the spark plug socket and turn it over with out starting it(disable the plug wires). After about three or four revolutions it will level out at max psi. Then just repeat seven more times.
alwaysakid’s Profile Photo
Jul 31, 2013 at 11:29 pm
Carburetors can be finicky sometimes, and I'm afraid the people who know how to adjust them just right have been dying off without leaving anyone to take their place in this new world of inject everything.

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Cars > Crazyfast79TA’s Garage > Blog > 1979 Pontiac Trans Am (Blackbird) > Searching for answers

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