fizzak

Hello, first post here.

I have a buddy with a 68' bird running a stock 400 with a quadrajet 4bbl. THe car was originally a 350 so we do not know whats done with the motor but it appears stock. He states the car has a tall rear-end. The car purrs like a cat and does not smoke. Sounds tip-top but cannot do a brake torque and the butt dyno tell me its pulling around 150-170 horse which is pretty sad. Even my old IROC running a 305 and 2:73's could bury this thing.

I did not look at it for long but could only determine that the Q-jet is messed up. I looked at the carb and it seems to be operating fine exept the secondaries would not open up during a rev test. I did temorarily zip-tie the secondary open and car did spin the wheels but ran terribly at mid throttle. Im a fuel-injection man and know nothing about carbs. Any ideas?

Also he has $2k put away to mod the car, aside from the obvious exhaust upgrade, any direction he can take? Links to vendors appreciated.

Flaminchiten67

Sounds like the secondary linkage is not working. Quadrajets have mechanical secondary's which means when the throttle reaches a certain point the secondarys are opened mechanically not through vaccuum operation.

With the car off open the throttle on the carb by hand and watch the linkage work, you should be able to see the linkage work and open up the secondary's. Do not wire the secondary's to be open all the time, the carb will not function properly and be severley out of tune.

As for mods it depends on what the motor came out of and what casting the heads are. There should be a number on the heads, when you find it post it or do a search on google and see if the heads are good. If not I would suggest going to a swap meet and finding a more desirable set of heads. Use this site http://www.wallaceracing.com/head1.htm when you find the number on the heads, for example my firebird has a set of 670 heads which are a good foundation. There are also aluminum cylinder heads available but they are very pricey.

With a good set of cylinder heads, decent cam, dual plane intake, headers and a fully functioning carb that thing will spin the tires at will.

Also everyone knocks the quadrajet for sucking but you will find quite a few hard running pontiacs using them...the motors love these carbs.

fizzak

Thanks for the reply.

It was a couple months ago when I looked at the car but I could swear the secondaries were vacuum operated. Since I know so little about Q-jets I decided to rig them open just to see if any change in low end torque and there was.

I'll take another look at it this weekend and post some more accuate data.

Regards

Captainofiron

iTrader: (1)

Also try setting up the timing while you are there, a good carb tune and timing set up will let a lot of horses out of an old engine

~JOSHUA

iTrader: (92)

Buy a new carb first of all... along with a full tune-up.

Then add some headers/pipes, and if you have any money left plan a weekend Cam/lifter/spring instal.

If it doesn't get mean as a junk yard dog... then sell it.

Formula350

iTrader: (3)

My friend used to wire the secondaries to open up when the primaries reached a certain point Basically like an aftermarket carb.

I couldn't figure out wtf you meant by "brake torque" lol So I had to click. We call it a Brake Stand.

At any rate, I wasn't aware that the 68 had a 350. Then again, I don't know my older Pontiacs :\

A good tune up, timing check and even a carb rebuild probably wouldn't be a bad idea. Maybe try and find a Quadrajunk off a 454. Those run like 800cfm factory.

Flaminchiten67

I haven't seen a Q-jet with vaccuum secondary's but I haven't seen a lot of stuff. Maybe in the late 70's they had vaccuum secondary's.

That motor should be a torque monster just like all pontiac motors

EchoMirage

iTrader: (3)

my 1978 TA 400 has mechanical secondaries. your friends Qjet probably isnt working right. without pics or looking at it, who knows. someone could have severly screwed with the metering rods and jets. best thing is to buy a repair book on Q jets. autozone has them, for a few bucks theyll tell you every single thing about every Qjet ever made, from single barrels from the 50s up to 4 barrels in late 70s-early 80s.

with it off, either work the linkage yourself or have someone slowly floor the pedal, and watch the linkage, see if it binds or doesnt work at all. see if you can get a date code off the motor, so you at least know what year youre working with, if it is indeed stock. big differance between a 69 400 and a 79 400.

side note, 326s were available in 67, till the 350/350HO replaced them in 68.