I heard something interesting while watching the Barrett Jackson auto auction that might affect some Olds engines. The commentator ( Steve M.) , who usually knows his stuff, was talking about the QuadraJet 4 bbl. carburetor that came on the 1967 Pontiac Firebird with the 400 CID engine.
He said that GM intentionally adjusted the air valves that open the secondaries on the carb. so that they don't open all the way. If you do some slight modifications on the carb., you can get about 25 more horsepower .
This was reportedly done so that the GTO would still be faster than the Firebird. Certainly an odd story, but if true, Olds fans should be careful about using a carburetor that may have come from one of those Pontiacs. Can anyone confirm this carburetor issue ?

 

I haven't heard that one, but if you check some 800 Qjets used in the late 70s, you will find that some don't open the throttle plates all the way. That too can be adjusted.

 

I've heard so much B.S. from those guys @ B-J, I actually quit watching it!
Total untruths, inaccurate descriptions, even wrong years of some nice cars, and now this - - - - ????
And Magenta [?] was a editor from many magazines - can't believe the mistakes he makes!
And he's their 'expert'?
With a 5-800 lb. difference in weight, they might be even, with a 25 hp difference!

 

I also get a bit irritated by the repeated mistakes all of the auction company commentators make on American cars from the 1950s and 1960s. With the exception of 55-57 Chevies, not one of them seems to know a thing about the automatic transmissions available . They can tell us every detail about a Porsche ( yawn) , but they don't know the difference between a 2 speed Powerglide and a 4 speed Hydra-matic ! I've emailed them three years in a row with detailed information, but they aren't interested in learning anything new. In all fairness, they can't be expected to know everything, and I certainly don't know every detail either. But for them to make the same mistakes for years in a row is odd indeed.

 

sounds like just another asshat that thinks he knows something.
what gm(rochester products division) did do, was play with the length of the secondary air valve opening tangs(they had several different part numbers). they effectively limited the maximum opening angle of the air valves to restrict secondary air flow. these stops can be ground to provide the qj's full potential. you can also go too far and really mess things up.


bill

 

The Q-jets on the 80's Y-code 307 motors had limiters on the secondary valve also...

 

Actually it is true, the secondaries were set up not to open all of the way, hence the lower hp ratings for the Firebirds which were available with the same engines as the GTO. the RAIV in the GTO was rated at 370 hp, in the Firebird/Trans Am it was rated 345 HP.

 

I've heard of this a lot. Why would you spend the extra money on a GTO if the lesser Firebird could whoop it? Just like the Corvette. Camaros got the same motor, but weren't as fast. Not a surprise.

 

Steve is a good guy. He isnt just a commentator or a reporter. He is a real car guy that builds his own stuff. I see his work as he lives locally and he is far from an asshat.

Matt on the other hand.....

 

Had a lot to do with that horsepower to weight formula GM used, as well as advertising. The analogies between GTO/Firebird and Corvette/Camaro are well taken.

Later versions such as that on the 307Y were done more for emissions than anything.

 

It is true. The secondaries were adjusted to only open about 90%. But it was a pretty easy fix to get rid of that so they opened all the way, and most guys had that fixed before the car had 25 miles on it.

 

Check page 37 of Cliff Ruggles Rochester Quadrajet Carburetors book where he shows the stop to limit the opening of the secondary air-flap to control CFM for specific applications. Now I don't know if it was an internal Pontiac conspiracy to promote the GTO at the expense of the Firebird, but I remember watching a guy back when I was a teen adjusting that stop on his brand new Firebird so it would open all the way.

 

My 85 442 was also set up this way from the factory. I bent some rods and adjusted some flaps and got it to open all the way. It would run low 15's at the Texas Motorplex. Nothing else done to it.

 

I found that EVERY quadrajet I've ever had did not open the secondaries all the way until prying the linkage arm over enough to allow for full travel. I don't think it was any conspiracy on GM's part. I've been a big fan of Steve Magnante for a long time but sometimes he's just totally incorrect with his data on BJ. The other night he said the functional Cowl Induction hood on Chevelles came "Standard" with the LS6 option. TOTALLY not true. It was RPO ZL2 and was an OPTION even on the LS6 equipped cars.

 

My experience with Steve Magnante was very positive. He is knowledgeable and eager to learn more.

 

Magnante seems like a good guy, and certainly knows a lot about 1960s muscle cars, and drag racing history . A few years back, he helped turn Hot Rod magazine back toward a " build it yourself " publication , instead of just a " spend big bucks to have it built" magazine. Over at Mecum, John Kraman seems to be the most knowledgeable commentator. Regardless of the auction, however, when a mid 1950s Olds rolls up on the block, they all go silent with ignorance, as though the car just dropped out of outer space. Then we get comments like " parade float", and "nice paint color", but little else. I've never once heard any significant educated commentary about a 1949 through 1964 Olds , with one exception. At the most recent Mecum auction, a red '62 Starfire sold, and John Kraman not only knew a lot about the car, but actually had some nice things to say about it. Amazing ! There's hope yet . ( But they still don't know a thing about automatic transmissions .)

 

I couldn't beleive he said that when I heard it , he knows better !

 

The Firebird carb was not due to the GTO needing all the glory, but to keep the Firebird from GM's hp/lb limit, as it weighed less than the GTO.

Why the Camaro didn't experience a similar thing, I dunno, but perhaps this is the reason why the 396/375 motor wasn't advertised.

 

Here's what my friend Mike, an F-body guy, says about this:

While the official reason for limiting the carb on the 67-68 Firebird 400's was to keep the horsepower in check, there is some truth to the fact that the Pontiac marketing guys saw a problem with having a car sitting on the same showroom floor as the GTO, a car that was sportier and handled better than the GTO, being a tad faster than the GTO. The Firebird was marketed to a more upscale buyer than the GTO, and as such was more expensive. But they didn't want to hurt the image of the hot selling GTO, so it was just a prudent thing to do. Make the cars equal in terms of acceleration, don't mention the throttle limiter in any literature, and rate the Firebird 400 hp level accordingly to meet the 10lbs per 1hp guideline.

If these guys truly don't believe Pontiac did this, here's a nice pic to post. Have lots more articles and pics too.

 

I was a GM tech , and I never saw an untouched Q-jet that opened all secondary throttle plates all the way . With that being said , it was only one way of limiting that the factory used . Exhaust manifolds , exhaust size , limiters in the card , and even the air doors on the secondaries can be adjusted to open at different rates , and probably has more affect on power than getting the butterflies to open all the way . The Q-jet's secondary is in fact a variable flow design , and give the opportunity to set-up a 850 cfm carb as a 600 cfm carb by spring tension on the secondary air door .