pontiacgp said:
Don't understand your point. I had examined it for the larger cfm and had EDP verify the larger bores as being 800 cfm
Everyday Performance Buick Qjet
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Don't understand your point. I had examined it for the larger cfm and had EDP verify the larger bores as being 800 cfm
if you open the primary air valve you'll see a small bump on the wall if it's an 800. The booster ring is thinner but unless you have a 750 beside it to compare you can't really tell that way. Can you open the air valve and take a picture?
this is what I mean...a 750
the 800 with the bump
this is what I mean...a 750
the 800 with the bump
Both Cliff's and Doug's books are must haves. The Doug Roe book does cover CCC Qjets more though.
pontiacgp said:
I of course understand your point of it being more difficult at times knowing you have something of a certain size or weight without having anything to compare it to, but as you stated, bump = 800 CFM and no bump = 750 CFM. Since anyone can clearly see the bump or not without having to compare it to anything, I'm not following your statement highlighted above.
On another note, aren't ALL the 'newer style' Qjets 800 CFM? I've never seen a newer style Qjet without the bump, hense all newer style Qjets I have ever seen have been 800 CFM. Odd considering the choked down smogger engines would've been better off with the 750's I would think.
I was just mentioning another difference, in addition to the bump, which is hard to see without the 750 to compare it to. And for the new models do you mean the feedback versions?
"hense all newer style Qjets I have ever seen have been 800 CFM. Odd considering the choked down smogger engines would've been better off with the 750's I would think."
That is one of the benefits of a Q-jet as compared to a square bore carb, you don't have to get a smaller carb to match the motor size because the triple venturi system along with the natural engine vacuum always keeps the air speed up hence its properly sized crisp and responsive no matter the size of the engine. (assuming you also have the fueling right) Its also why part throttle adjustments when cruising are crisp smooth and efficient. But properly sized and fueled square bore carbs will always be slightly better at WOT. Its never which is a better carb its dependent on your use. Q-jets are better for street use square bores are better for race use.
That is one of the benefits of a Q-jet as compared to a square bore carb, you don't have to get a smaller carb to match the motor size because the triple venturi system along with the natural engine vacuum always keeps the air speed up hence its properly sized crisp and responsive no matter the size of the engine. (assuming you also have the fueling right) Its also why part throttle adjustments when cruising are crisp smooth and efficient. But properly sized and fueled square bore carbs will always be slightly better at WOT. Its never which is a better carb its dependent on your use. Q-jets are better for street use square bores are better for race use.
Pontiacgp, by newer style carb I meant the sleightly larger ones with the carb numbers that start with '170' which would include the CCC carbs. I know the CCC carbs were all 800 CFM castings, but I wasn't sure about the ones from 74-75 ( ? ) and later ones ( before they all went CCC ).
Dogshit, the reason why I think it was odd is because the difference between a 750 and 800 was the primary side only with the 750's being smaller. I would think in the era of daily driving smog motors and low performance, the smaller 750 would've provided snapper throttle responce and a bit better lower end performance, with possibly better milage too.
Dogshit, the reason why I think it was odd is because the difference between a 750 and 800 was the primary side only with the 750's being smaller. I would think in the era of daily driving smog motors and low performance, the smaller 750 would've provided snapper throttle responce and a bit better lower end performance, with possibly better milage too.
DoubleV said:
You have to take into account that all Qjets are a variable CFM design. 800 & 750 only indicate the maximum flow they are capable of. That's why you see them on so many varied engines. GM limited them on the secondary side with different stops. look at the lower right corner of this picture.
Back in the 60's, When Pontiac put the GTO 400 in the Firebird, they changed the carb to limit how far the secondaries would open. About the primaries, i fail to see how the 750 would provide a snappier throttle response or better mileage. That all depends on your foot.
[quote="RegalBega]You have to take into account that all Qjets are a variable CFM design. 800 & 750 only indicate the maximum flow they are capable of. That's why you see them on so many varied engines. GM limited them on the secondary side with different stops. look at the lower right corner of this picture.[/quote]
I think that's well known about the q-jet, it only gives what the engine is needing...
I think that's well known about the q-jet, it only gives what the engine is needing...
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