Why is it, that on a Carbureted engine, when you open up the throttles all the way (Q-Jet), you get the sound of "Ba Waaa", and when you open up a throttle body all the way all you get is a Hiss or sucking sound, ( know what I mean )? ?

Ive never paid that much attention to be sure, but Id say the throttle body hole into the intake is only a few inches wide at most. A 4bbl carb has a 6-7" hole (or 4 1 1/2" ones). Thats just a guess though.

You get the induction roar from an FI engine as well. It sounds different because the size and shape of the runners and throttle body are different, just as a trumpet sounds different than a trombone.

Since a carb flows air and fuel, it has larger openings than FI that only has to flow air. That tends to create a lower pitch sound. That's oversimplification, because there's a lot of other factors at work. Try a throttle body injected engine - it has more of that carb sound than a port injected engine. It's throttle body has to flow both air and fuel, so it's sized accordingly.

Of course, that only accounts for the "Waaaa" part of the "Baa Waaaa!" The "Baa" part is bog because you don't know how to tune a carb.

[This message has been edited by Formula88 (edited 04-28-2014).]

OK, so the" Ba" part is for "BOG". LOL

My dad used to turn the air cleaner cover over on his Q jet on an old Jetstar he had and his 73 olds cutlass that had the 454 in it, you think it sounds good when you tromp on the throttle before, turn the air cleaner cover upside down,

You could try that on the throttle body, just not sure what it would sound like, hell on the Jetstar he even drilled a few holes in the cover as well if I remember right, or maybe it was the 73, my memory is shot, one of them turning the cover over did nothing as it set almost the same. so he drilled some holes outside the air cleaner so that air still had to go threw the air cleaner, but let a lot more in because it didn't have to go threw the snorkel of the air cleaner.

I think the Jetstar was ether a 396 or a 425 CI engine I can't remember what year it was, mainly because it was like 1969 or so and that was before I was driving, well legally anyway ether way they both had over 300 HP, the 425 was like 375 HP or something like that.

Ayup

345 hp (257 kW) 394 cubic-inch Starfire Rocket V8 engine, in the 64 and'
425 had 370 HP. in the 65, for the life of me I can't remember what year his was.

http://en.wikipedia.org/wiki/Oldsmobile_Jetstar_I

I loved those 60s cars, balls and style.

Ayup, it was a 65

http://globalcarbrands.com/...star-i/03/index.html

of course you have to remember with a Q Jet carb you are also opening up a lot more space for the 4 barrels when you open the secondary's up. adding to the sound

Steve

------------------
Technology is great when it works,
and one big pain in the ass when it doesn't



Detroit iron rules all the rest are just toys.

[This message has been edited by 84fiero123 (edited 04-29-2014).]

Cam timing is also a lot different on the computer controled engines now, biggest difference is the Lobe Seperation Angle, with a carb they were running around 106 degrees and now with computers they are around 114 degrees or so. On a Q jet, when you stomp it to the floor, only the primary opens up, the secondary is opened by vacuum as needed. Larry

[This message has been edited by trotterlg (edited 04-29-2014).]

quote Originally posted by trotterlg: ... On a Q jet, when you stomp it to the floor, only the primary opens up, the secondary is opened by vacuum as needed. Larry

You're thinking of Holleys that have vacuum secondaries. The secondaries on the Q-Jet are controlled by an air valve.

Q-jet, ok, the secondary's open mechanically, but the air valve only lets as much Air Through, "as is needed", just like vac secondary's. As far as I'm concerned a Q-jet is Much better than a Holley, less grief. Had both, worked on both. just my opinion.

I had a TBI on my old 305 88 Firebird Formula.
If you turned the lid over it exposed the entire outside of the the filter.
It had a little bit of the Q-jet sound, but not as loud.

For some reason the carbs with air valve secondaries were always louder than Holleys.
I used to have a Monza with a 350 and a Carter AFB. You could hear that thing for blocks.
Thermoquads were even louder than that. 340 Mopars would wail!

Edit - I hated Holleys.

[This message has been edited by Raydar (edited 04-30-2014).]

He had a 425. The last year for the 394 was 1964.

quote Originally posted by 84fiero123: My dad used to turn the air cleaner cover over on his Q jet on an old Jetstar he had and his 73 olds cutlass that had the 454 in it, you think it sounds good when you tromp on the throttle before, turn the air cleaner cover upside down,

Aahhhh, the good ole' days

in' 85 I had a 1965 cutlass with a 500 cube Caddy in it, that was "Something Else" ! just hitting the gas In PARK would twist the front of the car. and when that Q-jet opened up,(in 1st gear) the was NO traction ! LOL