Guys,

I need some suggestions and input about Carburetors for my combination. After being away from "cars" for over 20 years, the "bug" has bitten me again. Let me be as brief as I can . . . Here is my combination.

1989 CAMARO RS / Turbo 400 / Strange S60 - 3.73 Gears (may change, if needed)

Motor Specs :

GM ZZ383 Crate Motor (9.6:1, Aluminum "fast burn" heads) 425HP @5400 RPM / 449 ft/lb @ 4500 RPM
Hydraulic roller, 222/230 degrees @ .050", .509"/.528" lift, 112 degree lobe center
WEIAND "Speed Warrior" #8502 Intake Manifold (like Edelbrock RPM Air Gap)
Hooker Super Competition 1 3/4" Headers - Coated

The car will be 95% street driven as a "daily driver" and bracket-raced on weekends. Target E.T. is mid-12's at full street weight ( not stripped down ).

CARBURETORS I am considering . . . Need your INPUT !

(1) DEMON "Speed Demon" #1282020VE 650 cfm / Vacuum Secondary/ Annular Boosters/ Electric Choke

(2) DEMON 'Speed Demon" #1402020VE 750 cfm / Vacuum Secondary/ Annular Boosters/ Electric Choke

Thank you, in advance, for your help !

 

Anyone got Demon carb info ?

 

For a street car, I'd run a non CC-Qjet. Same if not better power than just about everything out there with better mpg's and part throttle.

 

The stroker motors are real torque monsters. We ran a 388 with nearly 11:1 compression, .506/.519 lift, 240/245 @ .050 dru., 106LSA and ran 10.8's-10.9's in our 67 Camaro.

With racing and your gear ratio I'd go with a 750 cfm carb. The brand choice is up to you. Everyone has their personal favorite and I've raced mostly with Holley style carbs so that is what I mostly use. I cannot give an opinion on Demon since I haven't mess with any. When they first came out and they were built by Barry Grant they looked good and seemed to be a quality product. I haven't kept up with them since.

 

750 double pumper
Annular boosters are great if you don't mind spending the extra cash.

Personally i'm not a fan of demon carbs. Years ago when they first came out they had terrible quality control issues. Carbs actually missing parts! I have no idea how it is now, but after dealing with a few different demon carbs that were all messed up out of the box i won't give them my money any more.
I personally have used and tuned many quick fuel and proform carbs and have never had a problem.

 

Really, a Quadrajet ?

I still have a Q-Jet off a 1979 6.6L T/A I bought new in 1979 ( 190 HP 403 Olds motor ) It was S-L-O-W, but it looked cool . . . What is a "CC" Quadrajet" ? Did you mean "computer-controlled" ?

Which model should I consider, as I want to do some research on it ?

Thanks !

 

Are annular boosters OK, if the cam is a mild profile ? I've heard that annular boosters are primarily used on wild cam profiles, due to better fuel atomization at low intake vacuum levels.

Thanks!

 

Yeah, I figured 750 to be about right. Initially, I was thinking 650.

On your Camaro, what did it weigh with driver ? Transmission ? Converter ? Gears ? Shift Points ? MPH in the 1/4 ? I assume you were running slicks.

Thanks !

 

yea, they work just as good with smaller cams

 

Quadrajet's were the only carbs that "evolved" so to speak with the times as emissions controls came more and more into play. The "CC" or computer controlled quadrajets were found on many 82-87/88 Camaro's and firebirds. They are mechanically set for idle and WOT just like all carbs but there is a mixture control solenoid and throttle position sensor that monitor and run the part throttle mixture, all based on the readings from the O2 sensor and what the ECM says. So they were the step between carb and TBI. the other CC part of them meant that they didn't supply vacuum to the distributor, timing also came from the computer though like all cars, you set the base timing with the ECM disconnected.

As for which model, Qjets came in two sizes. 750 and some 850 cfm models. Their design also precludes "over-carbing" the engine, like you can do if you get too big of a Holley or Edelbrock. Any mid-late 70's Qjet will work for this purpose. Just get it re-built and then tune it once it's on the motor.

 

Comparing the 750 version vs. the 850, is the flow increased on both the Primaries and Secondaries, or just the Secondaries ?

The reason I ask is that it might be beneficial to get the 850 cfm version, if the Primaries flow more cfm, as it might allow high-speed, freeway driving (70-80 mph) without "tipping in" the Secondaries, for better MPG . . . Thoughts ?

Thanks !

 

To be honest, I haven't looked into it that far. What I do know is that my mild-build 355 (320bhp) in my 84 T/A with a CC Qjet runs 19mpg on the highway with a 700R4 and 3.73 gears pulling 2600rpm at 70mph. I know some of it is from the OD gear in the transmission, but some of it is also the carb.

My 67 Camaro with a Holley 650, 3.42 gears and a 4-speed manual gets 15 highway and pushes nearly 3000rpm at 70mph.

Aperion, NAF or Five7kid might know more to be able to answer your question.

 

The car still had the stock fender wells, no tubs or mini tubs. We used Hoosier slicks 29x10x15. Car weighed 3040 with driver. The transmission was a 1.82 geared Powerglide with a 5500 stall. Both were from Coan. 4.56 gears, shift point at 6500 and crossed the finish line around 7K rpms at 121 mph. This was with Dart aluminum heads, 64cc combustion chambers with 2.08/1.60 valves ported to Fel-Pro's extra large port intake gaskets. The dyno chart is with this combination

The motor with cast iron Bowtie heads with 65cc combustion chambers ran 11.2's-11.3's with a best run of 11.11. Same set-up as above but with 4.88 gears.

 

Nice car - Love that Blue !

The dyno slip has me scratching my head . . . Numbers look "strange" to me. The HP curve is "FLAT" while Torque DROPS throughout the test ???

Maximum Power - 304.3 HP @ 4500 RPM ( about 375 HP at the Flywheel ? )
Maximum Torque - 481.9 FT/LB @ 3000 RPM

 

Thanks, Ill ask them . . .

To see the effect of the OD on MPG, you could drive it in "D" (1:1), instead of "OD" ( .70:1, I think ? )

 

It's either because of the 5500 stall converter which will cause some weird graphs or the tires were slipping on the dyno.

 

At least I wasn't imagining it . . . Very strange !

 

It's mostly the converter (8") although we did sling a little rubber up on the walls in the dyno room

 

So, obviously, that 300 HP reading is totally inaccurate and the TQ is off, too, once tire slippage started . . . Right ?

 

Well this was a Mustang dyno and it did read lower on the HP numbers than the local Dynojet dyno. The HP and torque numbers are close because when it didn't slip the numbers were not far off. (Can't tell you if that is one of the slip runs or not) What the chart doesn't show is the wide band readings and really that is what we were using to set the car up and we were not paying too much attention to the peak numbers.

 

I suspect that it was slipping during the test. I ran the car's 3040 lb w/driver and 11.20 ET through an ET calculator. It indicated that 425 RWHP was required to run 11.20 @ 121 mph. So, you should be close to 500 HP at the Flywheel.

 

It's not just HP that gets you down the track, it's torque as well.

Same car, trans, weight and gear ratio:
Running the 388 motor we ran 10.8's to 10.9's with a 1.44-.45 sec 60' time.
Running the 355 motor we ran 10.8's to 10.9's with a 1.56-.57 sec 60' time.

The 388 got us off the line quicker but the 355 was quicker at the top end (60' to 330' and 660' to 1320'). Shift point was near the 330' mark on the track.

 

So, with identical ET's, what was gained by going to the larger displacement motor, with the combination you were running ?

 

The 388 was a flat top piston motor, ~10.7:1, and was a hydraulic flat tappet cam.

The 355 was a domed top piston motor, ~12.5:1 and was a solid roller cam motor and had more lift than the 388 cam. I can't exactly remember the cam specs off the top of my head right now. That required stronger valve springs and more maintenance during the season than the 388. We were just getting started in 1991 when we had the 388 motor built.

Originally the 388 motor was built using an old set of cast iron bowtie heads that was milled down from 68cc combustion chambers to 65cc with a mild port job on the intake runners and 2.02/1.60 valves. With those heads the car ran in the 11.30's during the hottest days and had a best run of 11.10 one evening in October.

 

"No replacement for displacement" . . . I understand that well !

It's interesting that the car ran identical numbers, after the head upgrade . . . Coincidence ?

Did you go with the 383 so you could re-use the 350 block ? Did you consider a 400 or 406 ( possibly with the Dart SHP block ) ?

 

The 355 and 388 10 sec numbers were with identical dart heads. Just a coincidence.

This was all back in 1992 with the 388 to start with. We went the 350 stroker design because we had a spare 350 block and we were going to buy all new internals anyway and my brother and I wanted to try a stroker motor.

In the winter of 97,98 we rebuilt the 355 that came with the car using a new block, bolts bearings, balanced the rods to within 0.5 grams across the board and balanced the pistons to within 1 gram across the board and then rebalanced the whole assembly and added the dart heads. Ran that motor until 2001 when an external crack showed up on the block and then put the 388 short block back into the car with the dart heads and ran it for the 2001 and 2002 season.

 

So, what's the combination now ?

 

A 468 cu. in. Big Block Chevy motor installed into a dragster running 5.20's in the 1/8th mile.

The 67 is retired right now. The dog house and the driver side rocker panel needs some minor repairs and we need a new rear end. During an inspection we noticed that the axle tube at the leaf spring mount was starting to tear. It was still the original 12 bolt housing that had the axle tubes welded to the center section and had Ford big bearing ends welded on the ends to eliminate the c-clips.

 

Well, I see you have "stepped things up" - LOL !