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

I am considering moving up to a SLIGHTLY more aggressive CROWER Hydraulic Roller Cam . . .

Considering these choices:

(1) #00403S 226/236 @.050" .519"/.540"(1.5 rockers) 114 deg Lobe Center

http://www.crower.com/index.php/cams...rcle-4278.html

(2) #00468S 225/232 @.050" .535"/.550"(1.5 rockers) 110 deg Lobe Center

http://www.crower.com/index.php/cams...rcle-4578.html

(3) #00469S 230/236 @.050" .540"/.555"(1.5 rockers) 110 deg Lobe Center

http://www.crower.com/index.php/cams...rcle-4579.html

Thank you, in advance, for your help !

 

Is there any reason you want to use a vacuum secondary?
I would use a 750 double pumper. I prefer either proform or quickfuel. I have had numerous issues with build quality on demon carbs in the past. I don't know if they have fixed this but I not going to give them my money any more.

As far as the cams, the first 2 are marginally bigger than what it comes with. Probably not even worth the time and money.
I would go with something like a lunati 60112 if i was changing the cam.

 

My preference for the Vaccum Secondary comes from the car being primarily street driven and not wanting to kill mpg too badly. Also, I like a vac. sec. with an Automatic transmission. It helps to "smooth things out", even at the cost of a tenth or two on the strip.

I'll take a look at the Lunati 60112 cam . . . I'm trying to stay around 235 or less on the Intake & Exhaust durations. I'd rather have "street manners" than a "pro street" sound, without drive-ability headaches, and having to run a lot of stall converter . . . I'm looking to pick up another 30 to 50 HP "ballpark". I believe I need a Small Base Circle camshaft with the 383, right ?

Thanks !

 

That fuel economy thing is just a old myth. A properly tuned double pumper will get the same mileage under normal driving than a properly tuned vac secondary. If your really worried about fuel mileage get rid of the 3 speed trans for one with overdrive with a lockup converter.
I don't know what you mean by a vac secondary smooths things out.
As far as the cam. The base circle thing has to do with how much lift the cam has and the rod bolt. I don't know what works and what doesn't but any cam manufacturer can tell you if you need a small base or not.
As far as stall... personally I would use around 3000 for either the stock cam or lunati.

 

By "smooths things out", I was referring to potential "bogging" when you hammer it at low rpm. On a mechanical secondary carb, everything goes 100% wide open, instantly. A Vac Sec carb allows the motor to tell the carb "what it needs" and let the secondaries open more gradually.

If this was a manual transmission car, a "dedicated" race car, or just a "weekend toy", I would definitely choose a double-pumper. My car will be truly daily driven, 60-70 miles a day round-trip, every day. I have been told that a small base circle cam is necessary for clearance on 383 stroker motors, whether that is always the case or not, I don't know.

Something else "on the back burner" might be the installation of a 4L80E transmission, which would give me the double benefit of an Overdrive and a Lock-Up Torque Converter.

 

Depends on the make of rods and the style of bolts used.
The SCAT H beams in my 383 have no problems with a .560 cam lobe because the bolts are cap screws so there is no bolt head in the area that hits the lobe
The problem area can be ground down on cheaper rods

 

For a DD I agree with you.

I am partial to a old skool Q-Jet (780CFM potential ) with the tiny primaries for instant low speed throttle response and great economy
combined with the massive secondaries that only open up when and as much as the engine load demands

 

You should not have any bogging from a double pumper when going 100% throttle at any rpm. If you do something else is wrong. That is not a normal issue for a double pumper carb.
I have personally tuned cars with 650 double pumpers with overdrive and lockup converters that get 20mpg or better on the highway.



I agree, for the best fuel mileage you should use a quadrajet. But even though a quadrajet is a vacuum secondary carb, it is nothing like a holley vacuum secondary. It is a totally different style carb with a totally diferent way of metering fuel. Where as a holley dp and vs meter fuel exactly the same.

 

Great info . . . I didn't know that !

Many thanks for your help. Please feel free to comment any time !

 

I'm learning and re-learning a lot of things here. It's amazing how more than 20 years causes you to forget - LOL !

 

Do you, or anyone else, know if anyone has done a dyno comparison, where the only variable is changing carbs ( all same CFM range), using a Quadrajet, Vacuum Secondary Square-Bore, and a Double-Pumper, head to head ???

I'd like to see a test like that done TWO ways . . . First, the traditional "slow-pull" Dyno test, to maximum RPM . . . Second, "real world", where they "hammer it" from a Dead-Idle. I think the second test would clearly show the differences, rather than just "dyno numbers" .

Many thanks !

Thanks!

 

I have never switched from a vs to a dp back to back on the chassis dyno. I can tell you form my experience I have found that a dp will have a harder and faster initial hit when you go wot. As long as your tires can take it the dp usually will launch harder. I have in the past used a vs carb to leave softer to not blow away the tires by adjust the secondary rate.
I seems your under the impression that a dp will bog or be sluggish when going wot from a dead stop. That's the farthest from the truth. If that happens there are other issues like the carb isn't tuned right or you have some timing issues also.

 

I would go with the DP from a performance point of view. I'm sure you could dial in a VS carb for nearly the same performance though...but IMO it'll take a bit more tinkering.

If going with annular boosters, I've always read the size of the annular boosters takes up more room in the venturies...in other words, you lose a little bit (up to 50 cfm) of air flow up top as compared to your normal downleg boosters. I'd love to try a annular booster carb myself, but I'd go with nothing smaller than a 750 annular booster carb on a 383 cube motor...I think it would work out well for it as a matter of fact...

EDIT: And as far as changing cams...up to you, but I'd stick with what it has. Sounds like a good setup that'll make good power up to 6K...a great range for the street.

 

I recently read something similar, too, but I'm not sure where. It was said that even if annular boosters do take up more room, the flow numbers are based on what it actually flows, as designed.

 

Recently a magazine tested annular vs downleg (can't remember which one). The annular made more power than the equivalent downleg and did it at a higher afr due to better atomization. They were surprised that the lost cfm due to the bigger booster didn't make a negative difference in power.

 

Quote:

Originally Posted by JaBoT

I would go with something like a lunati 60112 if i was changing the cam.

I took a look at the Lunati 60112 ( The part number has changed ), as well as this Crower cam . . . They are very similar to each other.

http://www.lunatipower.com/Product.aspx?id=1989

http://www.crower.com/index.php/chev...rcle-4950.html

LUNATI "VOODOO" #60112 (20120712)

Hydraulic roller, lopey idle. Great street machine cam! Likes upgraded intake carburetor and exhaust. Needs 9.5:1 or better compression and 2500 RPM stall speed converter and a 3.42 or better rear gear ratio.

• Advertised Duration (Int/Exh): 282/290
• Duration @ .050 (Int/Exh): 231/239
• Gross Valve Lift (Int/Exh): .535/.550
• LSA/ICL: 110/106
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 2400-6200
• Includes: Cam Only

Part Number: 20120712
Previoius Part Number: 60112




CROWER #00470S


Lobe center: 110
Advertised Duration: Intake / Exhaust 286 / 292
Duration @ .050" Lift: Intake / Exhaust 232 / 240
Duration @ .200" Lift: Intake / Exhaust 155 / 163
Lobe Lift: Intake / Exhaust .366 / .373
Rocker Ratio: Intake / Exhaust 1.5 / 1.5
Gross Valve Lift: Intake / Exhaust .549 / .559CID


383 - 400
Performance Level 3

Low RPM 2400 Peak HP 5850 Redline 6350

Performance Description : Rough idle, aftermarket intake and headers a must.

Engine Application : Level 3 camshafts are designed for moderately modified engines. Intended for performance hot street/strip and performance marine applications.

Recommended Modifications : These higher lift and longer duration camshafts demand close attention to rear end gearing and tire diameter combinations. The secret here is to pick a ring and pinion gear set and tire diameter that keeps the engine in its optimum rpm power range. Automatic transmissions with an aftermarket high stall torque converter and manual transmissions. Headers, dual exhaust, larger than stack carburetor, performance manifold and increased compression (9.5:1 to 10.5:1) are required. Mild porting and larger valves will improve performance.

Product Characteristics : Moderate lope at idle. Extended rpm range with emphasis on upper bottom to top end power and a strong mid range.

 

I would go with the lunati. It will probably idle a little better. As the crower is listed as rough idle.
I agree with Confuzed1. I would just use the cam it comes with. 425hp should be more than enough to be at your goal of running mid 12's

 

I'm kind of leaning that way myself, but you know how the "more is better bug" starts working on a person's mind - LOL !

Thanks !

I am also debating COMP CAM Ultra-Pro Magnum 8650 Chrome Moly Roller Rockers or the "HI-Tech" Stainless Steel Rockers, vs. the Crower Stainless Stainless Steel Roller Rockers . . . Aluminum Rockers are out of the question for me, since there is so much street mileage involved.

http://www.crower.com/index.php/rock....html?cat=2153

http://www.compperformancegroupstore...UltraProMagnum

http://www.compperformancegroupstore...UltraProMagnum

COMP Cams "Hi-Tech" STAINLESS Roller Rockers ( come in 1.5 / 1.6 / 1.65 ratios )
http://www.summitracing.com/parts/cc...make/chevrolet

 

To me one of it's appealing features for tweaking as you have 3 fueling adjustments on the sec side as the rod comes out of it's seat;
as opposed to a fixed jet size on the Holley

 

I'd keep the engine all stock, and stick with a vacuum secondary carb in a 'full weight' street car until the warranty on the engine has run out and then up the power with a bigger cam

You probably will see a few more HP in a double pumper but if you're like 99% of the guys that just want to slap a carb on and go the vacuum secondary carbs make more sense.

In my expierence double pumpers tend to use more fuel on the street in a daily driver - I'm going to go out on a limb and say it might be due to the secondary accelerator pump shot every time the throttle is tipped in - that can be reduced by getting the progressive linkage instead of the 'race' synchronous linkage...

 

This motor imo is overpriced. The crank is a special 3.800" if i recall correctly. Its 1100$ by itself. Good forged cranks can be had under 750

For your goals and talks of longevity in your other thread, i wouldnt get aggressive with the cam or else you willl be changing springs every 15-20k miles. I'd call Mike Jones or Bullet cams for a cam that has mild lobes for valvetrain life. You can get mid 12's easily.

But you could have a better motor than this crate for same price

 

The more time passes, the more my thinking is going in that direction.

The advantages to the crate motor are the warranty, it's already assembled, and the balancing and machine work are already done.

The disadvantages are higher prices for each component, limited intake selection, and not being able to choose components.