Basic 4BBL carb questions

[crispyboy]

I have some upgrades planned for my 1990 GW. I have searched the database here but still have some questions.

- Install Edelbrock performer intake manifold
- Install 4 BBL carburetor - Holley or Edelbrock depending on ease of installation of the throttle linkage, cruise control, idle compensator for the AC and AT kickdown. I want to make a clean and complete installation.
- GW has headers, 2.5" exhaust, magnaflow and upgraded Engle cam (can't remember the specifics

1.) CFM rating? My search revealed that most use 650 cfm on the Edelbrock but I'm confused on the Holley - 470 or 670?

2.) I assume a phenolic spacer will be needed. Is this available for either carb?

3.)Is there any special brackets needed for the accelerator cable, cruise control, idle compensator for a/c and a/t kickdown.

4.)Is there an idle compensator available for either carb or is there a way to retrofit the one off of the original MC2150?

Tell me how you did it, was it successful, would you do it differently this time.

Pictures, opinions, part numbers etc... Please!

[tgreese]

Re CFM, the CFM rating mostly depends on the diameter of the carburetor venturis. The carburetor uses vacuum, produced by the pumping action of the engine through the venturi, to control fuel. At some point, the venturi gets so large that the vacuum is no longer sufficient for good fuel control. This point is determined by size of the engine (CID) and the engine RPM desired. So you want more control from higher vacuum, but a higher vacuum means less fuel-air charge to the cylinder, so that reduces top end power.

It's always a compromise, and so much depends on tuning. Choose a smaller carburetor if you want better fuel control and plan to operate the engine at lower speeds. A smaller carburetor will also provide better fuel economy because of better fuel control, not because a small carburetor would necessarily deliver less fuel. A poorly tuned smaller carburetor will deliver poor economy just as well as a larger carburetor.

[Blake]

I ran a Holley TA 670 on my 360 Honcho and LOVED it. I always wanted to try out a 470 though...

But why not do a junkyard TBI? You can do it for less than what a new carb will cost and it will probably run a little better.

[derf]

1. With an upgraded cam and headers you'll want the 650/670 range to take full advantage.

2. Look at 4bbl spacers at any major parts store website. You'll want square bore (often referred to as Holley 4150 pattern). There's many different materials and thicknesses. The Performer intake has a tall plenum already so you don't need a tall spacer but a 1/4" phenolic spacer helps prevent heat soak.

3. For the accelerator linkage I buy a Holley 20-2 throttle stud kit. One of them fights just right. I remember being able to attach the kickdown to the factory throttle bracket on the Holley Truck Avenger I installed. I don't know about cruise control because I've never had it in any FSJ.

4. I never used the idle compensator with AC because I never had working AC. I would imagine a little creative work would let you attach the 2150 compensator on the carburetor you choose.