[This message has been edited by 30+mpg (edited 12-06-2008).]

quote Originally posted by fierosound: ... The stock cruise control parts (vacuum canister, diaphram, solenoid etc) were removed and a less bulky Delco electronic cruise unit was installed below the air cleaner.

Still haven't fixed the head, but I thought I'd post this today...

I needed room to mount the air cleaner where the cruise control vacuum canister, solenoid etc were.
So I switched to the much more compact Delco electronic cruise module used after 1996 on many GM cars.

Details of the electronic cruise installed on this SD4 Indy here:
https://www.fiero.nl/forum/...110502-2-090358.html

[This message has been edited by fierosound (edited 09-02-2023).]

As I said earlier, the Edelbrock AVS 500cfm is too damn big, and it's the smallest they make.
Idle is not bad but could be better, part throttle driving is pretty good but WOT is terrible.
The engine doesn't draw enough air to open the secondary air valve and pull the fuel properly.



Even though it's listed as a 500cfm, mechanically it looks identical to the 600cfm - the primary difference being the jet sizes.
Specifically, we're looking at the throttle bores and venturi diameters. Smaller primaries and smaller secondaries are what's needed
because at 3.3L displacement, the engine will only ever draw about 400cfm.



The Edelbrocks are a clone of the Carter Super-Quad AFB /AVS series of carburetors and are physically identical.
Well, Carter DID make a 400cfm carb - the AFB 9400/9410 and it had smaller venturis and bores compared to the Edelbrock 500cfm.
This should make it perfect for the 3.3L SD4.

Unfortunately, Carter hasn't made any for 20 years and since they were only made as a replacement carb for the GM 231 V6, they are very rare.
A rebuilt one just sold on eBay 2 weeks earlier for $350 - darn!! And emailing all the carb rebuilders came up with nothing.

As luck would have it, I finally DID find a brand new, in the box Carter AFB 9410 400cfm from The Carb Shop. http://www.thecarburetorshop.com

It was likely the last and ONLY new one in existence and I paid dearly for it. It seems nothing is cheap with an SD4!



Unfortunately, it doesn't have the nice polished finish of the Edelbrock.

The smaller primary venturies would produce faster air velocity at idle and would greatly improve that function.
And smaller secondaries are what's needed because at 3.3L displacement, the engine will only ever draw about 400cfm.



Here's a comparison of the throttle bores back-to-back (secondaries in middle).
The primary bores are the same, but the secondaries are very different.

Carter 1-7/16" 400cfm on Left - Right is 500cfm 1-11/16" Edelbrock


Here's a comparison of the venturies back-to-back (secondaries in middle).
The primary venturi on the 400 is slightly smaller, and the booster is a different shape.
But here again, the bigger difference is in the secondary's primary venturi size.

Carter 1-1/4" 400cfm on Left - Right is 500cfm 1-9/16" Edelbrock



Because the Carter and Edelbrock are physically identical, installation requires nothing more than swapping carbs.
All the lines and throttle linkages connected as before without modification.

[This message has been edited by fierosound (edited 03-04-2019).]

Holley 2-bbl carb, showing primary venturi (A), secondary venturi (B) and discharge tube (C). Secondary = Booster.

Yeah, I know. There's primary and secondary bores in the carb, then each bore has a venturi that has a primary and secondary component.

[This message has been edited by fierosound (edited 12-15-2008).]

[This message has been edited by fierosound (edited 12-11-2008).]

[This message has been edited by fierosound (edited 03-04-2019).]