: Single vs. Dual plane intake using MPFI

04-01-04, 02:24 PM
Ok, here is my next question. If I wanted to use Holley's Universal MultiPoint Fuel Injection setup (where you tap your own intake).

Should I use a dual or single plane manifold with this kit? The motor I'm planning to build is a 472.

Holley mentioned using a single plane. I'm familar with the differences and pros/cons with both in a carb'd setup, but not fuel injection.

It would really be nice to use the Edelbrock dual plane since it's nearly 1/2 the price of the Bulldog single plane.

I'm leary of the single plane...thinking it'll perform poorly down low where the caddy motors make all their torque and also hinder off idle throttle response.

This setup will be used in a '92 Z71 4x4 for towing and off roading.

04-01-04, 08:42 PM
Dual plane manifolds are so named because the manifold is split into two different chambers. This divides the total plenum/runner volume, making the vacuum signal created by the engine much stronger at the carburetor's venturi. This promotes better air/fuel mixtures at part throttle and at low-RPM ranges. With port fuel injection, you can bypass most of this, as fuel is injected directly at the back of the intake valve. The manifold is dry and only moves air. The runner length and overall plenum volume still affect where the engine produces peak torque, but you can get away with using a larger plenum volume than you would with a carb. Single planes are also preferred for EFI because the runners tend to be at the same height, making it easier to mount injectors and rails. The Bulldog manifold looks like a nice piece, and it already has cast-in bosses on each runner. On the other hand, the Edelbrock piece has runners at different heights and would be more difficult to modify. First things first: I would find out what Bulldog's recommended RPM range is for their intake. If it isn't sky-high, I would use that intake as the basis for a conversion.

04-02-04, 03:44 PM
Wow, that's EXACTLY what I needed to hear. Thank you very much for the info. I'll contact Bulldog and see what they say.

04-02-04, 10:28 PM
No problem. Let me know what Bulldog says. I know a little about fuel injection conversions, so I'd be happy to share whatever information I have available to me.

04-02-04, 10:48 PM
Almost forgot. If you want to see a truly sick example of an injected Cad big block, buy, borrow, or steal a book called Fuel Injection: Installation, Performance Tuning, Modifications by Jeff Hartman. The book is out of date now (it is 10+ years old) and is not entirely comprehensive, but there is a short article on a twin-turbo Cad engine powering a (I'm not making this up) GMC Motorhome! There's even a pic of the monstrous motorhome doing a smoky front-wheel-drive burnout! The stroked 530 CID Cad engine uses a factory EFI manifold and throttle body, twin turbos mounted to what look like factory Eldorado manifolds, and a Haltech engine management system. Power is fed thru a Turbo 425 transaxle or a Turbo 400 (not sure which, but they are very similar from a design standpoint). Now if that doesn't prove the strength of these engines/transmissions... Definitely worth a glance if you're in the bookstore.

04-03-04, 12:36 AM
If you get that book, you should scan that pic and let me see it.

04-03-04, 11:56 AM
I posted two pics in the general Cadillac pics gallery (under capn_zoom). If you're searching, use twin turbo as keywords. They're grainy, but you'll see what I'm talking about. Anyone doing EFI swaps, please share info, pics, recommendations, etc.

Big Jim
04-20-04, 11:26 PM
Just for general background, 2 companies built front wheel drive motorhomes based on the Olds 455 Toranado driveline, GMC and Cortez. A fair number of them have been repowered with the big Cad, very sucessfully. (OK, I know this because I have a Cortez in my backyard, only the Olds at this point :-[ )

04-21-04, 11:43 PM
I must say that motorhome burnout pic is the coolest pic I've seen in a while. :)

04-23-04, 01:01 PM
Well after asking several sources they all seem to agree that the single plane is superior when it comes to MPFI. Mainly because the throttle body is only metering air instead of an air/fuel mix.

Holley themselves suggest a single plane and Bulldog makes one with spots for the bungs already, so I'm sure this is for a reason.

06-26-04, 10:04 PM
can someone tell in more detail what exact parts i'd need for FI and if MPFI would cost significantly more than TBI on a 500? Heres what I think so far

all I have so far in mind is that I might need a new gas tank

as you can tell Iím a total noob, so please bear with me

:bonkers: :)