Rochester Fuel Injection for 390

[bcroe]

I would like to note, that some advantage to many early FIs was in the
use of tuned intake runners.  This works when the fuel is injected at each
intake valve.  A single carb at the inlet to (wet) runners would drop a lot
of fuel along the length of the runners, causing response issues on the
street, though Chrysler did try it once.  Bruce Roe

[TJ Hopland]

Its hard to tell in the photos but the mass produced cast version of the intake has the same tuned port design as the sheet metal one we are looking at here.   Presumably they are tuned for the engines and cars they went in.    The Vette's high revving 283 likely required a much different design than the low revving Cadillac 390.   Who knows maybe that was a reason they decided it wasn't worth it.   Maybe the advantages only really kicked in at higher R's which just wasn't Cadillac's style at the time. 

[The Tassie Devil(le)]

I would like to note, that some advantage to many early FIs was in the
use of tuned intake runners.  This works when the fuel is injected at each
intake valve.  A single carb at the inlet to (wet) runners would drop a lot
of fuel along the length of the runners, causing response issues on the
street, though Chrysler did try it once.  Bruce Roe

I have always wondered about the fuel in the runners on those Chrysler Cross Ram Intakes where each 4bbl carby would sit way outside the width of the engine, and feed the opposite cylinder head.

They do look neat though.

Bruce.

[TJ Hopland]

Wasn't long runners one of the reason inline 6's and especially the 8's kinda hit a performance wall?  Had to be really difficult to get the same mixture to a port 20 inches away as the one 4 inches away from the carb.    It likely wasn't a big deal with 5:1 compression motors that were making 10 horse per liter.   When port EFI came in they seemed to solve it by just having a massive long plenum with equal runners coming off it sorta like you can see in the photos of the Cadillac unit here.   

Didn't someone also try a variable length intake in that late 50's time period?   I know there were some in the 90's doing it and I presume some are doing it today.   The one I saw apart was I think a Yamaha built motor in a Ford and there were essentially throttle blades in the runners to divert the flow to either a longer or shorter path depending on the current needs.

[spoon]

The variable displacement manifolds were intended to maximize the velocity across the engine operating speed. The higher velocity improves the VE, (volumetric efficiency).

[spoon]

Step 1 is complete and I will begin to work on other components. During the cleanup the identification showed that this was manifold #4 from 1958 stamped in the flange for the air meter.

[TJ Hopland]

Amazing what difference a little paint makes.   Looks like a new piece just off the production line.

[spoon]

Slow and steady .  The meters are soon to be sent out for rebuild.

[bcroe]

Hope it works.  If not you could bolt a modern MAF sensor and injectors
to it.  Bruce Roe

[spoon]

Pretty sure that it work. This unit came off of a running engine. As far as a MAF and injectors, that can't happen with any of these components. This is a mechanical system that was never intended for that use.
Very familiar with the electronic fuel injection, I am a dealer of FAST and do calibration work for my customers.
I also race a C4 corvette that uses the FAST system.

[bcroe]

What sort of performance gain do you expect from the tuned runners,
and what else needs to upgraded on the car (such as exhaust)? 

Had a FAST analog system running in 1990, but now the car is gone
and the FAST is on a shelf.  Bruce Roe