Carb size blower motor

[cjm76]

Hi there has anyone fit a 4-71 to rover 3.5?
I'm looking for info on carb size choice please

[BlownMGB-V8]

I used an Eaton M-90. Also a turbo, and M120/340cid. I used EFI except for the turbo.

For draw through applications the blower will boost the draw through the carb well beyond the 1.2 inches a modern 4bbl carb is rated at, so that in practical terms a blower engine will not be carb limited. If you want to get way down in the weeds about it there are efficiency curves that you can use to determine optimal carb size and inlet vacuum under full boost but bear in mind that idle, off idle and midrange performance are frequently even more important.

I tend to calculate the effective displacement using the expected boost as a multiplier and use that as an upper limit, based on the specs of the engine itself. A race engine and a street engine will have very different needs of course.

Jim

[Moderator]

Welcome to BritishV8, Chris.

This article doesn't begin to answer your question, but I'd bet it will interest and inspire you nonetheless:

<a href="http://www.britishv8.org/Articles/MGB-V8-Supercharger.htm">Under-Hood Eaton M90 Supercharger (on an MGB w/ Buick 215 V8)</a>

[cjm76]

Thank you for the replies

[Blown v8]

When I had the wade Ro34 on a 3:5 I used a jetted 390cfm
When I went to the 4:71 I used a 600 cfm, I had it set up on a rolling road, Worked really well,
I never used the choke, on either

[ag1234]

Using 4-71 for looks, not efficiency ?  Boost target ?    I selected a 6V-71.  Perfect length and size. Weld adapted an Offy single plane intake.  This makes for a clean package and will make adequate boost.
                                                                                   Onward,  Art.

[ag1234]

Beautiful build, Bill !  How much boost ?  How doest it scoot ?
                                                                                              Onward,  Art.

[MG four six eight]

Thanks Art,

I run 11 psi of boost and she goes pretty good. I beefed up the bottom end with forged pistons, ARP studs, line bored the block, balanced, etc, so I'm sure that the motor could take a little more boost. However the car can struggle for traction at times as is, so additional boost would probably mean just more "smoke and noise" ;-)

Bill

[DiDueColpi]

Turning gasoline into smoke and noise,
I love it!
Live like you mean it
Fred

Go Canucks Go!