[Ferrari] Throttle body sizing question for carb to EFI 308

[Bill Shaw]

Hi guys,

I'm forwarding this from the Ferrari list for a friend there.  He's working on an EFI conversion and
is in need of a bit of help in selecting the right throttle bodies.  Any help would be greatly
appreciated.

Thanks,

Bill
'78 FI 124 Spider
'84 Mondial Cabriolet
'94 Z28

>
> Alan Ing wrote:
>
> Okay guys, once again, I need some advice.
>
> I've decided to bite the bullet and buy a set of TWM Weber DCNF style
> throttle bodies to complete my carb to EFI 308 motor project.  The question
> is, what size?  These throttle bodies come in three sizes, 40mm, 44mm, and
> 46mm.  At first TWM wanted to sell me a set of the 46mm sizes.  Although, I
> know that it is supposedly hard to oversize a thottle body, 46mm seemed like
> a huge step to me so I questioned them about the fit.  It turns out, that
> this would be the choice for a racing motor making that would be running
> mostly at 4,500 rpm or higher. Part of the reason they at first recommended
> this size is because they ran out of the 40mm and 44mm size and it will take
> two months to get the other sizes.  I told them I could wait two months just
> to get the best fit for the car.  Are there any experts out there who can
> recommend the appropriate size?
>
> I basically want a hot motor that can be driven on the street but with the
> occasional track visit. I guess the safe bet would be to choose the 40mm
> unit which will still have more airflow than the stock 40 DCNF carbs, but I
> can't help thinking that I might be giving up something by not choosing the
> 44mm units.  The 44mm unit will also require mild grinding of the intake
> manifold for increase in throttle bore diameter. If anyone can give me solid
> advice, I'd appreciate it. I can only afford to do this once as they are
> expensive.  I guess I should have chose a different engine for my first
> rebuild project.
>
> My 308 motor will have the following specs:
>
> Electromotive TEC II
> 10:1 pistons (Want to run 92 unleaded with no additional additives)
> 328 crank (2.6mm more stroke over the 308 and displacing about 3.1 L)
> Aluminum flywheel/dual disc clutch with sprung hubs
> Ported Heads
> Upgraded springs and retainers
> Camshafts with the following specs
>
> Intake
> Cam Lift:               .408"
> Duration Adv.:  303
> Duration @050:  262
> Valve Clearance:        .008"
> Valve Lift:             .400"
> Cam Lift tdc:   171
> Phase:          105
>
> Exhaust
> Cam Lift:               .408"
> Duration Adv.:  303
> Duration @050:  262
> Valve Clearance:        .008"
> Valve Lift:             .400"
> Cam Lift tdc:   157
> Phase:          NA
>
> Regards,
> Alan Ing


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