CIS to Webers Question... on a RoW 3.0SC

[Ferrariguyma]

I am buying a set of 40IDA webers for my 1978 RoW 3.0SC.

The webers are being sold as "complete" and ready to install. The seller is also selling me a used Bendix (?) fuel pump for $100.

My questions:

- What else will I need for this conversion?
- Can I keep my A/C "as is" and run webers?
- I assume I will need a new gasket set for the conversion? Where can I get a gasket kit?
- Is the Bendix fuel pump the one to go with?
- What brand/model Electronic Ignition should I buy? MSD?
- From what I have read I should really change the cams to get the most out of the swap? Any recommendations? I already have SSI's and a dual out Monty
- Should I go with new wires?
- Anything else I should buy before I undertake the swap?

Thanks in advance!

Andrew

[Ferrariguyma]

Also the webers I am buying have 36mm venturi's is this the correct size for a primarily "street" application?

[Ferrariguyma]

Not venturis!

I meant:36mm intake manifolds

Here are the details.

Weber 40IDA ( triple throat ) carbs in superb, virtually new condition with 36mm intake manifolds, K&N filters, Weathershields and throttle bar with linkage & ball joints.


Thanks again!

Andrew

[randywebb]

search for a few threads on this...

there is no power gain, but it sounds and feels a lot better than CIS.

Get a rebuild kit and rebuild them and set them up carefully

jet them rich to compensate (partly) for the cams

for a few thou more you can do it right with new cams & pistons that are meant for carbs

[Ferrariguyma]

What cams and pistons do you recommend for carbs?
Size/model/brand of both please. As you might have guessed I am new to all this.

[}{arlequin]

not sure about the fuel pump, but it's also good to invest in quality (very fine) fuel filter. carbs like clean fuel otherwise they clog and sputter...

in the same vein, cleaning, sealing, and refreshing your gas tank is a good idea for the same reason...

[}{arlequin]

another:

i've also been told that 36's might be a bit large-ish but good for top end. they are not inappropriate just that you may feel a bit sluggish below 3k rpm

[Steve@Rennsport]

Originally posted by randywebb
search for a few threads on this...

there is no power gain, but it sonds and feels a lot better than CIS.

Get a rebuild kit and rebuild them and set them up carefully

jet them rich to compensate (partly) for the cams

for a few thou more you can do it right with new cams & pistons that are meant for carbs

Randy, et all:

Au contraire, dear sir. There most certainly IS a nice power gain converting from CIS to carbs! Further, the throttle response difference is astounding as long as the carburetors are correctly configured and setup.

Thats the whole trick, you see? Jetting, configuration and setup makes ALL the difference in the world and honestly, few people get it right since its time consuming, a bit expensive, and requires patience.

Rebuilding any used carb is always considered good practices.

Don't jet them rich! Jet them right! Excess fuel washes oil away from cylinder walls and costs you performance. Carbs (especially Webers) do run richer than CIS systems do and merely need to be jetted for the displacement, compression, and camshaft configuration of your SC motor.

Use an MSD ignition system with matching MSD coil. These make a big difference in the drivability of any carbureted or MFI'ed car. USe Magnecor wires and make sure your cap and rotor are new.

Don't use that Bendix fuel pump. Get the the Fuel Pressure Regulator that PMO sells so you keep your SC's original fuel pump and set FP to 3.5 psi before you begin the float level setup.

Hope this helps,

[deanp]

You'll want to get the insulators that go under the intake manifolds, these will come with longer studs. I double nutted the old studs and they came out easily.

When I did the conversion on my 2.7 I used my CIS fuel pump, new braided supply and return line, PMO regulator, a Russell fuel filter and the PMO fuel bars.

I didn't change the pistons or cams, I don't need a rebuild yet and while I left power on the table, it wasn't worth the expense at the time to do it. If the 3.0 is in otherwise good shape you don't need to be concerned about driveablility with carbs with the CIS pistons. If you need to rebuild anyway, then go for the whole deal.

Let me know if you need any help.

[deanp]

Steve,

I am still using the stock ignition system with the Petronix Ignitor in place of points. Is there a big difference by switching to the MSD set up?

[randywebb]

You are saying there is an increase in hp without changing the cams or pistons??

If so, how much is it?

[Ferrariguyma]

Steve thanks for the advice especially on keeping the stock fuel pump, dean thanks for the information and offer to help me out.
I will take you up on it when I get to starting.
Dean did we meet at the Scituate, MA Porsche gathering 2 yrs ago? I had my 1988 Cab there and I thought we might have met there?

Andrew

[deanp]

Yup we met at the Scituate meet and I think I spoke to you briefly at the Larz Anderson event last Sept.

The braided lines and associated fittings are overkill, but I only wanted to do it once and I wanted it to look clean. Rubber fuel line with clamps etc get the job done for far less $$.

[Ferrariguyma]

Dean,
I too am in the "do it once" camp and have no problem spending the extra to avoid future problems. Who installed your carbs and set them up?

[Wrecked944]

Originally posted by }{arlequin
not sure about the fuel pump, but it's also good to invest in quality (very fine) fuel filter. carbs like clean fuel otherwise they clog and sputter...

You probably already know this but I feel compelled to say it again and again. Be sure to use a metal fuel filter - not plastic. Don't ask me how I know.

[deanp]

Andrew - I am pretty strictly DIY, no mechanics for me unless I am short on time or completely stumped. I did the carbs and associated set up myself.

[Duckworth]

You probably already know this but I feel compelled to say it again and again. Be sure to use a metal fuel filter - not plastic. Don't ask me how I know. ...JanusCole

I've got a plastic filter in a Spitfire and would love to know what trouble I'm asking for if I leave it in...It's up against the firewall - 'away' from hot components....but - Murphy's law is a good way to keep ahead of problems and ask yourself, "what if...?"


Btw, can someone mention if any 911 can do 27 mpg w/Webers on the freeway at cruising speeds ?

Typically, it's mentioned that webers get 'half' of CIS...(15).

Believe me I understand how CIS differs from weber - but wonder
if in fact it "doubles" your economy over weber ? ?


Phil

[RoninLB]

my carbs & cams get around 2/3 of what I previously had with CIS. My carbs are very adjusted.

[MURF]

no more webers for me lousy milage and drivability i just finished efi conversion and am delighted at difference check out bitz racing

[dd74]

Originally posted by randywebb
You are saying there is an increase in hp without changing the cams or pistons??

If so, how much is it?

Do a search. There was a thread about this last year, where someone posted the dynoed hp on their rebuilt stock 3.0 with PMO/Webers. TRE added some insight as well, which was quite enlightening.