carbs

[massivesplitproject]

Hello does anyone know if my carbs from my 69t 2.0 be ok to use on a 3.0sc motor please, Are the parts interchangeable with idas ?

[coomo]

Your going to need 46mm carbs for a 3.0 to breath well Matt.Im on lookout for set.I was going EFI and have PMO bodies but decided against.

[greg356a]

For either Weber or the Zenith 40 Tin carbs parts are readily available via eBay, various USA sites etc. I use ebayer alfa1750 in Italy great services. Seems to take ages to get the carbs setup and I am still battling with my Zeniths on a 3.2 but nearly got them right. It wont be as easy as just bolt them on and go but with careful set up, lot of posts on here and Pelicanparts about setting they should be great.

[rhd racer]

I ran Weber 40 IDA 3cs with standard chokes on my 3.0sc powered 914/6. It was the 188 bhp model, and carbs, equal length headers and MSD developed 209bhp and loads of torque. There was certainly no need to go as big as 46mm chokes. It pulled like a train.....

Hope that helps
Wayne

[MikeB]

I run IDAs on my SC, which is mildly tuned, better cams, pistons and SSIs, Bruce Anderson recommends as a base set up 34 chokes F3 emulsion tubes, 160 mains and 175 air correction, with idle jets 60, 65 or higher to get a smoother progression from the idle to main circuits. I think if you want a big horse power motor then you need 46s but for fast road with low down pick up then the 40s are fine.

[massivesplitproject]

I run IDAs on my SC, which is mildly tuned, better cams, pistons and SSIs, Bruce Anderson recommends as a base set up 34 chokes F3 emulsion tubes, 160 mains and 175 air correction, with idle jets 60, 65 or higher to get a smoother progression from the idle to main circuits. I think if you want a big horse power motor then you need 46s but for fast road with low down pick up then the 40s are fine.

Yeah i read those setting in my bruce anderson book, i was wondering will my 40idt do same job as a 40ida , I am not racing so 40s will probably be ok for me, however if i am buying carbs instead of using mine i may consider 46

[gtBen]

Take a look at the "Happy Jetting" data sheet on the Performance Oriented site (scroll down a bit) - http://www.performanceoriented.com/perf ... ing-part-2
There's a lot more useful info under the Tech tabs.

Bengt

[rhd racer]

I run IDAs on my SC, which is mildly tuned, better cams, pistons and SSIs, Bruce Anderson recommends as a base set up 34 chokes F3 emulsion tubes, 160 mains and 175 air correction, with idle jets 60, 65 or higher to get a smoother progression from the idle to main circuits. I think if you want a big horse power motor then you need 46s but for fast road with low down pick up then the 40s are fine.

Yeah i read those setting in my bruce anderson book, i was wondering will my 40idt do same job as a 40ida , I am not racing so 40s will probably be ok for me, however if i am buying carbs instead of using mine i may consider 46

Well as it turns out was racing, Doing sprints and hill climbs which are much closer to fast road use. A co competitor (who may be along in a mo) tried 46s and lost all the low down torque and drive ability that is so important in the discipline. You also loose the key qualities of the SC engine.

I really would not put 46s on one unless drag racing or trying to win a Dyno shoot out. Sorry I can’t comment on your carbs as no experience. Good luck

[911hillclimber]

Totally agree with the above.
Hill climbs are going fast as possible up a country twisty lane knowing nobody is coming the other way over a measured and timed distance.

Too big a carb will kill the engine for doing this asap.

I have a 3.2 on 50mm PMO carbs, and it is over carb'd and looses some of the low rev torque, the 3.2 really needs 46mm but would love to try it on 40's. The engine is in a hill climb special and I have to wait for the engine to get going below 2K rpm.

Getting through this famous ribbon of curves at Prescott hill climb needs good low down engine response

[Lightweight_911]

.
I had a fairly highly tuned/high compression 2.8 twin-plug engine in one of my (road) cars which was equipped with 40 IDA Webers - revved regularly to 7500+ rpm & never seemed to run out of breath ...

.

[911hillclimber]

Bob Watson said my 3.2 was over carded and gave him some grief on the rollers.
46 size kicks-in at 3.2 so I would think 40's are great on 3 litre and smaller.

Ref Bruce Anderson book.

[wadsworthi]

I suspect that I am the co competitor mentioned above! I currently run a 3 litre SC engined 911 that runs with 46 PMO carbs. It was a great debate between me and the engine builder as to what size of carbs to run with me favouring 40's and builder 46's, but after consultation with Richard at PMO who is adamant that they have tested with both 40's and 46's and it is the 46's that run better with 3 litre SC engines. In my experience the car does run very well at the top end, but does have some hesitation out of slow speed corners (it does of course depend upon camshafts). If you are running a road specification 3 litre SC engine then I would stick to 40's.

Good luck!

Ian

[massivesplitproject]

thanks for the answers but nobody as actually addressed my actual question due to my original question being vague, i want to know if my idt will do the job as well as ida, I didn't quite word it properly sorry and point out my carbs are not idas

[Lightweight_911]

.

Check exactly which version of Weber carb you currently have - there were 40 IDT & 40 IDTP versions.

If you have the former then they should be fine (assuming the throttle shafts aren't worn/leaking & you fit appropriate jets) whereas the IDTP will not work effectively/efficiently without a number of modifications ...

.

[massivesplitproject]

i have the latter unfortunately, what modifications are needed please