3.0L CIS to Carb conversion?

[speed hole]

I am rebuilding the engine for my 1981 911SC, and am considering converting to carbs. This is strictly a track car, and won't be driven in cold weather. (some street use with a Dealer tag) I was having some issues with the existing CIS system, because of the remnants of the smog system. (removed O2 sensor) I know that converting to the 78-79 CIS system would take care of these issues, but I think carbs will open up my options. Wondering if anyone can advise for/against this choice?

[ianc]

Read here: carburetors vs CIS

Should be plenty of food for thought there,

ianc

[Mike Bonkalski]

If you are planning on PMO's, don't count out EFI -http://forums.pelicanparts.com/showthread.php?s=&threadid=225593

[mb911]

Even though I am having some issues figuring out the software for my efi conversion(81sc engine) I would still reccomend it over carbs for sure. Carbs are a pain however they sound better and SEAM that they produce more power I would stay away .

[Vipergrün]

I want item# 9004-03 on this page. Check out the other stuff as well. Item# 9007-01 looks pretty slick for an SC, just add Carrera intake manifold.

http://www.clewett.com/products/engnmgmt/emsys.htm

[EWPurdy]

Luke, come to the dark side.....

[speed hole]

Thanks for the info, gives me alot to think about. EFI would be great, just a bit pricey. I am not expecting a difference in power, just a system I can deal with at the track. Seems to me that carbs would simplify the system, but I started with VW's, so it's just more comfortable to me I guess. No arguement that CIS is a simple system, and easy to manage when functioning properly. Thanks again, still scratching my head....

[NineEleven]

Originally posted by EWPurdy
Luke, come to the dark side.....

Eric, can you tell us more on your EFI twin throttle conversion? How's the set-up, cost, maintenance & difference from orig. CIS? Thanks.

I've just entered the darkside 2days ago with an 80 911SC.

[ianc]

Whaddya got to say to that Eric?

ianc

[EWPurdy]

Sorry folks those are 46mm PMOs. Original setup was not too bad but you need to understand carburetors if you're going this route. Once they are dialed in, it's a piece of cake. Just keep the fuel to them clean and the rest is easy. I think I dropped about $4K with the PMOs, plumbing, and recurved distributor.

Here's some old posts:
PMO Conversion Nearly Complete - Thanks to all!

Carbs on a 911SC

[speed hole]

Thanks for all the imput. I'm sold on carbs. It opens my options greatly, especially with the case split. I'm currently running Bursch headers and a GHL exhaust, and planning on adding hi-comp pistons, larger cams and port/polished heads at time of rebuild. Carbs seem like the next obvious step. Eric, very nice setup... I'll keep you posted on the outcome.
Gabe

[Brother]

Think on this one for a second, Speedhole.

If you use Eric's costs, roughly 4000+ for the carbs and nearly 2 grand for the exhaust, you could get an ITB EFI set up from Clewett. Those PMO's are going up in price every time you look, but the EFI prices are pretty stable.

[ianc]

$1600 for Tony Bitz's EFI setup, and it will give you better economy and driveability and every bit of the performance potential that carbs will.

Read the thread I posted.

ianc

[MotoSook]

[ianc]

Or, there is the best of both worlds, as Souk demonstrates.

ianc

[}{arlequin]

seems like as good a place as any to post this question:

you guys that have done the cis--> carbs conversion, what kind of cooler are you running and is it as effective as you'd like?

thanks.