I want to buy carbs but I'm clueless

xjoegtix · 06-08-2014, 09:28 AM

Hey guys I've got a 1980 911sc euro and the cis is giving me such a hassle that I'm giving up on it. I want to buy carbs but I have no clue where to start. I'd love to buy a used set that works but I don't know what to look for. Any ideas?

Jack Stands · Jack Stands's Garage

Unless you are changing cams and other internals, you might be disappointed in the performance after the change. The CIS system is really pretty simple, and keeping clean fuel running through it is probably the best thing you can doth keep it running.

What problems have you had with the CIS system? Are you sure that your ignition system is working properly?

BTW, the old saying that most carb problems are actually ignition problems is probably as true for the CIS system as well.

mreid · 06-08-2014, 09:56 AM

PMO 46 with the proper set up and you will be good to go.

gamin · 06-08-2014, 10:27 AM

Have PMO carbs on my 70 and I am very pleased with them. Richard Parr at PMO is great to deal with. Great customer service. Richard can give you all the tips for set up if you go the PMO route. If I am not mistaken, Richard is also expert on weber carbs in case you do webers. I really like carbs. They make glorious intake sounds.

James Brown · James Brown's Garage

bling factor high, sound factor off the chart, cost high (compared to repairing the CIS to factory), fuel milage poor, "perceived" performance outstanding, sliding off the slope high.
And, constant tweaking of the carbs necessary to maintain balance/AFR. BUT all said and done, i would do it, the CIS cams do work well with carbs but there is better choices, a good exhaust system helps also and re-curving the dissy will wake up the engine.

juanbenae · juanbenae's Garage

Quote:

Originally Posted by Jack Stands

Unless you are changing cams and other internals, you might be disappointed in the performance after the change.

not likely ^^^^^^

the spec 911 rules for 3.0L motor allow up to 46mm carbs and some of the cars with that set up are getting 235hp at the wheels. this is with CIS cams & euro pistons, limited head work (the larger 78-79 heads are desired) running on 91 octane pump gas. my car freshly rebuilt did 254hp at the crank during the break in & tuning dyno session two years ago.

will the car be road or track driven more? if predominantly a road going car I would suggest a 40mm set up, if track or very spirited driving is the intent the 46's might be more enjoyable. there are many threads on this, but will require a recurved distributer (is this the case on a euro model?), fuel delivery mods (which there is a thread on page one now discussing the very topic) & gaskets. headers and a freer flowing exhaust will help too.

the new found power and sucking sound will not suck in the least.

xjoegtix · 06-08-2014, 11:32 AM

It'll be my fun on the weekend car so I'd most likely do 40s as said before. The problems I'm having with the cis is on going and hasn't been the greatest fun. Got the car with no spart not running. New CDI box made it have spark put a new Bosch fuel pump in and fuel filter and I'm getting fuel but my gauge says I'm only getting 30psi. I tested to see if I get 1 liter of fuel in 30 seconds from the pump and I do but the test I ran from the wur to the cis model only says 2 bar. I'm just tires of dumping money into it.

Joe Bob · Joe Bob's Garage

PMO.....end.....

RichardNew · RichardNew's Garage

Someone took the CIS off my '73 and installed Webers. I'm not sure that was the best move.You just need to find someone who can handle the CIS.

My car is worth less because of the Webers. People will pay for original. They won't pay for Webers. Take that into consideration.

Richard Newton
Historic Racing Images

Joe Bob · Joe Bob's Garage

Lots of CIS systems out there. A competent wrench can re-install with a MY specific system.

Carbs alone are a waste of time unless you upgrade cams and timing.

mreid · 06-08-2014, 01:37 PM

How about these:

PMO 46mm carb kit

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by xjoegtix

Hey guys I've got a 1980 911sc euro and the cis is giving me such a hassle that I'm giving up on it. I want to buy carbs but I have no clue where to start. I'd love to buy a used set that works but I don't know what to look for. Any ideas?

What problems are you having that you could not make your CIS engine run like a top? Who is working on you car? Want to try one last time? Decide and PM if you want to stay with CIS. It is simple and easy to maintain a CIS engine once you understand how the system works. Stay away from guess-work troubleshooting and you'll have a well running car very soon!!!!!

Tony

juanbenae · juanbenae's Garage

Quote:

Originally Posted by RichardNew

Someone took the CIS off my '73 and installed Webers. I'm not sure that was the best move.You just need to find someone who can handle the CIS.

My car is worth less because of the Webers. People will pay for original. They won't pay for Webers. Take that into consideration.

Richard Newton
Historic Racing Images

worthless? are looking to sell? with a price like that I am very interested...

if yir considering what the next owner of your car might desire it's really not your car, yir just borrowing it. the OP does not note mileage, condition or the like of his SC so I had not considered originality. also does not mention location & if smog testing or inspections are an issue... a 73 is not 80's SC either, im sure a well preserved long hood is a thing of beauty and would make any impact bumper guy droooooolll....

if originality is important, well then find the issue with the CIS and go that route. if clearing your motor compartment of a shoots and ladders game for two rows of art, then you've got the right idea..