What size carbs for a 2.7L?

[Porsche-O-Phile]

With SC grind cams? 40mm? 46mm? 50mm?

Just curious. No reason.

[911pcars]

40.

Sherwood

[Fishcop]

Yep, 40mm carbs with 32mm venturis

[Evans, Marv]

Maybe 34mm venturis ??

[Hotrod911T]

I have a 2.7 with Euro RS p/c's and S+ cams, running 46 PMO's with 36 mm venturiis. When I built the engine I thought 40's would be the correct size. I sent the engine and cam specs to PMO, told them it was for high performance street and autocrossing. PMO recommended the 46's and sent me the carbs set up for my engine specs. Other than initial tuning, the carbs have worked perfectly with no jetting or other changes needed. No flat spots, gobs of torque and revs easily to 7,500 rpm.

Rod

[Porsche-O-Phile]

Have you used Webers in the past? Considering the possibility of going to some Webers (far cheaper than PMOs)

[JohnJL]

I am having adventures with a set of 40IDA3Cs.

I've had it running on 34 venturi, 60 Idles, 145 mains and 180 air jets. I am now about to try 34 venturi, 57 idles, 135 mains and 180 air jets.

[Hotrod911T]

Jeff,

I've used 40 IDS Webers on 2.0 S and 2.2 S engines, but not on a 2.7. I know the cost is higher for PMO's, but there is no substitute for them, which based on my experience are much better than the Webers. I sold my used Webers for $1,800 and bought the new PMO's because of the improved fuel circuits, ease in tuning, ball bearing throttle shafts and they idle steady, have better throttle response and make more power. I had the Webers for 30 years, but face it, they don't make them anymore and most of them are pretty worn by now. By the time you buy a good pair of Weber's, have the throttle shafts replaced, get the new venturiis, jets, emulsion tubes, etc., necessary to make them get good power on your 2.7, you won't have a cheap pair of Webers either. Then, there will probably be a time when you wish you had gone ahead and got the PMO's anyway. One downside is that with 46's (and maybe even the 40's), you will need to get a pair of the PMO taller intake manifolds and the K&N watershield air cleaners. The factory Weber throttle linkage will work with the PMO's.

Rod

[Porsche-O-Phile]

Okay, I'll rethink this. One option is to keep the factory CIS for now, but there's something intoxicating about the notion of going to carbs. MUCH simpler, IMO. And the sound is awesome. A fresh set of PMOs (probably 50s with small jets for a 2.7) is no small matter though - around $3500. I just want to be sure I'll be getting something out of this (more reliability and more performance) other than just louder and cool sounding.

[Hotrod911T]

Jeff,

As you know, the CIS will work O.K. with what you have, but the carbs, either Webers or PMO's will give you the opportunity to upgrade your cams, exhaust, etc., in the future. It might be a good idea to shoot PMO a fax, tell them the specs of your engine (or what you want it to be) and have them give you the recommended sizes, jets and settings for both PMO's and Webers. You can get some of that on PMO's website. It can be real frustrating if the carbs are not setup correctly for the engine in the first place.

The real justification for going to carbs on a 2.7 is if you are going to mod the engine beyond the capabilities of the CIS, like put in early 911S cams. For strictly a street-driven daily driver, you want to be careful not to over-carb your engine. It sounds like you don't have any carb parts to start with, so you would also need a new fuel pump, fuel regulator, fuel lines, throttle linkage, intake manifolds and air cleaners and breather setup. But you are right, there is nothing better than the sound of screaming along with wide-open carbs, especially with the K&N air cleaners.

Rod

[Hotrod911T]

Jeff,

They also look pretty neat too.

[Porsche-O-Phile]

Day-um that pic is sexy.

Yes I already ordered (and have) SC-grind cams for the engine. I was planning on ripping into it in the near future and installing upgraded hydraulic tensioners (PO wasn't sure if the engine had them or not, so if it doesn't I'm changing over), front oil cooler (currently the car doesn't have one) and the cams. Probably carbs too. That should make for a nice upgrade package.

While the engine is out I'm doing some other stuff to the car (body, etc.) but that's the mechanical portion. I'll check with PMO. Might be worth the bucks from the sound of it, especially with the SC-grind cams, which I know will exceed the CIS limitations.

[dd74]

Hey Rod - nice engine. I have a 2.7 with 40IDA Webers and 10.8:1 compression. What advantage, in your opinion, will there be if I switch to 46s - Weber or PMO?

And have you ever considered EFI for your engine?

[Steve@Rennsport]

Originally Posted by Hotrod911T

Jeff,

I've used 40 IDS Webers on 2.0 S and 2.2 S engines, but not on a 2.7. I know the cost is higher for PMO's, but there is no substitute for them, which based on my experience are much better than the Webers. I sold my used Webers for $1,800 and bought the new PMO's because of the improved fuel circuits, ease in tuning, ball bearing throttle shafts and they idle steady, have better throttle response and make more power. I had the Webers for 30 years, but face it, they don't make them anymore and most of them are pretty worn by now. By the time you buy a good pair of Weber's, have the throttle shafts replaced, get the new venturiis, jets, emulsion tubes, etc., necessary to make them get good power on your 2.7, you won't have a cheap pair of Webers either. Then, there will probably be a time when you wish you had gone ahead and got the PMO's anyway. One downside is that with 46's (and maybe even the 40's), you will need to get a pair of the PMO taller intake manifolds and the K&N watershield air cleaners. The factory Weber throttle linkage will work with the PMO's.

Rod

Thats a true piece of wisdom,...

[Porsche-O-Phile]

I can just HEAR the money being sucked out of my wallet now. You guys are mean.



I'll just tell my wife it was peer pressure.

I'll call PMO soon.

[RWebb]

and that is exactly why Richard Parr re-designed his carb (PMO) - to fix every issue with the Webers (which were already one the most highly regarded carbs ever made)

the intoxication (unless you put in new heads/pistons not just cams) is from the induction sound -- nothing wrong with that -- people pay a fortune for wines, perfumes, shoes (see "wife" in dictionary) and fancy meals at hot restaurants... this is no different.

Nonetheless, start thinking about some trades if you run into trouble - often a kitchen remodel can be traded for allowing a car purchase or a motor hotrodding.

[dd74]

Originally Posted by RWebb

Nonetheless, start thinking about some trades if you run into trouble - often a kitchen remodel can be traded for allowing a car purchase or a motor hotrodding.

I'll write ad copy for parts.

[Porsche-O-Phile]

I wonder if the guys at PMO need their lobby redesigned. . .

[Hotrod911T]

dd74,

I sent you a PM in response to your questions.

Rod