Max power from 2.7L w/ carbs and MSD ignition

[todor]

Hi, I'm about to buy a '76 911S that has been converted to carburetors (Webers) and has aftermarket MSD ignition (no idea what type, but it has an MSD coil and an MSD box on the side). With the best tune possible, what kind of power can I expect from this engine if everything is in good shape? The stock engine is rated at 165hp, but presumably the original FI system was tuned for low emissions and robbed the engine of its potential power. The car is now emissions-testing-exempt due to age. What kind of power can I hope for with proper tuning? I know no one can know exact numbers just from what I've said here, but I need some ballpark figures... for example, is it feasible to hope for something in the vicinity of 200hp at the crank? I know my question sounds retarded and clueless, but I'm just looking for a rough guesstimate. Thanks.

[RWebb]

yes

it will cost you tho

you need new pistons and more aggressive cams - some work on the ports; a higher rpm valvetrain (since you'll need to spin the motor faster so it can pump more air), and you should raise the compression and twin-plug the heads

[todor]

Originally Posted by RWebb

yes

it will cost you tho

you need new pistons and more aggressive cams - some work on the ports; a higher rpm valvetrain (since you'll need to spin the motor faster so it can pump more air), and you should raise the compression and twin-plug the heads

Wow... that sounds like a pretty major overhaul/upgrade. What I was asking really was how much power I can expect without ANY further upgrades, just a good tune of the fuel and timing.

[RWebb]

if you have the original CIS pistons & cam, and good header type heat exchangers like SSI, and properly set up Webers, then you should get at least 170 hp, maybe 175 hp

[todor]

Ok, thanks, that's the kind of info I was looking for.

Other than the tuning, what else changed from the previous-generation engines? Because the 2.2L and 2.4L engines were making the same or higher power than the '76 2.7L, but with considerably lower displacement... did they have more aggressive cams? Higher compression? Why is it that they can get that much power, but the 2.7L can't, even with custom tuning and carburetors?

[James Brown]

You can get 300+ hp out of one, just bring you good check book. That engine was designed with the new pollution control laws so out with the big cams, the higher compression pistons, smaller intake ports, leaner timing, ect. Engineers really do engineering. Changing everything to achieve the pollution standards. Hard to undo without a full rebuild. Or a 3.2 could fix your need for speed!!

[RWebb]

big change is CIS, which uses ultra-mild cams, special pistons, etc.

you will want to read the 911 book by Frere and the engine book by Tobias Aichele

Bruce Anderson & later Wayne have shorter more specific books out in pb with info on engines

you might also want a more general reference on sports car engines & how to make power - there are lists of book on here -- try a search for books + porsche and look for some prev. posts by me for more info than you want...

[al lkosmal]

I with Randy on this.....maybe 180 crank HP max. with this combo....but it is a sweet and responsive engine with the carbs....so the butt dyno will say more. I built a 2.7 with 9.5:1 JE pistons, E-cams, SSI's, Webers, Dansk sport muffler. It was agreat engine....according to Bruce Anderson's book, good for 220HP or so. Now, I'm going EFI with ITB's on my friends engine.......we'll probably try that one out on the dyno to tune and see what's up.

So you have many options....add Webers and SSI's to your stock 2.7 and drive it around for awhile...you'll like it....save up for high compression pistons, some e-cams, etc and over the winter you can make it a little wilder.

Regards,

Al

PS: the 2.7 is one of my favorite engines, but the 3.2 does push these around with a bit of authority.

[RWebb]

search on carbs + 2.7 to find some info

carbs FEEL great - all by themelves; but as Al noted, the actual power increase in small

best thing for low $$ is to install SSI's & of course, be sure it is all jetted correctly & etc. - I had that setup on a '75 and it was lots of fun

but, not as much fun as... Yet Another Boring Hot Rod Rgruppe Car - Part III, Powertrain

[RWebb]

if you are willing to throw down more than a single 10,000 dollar bill, you can have even MORE fun

[Walter_Middie]

Was it the red one? I see it's not listed anymore - you must have bought it. Looked like a fun project.

[todor]

Wow, lots of people from the Seattle area here
Yes, it was the red one, I just bought it today. I think it was a good deal, but it'll need a bunch of mechanical and cosmetic work, and it has had major body damage in the past... but it looks and drives fine and should be a fun summer car. It has a huge oil leak from the area where the engine meets the transmission... I hope it's not a main seal.

I'm not really planning any internal engine work. Most likely, I'll just leave it as is - it already has the carbs and the MSD ignition. Stock exhaust system, as far as I can tell.

I've always wanted to use Megasquirt on something, but that's a more major project than I'd want to take up, at least for now. I definitely want to DRIVE it for the summer.

[silver911rdb]

As others have stated earlier, SSI headers/heat exchangers with a 2 in/2 out muffler would be my first upgrade if it were my car. Your car (if it's still original) has the restrictive heat exchangers with the single in/single out muffler. Backdating to the 1974 system will probably give you the most bang for the buck. As time goes on you may want to upgrade to carrera rs pistons & cylinders and hotter cams. You already have the weber carbs so you're part of the way there already.

[silver911rdb]

You might want to check the oil seals between the oil cooler and engine case. Pretty common to see those leaking especially on an older 911.

[Walt Fricke]

+1 on getting rid of the stock exhaust and going to a 3 into 1 system like the '74 and earlier or the SSIs. You can modify your stock muffler to accept another inlet to save some $. That's about it for bolt-on HP. You might pick up a bit more with EFI, along with more tuneability.

More requires more.

To give you a reference point, my track 2.7 has Mahle 10.3/1 pistons, twin plugged, Weber 46s running through 38mm ports, and a big cam, and the relatively low buck Bursch headers with megaphones. Uses pump premium, partly because the actual CR is well below the nominal. I think this would work OK on the street (very tractable on the track), though it has never been there. Dynoed at 222 rear wheel HP at 7,100 rpm, which is in the vicinity of 250 flywheel HP depending on how wet your finger is when you stick it up in that wind. With the tranny it had, upshifts came at 7,600. No idea of mileage - uses less than 15 gallons per hour on the track. I was hoping to see something like 270 - 290 adjusted flywheel HP, as factory race motors tended to put out 110 DIN hp per liter. Showed me there were things the factory did on their race motors that a mere assembler of parts like me couldn't match. Maybe a really big cam with HP peak at 8,000 would have gotten it there. That's not very practical for the street, though.

Walt

Walt

[todor]

Thanks for the info guys. How much would a used set of 74 heat exchangers and mufflers go for? Is it only the 74s that fit, or are there other years as well (with the desirable configuration)?

[Walt Fricke]

My understanding is that the '74 design goes way back. When I updated my 2.7 to a 3.0 I kept the '74s which came with my (well used and somewhat modified ) ''77 2.7.

The 1966 S had 35mm exhaust ports, same as the 2.7s. My '72-3 parts catalog shows only one exhaust, even though it covers the T, E, and S, with their different port sizes.

[RWebb]

can you afford the SSIs? they are stainless

[todor]

I just checked the price on the SSIs... over $1k, so no, I wouldn't want to spend that much. I've gotta be able to find some cheap pre-75 ones, right?

Btw, here's what I have right now. Is this stock for a 76?

[todor]

Searching by the part number on the muffler shows that it's stock for 75-76 cars.