Advice on 2.7 Carrera MFI build
 

Hi,

Im looking at a rebuild of my 2.7 Carrera and wanted to find out what the common sense knowledge of the board is saying about rebuilds on these motors.

Ive read through some of the threads here like this one http://forums.pelicanparts.com/911-engine-rebuilding-forum/469282-2-7-mfi-how-far-go.html but most of the threads seem to have different parts (E cams, SS setups etc).

I am interested to find out how far away from stock I would need to go to get close to 250hp with 2.7 single plug (no interest in bigger capacity or twin plug because of historic racing regs, which this car needs to remain eligible for). This car is a 90% road car so it needs to be tractable and run on 98RON pump gas.

Because of the nature of the car, Im thinking about the market and potential future owners so I dont want this car to drive like a hot rod (a factory hot rod is ok!). Also, this build is to be done on the matching numbers case so I cant do anything irreversible.

The motor has all standard 2.7RS kit - 8.5:1, S Cams, 019 pump etc.

Advice most welcome on what spec would be best given the above?

You might be closer than you think already ... the RS was rated at 210 DIN hp, which is more like 230 SAE hp (the more common rating system used today). If you put on some headers and free flowing exhaust you could bump it up a bit. Re: internal mods, increasing compression would be one way to get more power pretty easily since the RS has a low stock compression ratio. Between those things I'd think you could get 250 hp.

Scott

If your engine is still ok and doesn't need a rebuild you might spend alot of money for not much return. The only correct way of bumping the compression up is a set of new pistons but I don't think the correct Mahle's are available anymore. You could try JE pistons . You can run single plug up to about 9.8. If you don't have SSI headers on your car now they are a good improvement and with a sport exhaust should come very close to what you are looking for.

Increase compression to 9.8. Use more modern cam profile, GE-60 or GE-80. Racing valve springs/retainers. Race exhaust (Georges Euro headers) with megaphones. Dyno engine to optimize ignition and fuel settings. I'd bet you could get close to 250 reving to 7500 RPM.

-Andy

Careful changing camshaft profiles if you're keeping the MFI -- you'll probably need to have the MFI pump recalibrated. Also, GE80s would be very aggressive if you plan to ever drive the car on the street. I have them in my 2.7L track car, and can't imagine having the drive that thing to the grocery store. If you just bump compression and do headers/exhaust, you probably won't need to recalibrate the MFI pump.

Scott

Thanks for the responses. The car is going to be rebuilt due to a top end issue. I put 250hp down because I thought that was reasonable for a mostly road car. More is good as long as its drivable (that is has plenty of low-mid torque and isnt ropey).

Im assuming that going to 9.8:1 I can still use pump gas? The OE heat exchangers will need to be replaced with SSIs but I wasnt expecting any more hp from that. I do want heat in the car so thats the only option there. I thought the early HE design was pretty efficient anyway? It will get a new custom 2 out exhaust.

Valve springs/retainers I can understand. Is there any advantage to going to bigger valves in stainless or titanium? What about porting?

GE80 would be too aggressive for this application from what Ive read. What would GE60 give me over S cams and would the space cam need to be changed or just the pump re-calibrated? I obviously want to use anything I can thats existing but fit for the application.

The mechanic told me they dyno'd a 2.7 single plug race car at 303hp the other day. No idea whats in the motor, secret stuff.

I have been told that the two gun 74/75 2.7 currentluy running in Grp SC in Aus are only getting 270hp.
250hp should be pretty easy with GE 60 best described as a modern day 2.7RS cam. Raise the compression to 9.8 and make sure you use ligtweight components in the valve train and should get you your desired result.

Michael

Limey had to use a Supertec pump cam on his to get 230bhp even with a proper Bob Watson build and decent balance/blueprint/flow job, but fairly stock pistons and cams as I recall. That was using SSIs but stockish muffler. 250 is going to call for some new bits for sure.

Got to be honest, I didn't think the 230 bhp was that hot versus my Carrera 3.0 with the shorter final drive. Nigel loved it though, had nothing but praise for it.

You could mix a fairly simple but polished rebuild and a regear - maybe.

Thats what I thought too. Sounds to me like the bar has risen quite a lot since then but it seems to me thats across the spectrum in Sc. I certainly wouldnt doubt the claim knowing those guys and the $ Im sure has been spent. Unlimited budget certainly helps!

Hey JG. Thats interesting on the pump cam. I would have thought the RS space cam would have been ok for 230hp. Perhaps not. RSR profile should be good for up to 300 or thereabouts so maybe thats the way to go.

Not surprised that there wasnt a major difference to the 3.0. 20hp isnt alot but I think 40 would be really noticeable from the seat. Being a road car too I really want it in the mid range but this might be asking a lot, I dont know.

The argument Im having with myself is how far to go away from stock with this car, given what it is. Im thinking its probably going to be quick enough for the purpose without re gearing the 7.31 which is fairly short anyway. Have to try to stay away from comparing it to the turbo which feels miles quicker from the seat.

John, i struggle when i hear people say the pumps need to be modified beyond 2.7 RS specs. My 3.2ss on MFI with stock 019 pump made 298hp . that was single plug the AF was causing a bit of issues as it was starting to run lean up high.

In view of the above i reckon that a 2.7 should make the 240 250hp fairly easy

my 2 cents

Michael

Sorry guys, I have expressed myself badly and confused the issue.

Limey used a Henry cam with a smoothed out engine and got 230bhp. I don't mean he was forced to modify the pump or that it was as much power as he could have got.

I don't have enough details easily to hand to say quite what else he did, but I know he was running in a pretty stock engine class in his sprinting, so that probably dictated what he was doing.

It is really interesting that it feels that much slower from the seat. I think they feel livelier than 930s on back roads on a good day, especially if you are comfortable with sliding the rear (not me, obviously). But I love them both.

It's late here and I have had an exciting but exhausting day (new 911) so I must be suffering from brain fade. I *DO* actually have the info, from a piece I wrote a few years back:

Participation in the 2006 Curborough Sprint Championship also brought rewards. Following a very competitive season, Limey eventually won the championship outright. The win earned the Carrera further specialist attention, this time at the hands of Bob Watson. Bob is well regarded amongst the 911 cognoscenti, particularly for his in-house chassis dyno and excellent results on tuning MFI-equipped cars. Wrapped up for the winter in Watson’s workshop, Limey’s engine was removed for rebuilding.

A knock from cold was traced to the intermediate gear, so a lighter (drilled) steel unit from a 993 replaced the worn aluminium original. The motor was balanced and blueprinted, with a flowed crankcase, matched combustion chamber capacities and the heads ported, polished and matched to the manifolds. Once reinstalled, the engine was run-in on the dyno and tuning began. MFI pump condition is critical to horsepower, and Limey’s pump turned out to be a cracker. With tweaked fuel rates and ignition timing, the refreshed powerplant produced an excellent 237bhp.


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