gringo

I've been reading "how to rebuild and modify Porsche 911 engines", by Wayne Dempsey. I love the idea of building a 2.7RS Spec High Compression motor(9.8:1) With RS pistons and a 70.4mm crank it looks like this motor is good for about 220 horse and about 265ft/lbs of torque. Any speculation on how this would run with an E-cam? I worry about an S-cam for around town driving and weekends when the wife is cruising to Starbucks. Would a 915 transmission tolerate this much power?

altonj

The 915 can handle 300hp if you want, lots of folks are running 3.6's with 915's with the 8:31 r/p. I love Wayne's torque figures! That one is high by about 60lb/ft or so............... The S cam in a 2.7 will not be as "peaky" as in a 2.4. I would suggest you contact John at DRcamshafts and get his opinion. www.drcamshafts.com

Cheers

JCP911S

Just a datapoint.... my 2.2S had plenty of torque to drive around town with... the S cam gets the rep for being "peaky" mostly becasue it comes on so strong at the top end.... but this does not mean it is wimpy down low.... for sure it's not a 3.2 or a small blockk V8... but part of the fun with these older hi-performance engines is the caminess of them.... a real hoot if you have a place to open them up...

Steve Weiner-Rennsport Systems

Gringo:

With all due respect to Wayne, those quoted power & torqque figures are too high,....

There were two different E cams; '69 E and '70-'73 E ones with the later versions being milder.

Both cams can work very nicely, but an S-cammed 2.7 with the right carburetor configuration is very torquey and still pulls strongly from 4000 to 7000. Its all about what you want,...........

915's can handle anywhere from 240 to 280 lbs-ft very reliably if they are set up & prepared right.

rstarga

I converted my 2.4s to 2.7 rs. Torque will not be a problem with the s cams. Mine is almost a stump puller. I don't know how you can get to 9.8 compression with a true rs conversion on this motor. The 2.2 had 9.8 but with your original heads you'd have to find some custom pistons to get to this compression.

GrantG

I concur that a highish compression 2.7RS with S cams has plenty of torque for city driving...

RoninLB

9.8:1 is very high for a street engine on street gas imo.

I wanted a streetable 2.7 engine w/as much torque as possible between 3.2-4.5k rpms in 4th gear to catch bait zooming past the legal drivers on the highways.

I've got great winter starting, great plug life, and was told by a stock 3.2 Carrera speed racer that my engine pulls better than his by a large margin.

Early E-cams, single plug, 8.5:1, and carbs.

911pcars

Seems like the magic number for torque is in the 3000-4000 rpm range. It's here that the milder E cam might have the edge over an S cam in a typical RS engine set up. The difference might be the compression ratio. Numbers above 9:1 (8.00-8.5:1 is the typical RS CR) should mitigate any void in torque in this rpm range, but if one stays with Mahles, those few add'l CR numbers will cost you.

Sherwood

r911

Ron - how do you get it started in the winter in NY?

RoninLB

I usually have to whack the throttle about 5x above 40F.

Below 32F may need a series of additional 5x whacks if it doesn't fire right up. Then I have to be careful of not flooding it after it fires up by quickly whacking it. Kinda like letting it come on at a low idle for a few seconds.

In the early days I was scared of flooding it but so far I never have.

My initial advance is 10deg which doesn't help cold starting.

Getting the plugs clean from initial starting carbon is important imo. I need about 10mi on the highway. And I run BPR5ES. Any colder plug never seems to clean up.

JCP911S

I used to have a bitch of a problem with plug fouling on my 2.2 S in sub-30 degree weather.... had the MFI... perhaps it was off adjustment, but even with hotter plugs, buy the time it warmed up, the plugs were so fouled, I couldn't clean them off with an Italian tune up...

For track, I;d get it warmed up and then switch plugs with the engine hot (ouch)....

Steve Weiner-Rennsport Systems

Ron's choice of camshaft is an excellent one,.......

There are two "E" cams: the early ones that are the same as the Solex grind & the milder versions found in the '70 and later E engines.

For those folks who are uncomfortable with any loss of low-end power, the Solex (early E) cams are superb.


One last comment,....MSD ignitions basically eliminate any plug fouling with carbureted or MFI'ed engines,.... Its a far cry from the OEM Bosch stuff.