Longer 2nd is a track driving benefit like mentioned. For street use most might find the long 2nd a bother. The upshift from 1st to 2nd in non-spirited driving (like lets say you get caught in slow traffic or crawling thru a parking lot or the like) can cause the engine to really bog down. When I upshift from 1st to 2nd at moderate rpms w/my long 2nd, the car "falls on its face" .

The 1.6__ 2nd gear is actually easier on the trans since its torque multiplication is less than the stock 1.833 2nd, or the 1.778 used in the 84-86 USA/Japan trans. I have a 1.684 2nd gear in my 915 racecar (effective ratio being 6.523 : 1 taking into account stock 8:31 ring & pinion) and i'm very happy with it. It allows for a much more usable 2nd gear with a mildly modified 3.0L engine (redline of 7200). I'm a bit biased about 2nd gear usage because I previously drove a G50 which has a much less useful 2.059 2nd (effective ratio = 7.061 with slower G50 9:31 R&P) and quite often I would run out of rpms in 2nd.

3rd takes the most abuse on the track (typically gets the most use of all gears) and is the weakest gear in the 915. So its worth consideration for replacement as long as you're in there. The dog teeth tend to pull off (this is due to having been replaced before = reduced press fit, and also from people who shift before the clutch has fully disengaged engine power) and the actual gear teeth strip off (higher powered cars + gear age) the fixed gear on the pinion shaft.

I would consider the WebCam 20/21 or Elgin's version (Super SC?) or Dougherty's version (DC19) of this cam. These profiles were specifically designed for the SC/Carrera cam upgrade (SC & Carrera have same cam profile by the way...) vs. the 964 being a "simpler" substitute that coincidentally is a nice upgrade to the original cam.

The original heat exchangers perform quite well on the whole, despite not being equal length. Might have something to do with its layout incorporating a merge/crossover effect vs. the SSI or other headers having separate secondary piping until the merge at the dual inlet muffler. A premuffler with a sport muffler makes for a nice & simple installation that performs well.

For pure HP gains the headers are better. But the stock exhaust seems to perform better throughout the entire RPM range, despite its design/layout being compromised in order to incorporate the cat. converter.

I'm currently helping MAF a engine build much like yours. With Max Moritz pistons at 10.0:1 comp.
You may want to follow along in this thread before you decide what to use in your 3.4
http://forums.pelicanparts.com/porsche-911-technical-forum/851912-my-87-3-4-maf-project.html

He's also using SSIs with 2in1out

My personal engine is a 87 Euro 3.2L with following mods:
- Web Cam 20/21
- Extrude Honed, flowed and polished intake
- SSIs with M&K 2in2out (very loud!)
- Light flywheel
- My custom S-CAR MAF that I developed.

Pushing about 235HP at the wheels at sea level.

Torque is all in at 5000RPMs and stays flat right up to 6000RPMs with this setup.

KTL- doughrery will be doing my cams so i will chat with bim about the profile you mentioned. Thanks

Scar, i am following that thread intently. What dyno are you using for your hp results? They numbers are looking strong, although i realize dyno numbers are hard to transfer to other cars on other dynos.

The dyno is a Land and Sea and I think the SAE conversion is a tad over optimistic. What matters most is the before and after numbers. We are waiting for the shop to finish installing and calibrating the MAF then back to the dyno, hopefully within a week.

I have an engine much like you are considering, and similar to Sal's.
It has:
Autothority MAF
Bored throttle body,
Extrude Honed manifold
Refurbed injectors (sent to Witchhunter)
Mahle 3.4 litre 9.8:1 P/C set
Balanced stock rods
ARP rod bolts
New valves and springs
Web Cam 20/21 cams
SSI's
Dansk 2-in 2-out muffler
Sachs aluminum Power Clutch kit
Custom tuned Steve Wong chip for 93 octane
New flywheel sensors, CHT sensor, O2 sensor, fuel pressure regulator and damper - only 'cause they were old
Plus all the usual stuff - bearings, seals, chains, ramps, valve job, etc.

CR is slightly lower at 9:1 measured with oil because we wanted a bigger margin for head clearance. Dyno is 230hp at 6100rpm dropping to 192 at 6800, at the wheels. Peak torque is 220 at about 4700.
Steve Wong feels the SSI is a restriction, but I need heat and that's what I have. He expects that the stock exhaust configuration would gain me up to 10 more hp, but I'm not inclined to swap it out (yet).
The Extrude Hone people said the manifold would flow more equally across the runners. The point as I understand it was not to increase the runner size, but smooth it out and improve and equalize the flow. I don't have any independent data on that.
The exhaust sound is louder than stock, but not that bad, and it passes Calabogie and Tremblant sound tests.
I'm quite happy with the engine and don't think I would do it differently if starting over. Perhaps a better exhaust solution. It runs out of breath at 6100 where power and torque start to drop.
I had an intermittent high rpm misfire that eventually turned out to be a loose pin in the 4-pin connector by the firewall.

Have fun with yours.

Mike

Those are good numbers. That is over 270 at the fly. Mind you, you are running 93 and intake mods. I am looking at my throttle body now and wondering if it is the choke point on the intake.

My rebuilder convinced me to stay with ssi's. I loose dyno bragging rights, but our track is more about agility and getting out of the curves. Torque and midrange are quite useful. A dansk sport 2:2 with a cap for street is helpful and on my menu.

No need for a cap with the Dansk Sport 2:2, its fine.

My previous one (still have it) M&K 2:2 could have use one but I never installed one. Boy that sound was great but I not sure I could have stand it in a coupe...

What would be real useful feature in the M&K 2in2out would be a vacuum actuated valve that closes off one outlet below 3200RPMs then opens it above 3200RPM. Some modern day sports cars have such valve on the exhaust.

Agreed, I don't use a cap on my Dansk 2:2. No need.

I did buy an electrical valve but never installed it.

I guess my original plan shifts a bit. My car actually has 7:31 ring and pinion (4.43 vs stock 3.38). Thus, being a close ratio diff, I would make better use of top end power... And negate some of the midrange benefits of the SSI's.

I thought i had my mind made uo to keep the ssi's, but this changes my pros/cons thoughts a bit.

Was there ever an outcome to this thread/build?

Erik

One of the best 3.4 single plug builds I've worked on, final results here:
https://forums.pelicanparts.com/porsche-911-technical-forum/962997-1984-911-3-4-sleeper-hotrod-end.html

I am not sure how I missed this one. Great info. Thank you!


Erik