lucroberts

I've been bugged and tempted to exchange my Euro CIS with larger intake runners for a new set of PMO's but I don't have too much idea of the extra HP and Torque benefit versus the Price and the smoothness of the current CIS. I use my car mainly for track but also drive it eventually on weekends. Any thoughts or experiences ?

TT Oversteer

I had a '78 SC with 46mm PMO's on it. The biggest benefit IMO is the immediate throttle response and the wonderful intake sound. To make it really work well you will have to get the cams reground, install a different distributor and SSI's with a sport muffler. Just bolting PMO's on an otherwise stock SC might not give you the improvement you're looking for. On the downside, you may have cold starting issues (maybe not in FL) and I was constantly fiddling with the adjustments on mine. With the above setup you should have a ballpark 225 to 250hp at the crank.

lucroberts

Thanks ! I already have reground 964 style WEB Cams done at the rebuilt and equal-lenght snake headers with no Heat Exchangers with a Dansk Sport Muffler. I also have Euro CIS with larger intake runners and I'm probably having 210 or 215 HP already . But as you well said, the HP pickup would be 25 to 35 horses and more torque only. And a lot of money invested with frequent tune ups on the carbs. The trade off is not worth. thanks !

Edward

Curiosity has bitten ...I hate this place
Sidenote question for those who have done PMOs:

What is a realistic HP gain for a stock but properly rebuilt (from main bearings up, orig p/c) 82SC engine? All she has in mods is a mild cam (was it the so-called "SC" cam ...IIRC from what I was told by the PO??) and SSIs with a sport 2 into 1; all else stock CIS etc. and runs great!

Is throttle response the only other plus? What about negatives (for a 95% track car)? FWIW, I used to have an Alfa Spider with Webers ...glorious sound and never had to futz with tuning once set.
Thanks!

Edward

Steve Weiner-Rennsport Systems

A few data points about this subject,.....

1) Properly installed and set up, PMO's (and Webers) do NOT require constant fiddling. I've installed hundreds of sets over the past 34 years and they are very reliable IF,........IF the installation is done right. Needless to say, all bets are off if someone does the work who takes shortcuts or doesn't pay close attention to details. I've had Webers on my own car that I've not needed to touch since 1979.

2) Carburetors are not for everyone and do require some mechanical "sense" learn how to start them from cold. Its certainly not brain surgery but its takes some feeling and understanding about how things work.

3) The difference in throttle response between the sluggish, single-throttle CIS induction and the 6-throttle carbs is staggering and that accounts for the biggest gain in performance. Further, the performance potential of a good carbureted induction is almost unlimited for a N/A engine.

4) 3.0 SC's with CIS will not make 215 HP without a LOT of modifications, some of which make pump gas impossible to use. Big power from CIS requires displacement increases, twin-ignition, cams, and exhaust, none of which are cheap to do.


JMHO,....certainly,...

Edward

Ha ..."JMHO" from Steve W. is quite the understatement! Thanks, Steve, as always your experience in these matters is priceless and most appreciated!

That certainly puts things in perspective. I loved the Webers in my Alfa Spider and yes, they never needed adjustment as that was my DD and occasional track appliance. Just great (and still sorry I sold her!).

I am not looking to do PMOs since my CIS is working great and completely seamless/trouble free. But if that badboy ever hints at an expensive repair, I may just bite the bullet and go carbs since I'm cat-less and have SSIs anyway. So it seems like the real perk is not so much a HP gain (as that will be a mild bump if I read you right) as much as much better throttle response and later HP-potential. No "negatives" to speak of is nice ...except the cost.

Edward

earlyapex

I have a 78SC with 46mm PMO's sourced from Steve Weiner. The car has stock cams and pistons. The exhaust runs through European racing headers and Phase 9 mufflers from Smart Racing Products. It put out 240 hp using 91 octane gas on the engine dyno at Jerry Woods Enterprises last month. The throttle response is amazing. I use about about 5 gallons of gas per 20 minute track session.

Steve Weiner-Rennsport Systems

You'd get better mileage if you didn't have such a heavy right foot,....

earlyapex

I'm working on getting poorer gas milage!

whalebird

+1 steve. I really like the carb option. Now I have seen CIS motors in the 245HP range. They also cost north of 24000$$.
The carb set up allows latitude in certain components that most injections don't including CIS and Motronic. Mainly cams. The 964 grind is a really nice cam designed to work well with injection. The biggest restriction on cam for injection applications is the lack of overlap. If you have carbs, you can opt for a more aggressive cam that will allow some overlap like the S and E cams which would really take advantage of the carbs. Dare I say 906 cams.
In addition, If you want maximise the carbs effectivness and you were in the motor, You really should look at the Mahle pistons and cylinders. Injection cars (SC, Carrera) have had differend piston crowns intended for injection. There are options for carbs.
Have your Euro heads gone thru by any of the reputable garages(Andial), 3.2 high compression pistons, PMOs, and early E, or S cams and seriously hold on. You will be in 911 heaven.
of course there are many options and talk with everybody.
Steve knows his stuff.
Franz Blam is haunting these threads more and more.
great project keep us posted.

lucroberts

Thanks for all the info, guys. Now I have things more into perspective as Edward said. I'll let you know if I go forward with this project.

Edward

Hi Eric,

That is very good to know, thanks! That you are getting that kind of performance on a largely stock engine with pump gas is phenomenal ...I had no idea it was that dramatic. Something to look forward toward ...if one can "look forward" to CIS dying so I can upgrade to PMO$

Edward

earlyapex

Ed, keep putting the pennies away. Carb's are the way to go unless you want to start talking about ITB's!

Steve Weiner-Rennsport Systems

What he said,....

ITB's and good Engine Management is a LOT more expensive.

Steve Weiner-Rennsport Systems

LOL,..I have too, but those were much bigger than 3 litres,...