2.0 -> 2.5 Ss?

[jluetjen]

Sigmund;
The best porting will depend on the cam that you're going to run. What cam did you settle on? This will be a street engine -- correct?

[SigmundF]

Hi, yes this would be a street car. I checked with John Dougherty and he recommended DC 40 cams, so I think I will go with that.

[kenikh]

DC40s would be awesome, but you will NEED the bigger ports. My feeling is that 35s might be a little small, regardless. I'd prefer 36 or even 37 if you want it to breathe on top. The DC40 makes great grunt but still makes mad power on top if you give it air. 7500RPM is happy time for those cams. BTW, using 2.2 rods is unnecessary; just ask Henry Schmidt. If you are using the 35 ports, I'd go with another cam, John Dougherty's Super-E or Mod-Solex cams. These are GREAT street cams.

Have you found P/Cs? I have a good set of 90mm JE pistons and Nikasil cylinders I am not using.

[356RS]

If you are going to use an S cam or bigger, the 35mm port heads will work better.
Did you decide on what cam you are going to use? GE-40, GE-60, GE-80?
If your car will be used on the street and some track time, I would go with the GE-60's.
Glad to see you back on the project.

[SigmundF]

I plan to use DC-40 cams, as suggested by John Dougherty. Would the 35 mm ports be big enough or should I increase the ports? If so, do I need to do both intake and exhaust?

I have a set of Mahle Nikasil 90mm cylinders I will use, but I need to get new pistons, since I am using the 66 mm crank and aiming for CR around 9.8, I plan to buy a set with JE pistons to get the desired CR.

[356RS]

On the ports; I agree with Kenik, 36 maybe 37 on intake and keep the exhaust at 35mm. I'm running GE-60's on my short stroke with 38mm intakes & MFI with twin plugs and 10.8 comp. I like the idea of the GE-40 for better low end power. Have you though about twin plugs?

[jluetjen]

Personally I'd be a little more conservative. While a 2.7 with 36 mm ports is somewhat port constrained, a 2.5 at 7000 RPM (my estimate for your peak HP engine speed) is drawing about 101 meters/second intake velocity, which is comparable to most T engines at their peak HP engine speed. Keeping your intake velocity up will help with part throttle driveability. This shows up in the peak torque engine speed (est. 5000 RPM) intake velocity of 74.2 m/s, which is also comparable to most T's at their peak torque engine speed, which was usually about 4000-4200 RPM.

If you open the ports out to 36 mm, you might pick up some HP at the very top of the rev range, around 7000 RPM since your intake velocity at 7000 RPM will drop to 96 m/s, which is a comparable peak HP intake velocity to the factory's E's. In the case of your peak torque intake velocity, this will drop to 70 m/s, which is right in between that of the 70 and 72 E's.

So 35 or 36 mm intake ports should both work. I'd use the 36's if I were racing the car, 35's if I were going to be spending time on the street with it since chances are you'll be spending most of the engine's hours at 4000 RPM or less. This is where the extra intake velocity will help the driveability. Either way, you'll still have a really fun motor which will rev willingly to 7000 RPM.

The other thing to consider is what sort of induction system you'll be using -- MFI or carbs? If you're going with MFI, it tends to be fairly forgiving of a low intake velocity. Carbs on the other hand might start to get reversion issues even from the somewhat moderate overlap of the DC40s (I estimate about 48 degrees, or comparable to a solex, but with faster opening and closing speeds then a solex). If you're going to be running Weber 40's, what sort of venturi's will be you be running? Having 37 mm intake parts with 36 mm venturi's in the carbs will not get you the peak HP that the 37 mm intake ports are capable of, but you'll also loose a little at low rev's as the mixture slows down after it passes the venturi into the larger diameter ports. If you go with larger carb venturi then 36 mm, you'll definitely be giving away some part throttle driveability as the large venturi will give a weak signal at part throttle.

That's my $0.02.

[356RS]

Your right John. It's funny how most of us go for the biggest ports for the very top end power gain, but you gotta love that sweet sound of power @ 7000 - 8000 rpm.

[SigmundF]

Since this is engine will be mostly street and some track, based on John's excellent explanation, I think I will stick with the 35 mm ports.

I have considered twin plugs, but I think that has to another project, looking at my budget Therefore I will go with single plugs and a CR around 9.5 - 9.8.

When it comes to the induction system, I have a set of Weber 40's, I am not sure of the venturis, that I plan to use. What size venturi would be the best with the 35 mm ports and DC 40 cams?

[SigmundF]

I took a look at the Weber I have, that came of the 2.0 L. As far as I understand the standard venturi on the 2.0 L Weber's are 30 mm? What would be the best venturi size for the setup with 35 mm ports and DC-40 cams?
And where would I get new venturis?

[jluetjen]

I'd call Richard Parr at PMO (he doesn't do email). Tell him the configuration of your motor and he should be able to set you up with the right parts. Specifically, just replacing the venturi won't do it, you'll need the correct venturi, jets and especially the correct emulsion tubes to match your carbs. Otherwise you'll just wind up with some flaking driveability issues that will be a pain to troubleshoot.

[SigmundF]

Now it is time to pick-up this project again... There was so much else going on last winter, that the project was postponed.

I have 2 sets of cam housings, the original from the 2.0 l and one set from a 2.7 CIS (-75) that came with the heads I am going to use. The original has the "old" type of rocker arms and have only 6 bolts for the valve cover on the exhaust side. Any opinions on which cam housing and rocker arms to use?

[dan67]

hallo! and sorry for my bad english, i have the same problems:
heads 2.7 S 35mm ports
2.2 E crankshaft with countershaft
rods 2.2
use with MFI E 2.2 modified vs 2.7Rs/r

my problem are the P&C 90 or 92(rsr) mm ?
i search CR max 1:10.5

which pistons JE (code if possible) for this CR?
(the kits of QSC are good? only for info not for publicity)

this engine whit this configuration (MFI) accept which Cams? only "S" or others?
street/mid race use

THANKS danilo italy

[dan67]

"doubts Amleticous" for my project engine: 66x92mm "RSR"
for street/mid race
(i have now engine 2.2E-six 2.7S heads-1 case 7R)
the 2.7 S heads porting or not?
i have possibility of custom trottle body or slide valves all diameter (38?40?41.5?50?mm)
I LIKE Mfi (rebuilding by specific RSR..) and 901 gearbox (with intermediate plate Ergal) (good or not?)
flywheel light?
HELP HELP HELP!
thanks all!

[dan67]

TARGA FLORIO 1969 n.240 Porsche 911 R 2000 , Dieter Spoerry - Pauli Toivonen
rear bumber cut...

[dan67]

Gt3 ? ))))