2.0 -> 2.5 Ss?
 

Hi, I need some help/advise.

I have a -67 2.0 L engine with a broken piston and cylinder and now I am planning to rebuild this engine. I have been reading quit a lot on the forum about short stroke engines and I would like to try to put together one of these engines based on my 2.0. This engine has original Webber that I am planning/hoping to use.

So the question is what parts do I need to replace, in order to end up with a 2.5 SS? As far as I have figured out I need:

A set of 2.7 L cylinders and pistons (I am not sure what pistons to use, based on compression rate)
The 2.0 heads are not the best, so I am also planning to get a set of 2.7 heads.

What else do I need?

A few things come to mind:
- Case needs to be bored for bigger cylinder spigots
- 90mm P&Cs
- 2.7 Heads
- 2.2 Rods - Some say they are beefier than the 2.0 and should be used with the larger piston
- Different jets and venturies for carbs

AM

A couple of years ago Bruce Anderson covered this in some detail in his Excellence column. I don't remember which issue, but if you search you'll find it.
regards,
Phil

"A couple of years ago Bruce Anderson covered this in some detail in his Excellence column."

Anderson's 911 Performance book or Wayne's book should provide all details. Typically, RS piston/cylinder kit, but there are many variations depending on your wallet. The S heads are doable, but the cylinder sealing surfaces must be machined to accomodate the 90mm cylinders (same as later heads).

Sherwood

Are you going to up the compression and cam? 2.2 heads are a better starting point if you want more CR as they have the non-peaunt plug holes. I't not a lot but every cc helps. IMHO there is nothing wrong with the 2.0 heads once twin plugged other than the smaller valve sizes. They actually bore out nicer (less material to blend in) to 38 mm than the 2.x heads because the valve angle is steeper.

Might I suggest that instead of cutting the case that you just go with a 70.4 crank and rods. They are pretty cheap and are a drop in. Then you could have a longstroke 2.5 and save some machining costs let alone the wait time. (this is assuming you will stick with the S cams. If you use more cam that needs more revs, C6, RSR, GE80 or what have you, I'd cut the case and use the 66 crank as it is more robust at higher revs since it doesn't have that nasty 4th harmonic from the huge 'push' of the power stroke.

Another option you might consider is a 2.1 long stroke, actually 2173 with 81 mm pistons (2.2?). You could bore your birals to 81 and bore your heads (or use supertec 906 type barrels with 2.x heads - they are made for the larger spigot bore). The rennsport web page says you can get 235hp out of this motor choice and was (is?) one of my rebuild choices. More bottom torque for the corners but still small enough to rev the crap out of with an S or modS cam. I've also heard really great things about this set of parts from a pretty respected engine builder. It's also nice if with the stock heads and barrels no one would be the wiser :D.

tadd

Another option you might consider is a 2.1 long stroke, actually 2173 with 81 mm pistons (2.2?). You could bore your birals to 81 and bore your heads (or use supertec 906 type barrels with 2.x heads - they are made for the larger spigot bore). The rennsport web page says you can get 235hp out of this motor choice and was (is?) one of my rebuild choices. More bottom torque for the corners but still small enough to rev the crap out of with an S or modS cam. I've also heard really great things about this set of parts from a pretty respected engine builder. It's also nice if with the stock heads and barrels no one would be the wiser .

tadd

I remember a discussion about this motor before. Seems, you were very enthusiastic. It was infectious. What happened?

shbop:
I still think the 2.1LS is a great motor... no make that a really great motor the more I read about this stuff. What happened was I gave into an impulse buy. There was a set of NOS 92 mm L&N nickies and NOS 92 mahles for sale from two differnent folks on this board. The price combo was far cheaper than a new set of 906 mahles and L&N cylinders to pass up so I 'leaped' onto the 2.8 bandwagon. I should have done more research before I bought as you just can't get the RSR heads anymore. In a nutshell, I think the 92 will sit on a shelf and I'm going to go back to the 2.1. The problem is that I waffle depending on who I've been talking to :D.

tadd

Thanks for the up-date Tadd! I don't want to veer to far off the trail of this post, so I'll end by saying that I hope you'll post the details, when it unfolds.

If this is just going to be a Street 2.5SS then 2.0L "S" rods are OK. The "S" rods are Nitrated and stronger then standard 2.0L rods. A lot of the guys I race with use 2.0L "S" rods on their 2.5SS race motors reving up to 7800 rpm.. Using 90mm Pistions. They have had no problems. I just built my new 2.5SS race motor and opted for the Pauter rods.

Choices:

2.0L "S" Rods (Light)
2.2 Rods (Heavier, stronger then stock 2.0 rods, not sure about "S" rods)
Pauter rods (Very light, strong)
Carillo rods (more expensive then Pauter (not neccasarily better)

Thanks for all the input.

I forgot to mention that the engine is for street use. I was also planning to get new cams, maybe S cams or something like that, and I think I will go with the 66 crank option.

Since the 2.0 heads I have is not a good starting point and therefore I need some new ones anyway. I was thinking a set of standard 2.7 heads might be easier with a set of 2.7 cylinders. Then I don't need to machine the heads to fit the cylinders. Is the there any difference in the 2.7 heads from 74 - 76 (ports/valves), except for the RS and RSR?

As far as I have figured out regular 90mm pistons with a 66 crank would give a low CR. I am going for a setup that uses standard fuel and does not need twin plugs. What kind of pistons would be the best? And could I use the rods I have from the 2.0l?

Tadd:
The 2.1 long stroke sounded interesting, is that with a 70.4 crank? I was looking at Rennsport's web-page for some more information, but I could not find anything about this. Do you have link or some more info.

Here ya go... it's buried in the 2L stuff.

http://www.rennsportsystems.com/engines%202.0-2.4.html

You should have an email as well.

tadd

It dependson what pistons you are using. If you cc the heads and have the pistons custom made to that cc you can get a pretty high compression ratio. I am using the 90MM pistons with 66mm crank. the pistons are J&E 10.5 : 1.. It actually ended up being 10.7 :1 when it was all said and done. I am not twin plugged. You are not going to need to worry about twin plugging that engine. At least I dont think so.

Mark

What type of heads and cams are you using, do you use the standard 2.0S? I was also planning to go for JE pistons.

I am running GE80 Cams.
I am using 1970-77 heads. They have 46mm intake valves, 40mm Exhaust and the ports are 39 intake and 37 exhaust using 1 5/8 headers.

Mark

It sounds like you have the same setup as I am going for, more or less. You said you use the 90 mm PE pistons 10.5:1, are those custom made so that's the CR you end up with using the 66 crank? And where would you recommend to get the pistons, I see that our host only have 95mm and up? And where did you get the GE80 Cams?

I had my heads CC'd and then had the pistons custom made at J&E to match those specs. The CR came in just a tad higher then 10.5:1 9more like 10.7:1). The cams came from my old 2.0L Motor. I had them maged and polished. I got them from Frank Beck in Phoenix AZ. He is the guy that built my 2.0L.

Sounds like you are going to have a stout motor as well.

Thanks for all the response.

I think I will go for JE pistons with CR around 10:1 with standard 2.7 heads and 66 crank, but when it comes to camshafts I am not sure which way to go.

Anyone have a link or some information on the difference between GE-40, GE-60, GE- 80 and S cams? Or is there any other options to be recommended? I am still planning to use my carbs (Weber) :)

Hi Happy New Year

Is there anyone how can help me out with some information/advise on camshafts?

Call John Dougherty, camgrinder on this board, or visit his web page. He will set you up. He even whipped up a cool set of custom cams for kenikh. he KNOWS his stuff.

tadd

Hi The winter is getting closer and it is time to pick up this project again...:)

I have two sets of heads, one set with 35 mm ports ('75-77 911S with air injection (CIS)) and another set with 30/33 mm ports ('73.5 911T (CIS)).

Which port size would be best for a 2,5 SS with Weber's?

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?

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.

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. :)

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.

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.

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?

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.

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.

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?

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?

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.

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?

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

"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!

TARGA FLORIO 1969 n.240 Porsche 911 R 2000 , Dieter Spoerry - Pauli Toivonenhttp://forums.pelicanparts.com/uploa...1217878677.jpg
rear bumber cut...

Gt3 ? )))) http://forums.pelicanparts.com/uploa...1217879368.jpg