How much of a power increase 3.0

[Dpmulvan]

Rebuilding my 3.0 and trying to figure out whether I should just build it stock again. I was thinking about adding je 9.5:1,carbs,and cams. Either way I'm definitely getting rid of CIS. Has anyone noticed a big difference when making these changes or is it not worth it.

[toddu]

You'll notice a difference with that. You know the old saying though - no replacement.......

Todd

[JOHN21BLACK]

Just rebuilt my 2.7 with JE pistons9.5:1 , carbs, 964 cams, 40mm port and polish on heads,msd ignition,lighten flywheel and aluminum pressure plate. rebuilt 915 trans with 7:31 gears.

[Dpmulvan]

Looks nice any idea how much horsepower it's putting out?

[JOHN21BLACK]

No not yet. Installing 930 turbo brakes now on car now. Then off to the dyno for fine tuning. Im hoping for some where around 180 to 190 if im lucky.

[Henry Schmidt]

Originally Posted by Dpmulvan

Rebuilding my 3.0 and trying to figure out whether I should just build it stock again. I was thinking about adding je 9.5:1,carbs,and cams. Either way I'm definitely getting rid of CIS. Has anyone noticed a big difference when making these changes or is it not worth it.

The changes you list offer almost unlimited choices. In correct combination these changes can/will make a huge increase in power.
I would consider a cleaner (than stock) exhaust.
The JE pistons offer valve pockets that allow you cam choices not available with the CIS pistons and the carbs allow for better cam choice.
Basically a blank page.
Increase performance? of course 50 hp is on tap without even breathing hard.

[Dpmulvan]

I already have a backdated exhaust new in box that came with the car. Motor is stripped (had to change cases due to bad crack repairs). I have Wayne's book but it only shows a few mods for the 3.0 So I thought I would ask you guys with all the experience. I know carbs can get pricey so I"ve been researching different efi systems et. I've seen some great looking motors in these forums and encourage any all advise.

[Matt Monson]

Bruce Anderson's performance handbook has some good 3.0l discussion. You could also make it into a 3.2. However, you've got Henry here providing input. You don't need to go out and but a book when one if the top air cooled engine builders in the country is commenting on your build.

[Henry Schmidt]

Phil Slate, one of my builders and I were speaking about your project this morning and both of us thought you might consider a cleaned up CIS.
They really are incredibly versatile, reliable and can be tuned to work quite well for a street hot rod.
The key is to eliminate the ancillary non sense that make it pass smog and eliminates driver input.
Over the years we've been able to build "stock" class CIS engine that really do run aggressively without the constant tuning and poor fuel mileage offer by carbs.
You have the big port runners already so if you build a 3.2 SS (70.4x98) with a 20/21 Cam or a DC19 using your new exhaust their is no reason why you shouldn't see a 40hp increase. maybe more. The best part is that you own it.

Here are a couple of shots of clean version of CIS.

[JOHN21BLACK]

Henry, what kind of exhaust should I consider on my 2.7? With all the changes iI have done already. I really wanted to keep my heat , but if it makes that much of a gain in HP. I will part with it.

[Henry Schmidt]

Originally Posted by JOHN21BLACK

Henry, what kind of exhaust should I consider on my 2.7? With all the changes iI have done already. I really wanted to keep my heat , but if it makes that much of a gain in HP. I will part with it.

HI John
The changes you are making will produce nice power but really won't want to rev so I would think any version of the early exhaust should suffice. I am a fan of the SSI stainless systems but the price has gone through the roof since Dansk purchased them. Dansk also makes a stock early style heat exchanger that has a better price so I guess I would suggest those for your project.




One quick question for you John. What have you done to the Zeniths to make them a good choice for a performance, 2.7 engine?

[JOHN21BLACK]

Thanks for advise Henry

[Henry Schmidt]

Originally Posted by JOHN21BLACK

Thanks for advise Henry

No worries, my pleasure.

I added a question you may not have seen.....

One quick question for you John. What have you done to the Zeniths to make them a good choice for a performance, 2.7 engine?

[JOHN21BLACK]

Henry, I far as I know the mechanic who built my motor rebuilt and changed the venturis to larger ones. Do you think they are not a good choice?

[Henry Schmidt]

Originally Posted by JOHN21BLACK

Henry, I far as I know the mechanic who built my motor rebuilt and changed the venturis to larger ones. Do you think they are not a good choice?

Over the years we've spent a considerable amount of time trying to make the Zenith triple work on larger engines with no success. I even built a set of 46mm Zeniths but we had very limited success. They worked wide open the but the transition was marginal.
The guys at Motor Meister claimed to have seceded in this endeavor but I don't really know if it's true.

That was the reason for my question. The Zenith seems like a well built carburetor so if they can be up graded to work well, I would love to know how.

[JOHN21BLACK]

Do you not think the zenith 40 tin carbs are not a good choice. With the mods done to my motor. Also you said i would not be able to get much revs out of it. I thought with the lighten flywheel and pressure plate. , also the 7:31 gears would let me rev quicker.

[Henry Schmidt]

Originally Posted by JOHN21BLACK

Do you not think the zenith 40 tin carbs are not a good choice. With the mods done to my motor. Also you said i would not be able to get much revs out of it. I thought with the lighten flywheel and pressure plate. , also the 7:31 gears would let me rev quicker.

If you can make them (Zeniths) work, I don't see a reason not to use them. My comment was based on the fact that I've had no success making them work on larger engines.

The 964 cams are not high revving cams and engine characteristics are generally determined by cam choice.
The 2.7 crank is not happy with sustain high RPM anyway so revving it is not a good way to go.
Of course when I say, "won't rev", I mean that the power curve is no longer climbing. The engine will continue to rev but shifting when you power curve drops off generally makes sense.

[JOHN21BLACK]

I think thats why he made that choice in cams. That makes sense. I really dont know yet until i get it on a dyno and fine tuned. Any advise on a good dyno person close to me. Im in the eaglerock area.

[Matt Monson]

Revs is a relative term. So many Porsche engines "redline" in the 6200-6500 range. Sometimes people perceive that an engine "revs" if it is built to go to 7000-7200 like an S. The factory race engines have pretty much always been able to rev to 8000+rpm. So, without defining the term for ones own application it doesn't mean much. Your revs may vary.

[Trackrash]

There is a thread or two on the 911 Forum about Zenith carbs supposedly modified to work on larger motors.

That said, I tried for a while without success, to get my Zeniths to work on my 2,5.

I gave up and bought some Webers.

With good compression and the right cam CIS can make a good running motor.