Noob Need advice

[911SC520]

I am very new to engine building so I apologize if I ask a noob question. I have a 1980sc and just got a leak down test and looks like I'm going to need a rebuild. If i do a rebuild i want to increase displacement. Also, I want to ditch the cis and go with efi. I don't know too many kits out there for efi other than DIY or bitz racing. What do you guys recommend?

One question I have is, if i go with over-sized pistons do I need new barrels or can you over bore the original ones? My goal is to make 250+ whp. Will a rebuilt SC motor to a 3.2 with 10.5cr and efi and 964 cams get me there. The whole goal is to have a streetable car that packs a punch.

Thank you in advance for the advice,

Mark

[Aurel]

I am a noob too, but I beleive that with 10.5cr, you will have to twin plug...

Aurel

[sabeo.m]

I'm in the process of rebuilding my 80sc engine; I'm going to start a new thread pertaining to my rebuild soon with pictures, etc. Any how, I'm gong to use my original Mahle cylinder's, having them bored to 98mm from 95mm using brand new 98mm JE Pistons. I also purchased a new set of SSI heat exchangers, Catalytic converter and a new Dansk sport exhaust... I think by making these changes I will be getting close to the 250 range but, I am also new to this, so who knows. I can only hope for the best! Good luck!!

[joetiii]

Originally Posted by sabeo.m

I'm in the process of rebuilding my 80sc engine; I'm going to start a new thread pertaining to my rebuild soon with pictures, etc. Any how, I'm gong to use my original Mahle cylinder's, having them bored to 98mm from 95mm using brand new 98mm JE Pistons. I also purchased a new set of SSI heat exchangers, Catalytic converter and a new Dansk sport exhaust... I think by making these changes I will be getting close to the 250 range but, I am also new to this, so who knows. I can only hope for the best! Good luck!!

It is my understanding that only a 3.2 L's 95mm cylinders can be bored out to 98mm. The 3.0 cylinder can not be bored out. Something in the design.

I think you are headed in the right direction. Ditching CIS will allow greater cam selection and thus power in the higher RPMs. Don't think you need to go w/ 10.5 compression, though. Rather spend the money to do some intake port work to get the heads to flow better. a 3.2 Short Stroke should net you 250 HP while still providing good low end grunt on the street.

[euro911sc]

Keep in mind, when you bore the barrels you will have to re-plate them. Its not like a domestic block in that regard.

If you are ditching the CIS and going bigger you should be able to get a good piston and cam (964 is way mild for what you have in mind; typical upgraded cam for CIS cars) combo that will bring you near 250. Anything above 9.8:1 (some say 9.5:1) you will need to twin plug.

There are several TBitz cars running around on here so you have some direct 911 knowledge base to draw upon. There are more expensive EFI setups (motronic comes to mind) , but IMHO, for a street car, TBitz should be fine. Since you are at higher altitudes you should make it closed loop with a nice wide band sensor. Maybe combine it with an Innovate setup.

BUY WAYNE's book. Lots of fun combinations are discussed with in and its a great education source for what you are about to undertake.

Keep in mind, stock CIS ROW SC '81-83 with SSI's and sport muffler should get you 220-225 (what they say... we'll see if THEY were right after I dyno in a few months). This is MUCH cheaper then a rebuild to a SS motor.

BTW, you do not mention what in the leak down makes you think you need a rebuild...???

Best regards,


Michael

[911SC520]

Thanks for all the input so far.

What cams do you guys suggest I go with? And as far as the leak down test, im getting no more than 6% loss on cylinders 1-5 but 6 is showing 30% loss. The car will drive but not like i want it to hence the rebuild.

And I agree with you, euro911sc, Wanye's book is an awesome source and one of the purchases I have made in a while.

Thanks again and keep the advice coming,

Mark

[joetiii]

Originally Posted by 911SC520

What cams do you guys suggest I go with?


Mark

I think a Mod "S" cam would work well. Elgin grinds them, as does Dougherty Racing aka Camgrinder here on the board. Do a search on both.... tons of posts.

If you search on rebuild, you will find some pelicans who have priced what their projects cost. A 3.2 SS is rather spendy and some people would argue you can install 3.6 for much less. Not trying to dissuade you, but cost most definitely needs to be considered. How much extra power will a 3.2 give you? 7% more. Can you feel 7%? Sure can, but whats the acceleration difference between a stock 3.2 and a 3.0. Not a whole lot really. An then, is it worth an extra $2k or $4k? The slope is slippery and Thats for you to decide.

I began planning my 3.0 upgrade much the same way as you. Ultimately, I am choosing to stick with 95 mm slugs. IMHO, the biggest bang for the buck in upgrading an 80 3.0 engine are ITBs or carbs, porting the intakes, and a more agressive S style cam. More can be spent, but for a street motor how far do you need to go?

Other areas that pay off big performance dividends are back dated exhaust, w SSIs and of course, a 7.3:1 CrWP in your trans.

Believe it or not, changing the fuel induction and a new axle ratio will give you the greatest gain when using a Butt dyno. All that throttle response will feel awesome in the lower rpms where we spend most of our time on the street. The cam and intake work will really shine through once you get above 4500 making for a real fun package.

Hope this helps

[911SC520]

Wow thanks for the input, i have definitely thought about the 3.6 convo but I decided that building the 3.0 to the 3.2. I understand that porting the intake really helps and thats why i plan to do that as well. I will begin to do research on the "S" cam and lets see if that changes my current plan.

But again, thank you for the input. It is greatly appreciated.

-Mark