What would you do?

shbop · 10-16-2006, 09:00 AM

I've got an 81'sc . I had so much fun building my 66' 2.0 that I would like to get into the sc motor, and with that, I'd like your thoughts. If you were in the same position, had an extra set of 40 ida's, and a budget of $5500, what would you build? Keep in mind that this is a driver, and yes, it's running well right now. Thanks in advance!

2.7RACER · 10-16-2006, 09:16 AM

Jon,
Does the SC need to pass smog in Oahu?

shbop · 10-16-2006, 09:23 AM

No smog! Thanks Doug, I forgot to mention that. No track, and no smog. I guess you can't have everything.

2.7RACER · 10-16-2006, 09:44 AM

Jon,
Lucky you. Most of us have the old smog nazi's hanging over our heads.
I like what I did to my 2.7.
No reason you can't do the same to your SC.
If you already have the webers, I would talk to John Dougherty about the best cam and piston combination for tooling around the island.
Get whatever additional carb parts you need from PMO, great people.
If you can get fuel over 91 octane for a reasonable price then a higher compression piston from your stock 9.3:1 is possible.
The euro version was 9.8:1 and made 204 hp.
Going to a '72 915 transaxle with a 7:31 ring and pinion gear made a big difference in my car on the track.
Since you usually don't see the high cruising speeds on the highway's like we get in New Mexico, I'd recommend going with the '71/'72 transaxle if you can find one.
I did the complete transaxle change, rather than getting the parts to change my original trans.
The labor plus the parts would cost as much or more than the $1500 I paid for the '72 transaxle, and I still have my original 915 in great shape. Maybe sell it sometime.
Yes, get a cam and pistons, freshen up the top end, maybe a new clutch to go with the transaxle, and let the fun begin.

sww914 · 10-16-2006, 10:01 AM

You would be plenny happy with some dakine exhaust too, brah. Try get rid of dakine cat & free da bugga up some.

kenikh · 10-16-2006, 11:01 AM

$5500? ARP rod bolts and Mod-S cams and maybe some better than stock valve springs, which is way cheaper than $5500. Are your heads big valve SC? If so, you are good to go. If not, I'd find a set.

That's all you need for a super torquey 7200 RPM rev monster. If you have to go further, you can bump the CR with new pistons, but the cost/performance benefit just doesn't warrant that move. I'd just cut your current pistons to clear the new cams.

shbop · 10-16-2006, 02:04 PM

Doug, It just so happens that I've got a 71' trans. , but I don't know the ring and pinion--I'll check it out. Makes sense, since freeway driving is minimal.

SWW914 "shoooots" Already running 1" 1/2 headers

Kenikh-- 81' heads, so small port, but I was thinking that they could be opened-up. ?? Your other mods leave cash on the table. Not that I'm opposed to that, but "s" cams with the cis pistons??
Thanks again!

kenikh · 10-16-2006, 02:54 PM

S cams with CIS pistons can be done if you machine valve pockets into the swirled domes to clear the valves. You can have those heads opened up by the usual suspects, too. I would probably just spend $900 on JEs, though.

Eagledriver · 10-16-2006, 05:48 PM

One of our spec racers opened up his own 81 SC heads with an air powered dremel like tool. He found a socket with an outer diameter of 39mm and cut away until the socket fit into the port. It was a very crude operation but it worked great. He has as much power as any of us.

If it were me I'd port the heads to 39mm or have them done and put a 964 cam in. I'm using stock rod bolts as I think they are plenty strong in this application. With no other mods and an early exhaust you'll get over 230 HP. You can get a little more by going to bigger carbs but why waste your money. I believe you'll also need to change the distributor to a 78-79 or get yours recurved for more advance.

One more suggestion would be to put racing valve springs in. That way you can rev to 7200 or so. With the more open intake and exhuast the peak power is at the higher RPMs.

-Andy

shbop · 10-16-2006, 06:18 PM

Thanks for the replys! I think enlarging the ports, springs, retainers and distributor work is for sure. Pistons and or cams seem to be the puzzle for me at the moment.
Andy-- the work that you described--did it include changing the pistons, or leaving the cis ones in?

Eagledriver · 10-17-2006, 05:13 PM

Our spec class requires stock CIS pistons so that is what he has and what I have. Your CIS pistons are 9.3 to 1 so I don't think you'll gain much by changing them. If you use the 964 cam profile you won't need to change pistons. This makes a great motor with good torque and pulls all the way to 7000 RPM. I don't think you can do much better unless you put aggressive cams in and spin it to 7500 plus. A motor like that won't last as long as the one we've been talking about.

-Andy

Henry Schmidt · Henry Schmidt's Garage

Clean up the exhaust , early or SSI, headers if you don't need heat.
If the pistons are good, put valve pockets in them. You won't need much and the compression change is minimal.
DC 40 cams stock valve springs are fine.
Port intakes to 38 mm.
38 x 40 mm PMO manifolds.
Sachs sport clutch (aluminum so the engine spins up)
3.0 SC engine use 10mm rod bolts so stock bolts are fine.
220-230 hp and wqay under your target price.
If the budget allows, by JE 9.5 :1 compression.
Now for the self promotion:
Get rid of the Diliavar studs and install Supertec heads studs.

shbop · 10-18-2006, 06:56 AM

Thanks Henry. I've got to try and plug-n-play. We don't have a machine shop that would know what to do, to the pistons. Maybe better off just going with the 9.5:1's. How about the distributor? Can I have mine re-done, or should I look at something else?

Henry Schmidt · Henry Schmidt's Garage

Send us the pistons and the distributor.

shbop · 10-18-2006, 08:36 AM

Thank you!

kenikh · 10-18-2006, 08:38 AM

Thanks for the photo, Henry. I have heard of, but never seen the results. Very cool.

cstreit · cstreit's Garage

Agreed with above...

GE40 or similar cam, webers, p&c's, and rod bolts...

Might be tough to fit in at $5500 but it's worth a shot and about 60-75 BHP conservatively....

kenikh · 10-18-2006, 08:53 AM

Why does he need cylinders? If he was going the JE/Nickie route, it would indeed be diffficult to fit the budget, but his CIS pistons, cut and reinstalled will not only be adequate, but very enjoyable.

Henry Schmidt · Henry Schmidt's Garage

Yeh, why new Ps&Cs?
Remember we're trying to stay within a limited budget.

Rods bolts (aftermarket) are not necessary under 7800 RPM.
The engine we're discussing will top out a high 6K low 7K.
911 SC rods are design to be stronger (perhaps the best Porsche rod design) and the stock bolts are more than adequate for this configuration.

Eagledriver · 10-18-2006, 08:28 PM

You'll need to use stiffer valve springs or be very careful to keep the revs to 6700 or so. John Doherty sells a set of uprated springs for a very reasonable cost. That is what I'm using on my engine. You'll find that with the carbs you'll like reving the engine to 7200. The stiffer springs will give you some insurance incase you exceed your intended revs.

-Andy