crashmy911

Thinking about having my cams changed to the 964 grinds and going with je pistons and upping the commpression to 9.8.1!!! What do you think this will do for my 1978sc? Also the exhaust has been back dated already to the pre 1974 exhaust and no cat.

Steve Weiner-Rennsport Systems

[quote]Originally posted by crashmy911:
<strong>Thinking about having my cams changed to the 964 grinds and going with je pistons and upping the commpression to 9.8.1!!! What do you think this will do for my 1978sc? Also the exhaust has been back dated already to the pre 1974 exhaust and no cat.</strong><hr></blockquote>


lol,.....I'm thinking that you will need 94 octane fuel if you wind up with a true 9.8:1 CR.

I'm also thinking that you will need to tweak the control pressures to make sure that you get enough fuel into your engine in that configuration.

This will perform quite well but that's a LOT of compression for these lean-running CIS engines on pump gas without twin-ignition. Caveat Emptor.

Martin S.

As Steve Weiner will tell you (I defer to anything Steve says...I am serious here), the SC CIS system is very sensitive to any changes in the system such as cams. It is rare to see a modified SC with CIS. Most who want to add cams go to Webbers or some such carburation system, or back to mechanical fuel injection.

SC cams in general, kick butt. You can advance them, and or retard them, one approach gives better low end, the other improves top end, or so the rumor goes. If you want to stay "stock" appearing you could change out you 78SC heads for 81 to 83 heads, they have higher compression. You can also extrude hone the intake runners, add a Euro Fuel distributor...hmmmmwhat other "cheater" things can I think of? Cheater in the sense that in Club Racing, some have been know to do these types of mods as they are nearly undetectable.

You could also go to SSI heat exchangers and a Bursch muffler, and finally, you could change out the ring and pinion to a lower final gear (higher numerical). If you have lots of money, you can build a close ratio tranny to go with your new ring and pinion.

And finally, if you want some painless performance, take some weight out of the car....by any means becessary. And that is my $0.02.

Martin <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

JBrown

i have an 83sc and after about 6 months of talking to many shops they told me and you will see that investing 6,000 to 8,000 you will see like 50 extra horses if lucky. i do not no what your buget is and what you are looking to get out of the motor but droping a 3.6 motor in there will outperform almost anything you do to the 3.0. the price you will pay for a 3.6 will be about the same as doing the work you are talking about to your motor and the results will be much better.but you still have to get the motor installed unless you are doing the work yourself and that can add up.

Steve Weiner-Rennsport Systems

Hi:

Excellent, sage advice from "JBrown" and I'd concur completely.

The installation, if properly done, of a late model 3.6 into an SC results in a car of staggering performance and excellent drivabilty. There is literally nothing that you can do to an SC engine that will come close, Webers, cams, or not.

Although is not cheap to do initially, IMHO, the end result is very satisfying and you'll recover some costs by selling your 3.0 litre should you decide to pursue this.

The only other combination that approaches this in performance is a 3.4 twin-plug, Carrera engine with a host of modifications and these cost the same as a stock 3.6 conversion.

Hope this saves you spending some unnecessary monies and getting focused on how you wish to improve the performance of your SC. Don't forget that the suspension and braking should match whatever powerplant you wind up with.

emcon5

Hi Steve, any thoughts on <a href="http://www.pelicanparts.com/techarticles/911_engine_rebuild/911_engine_rebuild2.htm" target="_blank">This article on CIS performance mods?</a>

The guy who wrote it is a regular on the Pelican BBS, and got dyno'd 203 at the rear wheels of a Carerra 3, using higher compression pistons (9.5:1 I think) and 946 profile cams with SSI's. He found out later that when his car was imported, the fuel distro was replaced with a unit from a 2.7.

I would think if your engine needed a rebuild anyway, this may not be a bad way to go, especially if you need to pass CA smog. Just swap the exhaust every 2 years, and you should be fine.

A displacement increase would be better, and twin plug with ~10:1 would be better still, of course.

As a side note, any thoughts on boring stock jugs out to 98mm and replating?

Tom

Otto

Guess what, Otto is finally here. I hope I can help. JE pistons crack under extended use. I have burned down more than a dozen 911 motors using them. Yes, the NASCAR guys love them, but they throw away their motors after quailfing AND after each race. They have budgets that allow them to have numerous motors. Do you? I have built more than a few motors using JE, Venolia, Ross, and have tried most of the other piston manufacturers that are there in the rebuild world. I have found MAHLE to be the best. They have been making pistons/barrel combinations for over a hundred years. Since 1970 alone, 23 of the winning cars in the 24 Hours of Le Mans have crossed the finish line with the help of pistons and cylinders from MAHLE.

emcon5

Hi Otto,

Were the JE piston failures on street or race engines?

Tom