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Posted by: moparrob Apr 26 2011, 07:30 PM

My engine is a stock (big port) '78 SC 3.0 from which I have removed the CIS injection. I have purchased some Weber 40's with 36mm venturis and manifolds that have been ported to match. I'll also be running some 1 5/8 headers (I know, they may be a tad big...)

I have been getting a lot of flack from a buddy for not re-camming the engine while it is a long block and out of the car. He claims I am leaving around 30 hp on the table by not stepping up now and doing it.



The car, at this point, will be strictly street driven but I would like to maximize torque and street/canyon potential. I have never driven a 914-6 before, so I really don't know what to expect if I don't cam it.

So two questions arise. Which would be a good cam grind and how much should I expect it to cost?

I see Porsche has some stock grinds, and others (like Elgin) grind cams to various specs. What would be a preferable cam design for this setup?

What are parts costs alone?

If I brought my long block to a reputable shop what could I expect to pay for labor and ancillaries like cam chains, gaskets, etc? A ballpark figure would be OK at this point.

Has anyone here done this specific upgrade from an early 3.0 with CIS to Webers, either with or w/o cams?

All feedback is appreciated.

Thanks.

Posted by: SirAndy Apr 26 2011, 07:32 PM

All i have to say is that this is a very schlippery schlope ...

Posted by: moparrob Apr 26 2011, 07:45 PM

That's OK, that's why they are called 'opinions'. What else is an open forum for...

Posted by: J P Stein Apr 26 2011, 08:18 PM

The short version is cam swaps can allow the cylinders to scavenge well.
Proper scavenging increases the intake charge speed & volume thus giving more HP/Torque in the higher (say from 3.5K upwards) rev range. The scavenging is accomplished by longer duration/more overlap on the cam grind. Your 172hp 3.0L (with the right cam selection) could jump to an easy 230/240 hp with no loss of drivability.

This comes a a price....what doesn't. You can't get enough overlap/duration with the stock CIS pistons. JE (or some such) pistons don't work in Alusail cylinders...Nikisal is what you need.

Easy for your buddies to talk, expensive for you.

Here's a pic of the PCs of my last 2.7L rebuild. Bout 205HP at the wheels and equal torque.


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Posted by: moparrob Apr 26 2011, 08:36 PM

Thanks J P. What type of increases would one realistically expect given the limitations of stock CIS pistons?

I imagine there is some cam out there designed as a 'stage I' upgrade for guys who don't want to spring for new P&C's.

Posted by: Eric_Shea Apr 26 2011, 08:39 PM

Agree... cams would be the best way but... there's something to be said about advancing the ones you have 6deg., sticking carbs and headers on it and enjoying just over 200 very reliable and very torquie horsies. You should be around 180hp stock, Carbs have been said to add 10-15. Headers have been said to add 20.

Cams = New pistons = Might as well do this = Might as well do that = $$,$$$.$$

Posted by: J P Stein Apr 26 2011, 08:59 PM

911 CIS guys say that the 964 cams are about as big as you can go.....but check valve/piston clearances. It's a near thing I hear. I've heard power numbers all over the map with the 964 cam swap.....few of which I believe.

The SC power is fine as Eric has written. It will seem like more just from the throttle response.

It's a vicious circle. More power needs more tire which means flares, wheels, yada......great fun tho.

Posted by: moparrob Apr 26 2011, 09:17 PM

Thanks. I have heard mention of changing the cam timing as Eric stated while still using the stock cams. I suppose I can research that further, possibly on the 911 forums (Pelican?). Is 6 degrees a commonly used figure?

That seems to make the most sense for the least investment. I suppose I can put some funds towards rebuilding/re-curving my stock distributor as well.

Posted by: brant Apr 26 2011, 10:02 PM

if your not rebuilding the motor... you might be better off leaving it alone.

New cams are about 1k
install is likely to be another 1k
plus there are always extra's

sure 10-20 hp sounds great, but at the cost of 100/hp its better to wait until your inside the motor for a rebuild anyways.

just my 2 cents, but a 3.0SC motor has gobs of torque and will feel VERY powerful without the cams

tell your buddy your going to smoke his silly 911 anyways since your 500lbs lighter than him.