uh, 964 cams are stock on the 964... they are an upgrade on earlier motors

- was that your question?

yes u answered my ques. thks damian

OK - if you search on those 2 terms you'll find a thread where someone explains the advantages

IIRC, it is a cam that allows better breathing but still works on on CIS motors

the ramps may have a newer, more complex desing also

All other things being equal - and I know that's very theoretic - the displacement increase will increase power in linear proportion. 3.0 to 3.2 is a 6.25% gain.

Gerge

It is not literally a cam from a 964, but it's respective grind / profile. Generally you send your cams out and have them reground. Or you do an exchange, with the same result. The 964 cam has been very popular on the 3.0 if you use CIS and have the higher compression engine (not the 8.5:1 early 3.0). Going with the pistons in the recipe you quoted will make the 964 a good choice for the street. People also pass smog with 964 cams in the 3.0 CIS or 3.2 Motronic. If you go to 9.8:1 compression, there is even better (little more agressive) choices of cams out there now. You will want to talk to John Dougherty aka "camgrinder" on this forum or check out his web page http://drcamshafts.com/

Cheers, George

I have spoken with John and I have selected him to regrind my cams.

I have decided to purchase the 98mm P+Cs from Henry. Just to temporarily place a halt on expenses, could I use the 20/21 or S cams, the stock CIS, but in the future be able to switch to carbs without tearing up the engine again? As a reminder, I do have the early 3.0 with bigger ports.

Thanks.

You want to put CIS on there for now and go to carbs later? The S cams will not work. The 20/21 cams are run by others with CIS, if I remember right. rdane? That should be a compromise. So, I'd go as hot as you can with CIS (Joh will know what cam will work best) and then not worry about it later. And if you have the carbs and you just have to tickle the last bit out of it, changing cams is not a big deal. You could wait until the first time you have to take the engine out for another reason, like a clutch or an oil leak...

Cheers, George

Right, "real" S cams will cause the valves to hit the CIS pistons. You can stay with the so-called 's' cams that were used on the CIS engined- 911S cars from 1974-77 -- they are not really S cams. So don't get confused about this. Most call them CIS cams.

You can however, put carbs on now (and SSIs) and enjoy the feel, the induction noise and maybe a tad more power. Then later, you can change the cams and pistons to get a real power increase. Steve Wiener has posted on this and I used ot have a '75 done this way.

So yes you will have to tear into the engine again. It will cost more eventually this way, but the cost per year or whatever increment will be lower.

You have to think about whether this makes more sense or if [2] you should get a loan to do it all now, or [3] just wait and save your $$ for a year or two (the cheapest for sure).

Randy,

The 98mm's are the QSC's. They will have JE pistons, not CIS pistons. Am I all confused?

The $$ is not really an issue. My approach takes into account that I am a newbie and I really do not want to buy all the hipo stuff, put it together, and it blows on my face. In other words, I want to take the 'baby step' approach.

BTW, the car actually came with non-SS exhaust (2-in 1 out muffler). Unfortunately, they are a little bit rusty and maybe would buy the SSI down the road.

The reason why you can not use "early" S cams on ANY CIS equipped engine, regardless of pistons, is the single plenum setup of the intake. The CIS air metering flapper will get too much "pulsing" from the cylinders and will get confused. Again, this is regardless of the pistons and limits your cam choice to something less aggressive.

George

I built an RSR spec 3 liter for my RSR clone. The engine makes gobs of power right up to 7500 RPM yet is is comfortable to drive on the street. Spent the day today at the Glen. What a blast to drive at the track!

Here's the details:
http://forums.pelicanparts.com/showthread.php?s=&threadid=246563&highlight=dyno+d ay

A Quiet Boom/Chris has turned me on to some great carb info over the course of our friendship..




http://forums.pelicanparts.com/uploa...1151204886.jpg

l guess carbs we go!

So, who's got webers? Could you supply me the part or model number?

Thanks.


ps.,

Maybe someday we'll go to PMO.

CE/Walt did my machining. Once afterwards when I stopped by he walked me through a few of what he does to engines. Shaping the heads to perform at desired rpms required working them differently. Even on my street engine where max torque is desired when 4th gear rpms at 55-60mph is expected to pull thru 100mph the heads will be shaped differently than something that's expected to be raced and needed to pull max from 5k-7k rpms..

Not to discount other build needs but the point being I'd wait it out for Competition Engineering.

imo pick a cam to perform max torque where it's needed instead of max HP and use CE for at least your head work.

You'll need 46mm PMO's if max HP is what you're after. Assuming 6500rpm for peak HP you'll need 35-36mm venturi's which are available for 40mm PMO's, Webers, and Zeniths but as the formula Ron shows you'll lose a little HP with anything over a 34mm venturi in a 40mm carb. If you must go with a 40mm carb then I recommend Zeniths since they have taller boosters and can handle a 36mm venturi better than a Weber IMO. I don't know about the booster size in PMO 40mm carbs. My eventual plan is either 46mm PMO's or custom IR fuel injection. Of course this will be coupled with converting the motor to a 3.2SS and appropriate cam. Also as Ron suggests go with a smaller cam if the car is a daily driver. Larger cams shift the powerband up as well as make it narrower effectively reducing torque in the lower rpm band which can be a drag on the street unless you expect it, are used to it, and plan to drive in a lower gear to take advantage of the larger cam.