I've read all the past threads and talked to several shops (sponsors here), and I definitely get a different answer from everyone I speak to. Needless to say I'm a little confused to find the optimum.

My idea is to do a cam now, then D1 in the future. My current mods are listed below. I do have to pass emissions. I have Edit, but I am one my own to tune the car as there are no good tuners around.

Three 'types' of cams have been proposed (ballpark specs):

1) the small cam approx 216/220 560/560 114
2) the generic cam 224/224 580/580 114
3) the big cams 224/230 590/590 114 or 226/232 580/580 114

I've had people tell me that each one of these is the "best" cam for me. The smaller cam will be easier on emissions and keep the powerband low, not sacrificing low end torque. The 224/224 seems to be good for everything, so sponsors seem to like to suggest this. The bigger cams I am guessing put me into the upper rpms for a powerband and could be tough for emissions, but some of the sponsors tell me "no problem" with a tune.

Main questions:
If I play it safe with a small cam, how much hp am I missing out on when I go S/C compared to the big cam? Or if I go with a 224/224, how much am I missing by not optimizing with a split duration?

 

This seems to be a tough question. None of the sponsors have reallly been able to answer it. And most opinions seem to dodge the issue. I'm surprised that no one has any knowledge on this or has tested much regarding it (and I have talked to virtually every sponsor and searched every forum for the past 6 mos)

I'm thinking a great blower cam would be a 214/224 560/570 116. Any thoughts? Good for emissions, decent power NA, and really nice for the S/C.

 

There are a number of considerations that go into selecting a cam, but the key ones for you are:

-good for emissions
-decent power n/a
-really nice for the supercharger
-How high you want to spin the engine
-How much boost you plan to run

116 LSA well, it's just not that simple. I in fact specified my LSA, 115, over the reccomended 114. It really comes down to keeping the overlap to a blower-friendly mininum. Chris @ Comp has suggested keeping it to down to 2 degrees of overlap and Terry @ Cam Motion has typically suggested about 3 degrees. In some cases a grinder will suggest a 112 LSA which might like 6-7 degrees of overlap but it will lower the power band. It will lower the power band but at the expense of the peak hp. Now in all out race setups, a class car MIGHT run like a 236/248//112 cam but that cam is designed to maybe work within the confines of a class that might limit valvespring selectino or limit the racer to a hydraulic camshaft, which then might be limited to like 7500 rpms... Big race supercharger setups miight not be as efficient as some of the stuff we are using but we are also for the most part not building all out race cars.

Since blowers push air, most folks will just pick an intake duration based on the power level and rpms they want to spin. They go with more exhaust duration to keep the exhaust valves open longer to maximize scavenging.

You will typically find cam grinders advocating 6 degree splits unless it's a mega race setup and then they will go to 10 degree splits. I have a 230/236//115//600/610 lift cam but if I did it all over again based on my research in the past twelve months I would have went with a bigger split, more duration on the exhaust side. My car is not going to ever pass emissions FYI.

It's been said in the past that a blown motor will peak 500 rpms higher than it's n/a twin.

All that being said, you probably want no more than a 6 degree split for a street car that needs to pass emissions. You probably want to keep the intake and exhaust durations at or below 230 to pass emissions. You probably want to keep the intake duration below 224 to keep the power band down to a stock rod bolt level of 6500 rpms.

My 230/236 Cam Motion cam from Futral Motorsports made power up to 6700 when we let off. It might peak at 7000. I will be buzzing this motor up to 7200 rpms.

 

And to add, how can you tell when a cam is too big.

Most of us have not had this happen yet. But what would happen is that the too-big cam will turn on at a higher rpm, and finish at a higher rpm. For example, had I gone with a 240/248//114 cam who knows what might have happened. PERHAPS instead of making 600rwhp at 5300, and ultimately 746rwhp at 6700, I would have made 600rwhp at 6000 rpms and 746rwhp at 7200, and maybe 800rwhp at 7700. Since I limited my setup to 7200 rpms (stock crank, hyd. setup), I wanted to run as much camshaft as I could that made usable power below 7000 rpms.

For a turbo car it's a variation of the same theme. Duration makes power. That is one of the axioms of spec'ing a camshaft. But you want to keep the intake duration to a duration that makes usuable power within the limitations of your valvetrain AND that spools up well. The downside of too large of a turbo camshaft will be predominantly spool up.

 

PSJ, where do you find the time to answer questions in such detail?

I understand that there are many factors to consider (and you have educated me further on some of this), such as: emissions, where the powerband will be, valvetrain life, tradeoff of low end torque vs high end hp, overlap and its effects on boost, etc...

But a couple of things are apparent: everyone has a different answer to a similar problem (or so it seems); and, all the cams I see recommended to me are either too small to be interesting (or worth the time to install over stock), too big to be practical (stressing valvetrain, failing emissions, and requiring a LOT of tuning for an A4), or not ideally suited to the application (like the standard 224/224).

It just make me wonder if I am wasting my time building a set up (in looking for the right cam to complement a blower), and that I should just skip to the blower itself. People are seemingly making excellent numbers with all sorts of different cams (and some that I would not consider good blower cams).

 

Call Comp at 800-999-0853 and ask them to spec a cam for your specific setup.

 

PSJ - I recognize your Comp cam specs because they look just like mine, except mine has 114 LSA and 4 degrees advance!

 

I did get a response from them that a 214/224 527/532 114 cam was what they recommended.

 

Well to me, if I was building a stock bottom end blower car, if I could get at least 50rwhp more from a cam swap it's worth it to me.

Hopefully we'll have a lot of different combos to compare this year. I hope to see some folks run too much camshaft and swap cams to see the benefit.

 

I don't know if this is worth the $.02, but...

PSJ has put down some good stuff. However a good NA cam just isn't a blower cam, I'm sorry. So the answer is, as I see it, do a good N/A cam until you're ready for the boost. When you are, consider a new cam as part of the blower package. It's really not that much more $$ considering the cost of the blower in the first place, and you can always sell the N/A cam to someone who needs it. That way, you're gonna be a lot happier with the performance that you get in both setups. You're also not gonna be leaving much hp on the table in either case. Just a thought, that's the way I've chosen to go.

Building now: 383 stroker, N/A, 9.7:1 ported Heads, 224/228-.581/.588-114 +2 cam.
Next year: 7 psi, new blower cam - figure that out then, probably custom specs.

 

That blower cam actually isn't too bad, its worth a shot running, I would work on getting the comp ratio down some more, what type of heads are you running?

I got a 214/218 .540/.550 114lsa in my iron block motor right now, car idles like stock.....I'm going to see what kind of power it makes w/this and 15-16psi......

I'm changing cams in the future to something that "fits" the motor a little better, also want to do a FMIC.......but then I will need F.A.S.T. because I will be at my limits.....

230/240 .600/.610 114lsa might be worth a shot, I'll call comp though when the time comes, there are so many different options out there, its hard to make up your mind....

 

My cam is very similar. 218/224 527/534 114
Put down 530/487 with a very conservative tune. For 346ci and 10PSI, I think it's a good cam.

 

Don't know if you were talking to me, but I'll answer anyhoo. If not, just ignore this. LOL PP 5.7 "cheepies". I figure the 9.7 will hold OK with about 6-7 psi. I probably will look for something around 224/230 - 115 to 116 LSA with around .600 exhaust lift depending on the exact psi I decide on. Sounds like a nice setup you've got.

 

I wonder how more duration and 114 lsa would affect the ability to use slightly higher compression for more low end TQ at the expense of higher peak HP. The overlap would allow for better off boost performance and still give sick peak HP. I would imagine the comp cams XER 224/230 .581 .592 114 right from their catalog would be fine at 10.1 CR. This is what Chris from East Coast Supercharging and Andy from A&A use (10.1-10.3 cr) on their silly 700rwhp cars and both are 9 sec runners.

 

Pick the power added first, then the cam.

 

What size chambers are on the PP's you have to get it to 9.7:1 or are you running a thicker gasket?

 

stealth.... where you from ... NHRA or IHRA ?

 

Denver, NHRA.

 

We race division 3 IHRA , ha ha prob wont run into you at a race ... sounds like a nice hot rod you got there

 

I got the 72cc chambers and 7cc notch pistons for a lower compression with the stock gasket (.053). That was on purpose for FI and no-sweat PV with high lift. I'm giving up some power N/A I'm sure, but I'll make up for it later with boost.