Ideal cam specs.

Slysc

Registered User
Just wondering what some of the fastest SCs are running for cam specs. Anywone willing to discuss what they think the ideal lift, duration, and overlap is?

I've been told the stock heads can only handle about .520 lift.

But with roller rockers and better springs, what would be best for all out power.
 
Well, the correct answer to that I can quote Bob Dole there. He was asked if he wore boxers or briefs. He said "Depends" There are way to many factors to say what is the best cam for you. I can say higher lift lower duration cams do better on roots blower motors and that you don't want to have a big overlap because we want to use the lower rpm range but specifics kind of depend on YOUR car and setup.

P.S. Wow, you're running a 13.34 on your stock cam and no internal work?
 
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Aaron is right it depends.And they are a lot of depends .
I your heads hit max CFM flow at .500 cam lift,you don't
need a cam wih a .550 lift.You just end up with ware on
the valve train thats not needed.plus you need more
spring pressure that rob hp.

The ldel cam is a match to your head port flow.Or the
flow match to the cam.

There is a whole lot more but it would take to long to type it all
and I am to lazy.

randy
 
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I'm currently running a .520 lift cam and just wondered if I could pick up some ponies by changing to something more aggressive.

I've got Ported heads with D-shaped exhaust ports that were welded and reshaped similar to what steigmier is doing. They have 1.84" intake and 1.60" exhaust valves and roller rockers.
I have comp cams 942 valve springs.

My car weighs 3640 lbs. empty, it's a 5 speed with 3.27 gear, I'm running 14 psi of boost with good exhaust and long tube headers.

Any cam suggestions for that set-up?
 
Here is something fun to play with but I would still go to a cam grinder.

http://stangstable.com/downloads.htm

Try the Dragstrip Plus progam. It allows for different cam options. Get your timeslip for your fastest run and then start with all the knowns of your setup. Once you have it all enetered in your time will be a little off. Try first to adjust traction to get times to match up then go to other things like launch rpm and leave engine stuff alone. Once you have it read what your time is save it and start to mess with cam specs. It is just a computer program but it will be fun to play with to see what changes what.
 
It depends a lot...

Just like Randy and Aaron have said it depends a lot. From the intention of the car to idle quality, to head flow data, to exhaust, to blown, to turbo, to RPM limit, etc etc...I think you get the idea.

I will say that it has been my experience with a "SC" engine that lift over .550 is only helpful if the heads are flowing really good in that range. It has also been my experience that "DURATION" yes duration is what makes a really long HIGH RPM powerband. That is what you would typically use for a DRAG engine. For example look at David Neibert's Dyno scan. His engine is making its peak power in the higher RPM band. It still has all the torque it did before with lots of duration because we are using a ROOTS style blower.

On the first engine I built for my car it had a .513 lift intake and a .531 lift exhaust with 220/220 duration @ .050 which I believe is 282/282 seat to seat duration on a 114 deg lobe seperation. That engine idled well had good around town performance and a long powerband. That car never got any faster than 12.88.

David Neibert's first cam was a different style. We took into consideration his torque converter, desired idle quality, and a few other details. That particular cam only yeilded us a car that would run consitent 13.3's. It had a intake valve lift of .573 and exhaust valve lift of .573. However in the duration department (208/216 @ .050 and 264/272 seat to seat) is was a little low to help idle quality and to keep the max power below 5500. It was a good everyday usage cam for someone that wanted only a street performer.

Well after dropping a valve into my first engine I set out to come up with something that would be very aggressive. It went totally against what everyone on this board had thought a blown cam should be. I was even told that it wouldn't idle and I was crazy. I build engines to handle 7000 RPMs. I also utilize the right parts in the valve train to accept radical lobe profiles. If you look at my dyno chart you will see I am still making useful power at 6200 RPMs. Totally against the theory of blower robbing HP in the higher RPM range. Not that the blower doesn't rob HP because it does. While I will not tell you what CAM regrind is in my car or David's car. I will tell you these things to help you select the cam for your application.

Start with your intent and stick with it don't change it half way through or you will change cams again.

Make sure your heads either follow your cams profile or vice versa. The latter being easier to do.

Make sure you have the proper bolt-ons for the cam selected or a performance degradation could occur.

Finally, get with someone who has done this and has experience with selecting camshafts and get their input.

Chris
 
All hail Chris ::bowing:: ...I'm still hoping I chose the right cam..Only time will tell...The biggest problem I have always forseen with these cars is choosing the cam...We do all the R&D..Imagine if a company actually stepped to the plate to create a cam blank for our cars and went to work..
 
Ideal cam specs

I went with more duration. My car stock seemed to nose over at higher R.P.M.S. I didnt go to nuts on lift only 500. I had the car running then ran into a priblem. I will share the info on how it runs when it is broken in.
 
If you are running 942 springs, you dont wanna go any higher on your lift unless you switch to stronger springs. Comp cams say they are good for .550, while Dr.Fred said they are only good for .530
 
The only thing I'll add to Chris's post is to have a MP inlet plenum and have your flow numbers handy.

My car had been choked off by a stock style (stock 91, stock 94, ESM Dominion III ) plenum and there's an ASTRONOMICAL difference with the MP plenum. I known Dave N. gained like 50 hp switching to a MP plenum and I wouldn't doubt that I gained somewhere close.

If you don't have super exhaust ports, crutch the exhaust lobe on the cam 8-16 degrees more than the intake. It's really not possible to over cam the exhaust unless you have super heads and REALLY mess up.
 
Re: It depends a lot...

Wzenheimer said:
I was even told that it wouldn't idle and I was crazy. I build engines to handle 7000 RPMs.

I too was told that my cam profile would be to big. I have a .590 lift and a 235 duration @.050 which I think is like 290 seat to seat, can't find cam card so not quite sure. But I would also throw in that I have a 3000 rpm stall. I can say that this engine doesn't work at all below 2000 rpm. It makes it tough to launch at the track because it will either nose over or spin the tires but it sounds nice and pulls hard after 3500 rpms. I can't tell you how many times I have had someone racing around behind me to catch up to only sit next to me lobing at a light to reconsider. I love that sound, rumph rumph rumph.

P.S. MP Intake Plenum for 50 hp huh? I might have to reconsider that, I know my engine gives up above 6000 rpm and that would probably help that out a lot.
 
I gain 29.7 RWHP with the MP plenum & MPII blower upgrade.
This is with a inturnal stock motor.

aND i GAINED O TORQUE.


RANDY
 
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Honestly with you being stock I think the blower upgrade made the power for you. Anyone out there with a lot of mods do just an MP Inlet upgrade?
 
I wonder who's going fastest without a MP inlet plenum.
I've got a stock IC and stock inlet plenum. Is there anyone in the 12's with a stock inlet plenum?
 
Aaoron P., That 29.7 HP increase was with a leaking head gasket.
And I don't know how you are going to get HP increase number from
just the plenum.when it will not fit the early style blower inlet.
The two did change my dyno curve up higher.I just thought that you
might want to know the range of these parts.From a fully moded SC
like David Neiberts to a stock SC with bolt ons.I am not for sure but
I think he did the same swap.MP plenum &MPII blower.From a ported
stock plenum & EMS ported blower blower.



randy
 
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I actually have the late model blower on it. That's why I was saying that I think most of your power increase was from the blower mod. When I bolted that on it was a HUGE improvement. The time doesn't really represent the car anymore. It was way out of tune and I didn't have good traction at all when I ran. I'd say I am a few tenths faster at least now.

P.S. Randy, I didn't mean any disrespect if it sounded that way. I just wanted a like comparison. I appreciated your input.
 
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I didn't take it that way,I just wasn't done posting.I was
trying to give you a better example.My post didn't sound
right so I came back to edit it.

randy
 
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Aaron,

I think Randy is correct in that most of my gains came from the MP plenum and not the blower housing. I swapped nothing but the blower case and plenum. I had an early style ESM ported blower with late model rotors and the plenum was custom with a larger than "S" model opening at the supercharger inlet. However the plenum can onlt be ported so much (about 68mm max) so it can only flow about what a 70mm TB will provide.

I gained 50 rwhp and 70 rwtq...not just top end, the gains were along the entire rpm range. I think it was mainly the plenum because Chris Wise got similar results when he changed from a late model ESM ported plenum to the MP plenum, but kept the ESM supercharger. Here is my dyno chart. Nothing was changed on the car except the supercharger case and the intake plenum.

dynoMPcase.jpg


David
 
Maybe you guys can give me some suggestions on just who to go to and what for my next big upgrade. I have an 89 xr7 with 255lph fuel pump, mpII and inlet,85mm throtlebody,raised top(wich I pollished the inside smooth),3 1/2 intake tube,76 C@L,9 inch cone,42lb lightning injectors,MP front mount,MN12 tunner for EEC,ARP head studs,1.73 roller rockers,kooks mid length coated headers,down tubes,high flow cats,2 1/2 X pipe,true 2 1/2 inch duells all the way back and 2 borla 40665 muflers and borla tips,10% jackshaft pully and a 2 1/2%,5% and 10% quick change pullies.My bottom end is stock and my heads are some what ported and pollished with 155 exhaust valves.The head gaskets are going again and it is time to redue the engine.I'm thinking of steigmier heads and a cam from Dr. Fred,now what should I do with the bottom end?
 
Greg,

I would start with the Stegimeier head and cam package and a set of APR head studs.

The bottom end depends on your goals and budget. Unless your going with a stroker crank it's mainly a durability thing.

Chris Wise built mine and it has a stock crankshaft, Ross pistons, Total seal rings, CAT H beam rods, Clevite bearings, APR Main studs and a late model oil pump. The BHJ dampner would also be much stronger than the stock dampner. It's also balanced and blueprinted, bored .020 over and still has stock compression.

David
 
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