482" FE, w/58mm TWM - cam choice - opinoins please

[BMEP]

Currently building a 482" (4.250" x 4.250") FE.

- 10.5:1 static CR
- Keith Craft stage 2 CNC Edelbrock heads
- TWM 58mm injection
- Going in a Factory Five Mk3, 3.55 rear gear w/5 speeed OD trans
- Mostly hot street car that will see some drag strip and road course time

I've presently got a KC grind Comp Cams hydruaulic roller - 248/252 @ .050" 112LC. (I just degreed it and now I'm having second thoughts... don't you just love/hate it when that happens? )

The other cam I'm thinking about is KC's 252/262 @ .050" 110LC, (hydraulic also).

The top end isn't together yet so there's no better time than the present to change.

There's lots of experience on this board so I'd love to hear opinoins and experiences with similar setups.

Rob

[blykins]

Where do you want the peak to be?

I had a Comp 248/254 solid roller in a 428ci FE. It peaked at 6500.

I also had a custom hydraulic roller in a 445ci Windsor, with a 250/250 duration. It peaked at 6000, but I was experiencing some valvetrain issues.

I would think with 482ci, that you could get away with the 252 cam and not have to use any exotic valvetrain pieces like titanium retainers, heavy springs, etc.

With a lighter car, a 5-speed, and large displacement, I'd go for the larger cam. I would imagine your peak hp rpm would be around 6000-6200. I think that's a good range for a hydraulic roller.

With the smaller cam, I guess your peak hp rpm to be around 5500-5700.

Either cam is going to give you good performance and with a lightweight car like a Cobra, you can live with a little wilder cam. Depending on what the advertised durations are, the larger cam will also lower your DCR, which may allow you to run a cheaper gasoline like 87-89 octane.

Be sure to recheck your P/V clearances. Even if both cams have the same lift, the valve timing events will change the results.

[RodKnock]

Without lift specs, it's hard to tell, but the 112 LSA would be the one I'd pick for idle characteristics and drivability.

[fkemmerer]

The CAM that you have now should provide peak torque at around 4500 RPM or so. That is already pretty well up there for a street car. The other cam that you are looking at has both more duration and overlap which will raise the RPM range of the motor even more. You are already probably making close to 600 hp/600 ft-lbs at the flywheel. If you're not going to race the car (ie an application where you need high RPM HP), I'd stick with the CAM that you've got. I have a 482FE with a TWM setup from Keith Craft with a cam with duration figures of 242/248 @ 0.50 and around .645 lift and a 112 degress LSA and I'm making 650 hp and a peak torque of 630 ft-lbs at abour 4500 PRM.

If it ain't broke, don't fix it ....

[RICK LAKE]

BMEP Rob the best thing to do is stay with what every KCR has givin you. Webers, Olbergs, TWM or any other stack setup don't like to have a narrow LSA number. Reversion starts to happen. If you find a 114 LSA cam thats better than a 112 LSA. I am building a 498 Shelby motor with 58 TWM setup. I have a KCR custom hydro cam with a .622" lift and your duration numbers. It will have 10.5 compression with a worked aluminium head like the stage 3 from KCR. I build torque motors not HP motors. I run either 3.31 or 3.08 gears in the rearend. I have 2 transmissions for the car, a 5 spd and 6 spd with overdrive. With the power and weight of a cobra you are going to be about 620ft of torque and about 560 HP with the 482. My 482 with a small hydro crane roller is about 480 hp and 540ft of tork, it's a hand full. This is with an FI system and a 1,200 cfm throttle body. I hope you are a custom to high powered cars and have QUICK REACTIONS. These cars are a handful. I would limit the stroker motor to 6,500 rpm MAX. If you are running a wide ratio 5 spd, I would also drop the gearing to the 3.00-3.20's. You didn't say which tires you are going to run on and size. If on the street 15" for the track unless the 15" are autocross tires like Hossiers or big letter GY you are going to have too much power in the mid range of the motor. I run 15" crappy BFG on the street and 17" pilots on the track in street class tires. Pilots are working OK for me. SFFiredog just finished a 511 motor with the same setup. See what numbers he came out with and cam he is running. He builds FE's part time. Check his photos here in CC. The motor was to get dynoed last week after breakin. There is alot more to talk about on this like exhaust system, suspension, SAFETY issues, and serious are you about racing?If you are going roadracing add an accusump to your oil system. 3 quart. You can use this as a preoiler for before start the motor, and leave it open on the track to maintain oil pressure on high "G" turns and coast down or hard braking. You will need 2 different shocks and springs setup if you want to really drive this car at the track and have it handle like it's stuck on rails. If you want to talk, call me at 732-254-3536 in the evening or private e-mail with a number to reach you at in the evening. I'm in NJ and have toll free phone calling. Rick L. There are some other things you can do with the motor also.

[Anthony]

I second to stay with the smaller cam. I don;t think you'd gain much with the bigger cam as your engine is limitied to just north of 6000 rpm's. Ask KC for some dyno sheets comparing the two cams, and make a decision. The smaller cam will be alot better at lower rpms especially since you're likely using a standard tranny.

[Barry_R]

Don't change it....
When I do Weber stuff we try to stick with the wider lobe centers and reduce the overlap.

The Weber style intakes open up a great deal of throttle area with small degrees of throttle movement - so you get a pretty big "lean hole" in the Air/Fuel demand curve. It's hard to fill that with fuel even with EFI mapping - you get an "on/off" switch effect.

The wider centerline cams will tend to soften the transient response there - you may not see it on a dyno but you will sure know it in the car. An added benefit for a road race style application is that - ASSUMING the same lobe - the wider centerline will give lower peak numbers but a wider, broader powerband.
(Please be aware that the above statement is a gross oversimplification and not gospel by a longshot - but is a valid generalization).

[blykins]

Good points Barry, I didn't really give much thought to the intake setup.

[BMEP]

Thanks for the input, all.

FWIW, I intentionally chose the cam I have and I think it was the right decision - especially based on feedback here. FYI, The same cam I have is also available in a higher overlap grind (110 deg LC), as well as the 112 I picked.

RICK LAKE: thanks for the offer to help - I appreciate it. I've got 17" (335 rr, 275 ft) rubber. Exhaust is still in the works but I'm starting with the FFR 2" primary headers (would rather have 2.125" or 2.250" but I already have these). After headers, I'm planning on merge collectors into some fairly open mufflers -- right now I'm thinking the Stainless Specialty 3" ceramic open core mufflers (not much of a muffler, I know). We'll see... I'm willing to tolerate a lot of noise but that may be too much. For a while, I was thinking that a fabricated baffle type muffler (e.g. a DNA or similar) would be nice but I can't find anything with a pretty looking O.D. - which matters to me since it's going to be a sidepipe. I'm also installing a 3 qt Accusump. Suspension: Front: SLA IFS (steel arms), rear: Gordon Levy 5 link. Levy Koni shocks, fairly big brakes (13" ft, 6 piston Wilwood calipers), 12" rear (4 piston calipers).

Barry_R: Really good point about the amount of throttle area/change with that induction setup. That makes the need for a decent progressive linkage even more important.

[SFfiredog]

That was pictured a few posts down.
504 ci. 10.75 to 1
CNC ported heads and hand ported intake.
The intake ports are as far over as the pushrod tubes will allow
and are a bit smaller than the heads.
The cam is 262/266 @.050 .691" .697" lift with 1.8 rockers on a 112 lobe center installed on a 107 intake centerline.
It is a mechanical flat tappet with Schubeck composite lifters.
Idles at 750 rpm with 11 to 12 inches of vacuum.
545 hp @5600 at the rear wheels with the crappy Superformance 1-7/8 headers and restrictive side pipes.
603 ft lbs of torque at 4700 rpm...at the rear wheels....
Drives like a stocker... pulls like a freight train...
The power and torque dips about 30 to 35 hp right about 4800 and picks back up at 5200.
It is reversion caused by the really short intake ports. I am trying to tune that out with the laptop but I wish I could put a longer stack on this size engine.
My calculations show it would really like a 12 to 13" stack... Not very practical or attrative on a Cobra...
Also the wide lobe centers help with drivability but ultimately hurts a tiny bit on the top of the torque and horsepower levels... not enough to really matter though...

[BMEP]

Originally Posted by SFfiredog

545 hp @5600 at the rear wheels with the crappy Superformance 1-7/8 headers and restrictive side pipes.
603 ft lbs of torque at 4700 rpm...at the rear wheels....

That's pretty good! Must be ~650 FWHP... and that exhaust has to be costing at least 50 hp - I bet more like 75-80. It would be interesting to know how well those lifters hold up.

I've been looking at the ports on my intake and can see that I'm going to be in the same situation -- against the pushrod tubes and still not as wide as the ports on the heads.