Help picking aftermarket camshaft

[SmokeOps]

@Midlife Crises, I don't think 7k rpm is all that crazy for a 3v in my opinion. I've heard from many people that they rev theirs to 6800-7200 on stock top ends. Now I think running up to 7k rpm on stock topend isn't sustainable. I'm pretty sure the OEM springs are rated for up to 6800rpm, so I think with some better springs, 7k is not a lot to ask for as long as I'm not holding it at 7k for long periods of time. Four Eyes has all OEM timing components and revs his to 7500 and 7800 bursts when shifting. I'm not saying the 4.6 3v can handle it as well as a coyote or a 4v, but I think it's doable with supporting mods. @Midlife Crises, I have the 2.97 first gear ratio. I don't plan on making huge power like 700-800 plus. I did put in Boss 302 rods when I rebuilt the engine, but I think the most I'll probably want to go with the 3v is around 550 wheel. I appreciate the feedback and concerns.

 

[SmokeOps]

@StockishS197 If you look at Christian Reyes build, I don't think his bottom end is as doggy as you make it out to be, and he revs his to 7400 rpm on the dyno graph. I would want my dyno graph to look similar to his. It starts to fall off around 7k-7200rpm, which is a good point to shift since you're back at a good spot in the power band after shifting into the next gear. If a SPR cam isn't what I need to get that, then I won't do a SPR, but since I have to upgrade the valve springs to get to that rpm, what's the harm in maybe squeezing out a little more power top-end? On a dyno graph, I'm sure that a SPR cam would probably make a little less power under 5k to 5500rpm, but I think if the increase in power is the majority of the rpm band when racing or doing pulls, that's worth it to me. The car only has a CAI right now, and I highly doubt that with all those mods, I'll be making less power bottom-end than what I make right now. I'm fine with how the bottom feels right now, so I don't really care if most of my gains are top-end which is what I care about.

 

[Badd GT]

Is this a street car?

 

[StockishS197]

@StockishS197 If you look at Christian Reyes build, I don't think his bottom end is as doggy as you make it out to be, and he revs his to 7400 rpm on the dyno graph. I would want my dyno graph to look similar to his. It starts to fall off around 7k-7200rpm, which is a good point to shift since you're back at a good spot in the power band after shifting into the next gear. If a SPR cam isn't what I need to get that, then I won't do a SPR, but since I have to upgrade the valve springs to get to that rpm, what's the harm in maybe squeezing out a little more power top-end? On a dyno graph, I'm sure that a SPR cam would probably make a little less power under 5k to 5500rpm, but I think if the increase in power is the majority of the rpm band when racing or doing pulls, that's worth it to me. The car only has a CAI right now, and I highly doubt that with all those mods, I'll be making less power bottom-end than what I make right now. I'm fine with how the bottom feels right now, so I don't really care if most of my gains are top-end which is what I care about.

It sounds like you just want to rev it high. The point being is you don’t need RPM to achieve a good ET if that is your goal. You can make 350-360RWHP at a safer RPM with more mid range torque on top vs moving the peak up a few hundred RPM. Also, dyno runs from 3k up at WOT aren’t showing the significant low end losses you would see during street driving with more aggressive cams. This also happens with NSR cams, just not as pronounced.

If you want to rev it above 7K reliably, you will want a stronger rod than the factory powdered rods. At those engine speeds, the stress on the rods increases exponentially.

 

[SmokeOps]

That is true about the under 3k rpm dyno pull, they do not show, but I wouldn't say I really ever full throttle the car under 2500rpm unless it's a dig in 1st gear, though, so I don't think that's an issue for me. @StockishS197 In one of my previous post if you read it I did say I put Boss 302 rods when I rebuilt the engine and those rev pretty high so my rods are definitely over built for what im going for. @Badd GT to answer your question it will be a street/track car so I will drive it on the street but I also want to do drag, track, and autocross with it.

 

[Midlife Crises]

Dollars to doughnuts the Livernois stage 2 cams your looking at are in fact the Comp cams 127500s in a Livernois box. That being the case you will have to lock the phasers and run the springs recommended by the manufacture. Don’t forget the retainers. If Livernois springs meet the manufactures spec. they should work. I still think 4.10s would be a good choice for the rear. I would match that cam with as much compression as I could get away with. 11 to 1 with good fuel and a Lito tune.

 

[Dino Dino Bambino]

It sounds like you just want to rev it high. The point being is you don’t need RPM to achieve a good ET if that is your goal. You can make 350-360RWHP at a safer RPM with more mid range torque on top vs moving the peak up a few hundred RPM. Also, dyno runs from 3k up at WOT aren’t showing the significant low end losses you would see during street driving with more aggressive cams. This also happens with NSR cams, just not as pronounced.

If you want to rev it above 7K reliably, you will want a stronger rod than the factory powdered rods. At those engine speeds, the stress on the rods increases exponentially.

There isn't a single aftermarket cam that'll outperform the stock cam from idle to 4400rpm, and all will sacrifice torque below that rpm to some degree. If you also add an aftermarket intake manifold, the combination of cams/manifold essentially takes a hit to the torque curve below 5000rpm and adds torque above that. This is Four Eyes before and after adding Detroit Rocker cams and the Ford Performance IM.



The stock powdered metal rods are light and strong enough for 7000rpm in a N/A 4.6 but for insurance and peace of mind, I'd prefer the Gen 2/3 Coyote (same as Boss 302) rods if anything nearer 7500rpm is the goal. You'd also need to consider a higher capacity oil pan and HV pump with billet gears for 7500rpm. Sustained engine speeds of 6500rpm & above will require locked out phasers to prevent their failure.

If you're looking for ~360rwhp your peak HP is going to be at or near 6500rpm with peak torque of ~330rwtq arriving at or near 5000rpm. The dyno graphs I posted tell the story. Therefore you'll want to rev the engine up to 7000 if you're going to exploit the extra top end performance. If you want a strong 2500-4500rpm midrange for street use, stick with the stock cams & IM with delete plates and settle for a ~6500rpm limit.

Dollars to doughnuts the Livernois stage 2 cams your looking at are in fact the Comp cams 127500s in a Livernois box. That being the case you will have to lock the phasers and run the springs recommended by the manufacture. Don’t forget the retainers. If Livernois springs meet the manufactures spec. they should work. I still think 4.10s would be a good choice for the rear. I would match that cam with as much compression as I could get away with. 11 to 1 with good fuel and a Lito tune.

With a stock 3.542" stroke you'll have a hard time finding a piston that'll give you much above 10.0:1 compression, and 11.0:1 is only possible with a longer stroke i.e. stroker build. With the high valve lift of SPR cams, you'd need to verify PTV clearance and lock out the phasers altogether if you zero deck the block and use flat top pistons for a higher compression ratio. This is where going down the rabbit hole of a maximum effort N/A build with CNC ported stage 3 heads (1mm oversize valves) gets really expensive to the point where it only makes sense if you have a YouTube channel with over 100k subscribers to fund the project! By this stage you're going to need 4.10 or even 4.30 ratio axle gears to make the sacrifice of lower rpm torque somewhat acceptable.

At the end of the day the 3V is a very good engine but it can never match the performance of a Coyote across a wider 1500-7500rpm range even when built as an 10.2:1 compression 301ci stroker (Four Eyes again ) simply because it's constrained by a single exhaust valve per cylinder, a single camshaft on each bank and, consequently, the inability to vary the lobe separation angle as well as the intake/exhaust centerline angles in order to widen the power band. Once you lock the cam phasers, the power band becomes even narrower.



Therefore it's important to recognise those constraints and try to make the best of what you have without sacrificing too much drivability for the sake of having a 7000+rpm screamer.

 

[SmokeOps]

Well, if I don't go with an SRP cam, I'm looking at Comp cams Big Mutha Thumpr NSR 242/262. I would set the rpm limit to 6800rpm if I went with this cam. Same bolt-ons and everything, just with the NSR cam I spec'ed. Any opinions on that?

 

[Midlife Crises]

Looking at the Rocker power curve makes me wonder what 16 lbs of boost would do to it.

 

[Dino Dino Bambino]

Well, if I don't go with an SRP cam, I'm looking at Comp cams Big Mutha Thumpr NSR 242/262. I would set the rpm limit to 6800rpm if I went with this cam. Same bolt-ons and everything, just with the NSR cam I spec'ed. Any opinions on that?

I think that cam is too big. The idle will be very rough and low rpm drivability will be pretty awful. I'd suggest the regular Mutha Thumpr instead. You could still use the stock valve springs, stock heads, and a 6800rpm rev limit. All you'd need in addition is phaser limiters.
Even the Mutha Thumpr cams will make the engine buck below 2000rpm but it'll be more tolerable than with the Big MT, and the idle will be choppy enough to sound mean.

 

[Badd GT]

Put the stage 1 Livernois cam or 127400’s in. Same power as stage 2 or 127500’s but have nice street manners. Livernois springs will use your factory retainers but I would not use their limiters,mine eventually disintegrated, use the Comp limiters.you might even catch a sale tomorrow or Monday