Hey guys - I'm considering a cam change for my 505 street engine in my Challenger. Currently it has stock stealth heads and Comp xe284 cam. Basically a 240@.050 and .507, 110lsa hydraulic ft. I was looking at the Comp xe295hl, also hyd ft with 251@.050 and .565 lift. I'm also planning CNC porting or trick flows. Seems like substantial enough potential gain to make it worth the work, but any opinions to share? I may just CNC the heads and add 1.6 rockers for the easiest swap. Or I may go all out and add hyd roller... It's a street car with a 4 speed and 3.55's. Might go down the strip now and then, but I enjoy making them faster regardless. Thanks

How do you like the engine with the existing cam? I have a 246 hyd roller in my 512 and I think it is a little too big for a street car with 3.54 rear gears. But if you think you can go larger then go for it. I have CNC ported Edelbrock heads on my 512 which is probably why I don't need a very big cam.

If you're looking for more power I'd put Trick Flow heads on there and then see what you think. You might like how it works with better heads but the same cam.

In general, good heads with a smaller cam is a better combo than poor heads with a big cam. Lots of Mopar guys got used to the bad head + big cam combo in the old days but now you can do it the other way.

Thanks Andy. I am leaning toward the trick flows...what do you think about running 1.6's with the existing cam?

My Hydro roller in my 512 is 255 / 258 @ .050, 3.54 gear OD trans, lock up converter, works GREAT on the street.

If it was me doing the changes I would go with a set of 270 Trick flows with 1.6 rocker with your current cam and see how I liked those two changes
Keep in mind that big C.I. motors like big cams also

I wouldn't bother with the 1.6 rocker arms with the Trick Flow heads. I also wouldn't change cams until you get it running with the Trick Flow heads. I assume you'll put the 240 heads on there since it is a street car.

I did a bunch of cam testing and rocker arm testing with the Trick Flow heads and the bottom line is that those heads are so good they don't need a bunch of cam. In fact, if you use too big of a cam the intake just goes out the exhaust since the low lift flow is so good.

I'm sure you could find more power with a different cam than what you have but you'll have to be careful and take small steps. People who tell you that you need a big cam probably haven't run 100 dyno pulls with Trick Flow heads.

Read this and see if you think you need more rocker arm ratio. I spent a bunch of time and money testing those heads. They don't need more cowbell.

https://www.hotrod.com/articles/trying-find-extra-power-rocker-arm-testing/

Your current cam gets a NO vote from me. The original COMP Xtreme hydraulics like yours go into valve train crash at a much lower RPM than most other hydraulic cams. Increasing the rocker ratio will only make it worse. I don't know if the HL series "fixed" that issue. Maybe Dwayne Porter can provide some input on how the HL lobes work.

I believe I'm experiencing this now with my xe274. I switched heads which includes what I would assume is a little stiffer spring and now, I'm experiencing crash at 5700-5800 rpm. Very frustrating. Get a cnc'd head that should flow around 50cfm more than my old heads and can't even test in higher rpm ranges to see what happens.

This has been my experience as well with typical heavy BB valve trains.
SB motors seem to be able to get closer to 6000....... even 6200 on something with light parts.
Ultimately, the lifters are the problem...... and more spring pressure only exacerbates the issue.

IMO, smoother hyd cam lobes or running a solid lifter cam(the better option) are the easiest way around it.
High rocker ratios usually cost you a couple hundred rpm.

Even if you choose to go hyd roller, lobes leaning towards “smoother” rather than “faster” are probably a safer option........ unless you feel like running the really high end lifters.

The XE/HL lobes work really well...... up to the point where the valvetrain becomes unstable...... which is almost never high enough for my liking.

Thanks everyone. Yes Andy, I'll be looking at the Trick Flow 240's and also looking at your trick flow and rocker arm testing! The current cam seems to do what its supposed to do. Idles nice at 850, its quiet and pulls pretty good from down low up to 5500. Havn't really tried spinning it higher than that. I dont have anything but the butt-meter to gauge the power, and it feels pretty decent as is...Butt, I want more .

Thanks Dwayne. In your experience with those cams, when do you typically start seeing the valvetrain become unstable?

I just change camshaft in my 512 with TF 240 and 10.4:1 komp.... Sitting in a bone stock E-body. Converter 4200 flashstall and 3.91 with 28" tires.
From dur 0.50 241° .564 lift to dur 0.50 251° and 594 lift (Mek FT)..... I like the "bigger" cam more because its still has a ridiculous amount of low end torque and now has little more on topp to play with.
Maybe a cam with that amount of dur in a 4 speed car can be annoying on the street?

Under 6k.
It’s not like it starts to get unstable, then you have a few hundred rpm left.
It’s like a switch........ it’s good right up until it’s total crap.
It runs into the wall.

Search for an old Mopar Muscle article called Mild Mannered Mauler, from like 2005.
They do a pretty good job of showing the challenges involved with getting those lobes to rpm.

Thanks. Its interesting that some have better experiences than others. Of course in my case, I havnt really pushed it to the limit to see what it does at higher rpms. I also have stock stamped rockers. Yes, thats what you get with a Muscle Motors street crate. Not judging, just sayin. They work fine. I have a couple sets of Crane roller rockers 1.5 (and 1.6) for the upgrade should I decide to do the Trick flow swap.

The slower the bleed rate of the lifters, the better your results will be.

You should read that article....... it’s the only one I’ve seen that doesn’t sugar coat the situation.

With my old 213 big valve heads from Hughes with an unknown valve spring, I had no issues revving mine up to 6300 rpm. I used to shift around 5900 or 6000 at the track. There was no hint of any issues on a chassis dyno spinning it to 6000.

For years, people have described what Dwayne mentioned above and now I'm experiencing it and I'm not happy about it.

It may be time for a cam change but, I think I'm just going to drive it for awhile. I'm tired of wrenching on it this year and have other irons in the fire.

Unfortunately, the seat of the pants feel is the same as “valve float”, so it’s not always clear as to what the problem is.
The old heads had a spring that could maintain control, and the lifters were cooperating.

I did an experiment on a BBC years ago that wouldn’t go over about 55-5600 with a hyd cam.
I swapped out the springs for something with about 20lbs more on the seat and like 40-50 open.
It gained maybe 100rpm, but when it nosed over with the stiffer springs it did so more abruptly than with the lighter springs.
Ultimately I swapped the cam for a small solid, and used springs which were in between the previous two........ the motor pulled effortlessly to 6500(never saw any float), and as a result picked up about 30hp.

As for the situation with the head swap in the post above, I would be comparing the open/closed spring loads between the two sets of heads as a starting point.
Is the rest of the valvetrain the same as before?
Same rockers and pushrods?
Same lifter preload?
Same brand and viscosity of oil?

Those can all be factors when running hyd lifters.

The takeaway here should be, the likelyhood of achieving good high rpm results when using hyd lifters is directly linked to the bleed rate of the lifters....... not just being sure the springs/rockers/pushrods are matched to the cam profile.
With a solid lifter cam, that very unpredictable variable is removed.

Dwayne - I get the impression you might prefer solid lifters .

Thank you for the valuable info. If this were a few years ago, I'd probably have a solid roller in there by now. I'm still intrigued by which combination of parts makes the most power, only now I'm realistic about if, how and when I can even use it. Not to mention how much wrenching am I willing to do.

Check out the old article I did for PHR: http://www.moparts.org/Tech/Archive/bb/Lobe.html

I used Comp Xtreme Chrysler Hyd flat tappet lobes in that engine and they worked way better than I hoped for. That setup would spin past 7000 rpm without any sign of problems. That was my old 470 engine with ported Edelbrock heads and I used 5965/5985 lobes which was 241/247. Lift was 0.545 with a 1.5 rocker arm. I was using a beehive spring which might be part of the answer.

That was a sweet cam in that engine. Nice and quiet, good low end and it would pull hard for as long as I wanted to stay in it on the street. I'd think a cam like that would work just about perfect in your engine.

I'm using a Crane hyd roller in my 512 and it spins as high as I want to go. I've had it up past 6500 rpm and it was still pulling but I was going way faster than I should on the street so I lifted. I'll get it on the chassis dyno later this month and we'll see how it works there but so far I haven't run into any issues.

But I've seen a fair number of hyd flat tappet and roller problems on the dyno. It does seem to be a bit of hit and miss on the combination. If the combination isn't happy then the cams just stop working at higher speeds.