Comp QXI Lobes

[RevTheory]

Do you guys have any experience with QXI, hyd/roller lobes that you can share? Are they noisy? Do they crash the valvetrain? Mike Jones mentioned years ago that a lot of Comp grinds were like opening the valves with a hammer.

I'm thinking of a SBC with 1.7 rockers here. 225 @ .050, .651 lift.

[CGT]

Comp certainly has that reputation of noisy hydraulic roller lobes. . And I have heard plenty of them. Can't stand it. Mostly due in part to their XE, XER, XFI, LSK, type lobes. I have specced a few cams recently from them, that were decently quiet and stable using HUC, Marine, Marine high lift, magnum and I believe maybe HLO etc.

The "quietest" hydraulic rollers that I have gotten in the past used Bullet lobes.

[blykins]

I haven't used the QXI lobes, but I've used the QXX and HUC lobes. They are quiet and did quite well.

The Thumpr lobes are also quiet.

XE and XFI lobes sound like a sewing machine.

Harvey Crane coined the term, "intensity".....hydraulic intensity with hydraulic cams or major intensity with solid cams, if I remember correctly.

That term has served me well over the years and it's simply just the difference between advertised duration and .050" duration. Now, don't get me wrong, there are many variables going into this that have to be eyeballed (lift, .200" duration, valvetrain weight, etc.), but in terms of hydraulic roller lobes, lobes with 55-56°(and up) of hydraulic intensity have proven to be quiet and easy on the valvetrain for me.

[RevTheory]

I haven't used the QXI lobes, but I've used the QXX and HUC lobes. They are quiet and did quite well.

The Thumpr lobes are also quiet.

XE and XFI lobes sound like a sewing machine.

That's what I was wondering. This sounds like a pretty aggressive lobe and even Comp told me that the XFI were noisy. I sure like the area but I don't like the idea of the valves snapping shut to the point where you can actually hear it.

I'm eyeballing a Bullet grind that appears to be similar but Bullet doesn't group their profiles. At least Comp lies to me, lol

Bullet HR279/3823 279 224 147 .3823 CRA .649 1.7
vs.
Comp Cams QXI 13445 277 225 146 .383 .575 .613 .651 1.7 rocker

Thinking of QXX lobes on the exhaust.

[blykins]

My gut says that QXI lobe will be noisy.

How about a Thumpr intake lobe? Or a QXX intake lobe?

Also, a more aggressive lobe with more area under the curve doesn't always make more hp/torque.

[RevTheory]

My gut says that QXI lobe will be noisy.

How about a Thumpr intake lobe? Or a QXX intake lobe?

Also, a more aggressive lobe with more area under the curve doesn't always make more hp/torque.

Everything is on the table right now.

[blykins]

What engine is this for? If you're working with lighter valve train, then you have some lee-way.

[CamKing]

Quiet
HR70375: 280@.006", 227@.050", 148@.200", .375" Lobe Lift

Kinda Quiet
HR70340: 272@.006", 224@.050", 147@.200", .340" Lobe Lift
HR71360: 276@.006", 228@.050", 151@.200", .360" Lobe Lift

[Walter R. Malik]

Do you guys have any experience with QXI, hyd/roller lobes that you can share? Are they noisy? Do they crash the valvetrain? Mike Jones mentioned years ago that a lot of Comp grinds were like opening the valves with a hammer.

I'm thinking of a SBC with 1.7 rockers here. 225 @ .050, .651 lift.

A LOT of the noisyness people hear is from using their trash hydraulic roller lifters.

[groberts101]

Quiet
HR70375: 280@.006", 227@.050", 148@.200", .375" Lobe Lift

Kinda Quiet
HR70340: 272@.006", 224@.050", 147@.200", .340" Lobe Lift
HR71360: 276@.006", 228@.050", 151@.200", .360" Lobe Lift

Sorry to be the needy guy here, Mike.. what about listing a "kinda noisy" lobe spec?

[groberts101]

Do you guys have any experience with QXI, hyd/roller lobes that you can share? Are they noisy? Do they crash the valvetrain? Mike Jones mentioned years ago that a lot of Comp grinds were like opening the valves with a hammer.

I'm thinking of a SBC with 1.7 rockers here. 225 @ .050, .651 lift.

A LOT of the noisyness people hear is from using their trash hydraulic roller lifters.

Yep.. heard many swaps in both directions through the years. Lots of trashy sounding roller rockers out there too!

[GARY C]

Noisy must be faster, Pete Jackson marked a gear drive based on it's sound.
I found if you turn up the volume on your stereo it makes the noise go away.

[CamKing]

Quiet
HR70375: 280@.006", 227@.050", 148@.200", .375" Lobe Lift

Kinda Quiet
HR70340: 272@.006", 224@.050", 147@.200", .340" Lobe Lift
HR71360: 276@.006", 228@.050", 151@.200", .360" Lobe Lift

Sorry to be the needy guy here, Mike.. what about listing a "kinda noisy" lobe spec?

Kinda quiet = kinda noisy

[Orr89rocz]

Its all in the ears of the beholder...

The faster looking lobes seem to be sewing machine like

Lifter tick can be prevalent in some setups as well but i have not had any problems with gm lifters or the sbc morel 4602’s despite the many claims they are noisy

I have run a jones 292 - 232 .353 lobe hyd roller in my sbc turbo car and it was quiet. But thats a relatively mild lobe imo

I ran a comp magnum hi lift lobe 306 246 .400 lobe in my other turbo combo with morel lifters and it also was relatively quiet imo. I had some minor pushrod rub on the head that ticked somewhat and my injectors ticked abit so hard to tell exactly. Slight sewing machine sound but nothing like xfi lobes i have heard

[CGT]

Just curious, In your guy's opinion. What is making the sewing machine noise? Is in the lifter, valves opening, closing? Im always left wondering, if they sound that raunchy...maybe your not even getting "all" of that mean lobe to begin with. I just stay away from those type lobes nowadays.