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Comp QXI Lobes

General engine tech -- Drag Racing to Circle Track

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CGT
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Re: Comp QXI Lobes

Post by CGT » Tue Sep 03, 2019 9:36 am

paulzig wrote:
Mon Sep 02, 2019 4:54 pm
One reason I go with a HR is less valvetrain noise, so this particular lobe would defeat the purpose...
I agree. I think a hydraulic cam should be quiet. The thing is, I don't mind solid lifter noise in some cases. But those XE type hydraulic lobes don't sound like solid lifter noise to me, they just sound like something is wrong.
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Re: Comp QXI Lobes

Post by dfarr67 » Tue Sep 03, 2019 11:14 am

With all the quality grinders out there- are Comps profiles that good to put up the the noise?

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Re: Comp QXI Lobes

Post by RevTheory » Tue Sep 03, 2019 11:26 am

dfarr67 wrote:
Tue Sep 03, 2019 11:14 am
With all the quality grinders out there- are Comps profiles that good to put up the the noise?
I've been wondering about this. Billy Godbold certainly has the physics credentials to design good lobes and he has in-house dynos and spintrons. Is there a need to design profiles that exceed the capabilities of the lifters? They have to know the damn things are noisy and people complain about that on forums.

I guess everyone has a little different opinion on what's acceptable. I do wish Comp would put a little disclaimer on their lobe descriptions: Caution! These lobes are noisy and will crash the valve train if you don't spend a fortune." :D

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Re: Comp QXI Lobes

Post by CamKing » Tue Sep 03, 2019 12:04 pm

dfarr67 wrote:
Tue Sep 03, 2019 11:14 am
are Comps profiles that good to put up the the noise?
Their marketing skills are much better then then their cam designing skills.
The average Comp Cams cam buyer, reads about how great it is to have short seat duration, and big .050" and .200" duration, so that what Comp sells. It doesn't matter that it beats the hell out of the valvetrain. How many of their customers would have a way to prove it it was the cam's fault?
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Re: Comp QXI Lobes

Post by n2xlr8n » Tue Sep 03, 2019 12:26 pm

RevTheory wrote:
Mon Sep 02, 2019 9:06 am
Thanks for the feedback, Mike. So to put it in technical terms, they're basically hammering the shit out of the plunger.
I was not entirely sure if Mike answered this- is it the plunger getting hammered?


I'm also having trouble understanding why one would desire a HR lobe with "intensity" and expect long life valvetrain. Is that possible? I've always used SR, so I don't know what improvements have been made in the Industry wrt HR.
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Re: Comp QXI Lobes

Post by Orr89rocz » Tue Sep 03, 2019 12:46 pm

CamKing wrote:
Mon Sep 02, 2019 10:49 am
RevTheory wrote:
Mon Sep 02, 2019 9:06 am
would a larger diameter lifter be more rigid and help prevent some of that?
No.
The force that is hammering the valve open, and slamming it closed, is the issue.
Mike answered it with this. Its not the lifter its the valve hammering the seat. Correct me if im wrong

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Re: Comp QXI Lobes

Post by CamKing » Tue Sep 03, 2019 1:09 pm

Orr89rocz wrote:
Tue Sep 03, 2019 12:46 pm
CamKing wrote:
Mon Sep 02, 2019 10:49 am
RevTheory wrote:
Mon Sep 02, 2019 9:06 am
would a larger diameter lifter be more rigid and help prevent some of that?
No.
The force that is hammering the valve open, and slamming it closed, is the issue.
Mike answered it with this. Its not the lifter its the valve hammering the seat. Correct me if im wrong
Correct. The plunger is getting hammer also, but that's not what you hear. The issue is the valve hitting the seat, and the rocker hitting the valve tip.
Now, when the plunger is getting hammered, and collapsing, it can actually increase the velocity/acceleration rate at which the valve is leaving and hitting the seat.
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Re: Comp QXI Lobes

Post by novadude » Tue Sep 03, 2019 2:12 pm

CamKing wrote:
Tue Sep 03, 2019 12:04 pm
dfarr67 wrote:
Tue Sep 03, 2019 11:14 am
are Comps profiles that good to put up the the noise?
Their marketing skills are much better then then their cam designing skills.
The average Comp Cams cam buyer, reads about how great it is to have short seat duration, and big .050" and .200" duration, so that what Comp sells. It doesn't matter that it beats the hell out of the valvetrain. How many of their customers would have a way to prove it it was the cam's fault?
Wonder why they don't just play games with the advertised numbers instead of sticking to the industry standard of 0.006" for adv duration? Since everyone that reads the magazines wants short advertised duration for a given 0.050" duration, why not just design lobes that work and published advertised numbers measured at 0.009" or something? I think Isky does something like this.

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Re: Comp QXI Lobes

Post by CamKing » Tue Sep 03, 2019 2:36 pm

novadude wrote:
Tue Sep 03, 2019 2:12 pm
Wonder why they don't just play games with the advertised numbers instead of sticking to the industry standard of 0.006" for adv duration? Since everyone that reads the magazines wants short advertised duration for a given 0.050" duration, why not just design lobes that work and published advertised numbers measured at 0.009" or something? I think Isky does something like this.
Because if someone has it measured, and it's not what Comp said it is, it's Comp's fault. If it matches the specs, and beats the hell out of the valvetrain,
Maybe it's the lifters? Maybe it's the rockers? Maybe it's the pushrods? Maybe it's the lifter bores? maybe it's the lifter bore clearances? Maybe it's the oil? Maybe it's the valves? maybe it's the valve seat? Maybe the engine builder should have known it was to aggressive for his application?
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Re: Comp QXI Lobes

Post by Orr89rocz » Tue Sep 03, 2019 2:51 pm

It be nice to see them show more dyno results, hp numbers would sell i would think

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Re: Comp QXI Lobes

Post by NewbVetteGuy » Tue Sep 03, 2019 3:04 pm

CamKing wrote:
Tue Sep 03, 2019 1:09 pm
Orr89rocz wrote:
Tue Sep 03, 2019 12:46 pm
CamKing wrote:
Mon Sep 02, 2019 10:49 am

No.
The force that is hammering the valve open, and slamming it closed, is the issue.
Mike answered it with this. Its not the lifter its the valve hammering the seat. Correct me if im wrong
Correct. The plunger is getting hammer also, but that's not what you hear. The issue is the valve hitting the seat, and the rocker hitting the valve tip.
Now, when the plunger is getting hammered, and collapsing, it can actually increase the velocity/acceleration rate at which the valve is leaving and hitting the seat.

Mike,

I often see people evaluating the accel rate based upon the difference between the 0.050" and 0.200" durations, but it sounds like noise / longevity / valve hammering shut is based upon the DECEL rate and not the ACCEL Rate, if the lobes are asymmetric and the profile is different on the closing side vs. the opening side, then the open side #'s don't mean squat, right?

-I'm also curious about how relevant 0.200" duration vs. 0.050" duration is on the close side when it comes to evaluating decel rates noise / longevity issues. -Can't you slow the deceleration rate down from 0.050" to the seat? (Would 0.050" - 0.000" durations be more relevant to trying to understand this?) Is there any ability to further slow the valve down from 0.006" to 0.000" such that some of what matters here is lost in the specs that normally get published? (or is 0.006" just way too little to matter?)


It seems to me that you could get your extra area under the curve and still have decent valve train noise levels and longevity if you yank the valve off the seat on the open side, and have an aggressive lobe from the seat to max lift (while avoiding lofting the valve) and then close the valve relatively quickly from max lift down to 0.050" when you'd want it to decelerate from 0.050" to close so you don't get valve bounce and noise /longevity issues.

(I thought I remembered a really long post by UDHarold on the Chevelles forum on this subject when comparing the Comp XE Flat Tappet valve destroyer lobes to one of his newer (probably Lunati-branded) lobes decel rates but I can't find it to save my life...)


I'm also curious if a little bit of valve train noise around peak RPM could be an indicator that you didn't leave anything on the table. (Similar to the idea / old GM quote that slight pinging at max load is the "sound of economy" / achieving max performance for your given fuel octane.) -Although that's probably just an indication that you went too light on your springs or too heavy on the valve side of your valve train for your lobes and HP RPM peak...



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Re: Comp QXI Lobes

Post by CamKing » Tue Sep 03, 2019 3:39 pm

Orr89rocz wrote:
Tue Sep 03, 2019 2:51 pm
It be nice to see them show more dyno results, hp numbers would sell i would think
If you spend $10k dyno testing, you would still need to spend X amount more to advertise those dyno results.
Most companies have figured out, If you just add those testing dollars to your advertising budget, and claim there's a power gain, you will sell even more parts.
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Re: Comp QXI Lobes

Post by PRH » Tue Sep 03, 2019 4:34 pm

I’ve sold a few cams for BB mopars with the QXI lobes.
No complaints of noise....... in fact on a couple it was noted from the users how quiet they were.

I’ve only had one on the dyno here, and I didn’t think it was bad at all.
Def quieter than a solid....... but not silent like an OE cam.

Related story with regards to the lifters and the noise.

Story from a customer......
XFI hyd roller in a BB Mopar, Comp lifters, Comp rockers.
Not real obnoxious when all warmed up........ really noisy at start up.

Calls around to different lifter suppliers, has a nice talk with one supplier who tells him why the current lifters are noisy, and why his wouldn’t be....... so he buys and installs them.
The noise is the exact opposite.
Dead quiet at start up, then just gets louder and louder with heat......... to the point where it sounds like something bad is happening.

I’ve got a cam with some XFI lobes coming, going to use beehives and the street lifters from Howard’s. We’ll see how that works out.
Owner wanted a hyd roller....... motor had a SFT in it before.
As long as it’s not really any louder than the solid was, it’ll be fine.
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Re: Comp QXI Lobes

Post by PRH » Tue Sep 03, 2019 6:39 pm

And then sometimes you get this:



I stumbled across that video while reading a thread on another forum about noisy lifters.
The scary part for me was the owner saying in the thread the motor had been dynoed like that!!

From what I recall, it eventually got a different cam and lifters and was supposedly much quieter with the new parts.

Imo, that type of noise is not from the valves hitting the seats.
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Re: Comp QXI Lobes

Post by Orr89rocz » Tue Sep 03, 2019 7:23 pm

Tuned two cars with xfi lobes. Sbc stuff and gm ls7 lifters. They werent super noisey. Alittle sewing machine but nothing out of the ordinary

The shelf xfi 230/236 cam for sbc is very popular and makes really nice power but does require a stiffer spring, i like the small dual ls type springs 150 seat or more and 375-400 open

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