Comp QXI Lobes
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Re: Comp QXI Lobes
Its everything. Lifter sliding thru bore faster, valvespring compressing faster, etc it just has a different sound i think. Not sure if the seating velocity is changing, and i hope its not too much or else it could be hammering the seats harder
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Re: Comp QXI Lobes
I concur. Depending on how aggressive the lobes are to begin with.. when only changing rocker ratio from stock 1.5 to 1.8 ratios can generate a BUNCH more sound.
Re: Comp QXI Lobes
I'd like to bring this thing back up and see if Mr. Jones has some input. Is it lifters that aren't up to the task? Can it actually be valves coming back on the seat too hard?CGT wrote: ↑Wed Mar 14, 2018 11:44 am 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.
CGT brought up an interesting point: if the acceleration is such that you've got lifter noise, are you just screwing yourself by upsetting things and losing the area you were hoping for anyways?
Here's another one: if it's the lifter not being able to keep up, would a larger diameter (more rigid) lifter body and wheel solve the problem?
Re: Comp QXI Lobes
The issue is the acceleration/velocity rates on the opening and closing ramps, right off the base circle. To make the cams look better in the catalog, Comp has no "Hydraulic ramps" on either side of the lobe, to gently start moving the lifter to the point the hydr unit goes solid, and starts moving the valve. This gives the profile a real short "Hydraulic Intensity" number, for all the yahoos that think that means something. Problem is, without the ramp, the velocity at which the valve leaves the seat, and is set back down on the seat, is as much as 10 times higher then a standard hydr roller profile.
That's gonna be noisy.
That's gonna be noisy.
Mike Jones
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
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Jones Cam Designs
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jonescams@bellsouth.net
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Re: Comp QXI Lobes
Can it be improved on by using more seat pressure, and larger diameter pushrods?
You are talking specifically about the 'noisy' lobes like XFI? The other, quiet lobes have a hydraulic ramp surely.?
You are talking specifically about the 'noisy' lobes like XFI? The other, quiet lobes have a hydraulic ramp surely.?
Re: Comp QXI Lobes
Thanks for the feedback, Mike. So to put it in technical terms, they're basically hammering the shit out of the plunger. Assuming that's a leakage issue, would a larger diameter lifter be more rigid and help prevent some of that?
I know the final answer is to buy a hydraulic profile for a hydraulic lifter or go solid but I'm milking this prick out for all it's worth.
I know the final answer is to buy a hydraulic profile for a hydraulic lifter or go solid but I'm milking this prick out for all it's worth.
Re: Comp QXI Lobes
Force= Mass x Acceleration
Different lifters, springs or Pushrods aren't going to change the force, at which the valve hits the seat.
Mike Jones
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Re: Comp QXI Lobes
No.
The force that is hammering the valve open, and slamming it closed, is the issue.
Mike Jones
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Re: Comp QXI Lobes
Well, I think I've addressed the issue from every angle I can think of and the conclusion is that no lightweight valves with boy-howdy springs and unobtanium pushrods and thousand-dollar lifters are going to make a hydraulic roller profile with that acceleration quiet. Is that about the extent of it?
Re: Comp QXI Lobes
Well, since Force is Mass x Acceleration, you can reduce the force, by reducing the mass. Ti valves would help, but that's an expensive bandaid.RevTheory wrote: ↑Mon Sep 02, 2019 11:41 am
Well, I think I've addressed the issue from every angle I can think of and the conclusion is that no lightweight valves with boy-howdy springs and unobtanium pushrods and thousand-dollar lifters are going to make a hydraulic roller profile with that acceleration quiet. Is that about the extent of it?
Mike Jones
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
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Re: Comp QXI Lobes
It's funny but, I have older street rod customers who WANT that sewing machine sound so, they won't use anything except a solid lifter.
That early Chevy F.I.sounding engine is what they are after.
It takes all kinds ...
Just changing valve covers can drastically change the volume of the valve train.
That early Chevy F.I.sounding engine is what they are after.
It takes all kinds ...
Just changing valve covers can drastically change the volume of the valve train.
http://www.rmcompetition.com
Specialty engine building at its finest.
Specialty engine building at its finest.
Re: Comp QXI Lobes
One reason I go with a HR is less valvetrain noise, so this particular lobe would defeat the purpose...
Re: Comp QXI Lobes
I tend to agree with you here. Maybe if you were bound by a rule or something but I'm not.