For those who want big nasty cams with lots of lift, etc...
10-03-2003, 08:23 AM
#22
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Re: For those who want big nasty cams with lots of lift, etc... No, in fact for Ti valves it is best to use a BeC valve seat. They shed heat better, and they take abuse better than a steel seat.
10-03-2003, 09:28 AM
#23
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Re: For those who want big nasty cams with lots of lift, etc...
Thats my whole deal, I think you can use a stock lifter, and a 918 with any of the cams currently out (even the really big ones) if the rest of the valvetrain is light enough. Say a Ti retainer, and either a NaK filled steel valve or a Ti valve...
10-03-2003, 09:44 AM
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Re: For those who want big nasty cams with lots of lift, etc... Thats my whole deal, I think you can use a stock lifter, and a 918 with any of the cams currently out (even the really big ones) if the rest of the valvetrain is light enough. Say a Ti retainer, and either a NaK filled steel valve or a Ti valve...
Now, here's the question, and folks like Comp better know the answer, and I would appreciate them publicizing it for once and for all.
What, SPECIFICALLY, is that valvetrain mass?
PS - this is exactly how GM designs springs.
10-03-2003, 11:50 AM
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Re: For those who want big nasty cams with lots of lift, etc... very informitive post j-rod, thanks for all that info...very interesting reading material
10-17-2005, 10:26 PM
#28
Here are a few more reference points for this.....
http://www.compcams.com/Community/Ar...ID=-1210991090
http://www.compcams.com/Community/Ar...ID=-1483018418
http://www.compcams.com/Community/Ar...ID=-1283403059
Bret
http://www.compcams.com/Community/Ar...ID=-1210991090
http://www.compcams.com/Community/Ar...ID=-1483018418
http://www.compcams.com/Community/Ar...ID=-1283403059
Bret
10-18-2005, 01:22 AM
#29
Has anyone found affordable Ti/NaK valves since then? I know the market value for those has to have dropped at least a bit. Or maybe, has anyone found a lighter and more affordable valvetrain combo that has worked well for them? If so, what was the combo, from cam specs to the type of retainers used?
10-18-2005, 10:25 AM
#32
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Originally Posted by PacerX
There are a few things I really wish for in this life:
First being a properly designed spring, spec'd out to the point of...
a. Maximum valvetrain mass
b. Maximum rpm for a given valvetrain mass
c. Most aggressive lobe profile possible
d. Maximum lift
Then you could have a (fairly) simple chart...
If your valvetrain weighs "x", then the maximum lift becomes "y", your max reliable rpm becomes "z" using lobe profile "a" at lift "b".
This is the type of issue that bothers the hell out of me. If ANYONE actually did their homework while designing springs, they HAD TO go through this process.
Otherwise, they're just shooting in the dark.
Sadly, most of the aftermarket shoots in the dark.
Just like pushrods. There ought to be a dmaned chart out there that says:
Deck the head .010, go to a .020 smaller base circle cam, with stock lifters and stock thickness gaskets and "Brand "x" rockers and your correct pushrod length is "y".
Holy hell. Somebody get GM to give me the CAD model and I'll calculate it out.
First being a properly designed spring, spec'd out to the point of...
a. Maximum valvetrain mass
b. Maximum rpm for a given valvetrain mass
c. Most aggressive lobe profile possible
d. Maximum lift
Then you could have a (fairly) simple chart...
If your valvetrain weighs "x", then the maximum lift becomes "y", your max reliable rpm becomes "z" using lobe profile "a" at lift "b".
This is the type of issue that bothers the hell out of me. If ANYONE actually did their homework while designing springs, they HAD TO go through this process.
Otherwise, they're just shooting in the dark.
Sadly, most of the aftermarket shoots in the dark.
Just like pushrods. There ought to be a dmaned chart out there that says:
Deck the head .010, go to a .020 smaller base circle cam, with stock lifters and stock thickness gaskets and "Brand "x" rockers and your correct pushrod length is "y".
Holy hell. Somebody get GM to give me the CAD model and I'll calculate it out.
11-05-2005, 01:16 PM
#33
What a great thread. I found it during my quest to learn which cams would deliver the kind of performance gains I want while maintaining reasonable valve train stability/dynamics/geometry. IE I want good "steetable" performance and low wear.
I see there's much more to it than just picking the right cam.
To do it right, I guess I'd be looking at using light weight valves, harder valve seats, strong valve springs with quality retaining hardware, and maybe even better lifters.
But since my desire is not to have an insane high RPM drag car, like most of you madmen lol, I may not need all the stuff I listed above. Nevertheless, excellent info in this thread.
Props!!!
...back to lurking and learning about cams. ....hmmm ramp rates, durations, lift, lsa 
I see there's much more to it than just picking the right cam.
To do it right, I guess I'd be looking at using light weight valves, harder valve seats, strong valve springs with quality retaining hardware, and maybe even better lifters.
But since my desire is not to have an insane high RPM drag car, like most of you madmen lol, I may not need all the stuff I listed above. Nevertheless, excellent info in this thread.
Props!!!
...back to lurking and learning about cams. ....hmmm ramp rates, durations, lift, lsa Last edited by ShevrolayZ28; 11-05-2005 at 01:21 PM.
11-05-2005, 01:36 PM
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excellent read. i'll have to go back and re-read it as i skimmed through it. A lot of it was myth I always questioned.
One thing I'm glad to hear is that the mass/spring/damper systems I studied in differential equations is true! In reading your write up, I flashed back to diff eq. mY'' + dY' + KY = F(t). sweet.
One question: consrvation of every. Takes energy (gas) to compress the spring. where does it go when its decompressing?
For example, losses to compress a mixture in a cylinder are typicaly not taken into the pumping loss concideration because aside from the heat loss- it is regained durring expansion. Whats going on with this spring. I like convervation laws, they make things easy. Cancel out = good.
One thing I'm glad to hear is that the mass/spring/damper systems I studied in differential equations is true! In reading your write up, I flashed back to diff eq. mY'' + dY' + KY = F(t). sweet.
One question: consrvation of every. Takes energy (gas) to compress the spring. where does it go when its decompressing?
For example, losses to compress a mixture in a cylinder are typicaly not taken into the pumping loss concideration because aside from the heat loss- it is regained durring expansion. Whats going on with this spring. I like convervation laws, they make things easy. Cancel out = good.
Last edited by treyZ28; 11-05-2005 at 01:42 PM.
11-05-2005, 02:06 PM
#36
Originally Posted by treyZ28
On a side and somewhat related note:
I've noticed a terrible tendancy for people to make poor camshaft selections.
I've noticed a terrible tendancy for people to make poor camshaft selections.
And your differential calculus? Don't go there!
The sping and dash pot problems...yuck! 
11-06-2005, 04:24 PM
#37
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Ferrea makes hollow stem valves for the LSx
http://www.ferrea.com/catalog/2004Domestic.pdf
Page 26. I got a quote from a LS1tech vendor for $32 a piece.
http://www.ferrea.com/catalog/2004Domestic.pdf
Page 26. I got a quote from a LS1tech vendor for $32 a piece.
11-07-2005, 07:09 PM
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When does lift enter into the picture? My cam has .608/.612 lift using XER lobes. I'm running Ferrea dual valve springs with stock lifters and spin it up to 7K. It has ferrea 2.055/1.575 valves.
From what I've read, the 918s don't have enough seat pressure or can handle the lift.
From what I've read, the 918s don't have enough seat pressure or can handle the lift.
Last edited by 04Yukonxl; 11-07-2005 at 07:25 PM.
11-07-2005, 07:27 PM
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Originally Posted by treyZ28
On a side and somewhat related note:
I've noticed a terrible tendancy for people to make poor camshaft selections.
I've noticed a terrible tendancy for people to make poor camshaft selections.