Valve stem seals crushed, LS7. More spring?

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tenxal
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Re: Valve stem seals crushed, LS7. More spring?

Postby tenxal » Fri Jan 06, 2017 6:59 pm

RW TECH wrote:The COPO has 100% of the stuff I've mentioned in earlier posts, including the stock guides, rockers, pushrods (some packages), valves, retainers, & locks.

What it had going for itself is someone must have been paying attention to make sure the valvetrain wasn't going to throw up all over itself at above 8K RPM with all those "stockish" parts.


Yep. Adding mass/weight/spring to the valve trains on these motors is about 50 steps in the wrong direction.

There's a reason that NHRA Stock and Super Stock cars use the factory rockers and even the hydraulic roller lifters in Super Stock.

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Re: Valve stem seals crushed, LS7. More spring?

Postby RW TECH » Fri Jan 06, 2017 10:11 pm

Newold1 wrote:Question here being how much more power up to 7000rpms and at +7400rpms could be made with this engine with a different camshaft spec. that allowed more than .641" valve lift?


If the only change is cam & valvetrain I''d bet a .800" solid roller would make 40 more.

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Re: Valve stem seals crushed, LS7. More spring?

Postby wyrmrider » Fri Jan 06, 2017 10:30 pm

Recall that RW said different heads one place and have the exhaust ported by a pro without a flowbench (sic)
We don't know how their heads would flow with-more than .641 lift because they are not allowed to do it nor are they allowed to port more than they can shave the exhaust flange
Ae there other heads out there to try or are these cores the best ones to start with?

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Re: Valve stem seals crushed, LS7. More spring?

Postby RW TECH » Fri Jan 06, 2017 11:32 pm

tenxal wrote:
Yep. Adding mass/weight/spring to the valve trains on these motors is about 50 steps in the wrong direction.

There's a reason that NHRA Stock and Super Stock cars use the factory rockers and even the hydraulic roller lifters in Super Stock.


Agree.

No offense intended to the OP, but it's unfortunate the current market leads customers down some of the paths they choose. Judging by his list of parts and the appearance of some items, your setup is very unhappy. Compare that to the off-road pic & posted......thousands of race miles at higher RPM and more power than yours with the parts I mentioned. You need to sort your stuff in testing so you can get that level of performance for yourself.

My very best suggestion is gather up your stuff & send it to a shop with a Spintron. Something is going to glare......And it'll save you time & money in the long run. I'm sure the cam guys who poke around in here could give you a recommendation who can get you where you need to be. Poof - done. More time to focus on other things.

Vendors: Packages should be made available in the market that include a whole valvetrain system (including valves) plus Spintron data that proves the combination will run clean until 'x' speed. Not hard to do on common platforms like LS, Gen II HEMI, etc. Include test parameters on the data sheet. No reason why a guy like this should ever have to shop the individual bits & hope it all works out.

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Re: Valve stem seals crushed, LS7. More spring?

Postby Kevin Johnson » Sat Jan 07, 2017 12:22 am

Newold1 wrote:...
The information from the article that confuses me is that they give the replacement camshaft specs. twice and they are different each call out. The seem to be saying that they greatly increased intake duration versus exhaust duration, but the printed numbers indicate the opposite. Confusing. ...



Three specific camshaft specs are mentioned other than the unspecified additional ones that SAM Tech tested and decided against using:

The COPO’s camshaft is a completely different animal as well, with 233/276 degrees of duration at .050 and .630/.630-inch lift. This is quite a bit larger than the 211/230-at-.050 cam (.591/.591-inch lift) found in the stock LS7. The 43-degree duration split on the COPO may seem radical, but when matched with CTS-VR hydraulic lifters, PSI beehive valve springs, titanium intake valves, and a COPO-specific CNC program that squeezes a smidgen more airflow out of the LS7 cylinder heads, the combination turns 8,000 rpm out of the box.

-snip-

In the not-so-distance past, turning 8,000 rpm was the exclusive territory of solid-roller race engines. Not only has Chevy managed to significantly increase the maximum engine speed of the COPO LS7’s hydraulic roller valvetrain, it gets the job done with parts that look deceivingly ordinary. Chevy fits the heads with stock LS7 titanium intake valves, sodium-filled exhaust valves, PSI beehive valve springs, and lightweight steel retainers. Managing valve actuation duties is a 233/276-at-.050 cam, 3/8-inch pushrods, stock 1.8:1 LS7 rocker arms, and lightweight ceramic ball lifters originally designed for GM’s CTS-V racing program.

-snip-

To wring some more RPM out of the COPO LS7, SAM Tech spec’d out a custom camshaft to take advantage of their improved cylinder head design, and also focused on stabilizing the valvetrain. After testing several different grinds, SAM Tech opted for a custom Comp 258/276-at-.050 cam. The additional 25 degrees of intake duration helps build cylinder pressure higher in the rpm range, and the wide 116-degree lobe-separation angle further extends the powerband at high RPM.

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Re: Valve stem seals crushed, LS7. More spring?

Postby Newold1 » Sat Jan 07, 2017 9:21 am

The confusion that is spread in this articlecomes from the what I and others have always used in a camshaft duration call out is that usually the intake duration is normally the first number and the exhaust being the second number. How it is listed and discussed in the article is confusing if one considers the usual way durations I/E are normally given.I propose we keep it simple and not move norms around.

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Re: Valve stem seals crushed, LS7. More spring?

Postby Kevin Johnson » Sat Jan 07, 2017 11:03 am

Newold1 wrote:The confusion that is spread in this articlecomes from the what I and others have always used in a camshaft duration call out is that usually the intake duration is normally the first number and the exhaust being the second number. How it is listed and discussed in the article is confusing if one considers the usual way durations I/E are normally given.I propose we keep it simple and not move norms around.


You are correct and it is confusing.

https://www.chevrolet.com/performance/copo-camaro.html lists GM's specs for the cams.

However, see this thread: http://ls1tech.com/forums/generation-ii ... hy-gm.html

The confusion was started over ten years ago. It may be that many readers recognize the cams by their incorrect designation and so correcting it at this point in time would be even more confusing.*

*Edit: It would be like the Yanks reminding the Brits that Davy decided to spell that element 'Aluminum' not 'Aluminium' in 1812. :lol:
Last edited by Kevin Johnson on Sat Jan 07, 2017 11:26 am, edited 1 time in total.

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Re: Valve stem seals crushed, LS7. More spring?

Postby mdrew » Sat Jan 07, 2017 11:18 am

New cam ordered.... EPS lobes, ground by CamMotion. 228/242 115+3, .667/.639

That was after several conversations, describing what my goals were and this unhappy valve train. He is still thinking about spring load requirements, and will be working the guys at PAC.

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Re: Valve stem seals crushed, LS7. More spring?

Postby allencr267 » Sat Jan 07, 2017 11:42 am

Do the guides have much of a bevel on them?
Some seals seem to want to gravitate towards that bevel & pop off if they aren't fully seated.

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Re: Valve stem seals crushed, LS7. More spring?

Postby RW TECH » Sat Jan 07, 2017 11:54 am

mdrew wrote:New cam ordered.... EPS lobes, ground by CamMotion. 228/242 115+3, .667/.639

That was after several conversations, describing what my goals were and this unhappy valve train. He is still thinking about spring load requirements, and will be working the guys at PAC.


This is a major step in the right direction for you. At least this way you are working with a single-source that is capable.

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Re: Valve stem seals crushed, LS7. More spring?

Postby Kevin Johnson » Sat Jan 07, 2017 11:55 am

^^^^^

Also, Mike, an important thing for people to note is that you did not have any perceptible sign of valve float while driving this build and this came right after you drove the car with an engine build that had no physical evidence of valve float upon teardown. Even the crushed stem seals this time around were a surprise.

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Re: Valve stem seals crushed, LS7. More spring?

Postby mdrew » Sat Jan 07, 2017 1:44 pm

Yes sir(s),

I did inform him that I "believed" the inner spring was doing the funky-chicken-dance and pulled the seal, and then proceeded to beat the crap out of it. This new cam is a custom deal.... I'm working directly with Geoff Skinner. He's pretty damn sharp with LS builds. Plus, the lobe profile is his creation.... He just doesn't have any experience with these particular rockers on this particular engine, but has seen about every other combination out there, many of which use MUCH HEAVIER valves than I am using. He thinks additional seat load may be needed, but that I should have plenty of open load already. He wanted to ponder this some more....

Sure wish I had one them fancy laser equipped spin rigs in my shop..... Someone could stand to make a bit of money if they had one, and an LS7 test mule..... There are several companies who are releasing new roller tipped rockers for this engine. Both bolt on, and base plate set ups that require machining. T&D, YT, and Jesel all have bolt on rockers that are available now. Texas Speed has a new one coming out this summer. Comp announced they have a non-roller tipped rocker coming out for increased lift.

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Re: Valve stem seals crushed, LS7. More spring?

Postby MadBill » Sat Jan 07, 2017 4:54 pm

Kevin Johnson wrote:..*Edit: It would be like the Yanks reminding the Brits that Davy decided to spell that element 'Aluminum' not 'Aluminium' in 1812. :lol:


Here's an additional "Kevinesque' digression :D : Davy first named the element 'Alumium' in 1807, then 'Aluminum' and finally in 1812, 'Aluminium', supposedly to dovetail with existing '-ium' elements. #-o
Felix, qui potuit rerum cognscere causas.

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Re: Valve stem seals crushed, LS7. More spring?

Postby mdrew » Sun Jan 08, 2017 11:54 am

Texas Speed rocker marketing video.

https://youtu.be/9DkvqtNbat4

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Re: Valve stem seals crushed, LS7. More spring?

Postby airflowdevelop » Tue Jan 10, 2017 11:21 pm

Mdrew I don't think that Texas Speed has all the answers. Along with that nothing against Geoff but I would prefer that you spoke to Kip Fabre @ CM if you can. If you want access to a spintron I might know a guy. On another note that RWTECH guy might just be spot on. Not that he or I know anything about LS motors.


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