Bill Dearborn

Actually that is pretty much standard practice in industry. You pay the supplier for building the part correctly and doing the proper inspections and certifications. It is cheaper than setting up a full time incoming inspection that requires multiple skill level employees depending on what has to be inspected. On top of that some items can't be inspected without expensive test equipment. Better to do that where the items are built and the skills exist to do the proper QC checks. I know where I spent most of my work life we paid the suppliers to do all of that back in the 60s and 70s and continued until I retired in 2006. Almost everything you buy from major OEMs no matter whether they build cars, refrigerators, washing machines, etc have parts inspected this way. It is a proven methodology which saves money and improves quality.


Bill

ticat928

Hib here is the thread the Moldstar90 info table appeared in:

https://www.corvetteforum.com/forums...nd-data-3.html

AzDave47

... except the pre-delivery inspection is supposed to include inspecting proper fluid levels. I guess the profit margin is high if you bill the customer and don't do the work, until the customer abandons you because of how you treat them.

Enjoy your southern winter, Bill.

Hib Halverson

"Partial blindness", perhaps a result of too much turkey and beer last night, has set in and I was unable to find the chart in that thread, however, I got the chart you posted earlier. Thanks for that.

In that earlier post, you said:I was uneducated, as well, about work hardening aspect, but now that I know about it, I agree with you.

My earlier post on this......was not correct. I wish I'd have had that chart before I posted.

In looking at that chart it seems to me that, in a practical sense, all the valves tested are about the same for hardness with the early LS7 valve (Eaton) have a very slight advantage over the later unit (Mahle/Edival)

As for the guides' various heat transfer qualities, clearly, the Moldstar90 guides are superior in that respect. In theory, because the numbers imply that the Moldstar90 guides are going to transfer heat from the valve to the head material more rapidly, using them may lower the temperature of the system which is the valve stem, the guide and any oil which is between the two because that system is transferring heat to the head material and, in turn, to the coolant more quickly.

As for hardness, looking at those numbers, in theory the hardness of the American Heritage PM guide is actually higher than the valve stem so the valve might wear as much as or more than does the guide. Of course, if the guides and seats are concentric and the guide ID is machined properly and the valve stems are finished properly, the wear rate of either is going to be low.

The Moldstar90 guide, once it's work hardened, is, also, almost as hard as or is as hard as the valve stems. Compared to the wear rate of stem and guide of OE parts, one would think stems would wear more and guides would wear less, but, again, if seats and guides are concentric, the guide ID is proper and stem finishes are correct, minimal wear is going to take place.

In any event, those who've got lots of money to spend on their heads need to look at those Moldstar90 guides.

Hib Halverson

That is, indeed, my conclusion.

Admittedly, not everyone agrees. There is a vocal group who believes the sodium-filled, hollow-stem valve is the core of the problem, but, again, as the article points out, there is not a lot of hard evidence to support that. Just the fact that a growing number of car companies, not just GM, either, are moving to sodium-cooled valves in applications where the engine has high specific output tends to raise questions about the belief that sodium-cooled valves cause failures.

I will cede this to the group who believes the valve is the problem: once enough guide wear has occurred such that contact between the guide and stem degrades to the point that heat transfer is impeded and the guide is worn enough that the valve head flexes each time it contacts the seat, the hollow-stem valves may be less durable than a solid stem valve, i.e. it can take the flexing better. That said, in either case–hollow stem or solid stem, when the head is flexing because of worn guides, both will eventually fail, but maybe the "eventually" with a hollow-stem will be sooner than later and the "eventually" with a solid stem will be later than sooner.

Hib Halverson

For those looking to read the revised LS7 article with additional material on the guide wear problem, please click here.

The wiggle test how-to sidebar article has still not been added. I'm having some difficulty getting some additional tools to feature in the article, so it's going to still be at least a week before it goes up on the CAC.

Either myself or someone else will post the link when it goes up at the CAC.

Zeaux6504

I believe that Moldstar 90 guide material maybe the missing piece to the elusive head fix... Here's my thoughts ... We have three choices to solve the problem (1) stanless solid (2) OEM sodium and (3) ferrea hollow. So far, based on Katech testing, the SS exhibit a valve bounce issue. While the OEM valve is believed to be a factor in the root cause. This leaves us with the Ferrea valve as the best choice. There has been testing done by forum members to validate such use in our motors. Since there is concern that the air filled ferrea valves may not transfer enough heat, as the intended design of the OEM set up, then the Moldstar 90 guides may recoup such attribute when used with the Ferreas (superior heat conductivity of the Moldstars) . I think the use of the Ferreas along with the Moldstar will get us closest to the attributes of the OEM design. Sure the Moldstar 90 cost an extra $500, but you guys are driving an $70k car. If people can't come up with $500 to fix their expensive cars, then maybe these people really can't afford to buy it in the first place. These people need to watch the Susie Orman Show.

'06 Quicksilver Z06

What happens in terms of valve bounce when one uses the hollow stem Ferreas with an aftermarket cam?

American Heritage

You are very correct if the guides wears out enough any valve will fail (eventually). Since the sodium valves are the thinnest walled of all the valves they will fail before a thicker walled valve (when run inside a worn/out of spec guide).
Bottom line have your heads reworked by someone who knows exactly what they are doing with these LS7 heads and you wont have to worry about this issue again.
http://www.americanheritageperformance.com/

Hib Halverson

You're, like...joking, right?

First the heat needs to move up the stem. It can't do that very well in an "air-filled" stem cavity, no matter how quickly the guide will transfer heat to the surrounding head.

Your thinking: that you can compensate for the poor thermal conductivity of an air-filled, hollow stem valve with increased conductivity in the guide is flawed.

Imagine this plumbing analogy: you put a ¼-in restrictor in your 3/4-in garden hose and just down stream of that you install a 2-in diameter hose. Will the 2-in hose negate the restriction?

Not.

Now...don't get me wrong. I think the Moldstar90 valve guides are an excellent performance upgrade for an LS7 head. If I was building a second set of heads–the ultimate set of heads for an engine using production castings–I'd likely use those guides. It's just that, as good as they are, the Moldstar90 guides cannot violate the laws of physics. That is, you first have to get the heat out of the valve stem. Once you do that, then you can choose to transfer it more quickly to the head material and, eventually, into the coolant.

'06 Quicksilver Z06

MyLastCorvette

You forgot a fourth choice, Del West ti intake/Del West ti exhaust finished to WCCH specifications. (I would know this, as their installed in my heads) PS I agree with your analogy on the afford thing; But who the "Heck" is Susie Orman...

Zeaux6504

You are absolutely right. I am sure your setup runs superbly. If people are willing to do as you, there would be no second guessing, debates, or arguments on the right "fix". It all comes down to how much you can spend... in the end, people are looking for a solution that cost less than the $1200 you must spend on the Ti valves alone. Anything less you would have lingering doubt. As with most problems in life, you can solve it with enough money.

AzDave47

Susie gives extensive financial advise, writes books and is on TV on the subject. Google her and you'll gets lots of information on financial matters including budgeting and investments.

LawrenceFromTorrance

I think he was joking

MyLastCorvette

If your referring to my "Who the heck" is Susie, your correct. I remember all too well, bout 20 yrs ago just before "Janet" sued MS in an effort to help the "Little Guy." My X "Edwards Jones" financial expert advised purchase MS it would never go down.

propain

As long as you fix the machining problem in your heads you wont need to use solid stem valves to "just in case" or "maybe" save yourself from failure if the guides wore out again to the point of being out of spec.

Sure they will last "longer". How much longer though? I have seen OEM valves stand up to some serious punishment without letting go. Its a game of Russian roulette for either valve. Both running in conditions far beyond their tolerances. This is a game no one wants to be playing.

Michael_D

Moving to a MoldStar 90 seat is a good option, if reduced heat transfer from using the non-filled, hollow stemmed valves is a concern. It is another costly 'upgrade', but they are an excellent seat. I had seriously considered moving to this seat, but after a rather lengthy conversation with both Ferrea and Performance Alloys (manufacturer of MoldStar alloys), I elected to not spend the money on seats and guides, but spend a bit extra to address rocker geometry with higher lift cam profiles. Ferrea was very adamant that the stainless alloy they use for their blanks was superior to the OE valve at the molecular level, and that it would transfer heat as well, if not better than the OE valve. To this, I believe I actually responded with " Oh Bullshiit, there's not way in hell", but the engineer held his ground. The Performance Alloys guys thought using MoldStar 90 in this particular application would not be necessary, unless I was to use a Titanium valve on the exhaust side.

'06 Quicksilver Z06

To that part in bold, I don't see how it would matter how "adamant" they were in making their claims, when one considers that they are after all, in the business of selling these valves. I wouldn't expect them to say anything else other than that or take any other position than that.

Did they bother to offer up any independent proof or studies which would support their sales pitch?

Because if they didn't, well until then, their engineer "holding his ground", quite possibly amounts to nothing more than saying what he needs to say in order to keep his job and the company line being an effort to sell valves.

Mark2009

Which would apply to any vendor on the planet, meaning none of them can be trusted. None.

Including the ones you trust.