repaired AHP heads
 

Alot of you are getting AHP PKG.4 heads! when you do which guides do you choose the standard or the MS90? If you go with the standard have you had good luck with them? The MS90 cost alot more but I think they may be worth it. Do you?

$600 for peace of mind, i'll take it.

What I did was call and talked to Kohle and we went over my application. I am not doing a cam and no porting or milling. I just want to keep my car stock ish for now so he recommended the hardened powder metal. If I was going with a larger cam he recommended MS90. I took his advice and now they should be arriving in a day. I cant wait! Best bet is to call and get the info to help make your decision. They are great and are more than happy to answer any and all questions you may have.

I still have stock cam and went with MS90 guides. I also had AHP mill and port, but my plan was to do it once.

Jake recommended the same for me, car is stock and not tracked.

:iagree: I just did the same thing with mine; except the cam. :thumbs:

I have the stock cam and I went with AHP PM guides. His PM guides are harder then the OEM guides and have spiral grove cut in them to retain oil for better lubrication of the valve stem/guide.

AHP is one of the only vendors to send the intake valves back to Del West for polishing. Kohle has said multiple times that customers have more than 50,000 miles and the heads are still within specification.

Over 30,200 C7 Z06's have been produced with polished titanium valve stems running in PM guides and you do not hear them having problems with worn out valve guides.

Its amazing, its as if someone yelled FIRE and everyone panics. "MS90 is the only thing that can save us!".

I also liked the fact that when I asked Kohle for his opinion he did t try and push me to spend another 600.00 because he didn't see it necessary. He seems like an honest person with good business values.

If you go to AHP, get the Moldstar guides.

Told him I tracked in Instructor's group, recommend Moldstar and springs, put in the 116 cam while I was there

I went with the MS90's

I also had this discussion with Kohle at AHP and he was great to talk with and correspond with through this process. His confidence seemed to be equal with both guides; even if I were to upgrade my cam in the future. So I opted for his powdered metal valve guides along with the AHP package 4 including .030 mil, CHE rocker arm upgrade kit, and BTR dual valve springs with titanium retainers. The only thing I struggled between were the BTR duals vs. the PSI 1511 springs. Kohle assured me that the spring seat pressure was set appropriately for my stock cam with my BTR duals and had no hesitation with their application. (135 lbs as I recall).

AHP's hardened valve guides are made of even a harder material than the MS90. https://www.corvetteforum.com/forums...k-miles-3.html (see post #42). However, as per the chart MTPZ06 posted, they are pretty similar yet as per the chart, the MS90 thermal conductivity is higher.

You can't go wrong with either one per Kohle and you can't argue with his experience and the success stories with both guides. https://www.corvetteforum.com/forums...ich-one-2.html (See post #25) However, two metallurgy engineers opined that the MS90's are "not a good material for guides because it is quite expensive and there are other materials which are better...". https://www.corvetteactioncenter.com...-engine21.html. This article might be the most thorough write-up ever done regarding the heads issue on the LS7's.

As mentioned above, the AHP PM guides use oil spirals to maintain high rpm oil lubrication. https://www.corvetteforum.com/forums...7-heads-3.html (see post #46).

I would say since there's never been a known failure with the PM guides by AHP's head rebuild process, save the extra money, the PM guides have proven themselves, have the extra spiral lubrication, are harder material, have been proven in the LS7's for years, and cost hundreds less. Just my two cents but you can't go wrong with either.

tw78911sc what you have is what I am thinking of going with. Same cam & guides. How long and how many miles on yours? most of all have you had an trouble with that set up?

I would take the Corvetteactioncenter.com article with a large grain of salt.

That article is written by Hib Hilburson who has a history of not being the most transparent writer out there. He used to be an advocate of our M90 guides until him and I had it out on a few PM's over some personal differences a few years back... In short Hib wrote us a PM saying that he thought our M90 guides were the best guide option out there but due to his personal dislike for myself that he would now began to bash our Moldstar90/M90 valve guides simply due to personal differences between him and I and no other reason. Just something to keep in mind when reading any Hib Hiberson article.
If anyone has any questions about this feel free to PM us as we are not looking to publicly bash anyone but we do feel everyone has the right to know the full un edited story (so to speak).

https://www.americanheritageperformance.com/

sorry that happened. it sounds very petty. people are entitled to their own options but not their own facts. some humans let emotions dictate their lives a little too much.

i'm going to share something with you though. i'm a longtime corvette owner and general sports car guy but new to the c6z scene. i started researching the valve problem and here's what i found about you guys {honest feedback}

1. you use a katech spintron tested combo with the stock ti / fererra hollow valve combo with stock springs {for stock cams}

2. you have addressed the wear issue from the non moly finish of the ti valve with polishing and a hard guide material. this may not be as ideal as the new katech moly ti valves but i realize those are $3200 a set. they should be better

3. you make sure the valve is centered to the guide which is another issue GM had

4. you correctly finish the head surface for the GM head gaskets. yes i'm aware different head gaskets require a different finish on the deck even though some people may wonder why you're more than joe's budget machine shop

5. you have tested clearance in 50k mile heads and they are still within spec which should {and this is my opinion} create a 200-250k mile street engine if it's not used in racing applications. this would be similar to other LS engines which have gone as high as 300-350k before rebuild.

6. your PM guides are spiral cut to retain some oil and allow you to hone fit a nice tight clearance without starvation issues

7. your ms90 guides are ideal for aggressive cams, the guy who drag races every weekend and or road racing applications which greatly accelerate wear everywhere over street driving

so again, this is someone new who researched you and this is what the online postings have lead me to conclude.

my opinion {again} is i wouldn't worry too much about random articles as i knew nothing about your company last month and have now come to understand all i posted

I went with the standard guides and a 116 cam.

I happened to have lunch with Hib today and we actually discussed the Moldstar guides and your interaction with him. Let me just say there are always 2 sides to the story! And FYI, he told me he would consider using you despite your PM interaction.

Bottom line for all of us is what guide to use. Not all end users are selecting the Moldstar and neither are you recommending it for all of us.

I don't think that you are bashing the Moldstar when you advise for PM. And I don't think others such as HIB who have done a ton of in depth research are bashing Moldstar when they recommend a good bronze guide like CHE. And I don't think Katech is bashing Moldstar either when they use (past tense) WCCH and bronze guides.

My heads will be getting checked in the near future and most likely I will have to decide on what guides to use. So far I am still undecided.

:cheers:
DH

That's one of the things among many that I like about AHP. They will tell you the truth vs selling you a part you don't need, and that goes a long way. I have bought countless car parts in the past, and for some I looked back and said, "Why did I get talked into buying that? I don't need it.".

It also helps to know your goals. When it came to my application I made it clear that my car was for enjoyment, street driving mostly, occasional track use for fun but I am not out to win competitions or break records. Jake at AHP told me that the "The Moldstar90 guides are not necessary but are a great option" for my application, and that included the street port and their 116 cam...which is being installed right now (and I am excited as hell about it...expect a video about it soon on my YouTube channel!).

I have absolute confidence in AHP. If nothing else, here's why...last year they did 233 pairs of heads(!). Out of those, 213 were LS7 heads. If they treat everyone like they treated me (which I am sure they do), not all of those heads have the MS90s. Ever heard of an AHP head failing? Me neither. That's why I have their banner hanging in my garage, and their shirt on my back, and their sticker on my car. :D

Bottom line...call or email AHP and tell them your goals. They will set you straight and get you everything you need and nothing you don't. If you need MS90 guides, they will tell you. If not, you have nothing to worry about.

Finally, if you need any more convincing, see my YouTube channel in my sig, and find the vid of me unboxing their heads and cam and related install kits. Live vicariously through me while I feel like a kid at Christmas! :)

I love that article coplete with all the pictures and truly appreciate the effort that it took to get into the level of detail on the LS7 that it did, but the argument against Moldstar 90 was unnecessary and weak at best. Do your own research on Moldstar 90 and you’ll learn more about Beryllium-Copper, (CuBe) and then draw your own conclusions.

The key to keep in mind when talking about the LS7 cylinder head is that is a production head that comes with Ti intake valves. Ti valves tend to hold more heat than stainless steel valves. Originally, whenever you were going to run Ti valves you needed to upgrade the valve seats to help transfer that heat from the valve, which was usually some sort of copper alloy because of copper's excellent thermal conductive properties which pull the heat out of the valve when it was closed. For years, copper-beryllium (CuBe) alloys were used in valve seats when Ti valves were specified and they did an excellent job transferring that heat, (and they still do.) But CuBe was really only used in heavy-duty or racing applications because it was very expensive and difficult to work with. Example: Indy and Formula 1 engines such as the F0110J 3.0L V10 engine produced by Ilmor/Mercedes for the 2000 F1 World Championship used CuBe valve seats and valve guides.

Bronze valve guides have good thermal conductive properties (better than cast iron,) but are a softer alloy that are typically not used in valve guides outside of race engines due to their relative accelerated wear rates. In GM LS/LT valvetrains, most bronze alloy valve guides will not be strong enough to support the loads of the LS rocker arms (1.7 ratio) put on the valve guides for 100k+ miles like the PM guides will, let alone the LS7 with its 1.8 rocker ratio, a high lift cam from the factory, and Ti intake valves. This is why on the LS7 you either go with Katech’s Mo coated Ti valves (not inexpensive) or roller tip rocker arms if you’re insistent on using bronze guides and Ti valves.

The marvel of CuBe is in its greater thermal conductive properties over bronze while its hardness levels are along the same lines as cast iron guides. However, CuBe is very expensive, in large part because the beryllium dust is very dangerous and requires extensive precautions when machining. This is where Moldstar 90 comes in - it's beryllium free but otherwise maintains all the desirable attributes of CuBe in thermal conductivity and durability (hardness.) Where bronze valve guides are suspect to high valve side loadings, Moldstar 90 excels in this area.

Is manganese bronze a superior valve guide alloy to Moldstar 90? It is well known that CuBe is a superior valve guide and valve seat alloy to bronze or cast iron, but it is dangerous to work with and is usually cost prohibitive for most applications. CuBe has superior thermal conductivity as well as hardness attributes over bronze or cast iron, and since Moldstar 90 essentially retains all the desirable properties and attributes of CuBe minus the associated health hazards, even if it is still more expensive than bronze, it would be disingenious at best to suggest that Moldstar 90 is a less desirable valve guide material than Manganese Bronze.

Asserting that Moldstar 90 is only worth the money on “street-high-performance and racing engines” with camshaft lifts exceeding a certain, specific value, is unscientific. First, if the LS7 isn’t the definition of a “street-high performance motor,” I don’t know what is. Second, Moldstar 90 is either a desirable alloy or it isn’t, and cost will always be a secondary determining factor. Cost is relative to the individual and before you can even get to that variable in the equation, you first have to decide if the alloy is even desirable to you, at any price. If it was desirable but very expensive, then it’s up to the individual to decide if that price is worth it to them. However, if the alloy was undesirable in and of itself, cost wouldn’t even become a factor because you wouldn’t select it at any price, would you?

You can try and discount Moldstar 90 by saying that it is expensive but you have to remember that cost is always relative to the individual paying the bills. For a NASCAR engine shop, they often make financial justifications for using exotic and expensive parts made in very low quantities because when it comes down to an engine being able to last 499 laps or 501 laps, that extra coin spent can make all the difference in the world. As I looked into rebuilding my LS7 heads, I said to myself that the single reason for me even pulling my heads on my stock 6k mile example LS7 was for the valve guides to begin with, and so ultimately it was for me to decide if $550 was cost-prohibitive or not. If cost was even cited as a factor than logically if you take away that factor of cost, aren’t you inferring that it is otherwise a desirable option?

Part of the reason Moldstar 90 is expensive is because of its tooling costs, and this is also part of the reason why you don’t see it offered in more applications. You might get two sets of guides out of three specially made carbide tips that cost a few hundred dollars apiece. The proof however, is in the pudding. Per AHP's independent testing, not only did their Moldstar 90 LS7 valve guide possess a 267% greater thermal conductive property to the Manganese Bronze valve guide, it also possessed a 173% greater level of hardness (more durable) than a comparable used OE PM LS7 valve guide from GM.

AHP didn't create the Moldstar 90 alloy but they were the first to explore the exotic alloy's application in an LS7 valve guide. Many kudos for that. Moldstar 90 has also been offered as the solution for many Nissan GTR R35 owners suffering from premature valve guide wear, and they are saying the same things that we already know about Moldstar 90:

• High Thermal Conductivity
• Excellent Hardness/Durability
• Resistant to High Temperatures
• Gets Tougher/Harder in Application
• Does not Develop Heat Cracks
• Resistant to Environmental Attack

https://www.gotboostperformance.com/...ve-guides-ms90