Originally Posted by Mark2009

Unless they've had the guide clearance checked then those reports will be meaningless. A forum member had 88K miles on his stock heads, no apparent problems, but when he checked the clearance they were way out of spec.

"Running fine", "sounds good", "pulls good", "revs fine", "no apparent problems", without any measurements or inspection none of it means anything.

Originally Posted by Tarostar

I'd be happy to conduct this experiment on mine if you guys pool together the money for the heads and cover a new engine if needed. For science!

Originally Posted by American Heritage

and we would be happy to install both our PM guide, Bronze guide, OEM factory guide and even a new guide that we are having made just for us that will revolutionize the guide industry. they you can have the heads wiggle tested at an independent facility.

Im all for this, we truly believe our guide is awesome and would love the opportunity to prove it to the community.

ps the longer guide is only used when you have seriouse concerns about heat... basically you don't think your material alone will solve your heat/guide wear issue so you lengthen the guide a little to help out. Its nothing new, used to do it back in the day on some SI engine that were pumping out 1200hp @ 45lbs of boost, the heat was just killing the exh guies, new material and longer guides fixed it. could have probably gone with just a better material but the shop I was working for at the time thought "same material we always use ( a slight variation of it), just more of it"

Originally Posted by American Heritage

The aftermarket bronze guide that the majority of rebuilders use may very well indeed be better than the factory's OEM PM guide. We recently sent a bunch of guides out to an independent facility to be tested. The Bronze guide was HRC25 (c scale,,,, this is in reference to how hard the metal is... lower number softer metal, higher number harder metal). We sent in a used oem gm ls7 guide that we knocked out of a head, it was HRC10 (c scale)... so in this case yes a bronze guide would be better than gm's oem pm guide. We also had our AHP aftermarket Hardened PM guided tested and it tested HRC40 (c scale). This would mean our hardened PM guide is harder than the factory's PM guide and harder than the aftermarkets bronze guide.

Originally Posted by '06 Quicksilver Z06

Buy a GMPP and keep it stock if those are options for you..

Originally Posted by Mark2009

If you can't see yourself performing one at least every year at that kind of annual mileage, I'd suggest another vehicle (one without an LS7).

Originally Posted by UsernameProtected

The car has Kooks headers & Corsa exhaust. The seller said the first engine was replaced not under warranty (at 19,000 miles, in 2011), because the car had been discovered by GM to have been tuned. I don't have a lot of faith a warranty would cover me, and the car is well out of warranty now. I'd rather just spend $2k-$3k to definitively resolve the problem.



Once a year might be reasonable, if I can find someone who can do it locally - and it doesn't take an unreasonable amount of time.

My compromise with myself was if I wasn't going to buy a C7, I was going to buy a widebody C6 in LeMans Blue. I'd have been happy with a Grand Sport, if GM hadn't discontinued LeMans Blue in 2007. I suppose I could have had one repainted for $10k. I also could replace the LS7 in my Z06 with an LS3 for that and be done with this issue.

What I need is an aftermarket/machine shop head package that comes with a reasonable warranty against valvetrain failure. If GM can warranty a new LS7 for 100,000 miles with known bad valve guides, why can't these guys who are selling a "solution" provide a similar warranty?

Originally Posted by '06 Quicksilver Z06

I'm going to have to agree with this.

There are a lot of cars out there yesterday, which were "running fine", "sounded good", "pulled good", "revved fine", and had "no apparent problems", which either are not running today, or might not be running tomorrow.

Show me a car that popped in here, and more often than not, I'll show you a car that was "running fine", "sounded good", "pulled good", "revved fine", and had "no apparent problems", the day before.

Originally Posted by American Heritage

The 24hr race engine you keep speaking of is/was running a shaft mount roller rocker system (no real side loading of the valve). In this application Bronze is great. Bronze is not the best choice of valve guide material with a non roller tip rocker that causes lots of valve side loading.

The aftermarket bronze guide that the majority of rebuilders use may very well indeed be better than the factory's OEM PM guide. We recently sent a bunch of guides out to an independent facility to be tested. The Bronze guide was HRC25 (c scale,,,, this is in reference to how hard the metal is... lower number softer metal, higher number harder metal). We sent in a used oem gm ls7 guide that we knocked out of a head, it was HRC10 (c scale)... so in this case yes a bronze guide would be better than gm's oem pm guide. We also had our AHP aftermarket Hardened PM guided tested and it tested HRC40 (c scale). This would mean our hardened PM guide is harder than the factory's PM guide and harder than the aftermarkets bronze guide.
The point being the harder the guide the more likely it is to resist valve side loading. In other words the harder the guide the less the guide will wear when exposed to high levels of valve side loading.
Theoretically a harder guide should wear less all around than a softer guide.

So application makes all the difference. Bronze with shaft mount roller rockers = good. Bronze with stock non roller tipped rockers = not the best material for the application.

Originally Posted by ClarksZ06

Very informative but what's the downside to the much harder pm guide that you are currently using? Does the actual valve now take more of the wear and abuse? Or could these harder guides possibly create more heat in the guide ? If there's no downside why wouldn't other aftermarket cylinder head companies use these harder pm guides?

Thanks!

Originally Posted by ClarksZ06

[...] Or could these harder guides possibly create more heat in the guide ?

Originally Posted by ClarksZ06

If there's no downside why wouldn't other aftermarket cylinder head companies use these harder pm guides?

Originally Posted by ClarksZ06

Very informative but what's the downside to the much harder pm guide that you are currently using? Does the actual valve now take more of the wear and abuse? Or could these harder guides possibly create more heat in the guide ? If there's no downside why wouldn't other aftermarket cylinder head companies use these harder pm guides?

Thanks!

Originally Posted by z76232

Originally Posted by Mark2009

No.

For two reasons:

1. For the same reason they use dual springs -- they are locked in the past.

2. It takes some thought and effort to bring new items to the marketplace. It is also risky because, like many shops, many customers are . . . . . . . . . locked in the past

Originally Posted by propain

Good point. I don't think its a hardness issue with the current PM guides. I don't think you would create any more heat issues however with the "harder" PM guides.

As well these guides have been in use for a very long time. As we all know as the years go by technology improves and its possible these guides that AH is using only recently became available. Aside from that even if they were available GM hasn't had guide issues up until this point. So why change something that's been working.

However, I do agree with AH and sticking with the PM guides would be best.

I am surely a mixed bag.... LOL. Ill take one order of PM guides from AH and One order of OEM valves and beehive springs. I appreciate all these vendors opinions but I want to stick as close to what the GM engineers had in mind as possible.

That is of course until I go beyond 650whp... then all bets are off.

Originally Posted by telly444

and right now I have a E force blower , LT's and custom tune. stock heads with 21,000 kms......tick tock , tick tock...... BOOM!!!! LOL

Originally Posted by '06 Quicksilver Z06

To that part in bold, you likely won't get it.