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Old 02-24-2021, 03:56 PM   #113
cmitchell17

 
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Quote:
Originally Posted by Puddin View Post
While I do believe they should just stop selling the heads its really not Texas Speeds fault if the valve guides are bad because they are coming from the factory like that so if anything this is a GM issue again like the Ls7. Hopefully since their custom heads are available now they have resolved any issues that the stock castings have.
Do you have any more info on the problem? Has any other aftermarket companies documented it? Is it the exact same issue as the LS7? (which I though the LS7 issue was due to bad manufacturing causing incorrect concentricity between seat and guide) Is there a GM TSB?

Also do you know if TSP does anything with the guides or seats? Do they replace them with new stock ones? Or do they just visually check them and if they look ok proceed with porting? I have asked them and they won't tell me any details.
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Old 02-24-2021, 04:35 PM   #114
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I remember it as katech specifically calling out lt4 heads
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Old 02-24-2021, 06:22 PM   #115
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Quote:
Originally Posted by cmitchell17 View Post
Do you have any more info on the problem? Has any other aftermarket companies documented it? Is it the exact same issue as the LS7? (which I though the LS7 issue was due to bad manufacturing causing incorrect concentricity between seat and guide) Is there a GM TSB?

Also do you know if TSP does anything with the guides or seats? Do they replace them with new stock ones? Or do they just visually check them and if they look ok proceed with porting? I have asked them and they won't tell me any details.
Your actually the first person I've seen with this problem and to be honest we're all just speculating what could be wrong. I believe all TSP does is just port the heads and send them out I don't think they touch the guides or seats. I can tell you my shop now recommends using aftermarket heads because for a while there were some bad castings out there that when ported they would leak. They had 3 gen 5 Lt motors being completely rebuilt (mine included) because of it. I do still have the emails from TSP confirming this because I did have them perform a test on their heads and it was confirmed an issue on their end. So maybe it was a factory defect with your heads and just didn't manifest itself untill you started adding more power and compression. I do feel bad for you though I know how it feels to have to rebuild everything because I had to do it twice last year.
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Old 02-24-2021, 06:57 PM   #116
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It just says competition 5 angle valve job and porting they really don't specify what the whole process is.
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Old 02-24-2021, 08:28 PM   #117
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Originally Posted by Puddin View Post
It just says competition 5 angle valve job and porting they really don't specify what the whole process is.
I believe the stock seats are just regular power metal, not sure if they are a special alloy or not.

I wonder what the difference is between the intake and exhaust seats?

I wonder if the LT4 uses different seats than the LT1?

I wonder how much the factory does in finish machining to the seats after they are out of the die or mold if they are cast?

I wonder if you just can't expect to machine stock seats? Maybe it induces cracking?

Either way, if my preload was off, even though TSP said I should be ok? (maybe ok for 10k miles haha) the valves would wear on the seat and more and more of the slack would be taken up until I have more slack and lash in the valvetrain and therefore more impacts to the seat?

If you go back and look at the pictures, I don't know what you could call the damage to the other intake seats, pitting? knicking? If you look close at some of them its very weird its almost looks like someone took a very small pick trying to pry the seat out of the aluminum bore. And on top of that in some places the edge of the aluminum bore that holds the seat is also damaged? How would that happen?
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Old 02-24-2021, 09:59 PM   #118
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I got the passengers side head off, overall a lot less intake seat damage, #8 actually had no visible damage that I can tell:
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Old 02-24-2021, 11:03 PM   #119
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Quote:
Originally Posted by KingLT1 View Post
With DI fuel sprays directly into combustion chamber so the intake valve doesn't get the cooling effect from fuel but it still sees some air cooling. I do agree it's normally an exhaust valve that burns up.
I'm picking up what you're laying down.

I was speaking in general (air/fuel i.e. meth vs. air and fuel). I should of just said air since were talking DI motors and save any confusion.

Thanks for clearing it up!
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Old 02-25-2021, 02:57 PM   #120
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I'm not certain but I would bet the seats are fully machined ductile iron. Typically replacement seats are basically just little short cylinders. The o.d. is controlled to within a half-mil or so. The i.d. is machined after installation in the head using the guide as a pilot.
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Old 02-25-2021, 06:12 PM   #121
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modern powder seats are super strong. IMO this is all caused by valve bounce.
The exhaust valve seat is subject to a lot of heat which can cause burned valves / seats
The intake is heavy and hollow, the heavy causes valve bounce (especially with boost), the hollow means it is easy to get out of kilter or just plain break.

I was worried about the OEM valve, truthfully I'm not worried at all about the seat given a blue printed and maintained valvetrain and reasonable expectations for application. sub .600 cam slow controlled ramps, change springs at 50K, I think 100K miles at 90% reliability. Building a full boost car for the Texas Mile, IMO nothing that leaves the facory is adequate, OK maybe the block.
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Old 02-25-2021, 06:14 PM   #122
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why does one seat have a scratch and the other has a few dings from the grinder collet? A scratch is a perfect place for the seat to start burning away.
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Old 02-25-2021, 06:31 PM   #123
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I looked back at my notes and found something interesting, i was going from memory but I thought I had excess lash (not enough preload) but it was actually the opposite. I was having trouble getting a lash measurement with the adjustable pushrod and called TSP. They said they sent me the wrong tool apparently and my best guess was around .048 but of course that's dependent on what you consider your base line zero lash. I'm reality i think it was more than that and TSP told me to run it like that with those pushrods.

So would having more preload than recommended cause extra wear and impact on the seats? I guess they could bottom out to eventually.

As for the seat material, i was wondering why the damage is limited to the intake? More valve mass? Seat area? Different metallurgy between the intake and exhaust?
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Old 02-25-2021, 07:27 PM   #124
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Quote:
Originally Posted by oldman View Post
why does one seat have a scratch and the other has a few dings from the grinder collet? A scratch is a perfect place for the seat to start burning away.
What I don't get is why does it start at the very edge of the valve seat? It's on the combustion chamber side but I don't think the valve makes contact in that area?

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I guess a valve seat shows up as iron haha

The 86k change was when I put my cam in, iron went from average to 55ppm.
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Old 02-25-2021, 07:28 PM   #125
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Originally Posted by cmitchell17 View Post
I looked back at my notes and found something interesting, i was going from memory but I thought I had excess lash (not enough preload) but it was actually the opposite. I was having trouble getting a lash measurement with the adjustable pushrod and called TSP. They said they sent me the wrong tool apparently and my best guess was around .048 but of course that's dependent on what you consider your base line zero lash. I'm reality i think it was more than that and TSP told me to run it like that with those pushrods.

So would having more preload than recommended cause extra wear and impact on the seats? I guess they could bottom out to eventually.

As for the seat material, i was wondering why the damage is limited to the intake? More valve mass? Seat area? Different metallurgy between the intake and exhaust?
intake more subject to float / bounce especially under boost.
IMO NO vendor can recommend a pushrod length unless you have adjustable rockers. All pushrods have to be individually spec and even more so with the R limited pump lifters. Now OEM LS7 lifters have a lot of movement so all else the same (never is), stock length pushrods should work. Alls I can say is that I reused ZERO pushrods from first to second cam change. I just don't remember if they had to be all shorter or longer. I must have purchased 50 to 60 pushrods for my motor over two cams. Maybe I got every length made now. LOL, so one again IMO, no way a vendor can tell you what pushrod will "work" in a large cam engine. GM hot cam and LS7 lifters = OK, but that is a factory ramp cam and factory lifters and factory pushrods on factory springs. There is a whole lot of forgiveness in the setup. I think max rev is either 6600 and .577 lift. https://www.jegs.com/p/Chevrolet-Per...4897/10002/-1#
That is easy peasy compared to .640 lift and 7200 RPM.
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Old 02-25-2021, 07:36 PM   #126
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Originally Posted by oldman View Post
intake more subject to float / bounce especially under boost.
IMO NO vendor can recommend a pushrod length unless you have adjustable rockers. All pushrods have to be individually spec and even more so with the R limited pump lifters. Now OEM LS7 lifters have a lot of movement so all else the same (never is), stock length pushrods should work. Alls I can say is that I reused ZERO pushrods from first to second cam change. I just don't remember if they had to be all shorter or longer. I must have purchased 50 to 60 pushrods for my motor over two cams. Maybe I got very length made now. LOL
I am just going to ask the question, I think I may already have, but I run at least E70 in this motor 100% of the time, I may have filled it up with gas one time. Especially since its DI I don't see it having any effect but I think there was long term durability issues to seats with E85. It's everywhere where I am at and a little cheaper than having to run 93.
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