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Boost induced valve float?

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Old Nov 19, 2020 | 11:06 AM
  #21  
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Originally Posted by stevieturbo
If you are prepared for some drilling and tapping, ideally with some proper guides...1/2" studs can be cheap

Or China studs, but that isn't a route I'd do.

LS head studs do seem unusually expensive.
yea I’m not doing all that to this motor. Not in the car anyways. I’d rather go back with my arp bolts than China studs, so yea I agree.

my situation is kinda dumb. Long story short. My son has a 2015 genesis, he broke it. Under warranty, the dealer sucks and takes forever. So I let him use my truck to get to work. So I’ve been driving the Gto. For some dumbass reason, I’m headed to my dads, stop at my buddies house to take him for a ride. He said he wanted to feel how that 5.3 pulled on 20-22psi which is usually what I get. So I make to hard rips back to back. I should have left it at one, because it would still be going. So now I’m vehicle-less. Borrowing a buddy’s car now. Lol. My luck. So i need to get it going fairly soon and I toy around with the idea another motor, but truth is, it’s Christmas time. I have three kids. We also slow down at work a lot this time of year. So that’s my unfortunate situation that I literally brought upon myself. I can scrape up money for valves and gaskets, but anything more will be tough. I do have a set of spare heads I was given a while back. Glad I didn’t sell em.

Last edited by Kfxguy; Nov 19, 2020 at 11:14 AM.
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Old Nov 19, 2020 | 11:36 AM
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And this is where the $300 junkyard motors are ideal lol.

Although I've always a few cheap motors about if I'm ever stuck. Then again my LS car hasn't moved since around April ! lol
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Old Nov 19, 2020 | 12:10 PM
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Originally Posted by stevieturbo
And this is where the $300 junkyard motors are ideal lol.

Although I've always a few cheap motors about if I'm ever stuck. Then again my LS car hasn't moved since around April ! lol
sadly I think the era of $300 junk yard motors is over. At least in my area it is. They caught on and jacked up prices. The motor I have in my car now costs over double what I paid for it from the same place.
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Old Nov 19, 2020 | 12:45 PM
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Not in my area I pulled and bought my LM7 minus ecu/harness for $300 plus fees/taxes.
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Old Nov 19, 2020 | 01:23 PM
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Originally Posted by SCLT1
Not in my area I pulled and bought my LM7 minus ecu/harness for $300 plus fees/taxes.
What area is this and how long have you been running it?
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Old Nov 19, 2020 | 02:27 PM
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Certainly a possibility that the exh valves stuck in the guides.
generally aftermarket pistons have large valve reliefs, you should have a ton of ptv. If you measured it.....
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Old Nov 19, 2020 | 02:47 PM
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Originally Posted by Kfxguy
sadly I think the era of $300 junk yard motors is over. At least in my area it is. They caught on and jacked up prices. The motor I have in my car now costs over double what I paid for it from the same place.
You just need a dirty LM7 with 200k miles on it. Slap it in, turn the boost down to a few psi and retune it so you can use it as a commuter for a while. Worry about everything else once the truck is back. Once you get the current engine fixed then pull the LM7 and sell it for what you paid for it.
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Old Nov 19, 2020 | 04:37 PM
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And swapping motors in a GTO is a piece of cake......
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Old Nov 19, 2020 | 04:41 PM
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I’ll just say, you have no clue what lurks inside a jy engine.
Good buddy that I tune is about 50% luck on those.
Honestly stupid advice
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Old Nov 19, 2020 | 08:03 PM
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Originally Posted by RonSSNova
I’ll just say, you have no clue what lurks inside a jy engine.
Good buddy that I tune is about 50% luck on those.
Honestly stupid advice
well I have a complete ls1 on the engine stand. I’m been hanging on to it to build a 383
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Old Nov 19, 2020 | 10:29 PM
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Originally Posted by RonSSNova
I’ll just say, you have no clue what lurks inside a jy engine.
Good buddy that I tune is about 50% luck on those.
Honestly stupid advice
Thats not ****! Here is a recent junkyard 5.3. Only wanted the rods out of it. Someone woulda been unhappy with this if they were hoping for a quick swap engine






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Old Nov 19, 2020 | 10:36 PM
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Only posted these pics in here because I just took this apart and had the same question.. why did it happen. . Bought this truck and it ran pretty rough... obviously. Didn’t make any real bad noises tho. Drove it home with intentions of swapping the engine anyways.

Got it out and took it apart... and the exhaust valve hit a piston. Cam destroyed. Lifter kinda chewed up. Cam bearings are toast too.

Same question... like.. why?




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Old Nov 19, 2020 | 11:37 PM
  #33  
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Was the cam still in time when you took it out? You may have jumped the chain at the high RPM,, DId the motor have a chain dampener?
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Old Nov 20, 2020 | 04:55 AM
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So was the buddy ever say he was impressed or not with your 20-22 PSI of boost?

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Old Nov 20, 2020 | 07:21 AM
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Originally Posted by Jimbo1367
So was the buddy ever say he was impressed or not with your 20-22 PSI of boost?
Asking the important questions here!!
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Old Nov 20, 2020 | 07:30 AM
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Originally Posted by Jimbo1367
So was the buddy ever say he was impressed or not with your 20-22 PSI of boost?
He told me several times he couldn’t believe how hard it pulled. I told him I thought he was gonna feel like he was riding in a Kia compared to his car and he said hell no. He said he thinks it’ll have no problem going low 10’s at 140ish. And he said it pulls real hard in 3rd and couldn’t believe the 4l60 was taking it and shifting as quick as it does. I hit 24.5 psi with him in the car.....that’s initially what I thought had happened, and it may have something to do with it it. I’ve never gone that high. His car had the same 5.3 setup as me but a bigger cam. He went 8.70 on like 25-26lbs, he’s the main reason I put a 5.3 in my car....o and seeing what ruby ran with a 5.3. I know they are lighter cars, but I’m not trying to run 8’s, I’ll be happy with a second slower. My goal is to push it to 9.90 @ 140 on pump 93. If I gotta shoot it with a little shot of meth, so be it.


I was trying to get rid of all the and’s.

Last edited by Kfxguy; Nov 20, 2020 at 07:38 AM.
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Old Nov 20, 2020 | 07:30 AM
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Originally Posted by biketopia
Asking the important questions here!!
lol...trying to impress people usually ends up badly whether it’s with cars or otherwise.
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Old Nov 20, 2020 | 07:33 AM
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Originally Posted by Kfxguy
He told me several times he couldn’t believe how hard it pulled. I told him I thought he was gonna feel like he was riding in a Kia compared to his car and he said hell no. He said he thinks it’ll have no problem going low 10’s at 140ish. And he said it pulls real hard in 3rd and couldn’t believe the 4l60 was taking it and shifting as quick as it does. And I hit 24.5 psi with him in the car.....that’s initially what I thought had happened, and it may have something to do with it it. I’ve never gone that high. His car had the same 5.3 setup as me but a bigger cam. He went 8.70 on like 25-26lbs, he’s the main reason I put a 5.3 in my car....o and seeing what ruby ran with a 5.3. I know they are lighter cars, but I’m not trying to run 8’s, I’ll be happy with a second slower. My goal is to push it to 9.90 @ 140 on pump 93. If I gotta shoot it with a little shot of meth, so be it.
Im curious what your EGT was like or if you leaned out at 24 psi. May have tuliped those exhaust valves getting them to hot.
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Old Nov 20, 2020 | 07:39 AM
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Originally Posted by BCNUL8R
lol...trying to impress people usually ends up badly whether it’s with cars or otherwise.
this is facts.
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Old Nov 20, 2020 | 07:43 AM
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Originally Posted by BCNUL8R
Im curious what your EGT was like or if you leaned out at 24 psi. May have tuliped those exhaust valves getting them to hot.
maybe. I wasn’t looking at my afr gauge do that’s a mystery to me too. It’s usually in the low 11’s, high 10’s at 22lbs so hopefully it was in that area. I’m gonna make some time this weekend and get the heads off. I’ll start draining coolant tonight. That’s my most dreadful thing of the whole process. I’m trying to think what I can do while it’s apart to make things better. Might get the proper bore size gasket. Right now I’m running ls9 gaskets. I was trying to find some used head studs too.
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