FBO Engine Misfire

whitmanink

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yea time will tell , either way it sucks it happened,,

i think the only valve strike is when the little bearing bits slammed into them when they made there way into the cylinder...

i also find it odd there is not paint marks on the head bolts , to show the 90deg after torq spec,, my paint stayed on ,,

,, i think the timing off isnt true,, the one experience ive known when timing jumped,, you knew something was horribly wrong and was throwing codes left and right, and the engine jumped and kicked so hard ,, before it eats itself .. if the pistion hit the valve , than the other bank the same thing should have happend?..

but i guess theres no use sitting here with tin foil hats on, ,, time will tell the cause for sure
 

whitmanink

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looking at the pic again,, it looks as tho the keeper is almost off,, the right side isnt touching itself
 

Midlife Crises

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looking at the pic again,, it looks as tho the keeper is almost off,, the right side isnt touching itself
Yep! The piston smacked that valve so hard it destroyed the follower and mangled the valve. That impact and the follower coming apart tore up the cam lobe and some of that trash is heading for the oil pan. Nothing is in the cylinder except maybe the head of that valve but I don’t think it has broke off yet. I also believe if the follower failed first, the valve would never open and could not get smacked by the piston. We need to see the heads off.
 

Redfire_Jimi

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I also believe if the follower failed first, the valve would never open and could not get smacked by the piston. We need to see the heads off.

This is what I am hoping for.

Update: I spoke with a machine shop that specializes in cylinder heads. I will be removing the passenger side cylinder head this weekend and drop it off hopefully early next week for a full diagnosis.
 

Redfire_Jimi

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Quick Update: I am half way through pulling the heads. I did take off the intake manifold and observed a broken intake valve (see image below). Also, I know that I need to have the head completely off the engine to do a full damage assessment.

Questions: Is this head salvageable?
broken valve.jpg
 

whitmanink

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if your luck is anything like mine,, the head is gonna be trashed ,, thats odd that yours looks like mine did ,,, (the valve broke off about half inch from valve head )

anywho , lets us know what you find,, my block is trashed so thats that ,, as well as my passenger side head,, still have no idea why or how the valve did what it did
 

Redfire_Jimi

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if your luck is anything like mine,, the head is gonna be trashed ,, thats odd that yours looks like mine did ,,, (the valve broke off about half inch from valve head )

anywho , lets us know what you find,, my block is trashed so thats that ,, as well as my passenger side head,, still have no idea why or how the valve did what it did

I honestly don’t know what to think at this moment. I’ve been in a quasi-depression state for the last month.
 
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Redfire_Jimi

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Okay gentlemen. Passenger cylinder head was removed (see pics below).

Observations:
  1. Cylinder head damage seems to be isolated to one area.
  2. Piston head has deep scoring.

Questions:
  1. Can I just replace the deeply scored piston head?
upload_2022-7-24_16-14-5.jpeg
upload_2022-7-24_16-13-35.jpeg
 

Dino Dino Bambino

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I'm glad the piston's still intact so there won't be any debris in the oil pan. The good news is that your engine is rebuildable. The bad news is that the MHS passenger side head is scrap. I suggest you look for a salvage engine so you can scavenge a piston/rod assembly plus the passenger side head to replace your damaged items.
The question then is whether to have the salvage passenger side head ported to match your MHS driver's side head, or just replace the heads on both sides with the salvage unported units.
 

Redfire_Jimi

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I'm glad the piston's still intact so there won't be any debris in the oil pan. The good news is that your engine is rebuildable. The bad news is that the MHS passenger side head is scrap. I suggest you look for a salvage engine so you can scavenge a piston/rod assembly plus the passenger side head to replace your damaged items.
The question then is whether to have the salvage passenger side head ported to match your MHS driver's side head, or just replace the heads on both sides with the salvage unported units.

Hey Dino, I havent had a machinist inspect the head yet, but I was hoping the head could be repaired by a professional.
 

whitmanink

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foreyes has a youtube channel , he is selling his used piston , connecting rod,combo for like 250 ,,

he also has a passanger side head , but theres like 3 or 4 deep exhaust bolts broke off in head that need extracting
 

whitmanink

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i would also clean out that bore and make sure there isnt scoring at all on that cylinder wall, if so , you will need to get that taken care of before installing new pistions
 

Dino Dino Bambino

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Hey Dino, I havent had a machinist inspect the head yet, but I was hoping the head could be repaired by a professional.

It's not impossible to repair but it would take quite a bit of time for a skilled machinist to weld in new aluminum to fill the defects, grind it back, insert a new intake valve seat, and replace a valve guide. You'd also need to find a single matching intake valve (I assume it's 1mm oversize).
Consider yourself EXTREMELY fortunate that the broken valve head wedged itself firmly in the valve throat and didn't get bounced around inside the cylinder by the piston, and that the valve stem was still in the guide. Otherwise you'd be looking for an entire replacement engine.
 

Redfire_Jimi

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i would also clean out that bore and make sure there isnt scoring at all on that cylinder wall, if so , you will need to get that taken care of before installing new pistions

I thoroughly inspected the cylinder wall and it surprisingly undamaged. I can replace the piston, but I am worried about the need to rebalance the rotating assembly afterwards. I am hoping that replacing the piston with the exact same copy shouldn't require the need to rebalance. *Fingers crossed*
 

Redfire_Jimi

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It's not impossible to repair but it would take quite a bit of time for a skilled machinist to weld in new aluminum to fill the defects, grind it back, insert a new intake valve seat, and replace a valve guide. You'd also need to find a single matching intake valve (I assume it's 1mm oversize).
Consider yourself EXTREMELY fortunate that the broken valve head wedged itself firmly in the valve throat and didn't get bounced around inside the cylinder by the piston, and that the valve stem was still in the guide. Otherwise you'd be looking for an entire replacement engine.

Hey Dino, I may have to explore this route solely because I want to keep this head. All the porting work that was done wasn't cheap.
 

whitmanink

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I can replace the piston, but I am worried about the need to rebalance the rotating assembly afterwards. I am hoping that replacing the piston with the exact same copy shouldn't require the need to rebalance. *Fingers crossed*

the odds of you getting a piston the exact same weight as the the original one is slim at best,,
altho the weight difference would be minimal and induce a slight bit of vibration if any,,

now if your going high HP or blower,, than i would want to match them ,,, but count on having to match the con rod
 

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