home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > maintenance & nonperformance

Reply
 
Thread Tools Display Modes
Old 11-19-2020, 07:15 PM   #1
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default My very bad day: shattered valve, gouged piston

Well, my Megasquirt/B20 project has come to a grinding halt. One of my exhaust valves sheared off at the lower retaining groove (I'm guessing it was defective, there is no sign of a broken valve guide) and dropped down into the block. Piston shattered the valve, but not before it made a pretty sizeable gouge in the piston. I haven't even assessed the head yet.

I'm trying to figure out next steps. Once I clean out the debris and carbon, I can get a good look at the piston. The block only has 5k on the rebuild, so I'm pretty frustrated.

So the question is, run it or replace the piston? I just put the engine in, so I'd rather not pull it. Is it possible to swap a piston from underneath, or am I just going to need to bite the bullet and pull the engine?

Shinchan is offline   Reply With Quote
Old 11-19-2020, 07:39 PM   #2
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

Better photo after I cleaned out all of the valve bits. I don't think I can save the piston.

Shinchan is offline   Reply With Quote
Old 11-19-2020, 07:53 PM   #3
JohnMc
PV Abuser
 
JohnMc's Avatar
 
Join Date: May 2004
Location: St. Louis
Default

Probably not a good idea. Better to swap it, rather than risk having it come apart later. You can replace pistons with the engine in the car, but generally speaking, it's going to be less work to pull the motor. It's not particularly easy to pull the oil pan with the motor in the car.
__________________
'63 PV Rat Rod
'93 245 16VT Classic #1141
JohnMc is offline   Reply With Quote
Old 11-19-2020, 08:13 PM   #4
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

I might try lifting the engine enough to get the oil pan out and then setting it back down to do the work. I reeeeeealy don't want to pull the engine.

Quote:
Originally Posted by JohnMc View Post
Probably not a good idea. Better to swap it, rather than risk having it come apart later. You can replace pistons with the engine in the car, but generally speaking, it's going to be less work to pull the motor. It's not particularly easy to pull the oil pan with the motor in the car.
Shinchan is offline   Reply With Quote
Old 11-19-2020, 09:41 PM   #5
carver
Redblock for life.
 
carver's Avatar
 
Join Date: Apr 2011
Location: Seattle
Default

Seems like it would be easier to pull the engine and trans all at once. Working under a car on a job like that sounds like a real pain in the a$$. That really sucks, sorry that happened to you OP.

Last edited by carver; 11-19-2020 at 09:50 PM..
carver is offline   Reply With Quote
Old 11-20-2020, 11:25 AM   #6
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

Ream the ridge at the top of the cylinder, pull the oil pan (the trickiest part), remove the 2 cap screws at the end of the rod, push the piston out through the top of the block.

At least I'm hoping that it's that simple.

Quote:
Originally Posted by carver View Post
Seems like it would be easier to pull the engine and trans all at once. Working under a car on a job like that sounds like a real pain in the a$$. That really sucks, sorry that happened to you OP.

Last edited by Shinchan; 11-20-2020 at 11:30 AM..
Shinchan is offline   Reply With Quote
Old 11-20-2020, 12:11 PM   #7
JohnMc
PV Abuser
 
JohnMc's Avatar
 
Join Date: May 2004
Location: St. Louis
Default

If you don't have an engine hoist and an engine stand, then doing it in the car might be easier.

I've pulled pans a couple of times, always seemed like a PITA. On a 140 I had to drop the front crossmember (while supporting the motor). You need enough clearance to remove all the oil pan bolts, then drop it down far enough to unbolt the oil pump. Then when reassembling, it's highly tricky to ensure you have the oil pump transfer tube seals in place properly when reinstalling the pump to the block while the oil pan sits in the way. Unless you *really* get a lot of room between the motor and crossmember and can fully install the pump, then put the pan on.
JohnMc is offline   Reply With Quote
Old 11-20-2020, 12:54 PM   #8
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

I have a hoist. The plan was to disconnect the driveshaft and lift the front of the engine while letting the nose of the trans drop down. Hoping this will give me enough clearance to pull the pan. I installed the engine by myself (no help where I'm at plus Covid) but I don't want to have to do that again by myself if I can avoid it.

Quote:
Originally Posted by JohnMc View Post
If you don't have an engine hoist and an engine stand, then doing it in the car might be easier.

I've pulled pans a couple of times, always seemed like a PITA. On a 140 I had to drop the front crossmember (while supporting the motor). You need enough clearance to remove all the oil pan bolts, then drop it down far enough to unbolt the oil pump. Then when reassembling, it's highly tricky to ensure you have the oil pump transfer tube seals in place properly when reinstalling the pump to the block while the oil pan sits in the way. Unless you *really* get a lot of room between the motor and crossmember and can fully install the pump, then put the pan on.
Shinchan is offline   Reply With Quote
Old 11-20-2020, 12:58 PM   #9
JohnMc
PV Abuser
 
JohnMc's Avatar
 
Join Date: May 2004
Location: St. Louis
Default

The motor generally only tilts back a little before the head hits the firewall, but in our case, with no head on it, might work.

With the head off you're just a few more bolts away from pulling the rest of it out.

I've pulled motors with the trans on, and without. It's pretty much a wash in terms of which is easier. With an OD trans, it's long enough that you generally need to lift the front of the car up to give it room. Just take the radiator out, no need to remove anything else.

Do you have a load leveler? That makes installing motors super easy. Just crank the handle to change the angle of the dangle. Almost feels like cheating.
JohnMc is offline   Reply With Quote
Old 11-20-2020, 01:11 PM   #10
Mr. V
Board Member
 
Mr. V's Avatar
 
Join Date: Jul 2004
Location: Portland, Oregon metro
Default

When pulling a red block and transmission I now remove not only the radiator / condenser / intercooler but also everything in front of and on top of it, including the light assembly: remove everything above the bumper and between the front fenders.
Mr. V is offline   Reply With Quote
Old 11-20-2020, 01:15 PM   #11
Lando
Arthur Digby Sellers
 
Lando's Avatar
 
Join Date: Mar 2011
Location: Rancho Relaxo
Default

Ouch! I had the same thing happen on my Tundra this summer. The valve just fell off the stem 18k miles after I rebuilt the motor. The reason I had to rebuild was because on drivers side bank, the valves hit pistons due to timing belt slip. There was no apparent damage to the passenger side head, so I reused it after inspection. Turns out it must have had a micro crack in the valve stem.

At least your rod is still ok. Mine was bent so the piston top was about a mm lower at TDC than the other cylinders.

image host
__________________
Quote:
Originally Posted by 11110000 View Post
I didn't think there was anything to the whole 7/9 thing, but I have to say that my 745T is the only Volvo I've owned that blew up and self-immolated.
Lando is online now   Reply With Quote
Old 11-20-2020, 01:16 PM   #12
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

T5 trans, which is a little beefier than the original trans and a shade longer than the M41

Quote:
Originally Posted by JohnMc View Post
The motor generally only tilts back a little before the head hits the firewall, but in our case, with no head on it, might work.

With the head off you're just a few more bolts away from pulling the rest of it out.

I've pulled motors with the trans on, and without. It's pretty much a wash in terms of which is easier. With an OD trans, it's long enough that you generally need to lift the front of the car up to give it room. Just take the radiator out, no need to remove anything else.

Do you have a load leveler? That makes installing motors super easy. Just crank the handle to change the angle of the dangle. Almost feels like cheating.
Shinchan is offline   Reply With Quote
Old 11-20-2020, 01:22 PM   #13
JohnMc
PV Abuser
 
JohnMc's Avatar
 
Join Date: May 2004
Location: St. Louis
Default

I had a T5 on the 16V motor. I'm not sure if I ever installed that with a complete 16V motor with the T5 bolted on. The 16V motor has a lot less room to tilt (at least in a 240). And the T5 was so easy to unbolt - leave the bellhousing on and just take 4 bolts off and slide the trans back.
JohnMc is offline   Reply With Quote
Old 11-20-2020, 01:28 PM   #14
DET17
Reformed SAABaholic
 
Join Date: Nov 2009
Location: NW Georgia
Default

This sad story again illustrates why you should replace exhaust valves when performing an overhaul. From my experience, it is rare to see an intake valve fail but the exhaust sides are the typical failure point due to the thermal stress on them.

I also pulled a redblock oil pan in situ in my 940; a PITA it was for sure..... and then I found out the rear thrust bearing was toast due to an incorrect AW71 swap, and ended up pulling the engine to replace it!

For the value of my time, I'm pulling the whole shebang.
__________________
Project "cheap thrills" build thread: http://forums.turbobricks.com/showth...67#post4211467

Feedback thread: http://forums.turbobricks.com/showthread.php?t=198746
DET17 is offline   Reply With Quote
Old 11-20-2020, 01:32 PM   #15
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

The entire valvetrain was brand new including valves, guides, seals, etc.
I'm guessing the valve was defective from manufacturing.

Quote:
Originally Posted by DET17 View Post
This sad story again illustrates why you should replace exhaust valves when performing an overhaul. From my experience, it is rare to see an intake valve fail but the exhaust sides are the typical failure point due to the thermal stress on them.

I also pulled a redblock oil pan in situ in my 940; a PITA it was for sure..... and then I found out the rear thrust bearing was toast due to an incorrect AW71 swap, and ended up pulling the engine to replace it!

For the value of my time, I'm pulling the whole shebang.
Shinchan is offline   Reply With Quote
Old 11-20-2020, 11:45 PM   #16
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

Well, I guess the head could be worse. The broken valve slammed into the intake valve and it ended up 'S'-shaped. Both valve guides broken. Valve seats have some damage that I'm not sure can be cleaned up without going to oversized valves. Overall a pretty ****ty week...

IMG-7678
Shinchan is offline   Reply With Quote
Old 11-21-2020, 10:45 PM   #17
vwbusman66
Stößelstange über alles!
 
vwbusman66's Avatar
 
Join Date: Oct 2016
Location: Kingsville, MD/ Morgantown, WV
Default

Quote:
Originally Posted by JohnMc View Post
Probably not a good idea. Better to swap it, rather than risk having it come apart later. You can replace pistons with the engine in the car, but generally speaking, it's going to be less work to pull the motor. It's not particularly easy to pull the oil pan with the motor in the car.
You mean, an in-frame rebuild? Now we're talking.
__________________
1971 142 beater/fake racecar
Quote:
Originally Posted by linuxman51 View Post
the only problem with that is what you define as cheap and fast
Quote:
Originally Posted by propav8r
The incest is implied.
vwbusman66 is offline   Reply With Quote
Old 11-22-2020, 06:30 PM   #18
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

Nah, just a piston swap.

Quote:
Originally Posted by vwbusman66 View Post
You mean, an in-frame rebuild? Now we're talking.
Shinchan is offline   Reply With Quote
Old 11-22-2020, 09:24 PM   #19
deadken
Board Member
 
Join Date: Mar 2009
Location: Long Island, NY
Default

Quote:
Originally Posted by Shinchan View Post
Ream the ridge at the top of the cylinder, pull the oil pan (the trickiest part), remove the 2 cap screws at the end of the rod, push the piston out through the top of the block.

At least I'm hoping that it's that simple.
I'll add my 2 cents here:

I'd bet that you could get away with just putting a head on it. I don't think I would, but you could.

Having said that, if this is a performance engine, I would be concerned about a hot spot, from a high spot along the edge of the gouge, causing detonation. It probably wouldn't, especially if you cleaned up the top of the piston aggressively. But, knowing that it could be detonating in that one cylinder without me even being able to hear it, would be enough to have me pull the block and swap the piston if it was my car.


If the block only has 5k on it since the rebuild, I would be surprised that you'd have a ridge. Are you sure that you have a ridge?
deadken is offline   Reply With Quote
Old 11-22-2020, 11:33 PM   #20
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

It doesn't have a ridge, so I'll just be popping the piston out tomorrow.

New piston is on the way, I'm not taking any chances on this piston, it could be cracked for all I know.

Quote:
Originally Posted by deadken View Post
I'll add my 2 cents here:

I'd bet that you could get away with just putting a head on it. I don't think I would, but you could.

Having said that, if this is a performance engine, I would be concerned about a hot spot, from a high spot along the edge of the gouge, causing detonation. It probably wouldn't, especially if you cleaned up the top of the piston aggressively. But, knowing that it could be detonating in that one cylinder without me even being able to hear it, would be enough to have me pull the block and swap the piston if it was my car.


If the block only has 5k on it since the rebuild, I would be surprised that you'd have a ridge. Are you sure that you have a ridge?
Shinchan is offline   Reply With Quote
Old 11-22-2020, 11:34 PM   #21
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

It's about half a mm lower than its neighbor at tdc. Going to get the rod checked when I take the head in for cleanup.

Quote:
Originally Posted by Lando View Post
Ouch! I had the same thing happen on my Tundra this summer. The valve just fell off the stem 18k miles after I rebuilt the motor. The reason I had to rebuild was because on drivers side bank, the valves hit pistons due to timing belt slip. There was no apparent damage to the passenger side head, so I reused it after inspection. Turns out it must have had a micro crack in the valve stem.

At least your rod is still ok. Mine was bent so the piston top was about a mm lower at TDC than the other cylinders.

image host
Shinchan is offline   Reply With Quote
Old 11-28-2020, 06:27 PM   #22
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

I'm sure I can still run it...
IMG-7693

Yes, you can remove the oil pan without removing the engine from the car. I dropped the nose of the trans and raised the front of the engine, just enough room to clear the oil pump and pull the pan out:
IMG-7690

Does this look like normal wear for a bearing? Crank journal shows no sign of scoring.
IMG-7692
Shinchan is offline   Reply With Quote
Old 11-29-2020, 11:38 AM   #23
matt b
Board Member
 
Join Date: Apr 2007
Location: Tucson
Default

I don't think that's normal wear at all, no. But I wonder how much of it is due to what just happened to your engine. Is the rod bent too ?

What are you running for an alternator ? I don't recognize it.
matt b is offline   Reply With Quote
Old 11-29-2020, 01:24 PM   #24
Shinchan
Board Member
 
Join Date: Jun 2018
Location: Lafayette, CO
Default

Not looking forward to trying to figure out the size of the bearing, I wish they would stamp them with the size. I'm sure all of it is due to what happened to the engine. The rod is also bent and twisted, I'm picking up a straight one this afternoon.

Alternator is a Volvo-stamped OEM unit, I'm pretty sure it's stock to the car.

Quote:
Originally Posted by matt b View Post
I don't think that's normal wear at all, no. But I wonder how much of it is due to what just happened to your engine. Is the rod bent too ?

What are you running for an alternator ? I don't recognize it.
Shinchan is offline   Reply With Quote
Old 11-29-2020, 02:24 PM   #25
mocambique-amazone
Board Member
 
Join Date: Jul 2012
Location: Germany
Default

Do yourself a favour and get the engine out.
The rod will not match with weight. Never.
And the piston too

The "new" "rebuild" engine will be destroyed very fast otherwise.
You will regret not pulling the engine.
And buy better valves. check the other 7 valves very closely too
My 2c

Good luck, Kay
mocambique-amazone is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 03:47 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.