93 SC (347 turbo) Engine damage and repair pics

David Neibert

SCCoA Admin
Finally got motivated to pull the motor on my 93 SC today. Big thanks to Chris Wise for coming over to help. Expected to find a bent valve and some damage to the piston on the #4 cylinder where a valve spring dampner broke. It ended up being a lot worse.

The head of the intake valve actually broke off and pretty much destroyed the combustion chamber, the piston and also damaged the cylinder wall slightly. Finally found the head of the #4 intake valve stuck inside the intake manifold in the #5 runner (opposite corner of motor). Turbine wheel also got damaged from smaller pieces of junk coming out of the cylinder. So instead of just fixing the heads and installing a new piston, it's going to need a full rebuild, with a new set of pistons and possibly a new set of heads.

Here are some pictures of the carnage.
 

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More pictures..............
 

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Ouch...well, at least you're over the hump and know the details now.

So instead of just fixing the heads and installing a new piston, it's going to need a full rebuild, with a new set of pistons and possibly a new set of heads.

...and a turbo :(

I had a valve break in a 289 one time and it did a 180, stabbed into the top of the piston and reverse fit into the valve seat in the head on the upstroke. Kind of turned a 4 cycle into a 2 1/2...
 
Sorry to hear....and see. That's gotta be a tough one to take. I almost feel more pain for vehicles than people. :(
 
Ouch! That is a major setback. Is that a dart block? If so, I think it can be bored out to 4.125", which would give you 363ci.
 
When did this happen? HOW does something like that happen? Wow.

Tom,

It happened in early November just before the local track closed for the winter. Since the car had some issues at the Shootout and only made one clean pass I wanted to take another crack at getting a 9 second time slip while the car was still full of race fuel and had the slicks and skinnys mounted.

This pass went pretty good except for spinning the tires hard coming off the starting line and resulted in a 10.067 @ 139.65


Decided to give it another try with tire pressure reduced a little and boost slightly higher. Everything was okay until about the 1/8 mile point when is suddenly lost a lot of power and felt like it was missing. Thought it was just a burnt a plug wire or something simple, but as you can see it turned out to be a lot worse. This is the video when it broke.

http://youtu.be/HRZgiW2lTHg

From what I can tell it all this damage was caused by a valve spring dampner breaking on the #4 cylinder intake valve. The springs were iffy at the rpms I was turning and probably should have been upgraded to beehive style a couple years ago.


David
 
Ouch! That is a major setback. Is that a dart block? If so, I think it can be bored out to 4.125", which would give you 363ci.

Yes, it's an iron eagle Dart block and can be bored another .125" for 363 cubic inches, but I'll probably just go another .020" or whatever it takes to clean up the damaged bore to keep the displacement as close to 347 as possible. The PT76-GTS turbo I'm currently using would need to be replaced by something with a bigger turbine to avoid increasing the exhaust back pressure if I went all the way to 363. Not really interested in doing that right now. The turbo can be repaired pretty easily and is the least of my concerns.

I need to take a little time and explore my options on machine work for the block and determine if the AFR 205 heads are even worth repairing.

David
 
From the pic, that head doesnt look too bad to repair.


Yes, it's an iron eagle Dart block and can be bored another .125" for 363 cubic inches, but I'll probably just go another .020" or whatever it takes to clean up the damaged bore to keep the displacement as close to 347 as possible. The PT76-GTS turbo I'm currently using would need to be replaced by something with a bigger turbine to avoid increasing the exhaust back pressure if I went all the way to 363. Not really interested in doing that right now. The turbo can be repaired pretty easily and is the least of my concerns.

I need to take a little time and explore my options on machine work for the block and determine if the AFR 205 heads are even worth repairing.

David
 
Sorry to hear....and see. That's gotta be a tough one to take. I almost feel more pain for vehicles than people. :(

It's nothing new...if you are going to try to make a mid 15 second SC run 9s, your gonna break a lot of stuff along the way. BTW, this is my 10th year of messing with this particular car. Here's a post from when the motor was first built. Since this picture was taken I've broken lots of stuff and changed/upgraded lots of things and I'm sure there will be more issues in the future.

http://www.sccoa.com/forums/showthread.php?47894-347-turbo-motor-progress-pics

David
 
From the pic, that head doesnt look too bad to repair.

The surface damage doesn't concern me as much as the area where the valve guide is pressed into the head. Because of the bent valve stem being driven into it, the guide is now egg shaped and split open on the thin side. Not saying it can't be repaired, but i question if the cost to fix them and do a full valve job with upgraded springs is worth it when I can buy a brand new set ready to bolt on for $2000.

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David
 
David,

My biggest concern is that valves don't often just pop their heads off. There was a cause for that which can likely be traced back to component selection and actual use. AFR is notorious for using crappy parts on their heads and a broken valve head is often the end result of undetected previous valve float conditions which may have resulted in a just slightly bent valve. A new set of heads from AFR isn't necessarily going to be better. As a matter of routine we would replace the valve springs even on a new set of AFR's. The valves themselves might be of question as well. I would recommend a set of proper Manley race valves.

The valve guide situation does not concern me and the head is easily repairable. If you don't want to run those heads as a matter of warm fuzzies I can understand that, in which case I would replace them with a set of bare AFR heads and put all my own parts in them.

David
 
I got to agree with Dave on this one.

I had dropped a few valve heads in my day and it always came down to bad valves or poor design parts. This is one time I would go with the master on this one... David, sorry for your loss, it sucks when you drop valves or even when just the heads come off. I know you will have this thing running in no time Take care and get it going again....Rich
 
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