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Bent exhaust valves


Scany
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So I thought I'd maybe make a story here about my situation and repairs as I am slowly trying to get back on my feet after mechanically overreving the engine due to a shift into 2nd instead of 4th.

 

Well, to start of I initially had to figure out what to do. M50 engines are plentyfold and fairly cheap. Should I buy a new used engine or hope to just rebuild the head or get a new head if the pistons were intact? First thing first. I had to figure out how bad I'd destroyed the engine. Only way to really know is to take the head off.

 

I decided to take the complete front off the car to better access, and if the engine was to come out it should slide out easier. However the bar going from left to right is tacwelded to the frame, so I chose to leave that in for now. As I started to disassemble the engine I found one clue that might be good news: the spark plugs were intact. Ed York from York Automotive could tell me that if it would have been real bad a valve would break off and fly around in the cylinder, banging up the spark plug. So far it looks like a few new exhaust valves and I'll be back on the track. Also, a glimpse into the cylinder only showed small half circles in two cylinders where the valves had made contact to the piston and left marks in the black deposit. Another good sign! Ed also said that the pistons can get a little dent in them without any trouble. I'm crossing my fingers!

 

Today I am almost to the point where I can take out the head bolts and pull the head to see the damage. I had to stop at the chain guide which needs to be unbolted with a slim (1/4"?) E8 Torx bit. Mine are 3/8", so I need to go shopping for a new Torx bit. Below is a picture from how I left it tonight:

 

m50%20head.jpg

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Great progress and good luck! I'll keep my fingers crossed!

 

Where'd you find a T8?! I'm trying to repair my xbox and need a torx that small to take some screws out...

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Great progress and good luck! I'll keep my fingers crossed!

 

Where'd you find a T8?! I'm trying to repair my xbox and need a torx that small to take some screws out...

 

I probably have a T8, but the externals are hard to find. Had to get a set of Craftsman for $40, but it works

 

I need a pair of strong hands to help me lift the head off the block. Maybe Monday or Tuesday night. I don't think my wife would be much help.

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Anders,

 

I know that money does not grow on trees and we are all a bit tighter in the wallet during these economic times, but I strongly urge you to consider a full rebuild on the head by a top tier shop. Often times with bent valves there can be more damage that goes unnoticed until you are running the car hard at an event. If you already have everything taken apart and you can find the cash somewhere, I really would press you to consider it.

 

It would be a terrible thing to have to take it all apart again because a cam shaft has been scored or your compression numbers are not strong after putting it back together.

 

Best of luck with the work and I hope to see you at an event soon.

Jon

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Anders,

 

I know that money does not grow on trees and we are all a bit tighter in the wallet during these economic times, but I strongly urge you to consider a full rebuild on the head by a top tier shop. Often times with bent valves there can be more damage that goes unnoticed until you are running the car hard at an event. If you already have everything taken apart and you can find the cash somewhere, I really would press you to consider it.

 

It would be a terrible thing to have to take it all apart again because a cam shaft has been scored or your compression numbers are not strong after putting it back together.

 

Best of luck with the work and I hope to see you at an event soon.

Jon

 

Thanks for good advice Jon. I and York Automotive will closely inspect the head and bottom. If there's any doubt there might be more extensive damage I will certainly do a more full rebuild, or a new engine. I also take this as a learning experience. I'm prepared to be disappointed when I take the head off But we'll see. The ironic thing is that the engine has already had this happened to it before I bought it, but dyno'ed very strong (very close to stock bhp). I appreciate the input.

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Great progress and good luck! I'll keep my fingers crossed!

 

Where'd you find a T8?! I'm trying to repair my xbox and need a torx that small to take some screws out...

 

I probably have a T8, but the externals are hard to find. Had to get a set of Craftsman for $40, but it works

 

I need a pair of strong hands to help me lift the head off the block. Maybe Monday or Tuesday night. I don't think my wife would be much help.

 

 

I found a T8. I'm free tonight and tomorrow (although I'm kind of in a pool league that plays Tuesdays) if you need some help. My cell is 804.357.4487.

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Got the head off last night (the wife was called in as I couldn't wait). The damage seems minimal. I will post pictures later. Thanks Andrew for offering.

 

Next the tranny comes out for a clutch replacement. Another big job

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I'm an expert at that if you want some help with that too. I've got all my tools here (or most of them) in the back of my car, so if you want an extra set of hands, let me know and we can knock it out in a few hours

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I'm an expert at that if you want some help with that too. I've got all my tools here (or most of them) in the back of my car, so if you want an extra set of hands, let me know and we can knock it out in a few hours

 

Sweet! I'm hoping the clutch will be fairly easy with the head off the car, but a few hours seems optimistic I'll start with the exhaust and driveshaft myself while I wait for parts to show up.

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Here's some pictures. I'll be cleaning up the pistons tonight to see if i can get a better view of the damage. I also need to carefully inspect the cylinderwalls for any scratches. No good if i find any apparently.

 

img_1908%20large.jpg

 

img_1913%20large.jpg

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You may want to drop the oil pan to inspect the bearings as long as the engine is being thoroughly inspected.

 

Also, sending out the oil for analysis ($30-40) might provide you some reassurance that the metal levels are not too high.

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You may want to drop the oil pan to inspect the bearings as long as the engine is being thoroughly inspected.

 

Also, sending out the oil for analysis ($30-40) might provide you some reassurance that the metal levels are not too high.

 

I'll probably rinse the engine with some oil and then send out the next oil for tests. I'm not sure if the bearings should be a problem. It seems like the pistons and the valves are what gives in the impact. Of course it can't hurt to check them, but it's a job in itself. I might leave it for now and rely on oilanalysis after some miles. Thanks again for the advice Jon!

 

 

Here's a closeup of the pistondamage (sorry about the huge picture):

 

piston%20damage.jpg

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Looks like you're making some good progress. The driveshaft and exhaust should be pretty easy to take apart now that the head is off.

 

Take the exhaust off as one piece and save the headache of seperating, if thats possible with the spec exhaust.

 

I usually just disconnect the DS from the transmission side and tie it up out of the way. Just make sure you don't seperate from the center support bearing our you'll be in trouble!

 

Good luck with the disassembly! Are you going with a stock clutch? You are allowed to change the clutch type if I'm remembering correctly, but have to retain the stock flywheel.

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Are you going with a stock clutch? You are allowed to change the clutch type if I'm remembering correctly, but have to retain the stock flywheel.

 

I was under the impression that stock clutch was the only thing allowed. I must look this up.

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9.3.12.6. Any clutch disc and pressure plate of original diameter may be used provided that they bolt directly to an unmodified flywheel.

 

After much research and debate, mine was replaced with a stock Sachs unit.

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I was planning on Sachs and now I'm more convinced. Don't know much about clutches

 

Talked to the mechanic today as I dropped off the head. Sounds like I'll be in good shape

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I talked to my mechanic about this same issue of replacing the clutch. There really isn't any advantage to going to something other than stock for the power our cars make and the cost to move to something more heavy duty.

 

I'd go with a stock Sachs replacement anyway, but just wanted to let you know you have some wiggle room if you come across something

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While I agree on the count of required holding force, there are reasons to use a non-stock clutch. "Stock diameter" means that you can shave some weight from the rotating assembly by using a lighter weight pressure plate and clutch disc. Since the dual-mass flywheel is a monster anyway, shaving a pound from the rotating mass doesn't return much on investment.

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I hope you could chime in here Jon. Am I allowed to use head studs instead of bolts? I was recommended by my mechanic to do so. These are the ones I'm thinking of getting:

 

ARP Steel Block Head Stud Kit

 

I don't see a performance advantage in these, but a maintenance and reliability advantage. So the way I read the rules I would say they are allowed. But I'm not an expert at reading rules

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  • 1 month later...

Now I have everything back and ready for assembly. Rebuilding a head is costly! A new used engine will be way cheaper as far as I see it. Next time I'll try to do some headwork myself. But right now i hope i remember where everything goes and that it will run like a champ

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Now I have everything back and ready for assembly. Rebuilding a head is costly! A new used engine will be way cheaper as far as I see it. Next time I'll try to do some headwork myself. But right now i hope i remember where everything goes and that it will run like a champ

 

 

Will it be ready to "break-in" come the March VIR event?

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Great to hear! Hopefully the reinstall will go smoothly!

 

How much was the rebuild if you don't mind me asking? Hopefully you can make it out for March, I'm already signed up, but need to book a room as of now. Haven't gotten around to making lodging arrangements yet

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Hoping for March but it's going to be hard. My parents are visiting between now and then, and getting my dad to help won't work. But I'll give it a fair shot. Also need a new trailer by that time.

 

The rebuild ended up at around 800. Changed all exhaust valves and some broken retainers plus some other parts Im not sure what's called right now.

 

Wife will be back Saturday from 2 weeks away. Then I can get some serious garage time

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Hoping for March but it's going to be hard. My parents are visiting between now and then, and getting my dad to help won't work. But I'll give it a fair shot. Also need a new trailer by that time.

 

The rebuild ended up at around 800. Changed all exhaust valves and some broken retainers plus some other parts Im not sure what's called right now.

 

Wife will be back Saturday from 2 weeks away. Then I can get some serious garage time

 

 

If you need some help, let us locals know if we can lend a hand.

 

Also, what kind of trailer are you looking for? Options, price range, how far away, etc?

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