bent valves

[dsm girl]

hey whats up everybody I have a question I have a friend that has bent valves on his 91 talon turbo and says that on the pistions you can see slight indentation marks where the valves hit. Would he have to replace the pistons or can he just get new valves and use the pistons. The pistons dont look really bad just like little curcular scratches if that where the valves were hiting. Thanks your answers will really help.

 

[QuickerDSM]

More than likey he should be able to slap a rebuilt head back on without any worries. There is always that slight possibility that a valve hit the side of the piston and cracked a ring land though. If the marks are small I'd probably take my chances with it. Definitely do a compression check after the new head is installed though.

BTW, this should probably be in Engine Performance rather than Tuning.

Mike

 

[Prodigy]

well if ur head gasket was gone to..i would not put a new head on unless u change the rings...because it will just burn oil...for the price of a new head u could almost get a new jdm motor..just and option good luck..

 

[dsm girl]

thanks for the info. I am going to take my chances and put new valves on the head. The head gasket looked in good shape.

 

[kpt4321]

1. Having a dead head gasket has nothing to do with whether or not the rings are gone.

2. The cost for a head rebuild is around $150, which gets you a better condition head then you could ever get on a used motor. Plus, while you're in there, you can also do stuff like timing belt, etc.

3. The valves can't hit the sides of the pistons, they can only hit the tops.

4. Odds are the pistons are fine. People bent valves like that all the time, and don't have to touch the block.

 

[91TalonTSiCT]

The cost for a head rebuild is usually closer to $300. They usually have to replace the guides because they get cracked when the valves bend and then they may have to do a little bit of machining.

 

[QuickerDSM]

Originally posted by kpt4321


3. The valves can't hit the sides of the pistons, they can only hit the tops.

Guess I should have clarified my answer a bit more. I meant to say the outside edge of the TOP of the piston. If the valve head broke off and ended up in between the head and the piston, it could definitely crack a ring land or more obviously. Doesn't sound like that happened though.

Also, if you do end up slapping the head back on, try to sand down the nicks in the piston tops. This will prevent hot spots which can cause detonation.

Mike

 

[dsm girl]

thanks for the help once more. Where would I be able to find valves that are cheap because mitsubishi dealership charge a grip, they cost more than performance valves.

 

[BUCK]

BTW - brand new stock Pistons for a 1g COME with 4 "slight indentation marks/ depressions" in them for the valves. 2 on one side of piston are bigger than the other 2. I was a rare case where I wrung the Timing Belt at the crank & bent no valves - knocked a little tan carbon off the edge of one but it wasn't bent.

 

[Suparata]

Originally posted by Prodigy
well if ur head gasket was gone to..i would not put a new head on unless u change the rings...because it will just burn oil...for the price of a new head u could almost get a new jdm motor..just and option good luck..

You started good and ended awful. Yes a head gasket failure can freeze the oil wipers and cause excessive oil consumption but that usually happen in time. But then you recommended him a JDM engine . I don't want to repeat myself so read this http://www.dsmtuners.com/forums/showthread.php?s=&postid=764287#post764287 if you want to know what I think about JDM's.

^^^ The cost for a head rebuild is usually closer to $300. They usually have to replace the guides because they get cracked when the valves bend and then they may have to do a little bit of machining^^^

Yes bent valves on a Mitsu usually mean cracked guides that need to be replaced , but do not expect to get a good job for only 300.

^^^ thanks for the help once more. Where would I be able to find valves that are cheap because mitsubishi dealership charge a grip, they cost more than performance valves.^^^

Your machinist should be able to help you out with that.