Melted Piston

[bubba2400]

Is this bad?


No just kidding!
Looks like a new top end kit is in order. If I go .50 over is there any mods that need to be done to the motor? Any suggestions on pistons? Any thought on what caused it? There is a little oil in hull but I dont see any hoses off the oil pump. It is out of a 02 GTI (717) I picked up for 400 bucks with a trailer. The crank looks good and I dont see any thing in the case. I was told by the owner that the engine never seized just lost compression in rear cylinder.

 

[seadoosnipe]

Welcome bubba....

Welcome to the forum Bubba. There are several things that can cause your piston to look like it does. I don't know if I'd bore .50 over though. For the money, I'd order a new top end kit, complete with cylinders and pistons. It'll set you back about $400 bucks.

Boring over, machine shop, pistons and all the extras will set you over $400 pretty easy.

Look at the bottom of this post and you'll see a link to my "snipes korner". There is a post about reading your pistons. Shows several scenerios of piston destruction. You might find something to compare to your situation.:cheers:

 

[bubba2400]

Seadoosnipe thanks for the fast response. I was looking at a WSM kit with gaskets for 200 and I know a local shop that will do each cylinder for 40 bucks. I may be able to go .25 over the scoring isnt too bad. SBT is up to 475 plus shipping for the cylinder exchange kit on that engine.

P.S. Very nice info on the pistons. After looking at it appears to be a oil failure problem. Although there is a little damage on the other side of the piston as well.

 

[bubba2400]

After checking again the oil in the hull does not appear to be coming from the hoses around the oil pump they all look fine. It looks like it is leaking a little form the connector at the bottom of the oil tank. I would like to continue to use the oil pump but it has me a little worried. Whats the best way to test the pump?

 

[nswillin]

Standard for 717 82 mm (3.228 in)
First oversize 82.25 mm (3.238 in)
Second oversize 82.50 mm (3.248 in)

If you have to go any bigger than that you will need the new cylinder exchange like Snipe said.

As far as the oil pump, you can test it a few ways.
First way start engine up and run at idle while holding the pump
lever all the way open. You should see oil passing through the small oil lines. The engine should kinda bogg a little a smoking at the exhaust.

Also, pull the pump and check the pump shaft for any sign of wear like cracking or melting, anything.