Alright, well finally got around to tearing into the motor. HG blew last year, I was running the car w/LBE and stupidly forgot that the banjo bolt was still installed from my old APE II chipset.

To my suprise, piston crowns and combustion chambers look farely clean.........To my even BIGGER suprise was lurking around the block so to speak

Check out the pictures, have you guys ever had a problem with electrolysis where the coolant eventually starts easting away at the metal? You can't see from the pictures, but the previous owner must have had the head replaced or just the valves because you can see where the intake valve had made love to my pistons...

Quick question...How much is an acceptable amount to have skimmed off of the head?

 

Your pistons just like it rough all the time

 

is it just me, or does it look like the #1 piston is installed backwards? shouldn't the arrow point towards the front of the engine?

 

Sorry for the poor quality pics. The arrows are all pointing towards the front of the motor.

So is there an acceptable range to be skimmed off the head? anybody??

Thanks

 

There are... I just don't know where my tolerances book ran off to...

 

Jared,
The corrosion is common with engines that had a failing OE HG and too little or old coolant in the system. The steel parts of the gasket are cathodic to the steel and the aluminum is anodic causing the wastage you see. A copper HG has even more potential for corrosion if the water/coolant ratio gets too low. You really have to keep the corrosion inhibitor concentration up in these cars. Take the head to Dels Machine at I-80 and El Camino. He can check it for flatness, leaks, and clean it up with a light pass cut. I would be more concerned about those larger corroded areas near the edge of the block. Any reduction in sealing area isn't good. Anytime you pull a HG and see a rusty exposed steel core the HG is well past it's useful lifespan.

 

On aluminium engines you should ALWAYS use phosphate free coolant with distilled water to prevent corrosion. This coolant costs more but it's worth it.

 

Thanks for the responses. Yea, this must have been adding up over time, we had always used phosphate free coolant, and it was changed once a year.
Steve, that's very interesting, I was trying to read up how electrolysis actually occurs.....too bad it occured on this motor haha. My neighbor actually recom. I went to Del's as well. After I take it in, will post more pics.

Thanks

 

Corrosion of the cooling passages is pretty common. I have a head off a 1989 where the cooling passages are enlarged at the gasket mating surface due to running poor or incompatible coolant. The machinist who rebuilt the head has done a lot on 944s, and he said it wasn't too bad; he has seen a number of 944NA heads that were unusable due to coolant passage corrosion.

Limit for machining of the head is 0.4 mm. Porsche has a thick head gasket available for machined heads (1.4 mm versus stock 1.1 mm.)

- Don

 

Thank you for that information Don, that's just what I was looking for!

 

Be careful with any headwork. From the 1st pic it 'appears' the head has been machined before since a few witness marks are gone. Take the spec sheet I PM'ed you to Dels since minimum head height is very critical. If that head is past it's prime I have a used one here at the house.