Cylinder head refurbs

[sawood12]

I'm posting for a work collegue who after selling his 944 6 months ago is once again pining for a Porsche and is now after a 3.2 Carrera. Anyway he's wanting to find more info out about head refurbs that he has been told is something that you need to look out for on these cars. His questions are:-
1. How common is it that these refurbs need to be done?
2. What are the symptoms to look out for (smoking exhaust?)?
3. Exactly what work is done at a refurb?

He's pretty handy with a toolbox so isn't put off by having to strip the head himself but just wants to understand exactly what to expect.

Cheers.

 

[Guest]

Presumably he means a top-end rebuild?

Usually required due to worn valves guides which varies dramatically from car to car. A good PPI should identify the issue or oil smoke on lift-off or overrun can be tell tales. Many cars have had it done but some are in fine health at 150,000+miles.

Probably costs circa £3,000 to pay someone to do a top-end without any "while you are in theres".

 

[Jonathan Collins]

Also take note of this. http://www.porscheclubgbforum.com/fb.asp?m=78132&key=smoke
Mine usually smokes on start up from cold but not always. I think you are recommended to fit new pistons while the engine is stripped, whereas the cylinders tend not to wear due to their hard coating.

 

[Guest]

ORIGINAL: Jonathan Collins

Also take note of this. http://www.porscheclubgbforum.com/fb.asp?m=78132&key=smoke
 Mine usually smokes on start up from cold  but not always. I think you are recommended to fit new pistons while the engine is stripped, whereas the cylinders tend not to wear due to their hard coating.

You mean new rings. The pistons themselves do not wear, its the rings. Even then, I would inspect it and see if it is necessary. I did mine even though they looked like new after 75,000miles as a "while you are in there".

 

[Jonathan Collins]

Well I have never rebuilt a 911 engine ,but I have done plenty of others and without exception pistons do wear.The most common places being the ring grooves and the lands of the piston on the thrust side, sending the piston oval.I have had one where the gudgeon pin became a loose fit due to it turning in the piston as well as the little end.I do not doubt you may be able to get away with just re- ringing the pistons depending on the mileage and type of use the engine has had.However if it was mine and the engine was so far dismantled, I would push the boat out and buy new pistons with the money saved by doing the job myself.

 

[Richard Savage]

ORIGINAL: Richard Bernau
You mean new rings. The pistons themselves do not wear, its the rings. Even then, I would inspect it and see if it is necessary. I did mine even though they looked like new after 75,000miles as a "while you are in there".

Richard - Sorry, that's a no, no! Try checking a ring / land clearance! Maybe you were considering ring face / sleeve wear only eh!

R.

 

[Richard Savage]

ORIGINAL: Jonathan Collins
I would push the boat out and buy new pistons with the money saved by doing the job myself.

Jomathan - Might as well go for new sleeves as well then, and do the job properly. After all, it's only Scott's money we're spending!

R.

 

[IanHighfield]

If it is Scott's money, why not junk the cylinders and pistons, and fit new Mahle 98mm for a nice 3.4, or go the whole hog and fit 100mm for 3.5 litre, although we will need more of his cash to enlarge the crankcase and twin plug the head.............easy to spend someone else's money isn't it - I like this

 

[Jacob]

O.k, so the engine is bored out to a 3.5. I reckon the next step would be to add a supercharger - just for a little extra poke[]

 

[Guest]

ORIGINAL: Richard Savage

Maybe you were considering ring face / sleeve wear only eh!

R.

Yes [] In my case, everything else measured in spec. If I was to do mine again, I would not have re-ringed - but you really only know that once you have pulled apart and measured and then its to late.