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Discussion Starter · #1 ·
Amazingly this vital bit of simple, but vital bit of information, seem to be missing or fudged from manuals and the net. Yes I am aware that it involves a straight edge and some feeler guages, but how about some specifics. I.E. 1. What is a good type of straight edge to use. 2. Where exactly do you place it. 3.What tolerances do you allow.

My 9000 K reg. Aero has done about 110k and I am trying to decide whether to have the head skimmed or not.

Incidently there is some corosion. About 2cm dia. and 2mm deep. Is it OK to JB weld this if the head is not skimmed?

I have not yet plucked up the courage to take off the exhaust manifold. If I do I am considering putting SS studs, so cuold anyone tell me where I can buy some,and what they cost?
 

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I have always used a steel straight edge. You can get these steel rulers in a 24 inch or 18 inch length. Sit it on edge across the head at different angels and try getting a feeler to pass beneath.

You can get the straight edges in most tool shops, B&Q etc.

A head usually only goes out of alignment if the engine has seriously overheated.
 

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Welcome to SaabScene.

Surely if you have 2mm of corrosion you should get the head skimmed. A decent machine shop won't charge that much to skim the head, and it's a more reliable long term solution than patching the thing up.
 

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Discussion Starter · #4 ·
Originally posted by sgould:
[qb]I have always used a steel straight edge.  You can get these steel rulers in a 24 inch or 18 inch length.  Sit it on edge across the head at different angels and try getting a feeler to pass beneath.

You can get the straight edges in most tool shops, B&Q etc.

A head usually only goes out of alignment if the engine has seriously overheated. [/qb][/b]
Thanks for your help,that sounds really good. What I now need to know is what size feelers to try
 

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Discussion Starter · #5 ·
Originally posted by Mark B:
[qb]Welcome to SaabScene.

Surely if you have 2mm of corrosion you should get the head skimmed.  A decent machine shop won't charge that much to skim the head, and it's a more reliable long term solution than patching the thing up. [/qb][/b]
Yes, I quite agree Mark, but the thing is I am only trying to do what is absolutely necessary. Bear in mind that the area around the cylinders is good for about a cm. The other thing is, if I have the head skimmed I would be tempted to do the valves and springs etc. And ofcourse I would have to get the exhaust manifold off. What do you think?
 

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I obviously wasn't thinking or typing particularly well yesterday. The average head skim is around 0.010" (0.25mm), with the range being 0.005" - 0.030" (0.1 - 0.7mm). The larger amounts are usually only required if the head has warped due to overheating.

I suppose the question then is: whereabouts is your corrosion? i.e. near a water way or the oil ways, or is it in the middle of nothing important?
 

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Discussion Starter · #8 ·
Thanks Dave225

That is very interesting technical information.

The only report I've seen from Saab for repairing small holes/blemishes is in the clyinder block where they recommmend I think, JB weld. Do you think this could be used with the cylinder head?
 

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Discussion Starter · #9 ·
Thanks for the extra info. MarkB.

Within the range 0.1-0.7mm where would you say is the tolerance that will determine if a cylinder head needs skimming or not?

I will try to upload a picture of the cylinder head so you can see where the damage is.
 

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The only report I've seen from Saab for repairing small holes/blemishes is in the clyinder block where they recommmend I think, JB weld. Do you think this could be used with the cylinder head?  [/b]
I filled some pitting on my cylinder head two years ago with JB Weld, with no subsequent problems (2ltr FPT). Just make sure the hole is clinically clean before you start.
 
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