im just about to check the cylinder head for warpage, dont think it will be too bad as its never overheated, caught it in plenty of time, noticed a bit of steam when i started it up so never even got hot, is there a maximum amount of warpage, what is the upper limit for warpage across the length and width of the head,
I don't know what the spec is, but if you have it off the car, have a machine shop shave the head. Its cheap.
In fact, I would have them go through the entire head. Labor is probably in the $100-150 range, they hot tank the head, will measure everything and tell you what needs to be replaced, you get the parts, they install them. What you get back looks like a new head.
I would not be happy if after I did a head gasket, the car starts smoking from valve guides leaking oil after a couple of months.
I don't have my Shop Manuals anymore but....
I'd ignore 0.010" lengthwise, 0.006" the narrow way. If you see corrosion or blowby between Cylinders, have it planed.
No shop manual handy either, but a very skilled machine head shop can use several methods involving heat and bolting down to remove at least the max warpage from the book specs, it is a bit of a black art but works more times than not.
0.010 seems alot across the length, i thought more like 0.003 would be the limit, can anyone give me a definate, spoke to a saab dealer today and he reckons that the head on the 9000 was not that suseptable to warping and he says unless its overheated big time that he would just check for major warpage and if it was ok they would just bolt it back on. problem is im on a tight budjet and have no more money to spend on the car, just want to get it running but obviously i dont want to just bolt it back on its outs out of specification for warpage because its just going to blow the gasket again within time,
Even though this post is OLD AF, I still want to chime in because if you have a non turbo then the answers here are great, but if you plane a turbo equiped head it will change the compression ratio, it's a small amount yes, but a small amount is enough to completely blow that engine apart. With a turbo head they heat and press it back to flat instead of shaving. Just a morsel to chew on.
How exactly do you heat a cast aluminum head to the point that it is easily malleable without causing crystalization?? Extrusions I might could see that but cast? Would love to read up on it, got references on the process?
Disagree .. Normally not enough is removed during resurfacing to harm /effect the venerable Saab engine.
These featured a LOT of over engineering / safety margin..
Totally. The reason you typically don't want to plane the head is because it messes up cam timing... You couldn't remove enough to materially affect compression ratio. Removing .05mm (.002") would result in a loss of .3cc, or about .6% of the combustion chamber volume. It would go completely unnoticed.
Yeah, but really, any machine work is trivial as far as compression is concerned. The carbon deposits in the average engine are probably more deleterious.
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