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Restoration Woes
Posted by David Prantl (more from David Prantl) on Mon, 8 May 2000 22:50:12
In Reply to: , Kok Chen, Sat, 17 Dec 1988 12:00:00 

My extensive efforts to restore an abused and neglected '89 900 base auto 
have still not come to an end.

It now has:
Rebuilt transmission (new clutches, bands, transfer chain, o-rings and 
seals).
Rebuilt head (new intake gasket, exhaust gasket, head gasket, valve-stem 
seals, valve-lapping and flatness-machining).
Numerous misc. filters, bushings, rubber-boots, etc..

The problem is that the engine sounds 'uneven' when cranking.  Hence it is 
very difficult to start, and does not idle well.  I thought this might be a 
misadjusted timing chain, so I purposely set it forward by one tooth, as 
well as backward by one tooth, with no substantial improvement in either 
case.

I now suspect that there is excessive blow-by past the pistons, resulting in 
severe-enough compression loss to make for uneven cranking and difficult 
starting.  One clue is that I can feel exhaust coming through the PCV 
bushing on the valve cover, with a volume flow much greater than my other 
16V SAABs.  If I block the PCV hole, the exhaust starts escaping past the 
oil dipstick/cap.

I know I should warm the engine up and do a proper compression test, with 
the oil-squirt test for cylinder/ring condition.  But first, my questions:

1.  Would someone who has experience with multiple severely-overheated 16V 
engines please tell me if it is common to lose compression past the pistons 
afterwards ?  I always thought that head warpage and head-gasket failure 
stops you before this happens, but it now seems otherwise.

2.  If it IS common to experience excessive blow-by from overheating, can a 
new set of rings usually fix the problem, or is an over-bore with oversize 
pistons the only way to go (besides a trip to the favorite junkyard for a 
'new' motor) ?

3.  Bottom line:  What is the concensus on solving the 
severely-overheated-engine problem ?  Head-flattening and ring-job ?  
Salvage replacement engine ?  Labor time and effort are not a concern for 
me.

TIA.

David Prantl
david_prantlno39sdcx6spamx782hotmail.com
'84 900S, 5M, 210kMi, RIP
'86 9000T, 5M, 178kMi
'88 9000S, 5M, 137kMi
'90 9000S, 4A, 133kMi
'89 900, 3A, 115kMi
'68 97 Sonett V4, 76kMi, #000467
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