My box-stock 22 year old Sierra's G13A engine was replaced about seven years ago but was getting a little tired (okay, VERY tired!). For the past two years I have been forced to use the Zook for all my work travel, so it was hard to take it off the road to have the suspected leaky head gasket or cracked head repaired. Zook was running on three cylinders, occasionally three and a half, and a couple of bottles of Chemiweld, added in desperation, only slightly improved it.
Finally managed to get it in with a mechanic who had done really good maintenance on the wife's Camry, got a serviced head and top overhaul kit sent up from Suzukishop in Perth and left him to it.
Instead of pulling the head off with carby and inlet manifold attached, he took those off first and discovered the inlet manifold gasket was blown at the bottom, where no-one could see. Water from the inlet manifold was being sucked into number two cylinder, along with generous amounts of air. The chemiweld had sealed the water leak but not the air.
Peter at Suzukishop kindly agreed to take back the head and o'haul kit, he's a great bloke to deal with, and mechanic Geoff used only new inlet manifold and tappet cover gaskets (even managed to re-use the seven years old extractor gasket), serviced the cooling system, replaced all the little cooling bypass hoses, replaced two missing bolts from the valve assembly, tightened everything up and gave Zook the tune-up of its life.
For a total cost of $530, it now starts on choke in the morning (I no longer warm it up with a brick on the accelerator pedal!), runs perfectly and quieter than ever, and pulls like a bull in springtime.
Moral of this long story: If you find a good mechanic, be nice to him - he's worth his weight in gold!
Cheers - Longbaser.