As the title states, after getting really fedup from mechanics present in Karachi, I decided to rebuild the engine myself. After studying and gathering required information available about the engine itself and resources involved, the overhaul began.
The actual problem which led to this overhaul was Oil and water mixing(Blown headgasket). As the car previously produced blue smoke out of tail pipe and engine had ran a fair amount already (33 years) since last overhaul in 1984 (also done by a relative, i wasnt born back then and he departed this world in 2011), the decision was made for complete overhaul.
Fast forward, I took the engine out of car with my friends's help. All was dissassembled. Each and every component (valves, springs, retainers,rockers, headbolts conrod bolts main bearing cap bolts, pushrods, and all other miscellaneous part/nut/bolt ) was placed on marked Cardboard with care.
Engine block had sleeves, ring size was standard, Main and conrod bearings were already of .50 oversize and crankshaft collars were 125 oversize.
Took the Head and block along with pistons, crankshaft, valves, retainers, springs to machinist (Salman Engineering at Preedy street- recommended by @Xulfiqar bhai here on forums.).
Told him to resurface head/block, install new valves, valve guides, make seats for new valves. For block, told him to check the bore thoroughly and rebore/ re sleeve it and hone the cylinders on finish.
For crankshaft, As there was no bearing knock etc, told him to check it and polish/grind it, whatsoever required.
Handed him all the parts on saturday evening and after all settlement it was decided that i will pick it back on monday evening.
Made an old known parts dealer available to him for any part needed.
Im a Software Engineer by profession so i couldnt allocate any time to this in weekdays.
On Monday evening, i went to pick all the stuff back-
Head was resurfaced, new guides(3 oversize) installed along with old valves. new seats were made- Not what i wanted.
Crankshaft was polished up.
Block was un touched. As per him: it is all good, just a ring was broken, so it was giving smoke, just install back with new rings. I was like WT*. after a long argument, got it honed (atleast something).
took these all home.
Verified crankshaft with screwgauge, all round and fine.
Valves seated fine too.
Upon inspection of block. One of the sleeves came out to be cracked from just near the top of cylinder.
Piston's top ring wouldnt reach its height but it couldnt be tolerated any ways.
Took it to another machinist- Tawakal Engineering near Naseerabad, F.B area.
Got new sleeves, told him to use new pistons, here is what went wrong, sleeves were installed and finished for the old piston. When i enquired, the guy there ensured me that old pistons were within spec and doesnt require replacement. He said he had measured it all.
During this procedure 3 weeks have already passed as im able to do it on weekends.
Used standard rings,I had to file them a little to get to factory spec of 0.004 inch.
all was assembled back with new bearings, oil pump, gaskets etc
Conrod and Main cap bolts torqued to 44 Ft-Lb.
Headbolts torqued down to 55 Ft-Lb.
Had to use thicker headgasket gasket against will. Not my decision.
Now Engine was all ready, gave it a 20 min 1500rpm run for rings to seat.
HERE IS THE PROBLEM: On first start, it poured out smoke like a KMC disinfectant sprayer. i ran it for 20 mins anyways.
After that i turned it off and left it for a while.on second start. Engine was cold. To my surprise there was zero smoke. I was a happy soul back then.
As happy times are less in life, i revved it a little, just a touch to accelerator, smoke came right back once engine warmed up to operating temperature and turned off it self.
It didnt start back till it became cold again. And again at cold start, zero smoke, same thing again.
Now i need help to identify this and what really went wrong (my guess is old pistons).
Timing was set to 8 degree btdc.
Valve gap ~ 0.002 inch. a minute more for exhaust.
All Pakwheelers are kindly requested to help me out of this problem, specially @Xulfiqar @capsat @SER_GTR .
Thanks in advance.