93 honda prelude 3 cylinders at 180 1 at 120.jus bought this prelude from auction has a after market turbo with a f22a1 bottom end in it.and a vtech head.the exshaust manifold has cracks in it looks like 1 cylinder semi shattered part of the manifol(not the cylinder that has low compresion)what would cause such a massive overheat? no heat wrap on it maybe?
Ignition timing that is advanced too much, and especially in conjunction with a turbocharger, can cause overheating and piston/piston ring damage.
And it can start this damage process with one cylinder and works it’s way progressively down the line with each cyl. becoming more progressively damaged.
(Just correcting a major typo.)
Looks like you bought a nightmare. You have lots of guts, buying an old car with an aftermarket turbocharger on it. Time for an engine teardown to see what happened inside.
Before yo go too far have a leak down test done on all cylinders. This will check the health of all the piston rings, valves, and head gasket. On the low compression cylinder if the leak down test verifies the high leakage, listen for where the air is going. If hissing is coming from the crankcase, it is rings. If the hissing is coming from the intake or exhaust, it is the corresponding valve. If air bubbles are coming out of the cooling system, it is a head gasket problem.
BTW turbos, especially overboosted, are tough on exhaust valves so look there first.
Hope that helps.
You have clear signs of this engine having been overboosted and raced. I’m willing to bet the internal damage is extensive.
Honestly, I think your best bet is to start looking for a boneyard engine and use that aftermarket turbo as a boat anchor.