My new 100kw 4AG apparently had new rings fitted about 7000 kms ago and has high compression pistions but when a mechanic did a compression test it was only 90-110 psi. I read that standard compression for these engines is about 180 psi so with high compression pistons it should be higher than this.
The mechanic said there is a good chance that having the valves adjusted could bring compression up to about 180psi but thats still only normal compression.
The guy I bought the car offs theory is that the engine only gets its power above about 3000 rpm so compression might be lower below that but the mechanic doesn't think so.
Does anyone know anything that could explain this? Are any of these theorys right? Will adjusting the valves give it full compression? Any help would be good thanks.
sounds like it needs a proper rebuild (bore and hone + oversize pistons)
could be compression escaping past the rings
compression will be the same no matter what rpm the engine is at
could also be valve seals
only one way to find out
full leakdown test
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