Hi I recently brought a p38 from auction... On driving home it was pinking bad so I did the right thing and changed plugs and leads...still the same...it's lpg so not sure if that helps but I have had a mobile mechanic tell me that four cylinders are not running on full compression 1 was only at 39% I've also been told that one side head gasket has failed....my question... Would head gasket fault show up as poor compression?... Thanking you for any help/knowledge in advance.

 

Hola
Yes if the head and gasket has been distressed there is every chance the gasket has cross blown between cylinders. The gasket is also known to blow out and allow compression gasses to vent to the crankcase causing excessive crankcase compression. In a similar fashion it can also blow out under the exhaust manifold(s) giving the impression its a manifiold gasket blown.

Sounds to me like the engine has suffered severe heat distress and do remember that the cooling system on a P38 needs extra care to bleed out trapped air especially from the block. Due to the thermostat siting being on the lower hose, a bleed/vent plug is located next to the top hose flange for this purpose.

Engines which have suffered like this often exhibit warped heads in excess of 0,03mm or 0.012" which renders them scrap. Equally the block can suffer with cylinder liner coolant leakage into the combustion chamber when subjected to excessive heat distress. All these factors should be taken into account before a repair decision is made.

T/V