Engine Knocking on Left Side after Head Gasket Replacement

My brother and I just finished doing a head gasket replacement on his car. When we went to start it, it turned over a few times before it would start. It’s having a rough idle and knocking on the left side of the engine. Is this likely a dirty fuel injector, or might we have messed something more major up?

What year model and engine? Did the head gasket fail due to severe overheating? It’s not a dirty fuel injector problem at least as far as the noise goes. Is the knocking on the same bank that got the new head gasket?

Without car in hand, I know what i would do as first steps. One would be to remove the spark plugs and make sure they are not wet from engine coolant. Coolant entering a combustion chamber from a head gasket or intake leak can cause the engine to knock.

I would then run a compression test on all cylinders. If overheating did the head gasket in that can often take out piston rings and cylinder walls. For what its worth, when there is a head gasket issue both head gaskets should be replaced and especially so if overheating was involved. This involves the old saying about the weakest link in the chain.

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