Loss of power on 4y

[alexth]

Hi all. So I had my head done by Allen Venter of Allbilt at about 303000km. Im now on 312000km. Despite numerous issues along the way, it finally started running quite well about 5000km ago. Then last week.....major overheating, it chucked most of the coolant out and I panicked. Could not find any obvious head gasket issues, no white smoke on start up, oil still black etc. I then did a radiator flush and chucked in a bottle of Blue Devil head gasket sealer. Did it all according to instruction. 2 days later I did a trip to the Cedarberg from Fish Hoek, a total of 600km with lots of mountain passes etc. No overheating or water/coolant loss BUT now I've lost a LOT of power. Really struggled up hills, using 2nd where I would normally do 3rd easily etc. Even on the flat in top, if you floor it there is no urgency at all, which I did have before all this. Any ideas what I should look for? There is no surging, so does not seem to be a fuel problem. Checked the leads and seem ok too. Thanks

[The Legend]

Did the the rings not get damage due to engine overheated? Did you check the oil? Is it not using more oil than before? I have an completely overhauled original 4y head should you need one.

[alexth]

Can't comment on rings but it used no oil or water in 600km of serious mountain passes. A little while after start up today, there was a watery black substance coming out the exhaust which then stopped again. This could just be deposit or a combustion issue? Or maybe timing or the carb?