Removed the engine to check for further damage, the head has bent valves and some cracked valve guides. I have removed the valves and stem seals to see the damage. To repair the head it will need a complete overhall with news guides and valves which is uneconomical to repair.
I have bought a replacement head from eBay in the US and paid £219 plus shipping. The head comes complete with standard cams, cam cover and throttle body rubbers. I can refit my uprated cams and replace the stem seals when the head arrives in a week or so.
Just need to order a new timing chain, stem seals and head gasket.
hello,
ReplyDeletein your opinion what is the cause that broke timing chain? failure of original tensioner?
have you change also piston? ceck shells?
Hi,
DeleteThanks for the comment. In seeking advice from Extreme Engines, I think that the cause of the chain breaking was mainly because I didn't change it when I completed the refresh and that it was quite well used before I bought the engine. In checking the top chain guide there are scores in it where a broken link has cut in to the rubber. I thought that because it's a chain it would last but good practice is to swap them out with a refresh. The other issue is my bad habit of using engine breaking, from many years of driving cars..
I have stripped down the tensioner and the pin and rubber head are in good order. Apparently when you decelerate the tensioner has some give in it to reduce the stress on the chain.
I have checked the pistons and there are a few marks but no cracks so all should be fine. I have removed the dry sump to clean out the plastic and shells look ok.
I feel that it's my own fault for not swapping the cam chain on a second hand engine that was out of a race car.