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| Damaged intake valve. Caused by excessive heat? |
I just had the engine disassembled, why didn't I examine the head more thoroughly? Stupid!
Anyway, head off. With the engine still in the car it took just a couple of hours to get it apart. It is funny how much easier things are when you've done it before. Separating the head from the engine was for me something unthinkable not long ago.
A water test confirmed that the middle two cylinder's valves was leaking. So, time to disassemble the head as well. That is a bit more time consuming but not very hard, and can be done inside at the kitchen table :-)
- Do you have to keep the engine in the kitchen?
- It is just the head, dear.
- Ah, ok then.
Almost all of the valves on the middle two cylinders was damaged, both on the intake and exhaust side. Fortunately all of the valve seats looks as new. The pitting on a couple of the valves looked like it could have been caused by a foreign object. But if that was the case wouldn't it be dents in the seats as well? No, I still believe in the fuel starvation theory.
Seven new valves. Some lapping compound and the valves sealed again.
Here is a really good YouTube video of how to make a basic valve job.
Piston-to-valve clearance check
Before I put the head back to engine I decided to do a piston-to-valve clearance test using modelling clay. It is a very tediously process where you put some clay in the cylinder, and then mount the head, cams and timing chain back together and then turn the engine two turns and disassemble it again. To my surprise the clearance was about half of the Cosworth recommended 1.00mm!Damn! Now what? I just want my engine back!
After a bit of grumble I decided to do the test again, this time being extra super careful with the cam timing. And the clearance was back. Now I know how sensitive it is. Under no circumstances the exhaust cam should be retarded. In fact, one or two degrees advanced exhaust timing is not wrong to be on the safe side. The same goes for the intake cam, but the other way around. I don't believe it was this sensitive with the old engine block.
Lash
"Lash" is the distance between the underside of the cam lobe and cam follower and is checked using feeler gauges. Because of the new valves I was required order four new cam followers from Burton. DHL is the best. They're the only freight company where my experiences has been positive most of the times.First start today and first test drive this tonight. Always hard to tell if all the power was back or not, especially when it is dark outside, but the engine felt good and a new compression test gave the same results on all the cylinders.
Yay!
