01-27-2010, 12:20 PM
Join Date: Jul 2005
Total Cats: 68
The most common problem in medium and hi miles heads is leaky exhaust valves.
Here's how to check it:
Lay the head on its side and point the exhaust ports up. Pick the 2 or 3 cylinders whose valves are closed and the lobes are pointing away from the valves. Pour some kerosene or thin oil or spirits into the ports. Watch for weeping into the combustion chamber. I'll bet you a donut some or most of the exh valves will weep, and the intake valves are fine.
If you get some weeping (but not dripping lol), the cheapass way to fix it is to lap the exhaust valves. This will improve your leakdown and increase the life of the valves. While your at it, check the guides by checking how much side to side play the exh valve heads have.
BTW of all the head porting trix the most bang for the buck is indeed to backcut the intake valves.
Next is to just pay extra for Supertech intake valves if the intake valves need replacing.
Next is a 3 angle job
Next is if the exh valves need replacing AND a 3 angle job is necessary, pay extra and get +1mm Supertech exh valves.
(Rebello tells me that +1mm intake valves need to have extra bowl work to make em flow better than standard.)
After that some mad skillz are necessary to do it right; bowl work is next bang for the buck, and that ridge in the short side when the air makes a turn.
Then teardropping the guides.