I've been browsing through all the tech information on this site, very nice. There are some things I can't seem to find. Looking around, I see the Champion heads have 1.90/1.60 valves, but I can't find what stock heads are like. How much larger are the valves on the Champion heads?
Also, M&N heads. Where can I find more information? I hear the valves on the M&N heads are close to stock, true?
How much lighter are these heads than the stock cast heads?
I have a 4.1 block, but all I have are 3.8L heads. As near as I can tell, the only difference between the 3.8 and 4.1 heads is the size of the intake passages? Is this true?
Stock is (from memory) 1.71 intake 1.5 exhaust... have to double check that. A common mode is to enlarge the intake to 1.77 when doing head porting.
The other heads are "M&A" heads. Just like with Champion, there are different levels of what valves and types of mods you can have.
Take a look at the picture guides... there are very slight differences in the 4.1 heads (some years, they are the SAME as 3.8 heads).