Hey guys, so this is what the valves on my old head look like:



The valve clearances were all so small that I couldn't fit the .02 in most of them. Needless to say, when I replaced the head, I did a valve job and got them all into spec.

I was getting miserable gas mileage with this head, like 30-35 mpg. Yea, I've got a bunch of mods that trash my mileage and I ride pretty aggressively with high rpm's often, and mostly do short trips, which I know aren't helping my fuel economy.

But now that I swapped my head and adjusted the valves, I have been getting much better mileage. I haven't run down a full tank yet, but I know that my mileage is going to be at least 40 mpg or greater, which still isn't great, but much better.

So I guess my question is do tight valves negatively influence mileage? Given my experience I would say yes, but I'd like input from anyone that has any.

Thanks,
Graham 

You need the following in order to make a gasoline internal combustion engine work:

1.  Correct fuel/air mixture
2.  Compression
3.  Spark

In the above reference, tight valves mean lower compression since 1 or more valves are partially open when they should be closed. The consequence is poor performance and your engine has to work very hard to do normal tasks such as scooting you down the road efficiently.

When I replaced my head, after messing up a valve check when my valve clearances were non-existant, my MPG also went up ~5 mpg.

your valves look a good colour to me ,put your spark plugs in and do a leak down test to check to see if the valveshave bad seats .That is done by laying the head on its back valves up and pouring kerosene into the chambers to cover valves then look into inlet and exhaust ports and see if kero leaks into any of them,if so your seats are probably your problem from to tight a valve or valves.

Quote from: twinrat on February 05, 2013, 11:56:14 PM
your valves look a good colour to me ,put your spark plugs in and do a leak down test to check to see if the valveshave bad seats .That is done by laying the head on its back valves up and pouring kerosene into the chambers to cover valves then look into inlet and exhaust ports and see if kero leaks into any of them,if so your seats are probably your problem from to tight a valve or valves.

There you have some knowledge! 

well I would do that...but the head pictured is dead to me, had cracked journal caps. Had to replace.

Graham