Hello everybody! I decided spontaneously that i would lap my valves today. Got the heads off, and spontaneously decided that i would do a mild porting on them while i was in there.... I noticed several interesting things. I only have one head off at the moment, but my questions are: 3 of the cylinders have bright white exhaust valves. I have seen the exhaust valves of a fuel-injected vehicle and they tend to run more in the golden or yellow color. White would indicate that i'm running lean, right? I have the stock jets in my carburetor and i live at a high elevation, so that is somewhat confusing to me.... My other question is that 1 of the exhaust valves is completely black. I checked my ignition system up to that point and it is working. Then i noticed when i removed the valve that the valve would NOT come out. I had to pound it out with a hammer. When i put a different valve into the head it slid in and out easily. Does this mean the valve is bent? How could that have happened? I have had a constant and very annoying valve tick, i guess this would explain it? Can i just go to the local cylinder head shop and pick up another valve and be done with it? The heads have about 5k miles on them, so the guides should be in good shape. I'll have to remember to check the cam on that lobe...hopefully i won't have to spend a whole lot of money to get this back up and running.
Valves Could be a compression problem or fuel mixture or leaking valve guide or vacumm leak or a dozen other things. Slow elimination of one thing at a time should find it. As far as the valve not coming out, from the ticking sound you describe could be a bad lifter or such. The end of the valve gets hammered on and then begins to mushroom, thats why it won't slide down the guide. Common problem on most high mileage engines, I always take small die grinder to tip of each one if they act like they are mushroomed. Pounding them out as you did is ok if you are going to replace the guides because that mushroomed end is tearing out metal as it forces its way down. The clearance is so tight on those guides that it may allow valve wobble and oil leakage if you don't replace them. You may not even be able to feel the mushrooming but when dealing in tens of thousandsth of and inch clearance, its going to bind up. One other note on the carbon buildup, some intake configurations and carbs will cause this, especially in racing applications. Have seen a lot of engines have to run different size jets in all four corners of the carb and also different heat range plugs in one or more cyl. Good thing is, most of these were GM products. Just a few thoughts on the matter.
Old guy to the rescue! (again!) Thanks for the response. I'll check into everything you mentioned. The funny thing is that the tip fits into the guide at the top and bottom easily, but after that is when it stops wanting to move. I had also replaced the lifter on that valve only, because i had noticed that it was the one that was ticking no matter how much i tightened it--the lifter had gone bad on it (even though it was a brand new lifter, it went bad after only about a thousand miles). Anyways, i will take it to the machine shop, i think it's only like $5 per guide, and it's the only one i need. Oh, also, that was one of the cylinders that had a higher compression (mine ranged anywhere from 140-125). To make a long story short: These are 1970 351 heads. They are the type where you torque to 20ft-lbs and they're "adjusted". When i first assembled the engine i simply torqued them down. Later i found out that the heads had been milled (starting to get pops out intake and exhaust), so the valves had been hanging. That's why i wanted to lap my valves. Thanks again!
351 milled heads I remember this too, one of my sons buddies had this same set up as yours and always was having lifter and adjustment problems. We checked it and found out the pushrods were to long, not much but enough to cause collapsed lifter and bent valve. Might check this out when your done with the heads.
