Birdman's 308 is going to need the valves adj pretty soon, this will be a big help if I can get them reasonably.
Grinding valve stems to adj. valves. is the most stupid way to adj. valves that I have ever heard of. valve stem height needs to be a certain height. what is so hard about adj. valves with pucks? If you need shims let me know I will sell them to you $3.00 each plus S&H
OK. I've been at Asia GT challenge race, Shanghai, for a week, so I've got some catching up to do..... What has still not been fully understood here by some I think, is the installed valve spring lengths. From posts here, it seems you (Americans) all buy some generic valve that requires tipping because it is too long. This is something I haven't come across, as I get valves made for me as and when I need them, in about 4 days, using samples and/or records for specs. BUT, what IS VERY IMPORTANT, is WHERE the length is greater... The collet ring position relative to the seat face determines spring height. SO, if your valves are longer between the seat face and the collet ring... then your valve springs have been effectively weakened. This can be fixed to within a small spec (about 1-1.5 mm) by installing shims under the spring base... BUT, doing this can raise the height of the stem seal.. which often gets damaged on a standard head if over revved (10,000?) and the valves float. If the aftermafket valve length gain is only above the collet ring to the tip, then YES, an initial tipping within surface hardening tolerances is acceptable... BUT ONLY ONCE, on the new valves, during the dummy build phase.. Fitting smaller shims to compensate for the length can work for a while but sooner or later you'll get caught out. The valves will wear back into the seats, requireing progressively smaller and smaller shims as miles accumulate. So now you have reduced the amount of adjustments you can make before you run out of tolerance with shims again. Also, using small shims can risk cam failure at the extreme limit.... as if the shim becomes thinner than the lip on top of the bucket, the cam will strike the bucket edge and not the shim. I've seen this on many 246 and some 308. So, I help that has clarified things further. I've just seen that Dan has now had a valve stick open on start up... so it looks like he has some bad help from somewhere....
FWIW : Many more years ago when I thought just doing things "while you were in there" was a good thing to do, I had a set of VW heads "rebuilt" while I had the motor apart. While the heads had not been any trouble previously, they now wouldnt stay in adjustment, and you could see the valve tips becoming hammered and mushroomed. The shop ground off the tips and lost the hardness. The adjustment initialy went away within 200 miles, and because the tip was hammered it made it difficult to find a clearance afterwards. So this tip grinding/hardening has some validity. As to cam lobe to bucket and shim interface as compared to a "Chevy", in both cases and in the case of just about all engines, the lobe of the cam sits slightly off center so as to "spin" the cam follower in an effort to spin the valve. This is done to keep the valve seat clean and make it last considerably longer. It also leads to a cupping of the follower, and a angle grinding effect on the cam lobe. Keeping new surfaces under the lobe occasionally could help to eleviate that effect. But comparing a Chevy cam to a Ferrari cam is utterly rediculous. The Ferrari has a far greater amount of metal and suface area to move a much smaller mass, so it should last multitudes longer. GM was just trying to save on steel and didnt care if the engine lasted beyond 5 years or 50K miles. Bad comparison. I would assume that the particular valve manufacture would be the authority to be questioning on this issue, as they would know not only the distance the hardening goes down into the stem, but also how to grind the tip. Making general assumptions about a broad range of parts made around the world can be very damaging and expensive. I agree with those posts made thus far, that "tipping" the valve stem should not be done except only within the guidelines of that "particular" valve manufacture, and only to establish the initial clearance as per the WSM. Any assumptions made beyond that point put Stevie Wonder in the pilots seat. All you need then is Ray Charles for a co-pilot. Ferrarifixer, Malcolm, Verell, etc, are on the right track here. These guys arent BS'ing anyone.
You need to read what I posted again, I was comparing different cam shaft designs, and how those designs effect the decision to reuse valve shims (pucks) compared to used lifters, etc. Not all here have first hand exposure to Ferrari engines, and allot of these people do have exposure to chevys, and fords, etc, thus they are familiar with the "don't use old lifters because it will wipe a cam lobe" statements. It is a valid comparison of the differences between cam designs. The cam offset is NOT there to spin the valves. the spring tension and keepers alone will keep the valve from spinning. This is true for overhead cams as much as it is for push rod engines. the lifters in chevys don't even touch the valve. the rocker arms do, and they do not induce any spin. spinning the lifter, is designed to cut down on friction and wear. not to help the valve "clean" its seat. Valves are lapped in for a reason. they do not spin. FYI: I do believe that my sticking Valve issue is due to an oversight by the machinist who installed the valves. Either he did not lube the valve or he did not inspect the guides like he should have. I plan to pull both heads as a result and have them reworked. Dan
Perhaps you dont recall cars that used valve rotators? factory thing they were. The way older cars didnt have offset valve geometry so they added rotators to compensate. You are correct in that the lifter never touches the valve, yet they are offset and they do spin so as to keep wear even. You are correct that a rocker arm doesnt spin, but it is "normally" offset slightly, so that the focus of pressure is slightly off center on the stem to make the valve rotate. This is why you see a circlular pattern on the used puck shim faces on your Ferrari as well. They dont just sit there in the same place. On US engines with lifters, you can only reuse them in there exact same positions after they have seated in, or you risk grinding out a lobe. I once made that mistake and the lobe went away in about 15 minutes! Spring pressure will not hold the valve from spinning. Try turning an open valve in a head and you will see it doesnt take a lot of energy. Now imagine the lobe smacking the bucket 50 times per second and smearing the face at an off angle.
