You have not read thread correctly. Your comments are correct as per your manual, and this value also applies to a stainless valve. You are a Ferrari rep? I would imagine a Ferrai workshop would only use factory valves? If in fact you were to use ystailess valves would you not tip valves to correct measurments?? Ferrarifixer made comments about tipping valves and leaving a sharp edge, valves soft, bad engineering practice! WRONG!!
I might as well chip in my $.02 worth. First off if you have a coolant on the grinding wheel, there should not be any change in the metallurgy as there would not be any heat, this is of course assuming that the operator has a clue on how to do the job. It is possible with a heavy cut to create heat, but an experienced valve grinder would not do that. If he leaves the edges sharp, and doesn't bevel them slightly, he does not know what he is doing, as it will surely cause problems. Depending on the valve manufacturer, a slight amount of grindng is OK with some valves. As to the spring settings, that is what they make shims for, to adjust installed height, etc. I believe it would be an advantage to leave the same lash disc with the lobe that it is worn to, providing they are in good shape, swapping shims arouind is like swapping lifters on a pushrod motor, asking for a ruined lobe too often is the result, especially if heavier springs are used. There are some very valid points made in posts, such as the problems that more than slight shortening can very well cause keeper/retainer failure. I would point out that my experiences are with non Ferrari valves as the aftermarket has IMO some better quality valves at prices that are a bit easier on thw wallet. My personal preferance is SI valves, but Ferrea also makes an excellent product. JMO
Yep, still going... And Another thing... Most Ferrari owners are keen to keep their car performing well of course... and this thread highlights another loss of thought process made my most... If the valves close their gap, to either need shimming or (heaven forbid it) tipping, then there is a reason for this..... This reason is because the valve is moving back up into the head through wear. This does at least two things to directly hurt performance... firstly, it slightly shrouds the window the valve opens... hurting flow, but more importantly it INCREASES the Clearance volume of the combustion chamber... reducing compression ratio. So, of course, there is a tolerance allowed..as dictated by the range of tappet shims and workshop manual specs... but to keep your edge, fix the cause, not the symptom. My heads all get valves made by my own supplier, which are re-profiled for better flow on the back, and also flat bottomed or domed underneath to pinch a bit more compression. You don't need to spend big money on valves either. Modern materials for valves, seats and guides are getting more and more available and affordable... you just need to keep up with times.
I guess you guys are just not listening, Wake up! If you install new stainless valves and do a valve job, your tip is already closer to the cam centerline than stock! Are you following me? If you use the stock shims and you slightly tip the valves you are bringing the tip to cam centerline relationship back closer to factory assembled specs, right? well, within reason. If you perform a valve job and you install new shims to take up the clearance, you have brought the valve tip closer to the cam centerline, or out of spec., but if you tip after your valve job you have maintained the tip to cam centerline relationship, or within factory specs. You can do it both ways as there are always extenuating circumstances to allow the mechanic with reason, logic, vision and knowledge to take a slightly different tac to arrive at the very same place, or better. To make claims that there is only one way is short sighted, wrong and close minded. This benefits no one. Posting pictures to bolster your theory just revealed the inadequate nature of your claim. The old saying goes: "If you give them enough rope they will hang themselves." Best of regards Gary
If you keep the same puck with the same lobe forever, the cam will eventually wear through the puck's hardening, and all hell will break loose under the valve cover. The proper way to approach this situation is to make sure the valve stem length is stock spec. If not, get a head shop to grind them to spec, in the proper machine. THEN install the complete valvetrain and, with the head on a bench, measure and record clearances, then figure out which valves are tight/loose, and compensate with some new pucks.
GTO84, The shims we are talking about are not case hardened or surface hardened, but rather are rendered full hardness through the entire shim. This means that they can be surface ground to renue the surface, there is a special tool available to hold the shim while grinding. As long as the shim looks smooth and without blemishes, you can reuse it as is. A good shim will have a nice smooth, polished look, and is reuseable. Its always best to replace rather than regrind as it is more difficult to achieve the smoothest of surfaces by grinding. Best of regards Gary
Gary, You're getting push back because you're talking about parts that are made differently from the OEM parts that the rest of us are familiar with. Please post some links to sites describing the SS valves that have to be tip ground, and the shims that are hardened all the way thru.
Why are you talking about regrinding shims? Theyre a $2 part! And in case you didn't know, they come in different sizes. So why grind them? To make up for the fact that your machinist didn't spec your new valves to stock length? Stop correcting the symptom rather than the problem.
Verell, I have already told you what I know, now tell me what you know, thats what you want to do right
If you have aftermarket stainless valves..the tips of the valves need to be ground to the stock height. This is a no brainer. The SI valves are very close..but I still had to grind a few of them. The amount removed was minimal the the tips were rebeveled. If you have a valve tip that is too long you will have all kinds of other problems with defelction and shiming issues. You may end up finding that the thinkness of shim you need is not even made. You will run into this if your valve stem height is to high or too low. Grinding valves shims is a big no no. They are only surfaced hardend (factory one and the Volvo shims anyway) I have never seen or used a completly hardend shim. Most shims are hardend only on one side anyway. The side with the number faces down. Grinding the factory valves for a valve adjustment..I would not do. You are in effect putting the stem height out of spec. The reason for the problem must be found first. Anytime you have a valve that needs to be adjusted more then a couple of thou..you have a problem, that should be looked into. Many machine shops do the valve tip grinding thing only when new valves have been installed..stanard practice. But I have never heard of anybody grinding a stock valve to make a shim fit.
tbakowsky, thank you for the useful information in a kind manner that is so hard to find. Best regards Gary
Sorry Gary, I didn't realise you wanted kindness! If you let a puppy 5hit in the house once, it will 5hit in the house again. Sometimes, cruel to be kind is a much better route to happiness. oops, edited to say.... "in my opinion"... I don't know everything.
FWIW category. Before landing in the good ol US, I had never seen any shop grind valve stems OR brake discs (rotors)! I was never taught those practices and still do not carry them out. The process is to replace the valve seat when the wear limit is reached and cut to spec., the valves should be to spec, therefore the stem/keeper/head relationships are a constant. Whenever I have had to tackle an unmolested 308, the shims are almost always the same and invariobly 3,95 or 4,00 mm. But as Brian and co have said, "What do those factory engineers know?" If you have found a variation in the shims, you will find a history of standard "bush work". It's your car, if good enough is, then why ask us? Brian
OK, was hoping to find out add'l specifics & about the uniformly hard all the way thru shims you described. Like tbakowsky, I've never encountered/heard of them. Used with a good surface grinder they could reduce downtime waiting for an out of stock thickness shim to come in. Given the relatively low cost of a shim, & the cost of labor, I'd think that the cost of surface grinding would be uneconomic if a new shim were readily available. Also wanted to learn more about the SS valves you were describing. No, didn't have much specific info to contribute beyond what tbakowsky just posted, & what's in the WSMs which was already more or less quoted by others in this thread, just trying to advance my knowledge of the state of the art. Umm, re: re-using a shim, there are a few threads about this a few years back which I believe included some specifics about the effect of wear on shims & cams. Back then bottom line was that it was better to always have a fresh shim surface against the cam when replacing as it kept the cam lobe wear pattern parallel to the cam's axis & uniform across the lobe's surface. Thus always having a fresh surface against the cam reduces the risk of wearing thru the surface's hardened layer.Otherwise the shim's surface becomes cupped with a corresponding pattern on the cam. Thought there were some pix showing this cupping effect posted. Th this rule was postulated: "Each surface of any shim can be used only 1 time in contact with a cam lobe." [/quote-tbakowsky]Most shims are hardend only on one side anyway. The side with the number faces down.[/quote] First I've heard that. Hardening is generally done by heat treating in a high carbon environment. Would have thought with something as small as a shim that the entire surface would have been uniformly hardened. This new (to me at least) would imply that shims can't be reused once by flipping them over! BTW, Some prior threads about valve shims are: http://70.85.40.84/~ferrari/discus/messages/256120/6545.html http://70.85.40.84/~ferrari/discus/messages/256120/269.html http://70.85.40.84/~ferrari/discus/messages/256120/216883.html
Verell, I have to regress and say I was wrong about the shims being hardened throughout. This was made on an assumption based on information given to me. After studying the surface nature and coloration of the shim the only way that the shim could attain that surface condition would be by furnace heat treatment with some absorbtion of carbon. The shims must have a very smooth surface prior to heat treatment and then treated to the spec or nature of the material being used, as they appear to not having any additional machining done to them after heat treat. If the shims are low miles and in very good condition, definitly reuse them in the same place that they were, however if they are not it is recommended to replace them with new. The SS valves that Ive used as replacements are Race Engineering Valves in Ft. Lauderdale FL. They will make just about any valve configuration. The new valves will have to be tipped as they come slightly oversize in length. This is done often to re-establish stock specs. Thank you for posting back and good luck Gary "Any intelligent fool can make things bigger,more complex, and more violent. It takes a touch of genius and a lot of courage to move in the opposite direction"
Sorry Guys, I have been under the Ferrari when not at work so I did not realize this tread was still going. The valve seats and guides did not have excessive wear. I simply replaced the Valves, which changed the clearances. I could not use the old shims because the clearances were too tight. I had installed the heads on the engine before I put the cams in and thus could not remove any material from the valves if I wanted to. thus the valve seat wear is not my sorce problem. I was able to find a Volvo repair shop that had some old shims and I found one thin enough to get my measurements. I then ordered the 10 shims That I needed from Ferrari. two days after that I got the shims I needed. clearances are good. The shims are surfaced hardened. they are not hardened all the way through. As for geometry with respect to the valve tip location and the cam. the final measurement that matters in this type of head is clearance between the cam and the shim. it does not matter if the shim is a little thicker and the valve is shorter, or vice versa. the valve/shim/spring/keepers do not travel through any other dirrection than up and down. thus the full length is what matters. Sense the cam rides dirrectly over the valve, there is not an issue with Valve geometry ( such as you would find in a small block chevy where you have rocker arm geometry). I would go as far as to say that the factory specs are given so that you know your target area. if you get too far out of this area you may not have the shims available to get you within target. As for the cam wear pattern. the area in which the pressure is distributed determines what kind of wear you will find with any given engine combination. In an engine with over head cams, where the cams ride dirrectly over the valves, a great advantage is the fact that the shim can have a large diameter and the cam lobe can be wide (compare the 308 cam lobe width to that of a small block chevy, and the shim diameter to that of a small bock chevy lifter). this greatly reduces cam and shim wear because it spreads out the pressure from the cam to the shim. Also, spring pressure requirements are different because you do not have all that valve train to move back and forth, thus reducing pressures). This is the reason that you do not "Break in" over head cams like you would a cam in a Small block chevy. they are designed diferent and the contact patch is greater in the overhead cams. If you doubt this, then next time you are at a parts house ask to see a small block chevy cam, flat tappet, not roller, and you will see that it has a matterial on the lobes (it is the dark color coating). this is there for the break in period. the overhead cams have no such matterial because they are designed different. also, the traditional cams in V8s are designed with a slight slope to the lobe so that they make the lifter spin in its bore. this is to reduce lifter/cam wear, which you can very easily see if you ever inspect a worn lifter from a small block. This is why you do not reuse lifters in small blocks. they are "Broke in" to a set wear pattern. Over head cam lobe/shim wear such as the 308 is different. As for the shims in question, it is okay to reuse these types of shims as long as you do not see a dipping type of wear pattern. Inspect them visually, and inspect your cam lobes. if everything looks good then carry one. FYI the Vovlo shop that I got the shims from said that they now grind the valve as a standard practice for setting the valve clearance. He did not mention any additional info, just that he rarely used the shims that he had. From the conversation I got the impression that he did not have any problems out of this type of practice, and I cannot think of any reason that a mild grinding of the top of the valve has any worse effect than doing a 3 angle valve job has. Thank you for your input to this thread, I hope to fire the 308 up tonight. Dan
FYI, going once, going twice... http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34202&item=4541272481&rd=1
