AleksS30 Posted February 22, 2012 Share Posted February 22, 2012 I have done soo much reading about this topic I just can't seem to find the answer I'm looking for. I'm looking to buy a regrind cam from Web cams. I spoke to a sales person and he told me the factory base circle is 1.305in and the regrinds use a 1.280in base circle. That's a overall difference of .025 divide that by 2 and you have a difference of .0125 at the lash pad. Now here's my question, I can't seem to find a replacement lash pad with that small of an increment over the factory size, would I be able to get away with using the factory lash pads in this case? My understanding is the stock lash pads are about .120 so according to this cam grind, I would need a .0125 thicker lash pad which works out to .1325 I'm still a little confused about this so If I'm totally wrong here please someone correct me! Quote Link to comment Share on other sites More sharing options...
luseboy Posted February 22, 2012 Share Posted February 22, 2012 As far as I understand it, the lash pads needed are different for every engine, dependent on valve-train wear, among other causes. As far as I understand it, you need to acctually install the cam and then measure which ones you need. Quote Link to comment Share on other sites More sharing options...
Zguy91 Posted February 22, 2012 Share Posted February 22, 2012 The whole lash pad thing is kinda confusing lol. It gives me headaches Quote Link to comment Share on other sites More sharing options...
Leon Posted February 23, 2012 Share Posted February 23, 2012 The whole lash pad thing is kinda confusing lol. It gives me headaches Ultimately, your wipe pattern is what you're trying to set correctly. The rocker has a pivot on one end (adjuster side) and a lash pad on top of a valve on the other. The cam hits the rocker somewhere in between. The lash pad combines with the pivot to set the rocker surface a certain distance away from the cam base circle. Draw up a sketch and it will sink in. Use search terms such as "cam wipe pattern" to help you. Thicker lash pads can be machined down to match your specs, and I think ZCCJDM is reproducing lash pads in different sizes as well. You can also use shims in place of (or underneath) lash pads when testing wipe patterns. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted February 23, 2012 Share Posted February 23, 2012 when you install the cam you should check the wipe pattern on every lobe .I used 1 of those permanent maker black felt pens and covered the top of the whole rocker arm with the marker.Install the rocker and turn the motor over by hand.Then remove the rocker and see where the ink is worn off.I know this by much misery. Quote Link to comment Share on other sites More sharing options...
AleksS30 Posted February 23, 2012 Author Share Posted February 23, 2012 thanks for the reply's guys. So would you suggest that I install the new cam with my factory lash pads, set my valve lash (cold specs) and check the wipe pattern on the rocker arms? Does the wipe pattern have to be perfectly centered on the rocker arm or can it be offset a little? Quote Link to comment Share on other sites More sharing options...
Z Greek Posted February 23, 2012 Share Posted February 23, 2012 OK, you guys are giving Alec sound advice, optimize the wipe pattern. One detail you neglected to tell him (or maybe you just assumed he knew), is what exactly is he looking for in an optimum wipe pattern, so I'll chime in. The wipe pattern on the rubbing surface of the rocker, or cam follower, should be as close to centered on the wear surface as possible. You do this by trial and error, using thicker or thinner lash pads. Once you figure it out on one valve, the rest of them should be damn close, unless some monkey did a lousy valve job, and did not set the valve stem heights the same (story for another day) After I get close, I personally take it one step further (and you can all chime in and call me insane). I set up a dial indicator on the valve retainer. I then set valve lash on the valve I am working on and slowly roll the engine over to see what the exact valve lift is with the rocker, and lash pad I have chosen. I do this on each valve and document as I go. When I find the valve with the highest lift, I leave that one alone. I then move one by one and try to duplicate that lift number. I do this two ways. 1) I have a whole box of cam followers that I had re-surfaced. I juggle cam followers around first (they are all slightly different, believe it or not). If I cannot get there by juggling cam followers, I go to number 2) I take the lash pad over to my belt sander, and take a thou or two off, and try it again. By taking a small amount off the lash pad, you are moving the contact patch back ever so slightly, creating an ever so slightly different (higher) rocker ratio. After a long evening or two of this, I have each wipe pattern optimized, and each valve lift identical. Or you can just set them all so the contact patch is as close to centered as you can, and it will work fine! Quote Link to comment Share on other sites More sharing options...
AleksS30 Posted February 23, 2012 Author Share Posted February 23, 2012 I just measured my lash pads and they happen to be 0.160 They actually range from 0.160 to 0.1635 Typically with a cam that has a smaller base circle do you go with a thicker lash pad or thinner lash pad? I'm going to say thicker but I'm not sure. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted February 24, 2012 Share Posted February 24, 2012 I just measured my lash pads and they happen to be 0.160 They actually range from 0.160 to 0.1635 Typically with a cam that has a smaller base circle do you go with a thicker lash pad or thinner lash pad? I'm going to say thicker but I'm not sure. Thicker, correct. Quote Link to comment Share on other sites More sharing options...
AleksS30 Posted February 24, 2012 Author Share Posted February 24, 2012 (edited) ok I'm a little confused here, I measured my lash pads and got .160 which is not factory so I assumed the head that I bought may already have a regrind cam in it so I measured the base circle and I have 1.308 which is factory spec. I have never run this head, I bought this P79 to do "the .080 mod" and the cam is the only thing I have left to do to it. The wipe pattern on the rocker arms are perfect which doesn't make sense for a stock cam using .160 lash pads. The only thing I can think of is maybe at one point this head had an aftermarket cam in it which was removed but the lash pads were left in place and a factory cam was put in place? What do you guys think? Also my .160 lash pads have a dish on the bottom, do you measure lash pad thickness from the dish or from the outer flat surface? Edited February 24, 2012 by AleksS30 Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted February 24, 2012 Share Posted February 24, 2012 You have to measure your pads from the recessed surface on the bottom, as that is what contacts the valve stem. Unless it is a solid pad (I've seen both in thicker lash pads), you don't measure overall thickness - my guess is you have stock .120 pads. Quote Link to comment Share on other sites More sharing options...
AleksS30 Posted February 24, 2012 Author Share Posted February 24, 2012 (edited) I just re measured my lash pads with a micrometer this time and they are indeed the factory pads. I got anywhere from .118 to .121 since the oem lash pads have the dish on the bottom, will I be able to run aftermarket flat bottom lash pads with the oem retainers? Edited February 25, 2012 by AleksS30 Quote Link to comment Share on other sites More sharing options...
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