fentin_fury Posted August 16, 2005 Share Posted August 16, 2005 With the amount of knowledge out there I am hoping someone can offer some advise - or comment on a similiar problem with a solution. The problem - my cam lobes wear off on the backside - not all of lobes - just some:mad: - and they wear a lot! Yes - new rockers are always installed. Yes - the rockers are wiping properly - but the wiping pad also wears. I have tried different oils I have tried differnt spring rates I have tried different rocker arms I have tried differnt cams - from Isky, Schneider, and my own regrinds. I am running an oil cooler How long does this take - one race - so 40 minutes of hard running. Latest cam specs - schneider .560 300 duration - life - about 5000 miles on my street Z (best yet!). Used the schneider springs, p90, 11.5:1, triple D's etc. Could this be a result of valve float????? At RPMs greater than 7500? Oil break down? I appreciate any input. thank you in advance - Q Quote Link to comment Share on other sites More sharing options...
jt1 Posted August 16, 2005 Share Posted August 16, 2005 When you say "backside", are you talking about the downramp from the nose to the base circle? If so, you are almost certainly floating the valves, the rocker is losing contact with the cam over the nose, then slamming into the downramp. More spring will probably help, contact the cam maker and see what they recommend for your cam and rpm. Also lighter valves and retainers will help. John Quote Link to comment Share on other sites More sharing options...
fentin_fury Posted August 16, 2005 Author Share Posted August 16, 2005 Yes - this is what I mean by the backside - I thought about the spring weights as well - but I am running what is recommended. I will try a heavier spring weight. thanks Quentin Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 16, 2005 Share Posted August 16, 2005 I had this issue on one of my old L series motors and had to go to Malvern Racing for rocker arm pads of a variety of thicknesses in order to get the geometry perfect. It was extremely expensive at the time, and I have no idea who else even sells these rocker pads these days... But make no bones about it, if you ink the rockers, and run them on the lobe of the cam, it is pretty easy to miss an improperlly aligned rocker arm at first. However, once you get one right, you can spot 'em plain as day! Did I mention I don't miss those days? Good luck! Mike Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 16, 2005 Share Posted August 16, 2005 Lash pads are $3 each from Nissan Comp IIRC, but he's saying that's not his problem. Quote Link to comment Share on other sites More sharing options...
jt1 Posted August 16, 2005 Share Posted August 16, 2005 Hmmm... back when I was running a L6, lash pad problems seemed to show up all the way around the cam. Anything in particular that makes it just show up on the downside? John Quote Link to comment Share on other sites More sharing options...
fentin_fury Posted August 16, 2005 Author Share Posted August 16, 2005 lash pads are set correctly - very time consuming and an individual basis. I am inclined to suspect valve float as mentioned - but I have no way to prove this. Tonight I am going to take some pictures and measure the spring weight of the lobe with the most wear vs. the least. As a test - what would you all think of adding a spacer to the springs? Effectivley increasing the tension? Thoughts? Quentin Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 17, 2005 Share Posted August 17, 2005 I had this happen on one of my motors, trashed a custom Isky cam and it turbed out to be the Lash Pads. They weren't sitting correctly on two of the lobes and ate the back fo the lobe and the rocker. I eventually found it was the pocket the shim sat in. It was worn at enough of an angle (And I couldn't see it) that it caused the arm to not track correctly and over time, wore the back of the lobe and the arm... Just relaying what happened to me... Cost me about $800 to get it all sorted by the time I chased it down... Guys at Datsun Dynamics, Malvern Racing, and Zdoctor of ROanoke Va. all scratched their heads. Quote Link to comment Share on other sites More sharing options...
fentin_fury Posted August 17, 2005 Author Share Posted August 17, 2005 Intertesting - how can I see this? It would seem to me the shim pocket is very small - was it obvious once you knew what to look for? I will check tonight. I took pictures of the rocker arms - but I am challanged to upload them. I will figure this out soon. quentin Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted August 17, 2005 Share Posted August 17, 2005 lash pads are set correctly - very time consuming and an individual basis. I am inclined to suspect valve float as mentioned - but I have no way to prove this. Tonight I am going to take some pictures and measure the spring weight of the lobe with the most wear vs. the least. As a test - what would you all think of adding a spacer to the springs? Effectivley increasing the tension? Thoughts? Quentin The spacer my add to the spring tension, but may cause binding in the spring as well with a large lift cam. Also, make sure that your valve springs are installed in the correct direction with the end of tighter wound coils down. I didn't realize that it made a difference until I was informed that they are progressive Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 17, 2005 Share Posted August 17, 2005 We couldn't see it at first, had to pull the head and inspect every inch of all the components before it was found... TWICE! This was in 1994 when we simply didn't have the luxury of the internet and information... Another Odd thing I had on a P79 head... The cam towers were worn out of spec at the base where they mount to the head... That one was a hard one to find on one motor... I have a bunch of these little stories from when I was building and racing L6 motors in the late 80s to mid 1990s. Mike Quote Link to comment Share on other sites More sharing options...
fentin_fury Posted August 18, 2005 Author Share Posted August 18, 2005 thanks to you all:) for the directions. I have a few things to try now. I will check all components and also the spring direction. I will let you all know how it goes... Next year RB26.... but that is a different forum. Q Quote Link to comment Share on other sites More sharing options...
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