fastzcars Posted April 15, 2010 Share Posted April 15, 2010 Hi Guys, I was going to change out my clutch when I decided to pull the drivetrain and do a refresh on my motor, just in case. After all it has 12,000 miles and I do race it on the drag strip as well as on the road course. Now there was no smoke and it ran pretty strong, the only indication that I had a problem was what I thought was an igition miss on high RPM (5800 to 5900 rpm) The motor shop found 2 cam lobes wiped out! This is a Comp cams XR294HR hydraulic roller. Here are some pictures. I hope you guys and give me some clues as to what might I look for to prevent this from happening again. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted April 16, 2010 Share Posted April 16, 2010 (edited) high spring loads don,t play well with roller cams over long term use, heres a very clear example of why you should only use Billet cam cores with roller cams having over about 320 lbs of spring pressure and why you MUST verify valve train geometry and clearances. billet cams are polished/machined between the lobes, and don,t look cast these are both cast core cams (look between the lobes) the dark surface is a flat tappet cam lobe coating, the polished is a roller cam Edited April 16, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
DavyZ Posted April 16, 2010 Share Posted April 16, 2010 I have never seen that happen with a roller cam. In fact, I didn't know it was even possible without ruining the roller rocker to cause that to happen. What was your valve spring rate if you know? I am curious. Davy Quote Link to comment Share on other sites More sharing options...
jt1 Posted April 16, 2010 Share Posted April 16, 2010 Check all the valve springs. There's a good possibility the springs matching those lobes are weak and let the lifter float and bounce. How does the crank look? jt Quote Link to comment Share on other sites More sharing options...
Turbo Meister Posted April 16, 2010 Share Posted April 16, 2010 Wow, that looks ugly! Sorry to see it. Think of it as an opportunity to buy a stronger cam. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted April 16, 2010 Author Share Posted April 16, 2010 So I guess the moral of the story is , get a billet cam made if your going to run a big roller cam. . O well it's just money! Can't take it with you! Quote Link to comment Share on other sites More sharing options...
fastzcars Posted April 21, 2010 Author Share Posted April 21, 2010 (edited) Just an update guys. My motor guy found the probable cause of the failure. We found that 2 of the valve springs lost tension. most if not all of the springs lost 10 to 20 lbs. They should have been in the 130lbs range for a 1.800 inch installed height. most were at 109 to 111 lbs and the 2 that failed were 86 and 87 lbs. We figured that the springs were letting the lifter pound the cam to death!!! The springs were the old style beehive blue stripped springs (26918)This was before the new updated replacement springs were avaiable. The new springs are suppose to handle 0.625 lifts and are stiffer than the old springs (375 lbs VS 313 lbs). I'm getting the new billet cam this friday. But it looks like I won't be able to make this weekends Motorsports BBQ! And I paid for the dyno run too!!! Edited April 21, 2010 by fastzcars Quote Link to comment Share on other sites More sharing options...
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