JMortensen Posted August 14, 2003 Share Posted August 14, 2003 Did the car sit for a long time? Could be the valve springs lost their spring, and you are floating some of the valves at 4500 rpm. I've heard numerous stories of this happening when cars sat for 10 years, but I've never seen it myself. The valve springs that sat compressed lose their tension, and then they float at low rpms. I still think that if you've got timing scatter that is your problem. Have you actually checked with a timing light to see what happens to the timing when this problem occurs? This is a tricky one. Jon Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted August 14, 2003 Share Posted August 14, 2003 Next thing is to check for weak valve springs or wiped cam lobes. Is this a new cam and did you follow the break-in procedure? Jon, a timing light is not necessary with the SDS as the monitor displays total timing. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 14, 2003 Share Posted August 14, 2003 Maybe I'm being dense here, and I obviously don't have SDS, so forgive me if this is a stupid question. Wouldn't it be easier to see scatter with a light? Can you see scatter with the monitor? Just trying to help because it seems like he's tried everything... Jon Quote Link to comment Share on other sites More sharing options...
Drax240z Posted August 14, 2003 Share Posted August 14, 2003 I'm not really sure what the refresh rate is on the SDS LCD monitor. I was thinking valve springs too actually... but it doesn't seem that it should 'brick wall' like that even with bad springs.... It would be good if we knew the history of the valvetrain/head. Quote Link to comment Share on other sites More sharing options...
240hoke Posted August 15, 2003 Author Share Posted August 15, 2003 The springs are brand new, i replaced them when i had the head rebuilt. however we did use the stock cam and rocker arms. The cam and rocker arms are the sketchy part. i wouldnt be surprised at all if the cam is wiped out. The guy that rebuilt my head threw all and rocker arms literally in a bag, so i had to just put them back on not knowing where they came from. in addition, the cam does have some groves and wear marks in it. I think the valve train could possibly be it since ive checked just about everything else out. How can i check for wiped cam lobes? Ive got a buddy with a brand new turbo cam and rockers. You guys think this might be the new step for me to try? Thanks for the help -Austin Quote Link to comment Share on other sites More sharing options...
spotfitz Posted August 29, 2003 Share Posted August 29, 2003 As you can tell by the late reply, I was reading old posts from a search and saw this one. Checking for wiped cam lobes, you'll need to take a caliper and check the overall lift and base measurement of each individual lobe and compare them. If one or more is drastically different, then you have found a problem. I would almost bet if there isn't a problem with the lobes then the springs are your next logical choice. I hope that you have already found the problem and I would love to hear the results. Quote Link to comment Share on other sites More sharing options...
240hoke Posted August 30, 2003 Author Share Posted August 30, 2003 hey, Actually i havent solved the problem or made any progress at all. i love excuses to buy performance parts so... I replaced the cam last weekend with a new cam from delta (260 dur / 440 lift). In doing so i also put in new rocker arms and lash pads. Noticed a smoother power band but no change in being able to rev past 5000 rpms. I also checked and double checked the cam timing while i had it apart. Springs are my next thing to check, I had them replaced when i had the engine rebuilt. But im going by the machine shop at the begining of next week to ask him about them. Keep te help coming, I need it! -Austin Hoke Quote Link to comment Share on other sites More sharing options...
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