SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: pure ndn on August 01, 2010, 09:25:35 PM
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ok got bbc with a big roller cam its got bad cam walk to the rear and it damaged the block is this fixiable i dont know why the cam walks so bad ive never seen one walk back its always been foward thats y theres a button right :banghead:
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A roller cam doesn't have the taper machined into the lobe that is needed on a flat tapped cam to rotate the lifters. The cam button will help keep the cam from walking forward but the surface on the back of the cam gear and the front of the block should keep the cam from walking back. Was something loose in the timing components or excessive wear at that surface that allowed the cam to walk back?
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How bad did it tear up the block?
A very tight high volume high pressure oil pump making a bunch of oil pressure will suck the cam back too....
These can typically be fixed, get a hardened steel cam gear shim from someone like Cloyes (Cloyes premium timing gears are steel and not cast, so they are hungry for the softer iron) and have the front of the block cleaned up and drill an oil hole through the front cam bearing oiling channel, typically 3/64 is more than enough oil, this lubricates the back side of the cam gear (old marathon motor trick) even when top end oil flow is limited...
Hope this helps even a little...I think I have some pictures of the whitewater motor somewhere that I have drilled and machined for this exact job...gotta go find them... :thumbup:
GT
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i used a good steel timeing set all brand new parts its an isky cam but when it walked back the edge of the rollers on the lifters kinda wore a line in a few off the lobes the lash was set at 17 and 19 thats what the cam card wanted idk ive had a few people alot smarter then trying to help as for the block it wore the flat part on the back off the timeing gear wore into the block and ate the cam bering groove in tthe block is about 16th to 1/8 deep i only ran the motor on the lake for a couple hours then noticed the shiney stuff in the oil if reparible would any machine shop be up for the task
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i used a good steel timeing set all brand new parts its an isky cam but when it walked back the edge of the rollers on the lifters kinda wore a line in a few off the lobes the lash was set at 17 and 19 thats what the cam card wanted idk ive had a few people alot smarter then trying to help as for the block it wore the flat part on the back off the timeing gear wore into the block and ate the cam bering groove in tthe block is about 16th to 1/8 deep i only ran the motor on the lake for a couple hours then noticed the shiney stuff in the oil if reparible would any machine shop be up for the task
Steel timing gear requires a hardened shim or a Torrington type thrust bearing......
Been there and done it.... :-\
GT
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that sucks didnt know that so i just f@#ked myself thanks for the info