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Push Rods
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Senior User
Joined: Nov 2003
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Push Rods
Pulled apart the top end of my motor due to head gasket. I got the heads redone and they had to be milled .020". When I got everything back together and got it running it has a tapping noise. I removed the valve cover and used my stethoscope I discovered it was tapping at every valve. Called the machine shop and he siad to get undersized push rods. Whats the deal with this? I thought that the lifter would make up for that much. Any comments and suggestions appreciated.
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
Is it running rough? If the pushrods are too long, they'll bottom the lifters out and force the valves to stay open slightly. This will result in it running rough. If they're too short, the lifter plunger won't take the slack out of the valve train and you'll end up with it making a ticking noise. Milling the heads .020 shouldn't result in the pushrods being too long. If the rocker shafts are the originals, then the wear in them would compensate for the .020 you removed from the heads.
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Senior User
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it is not running rough. But when I tighten the rocker shaft the valves springs are being compressed, but not much. I swapped in some old push rods(that are a hair shorter) and rockers and the noise got quieter but has not gone away. I am thinking that maybe I can swap the adj. rockers out of my 390 and see if that will help. By the way I also did a compression test and I am getting about 75 psi on every cylinder. Before getting the heads done I had about 155 on all cylinders except where the head gasket was blown.
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Joined: Jun 2006
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75 pounds, it sounds like your valves are staying open, as you stated the springs are compressed but shouldnt be. as stated above 020 should not have had any influence on the lifters. Did you take the cam out, is it installed properly
New User
Joined: Jul 2006
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From: Avondale, AZ
When your block was bored it should have been trued. This means that the block and heads may have had some meat removed to make them mate as they were designed. While this process makes the chamber a little smaller it can also cause the push rods to be too long. Shorter push rods should correct for the problem as suggested by the machine shop.
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Senior User
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ok I put the adj. rockers from my 390 and no more tap. I guess the non-adj just didn't have enough play to make up for the difference. So i guess it's about time to go with crane's roller rockers now that the 360 has the stock ones.
thanks for all the help, Chad
thanks for all the help, Chad
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I chime'd in late on this one..But that would have been my suggestion..was to go to adjustable rockers......020" shouldnt have made any difference....but stranger things have happened...
Glad its fixed!!
Russ
Glad its fixed!!
Russ