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Old 02-25-2012, 05:13 PM
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how to fix valve lash and timeing with chevy 350 in truck?

I just bought an 85 c20. the previous owner dropped in a 350, however he never really adjusted the valve's properly. So now I drove the truck home, removed the valve covers and distributor and intake manifold, I have read a method of adjusting exhaust valve's on 134 and 8 and then intake valves on 125 and 7 then rotate one complete turn and line up valves on number 6 cylinder and adjust exhaust valves for 256and 7 then intake valves on 346 and 8. IS THIS RIGHT, IT SOUND'S OFF. And how do I tell witch is intake and witch is exhaust valve. Please help.

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Old 02-25-2012, 07:52 PM
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There are a few different methods. The way I've always adjusted valves is adjust them based on companion cylinders. Basically, two cylinders always hit TDC at the same time and when one cylinder is at TDC exhaust both valves will be in overlap and a corresponding cylinder will be at TDC compression with both valves closed. The cylinder at TDC compression gets adjusted, then the engine gets rotated 90 degrees until the next pair of cylinders are at TDC. It's a little time consuming since it requires the engine to be rotated 90 degrees at a time through two revolutions to adjust them all but it works.

Just start with cylinder #1 at TDC compression and verify it by checking that cylinder #6 is in overlap then follow the firing order until they are all done.

When looking at the valves they are arranged EI - IE - EI - IE

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Old 02-25-2012, 09:43 PM
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blazin72 has a good method it works well, but yes can be time consuming. i would like to add: when adjusting your rockers down, feel the up and down play in the push rod, when it just stops up and down motion you should be at zero lash and then tighten 1/2 to 3/4 turn past zero lash... Assuming it is a hydraulic cam and lifters
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Old 02-26-2012, 02:54 AM
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I'm curious to why you removed the intake?
I always adjust the valves with the engine running which is a much faster process. I start by getting it up to temp, popping the valve covers, firing it off then idling it down as low as it will go, this is done to prevent excessive oil from shooting everywhere. Then I'll back the rocker off until it starts to clack, then slowly tighten it to the point that it stops then give it 1/4 turn.
Or if you would feel safer by going to 1/2 turn do so by giving it two 1/4 turns after the clack has stopped.
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Old 02-26-2012, 08:34 AM
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I've used the process of lining up number one and doing half the valves, and then lining up number six and doing the other half. I had to make a cheat sheet to remember which valves to do each time, but that was easy to figure out. I also used a TDC stop to verify TDC number one first, since I was not sure I had an accurate timing tab and balancer.

One caution I've seen several times for static settings is that you need to rattle the pushrod up and down to check clearance - do not try to spin it and feel for the clearance. Your can hear and see up and down movement, but your fingers are not calibrated to measure how hard it is to spin the rod.

I did not try to adjust the valves while the engine was running because I did not want the mess if there was any oil shooting around. However, it may not be that messy - YMMV.

I also replaced my valve cover gaskets with metal-reinforced rubber gaskets, and switched to studs instead of bolts to hold the valve covers on. I don't use any sealant, and I don't have any leaks. Just make sure you use a torque wrench on the nuts, and that you use the small tabs that spread the load as you tighten the nut, since its easy to get carried away and bend the flange.

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Old 02-26-2012, 10:26 AM
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