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Old 05-26-2003, 09:00 AM
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rkh3 rkh3 is offline
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Default rocker adjustment on a '70 340

This is driving me crazy. As you might have seen in previous posts, I adjusted the rockers to 0 lash, then the engine ran like crap. Thought it maybe carbs, so replaced main gasket, intake gasket, fuel pump, economizer valve (they all needed it). But only slight improvement. Now I am wondering if it has solid lifters (s/b hydralic). If it does have solid lifters, what should the lash be set at?????

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Old 05-26-2003, 12:01 PM
345Dart 345Dart is offline
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0 lash with hydraulic cam will not work properly and rockers will make lots of clatter. 0 lash with a mechanical will not work and could cause engine damage.
If you do have a hydraulic and follow the procedure for setting the pre-load (1 to1 1/2 turns) for hydraulic lifters using the 90* method you should be good to go. If you are setting at zero lash and then you cannot go 1 - 1 1/2 turns on the adjuster with minimal force you may well have a mechanical cam and will require ±0.03" of clearance between valve tip and rocker when set cold.
Strongly suggest you resolve which type of cam you have before proceeding further as engine damage may be immenent - if not already
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Old 05-26-2003, 01:28 PM
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amxauto-x amxauto-x is offline
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rkh3, read the topic "how to adjust -- adjustable roller rockers"
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Old 05-26-2003, 03:03 PM
rustycowl rustycowl is offline
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Default ?

If you don't know whether or not they're hydraulic, you can chk after it's been sitting for awhile(lifters have bled down), by pressing on the pushrod end of the rocker of one of the valves not open. If you can feel the 'spring' in the lifter, you've got hydraulics.
Hey, this is a small block! If you need to be 100% certain, just reach down with one of those lifter-puller tools, and pull it out and examine it.
If you are adjusting hydraulics, you have to turn each one in SLOWLY to allow time for the excess oil to bleed out. There will be a period of time on each one, where it may run rough until the hydraulic lifter stabilizes. For me, I think 1-1/2 turns is a little excessive, I run about 1/2t preload.
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