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Old 02-08-2006, 06:10:57 PM   #1
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what are symptoms of misadjusted valves?

my brothers truck has a reubuilt 350 motor.268 cam. its idle has been all over the place, some days at 1100 in park, 750 gear, some 750 in gear 500 park, some 1200 in park, etc. checked timing and it moves a little, meaning a slight bounce on reading, but doesnt MOVE when driven and rechecked. vacuum is 18 with a slight bounce. we first adjusted valves dry with intake/exhaust, firing order method. well didnt preload enought(rather safe than sorry on cam) and they clacked and poor idle. tried to readjust running, but his damn exhaust leaking i couldnt tell clicking from clacking. so shut it down and readjusted dry two ways, the 2 revolution where 1/2 are done, then the other, then rechecked the original way.(anal and bored i guess) anyways all had a tiny amount of play after adjusted. could spin the pushrod, not easily, but could spin, BUT all the slack of up and down was taken out. locked them and started up. no noise, pretty damn good pickup and go, no backfire, smoke, smell, all headers hot engine running cool, good pickup and go....but a bouncing vacuum and idle usually can be valve train right? adjusted the holley(new 670) all the way in till stumbles then back out 1/4. jacked with idle screw a million times, choke is wired to inst panel hot on key, and checke for vacuum leaks.

Is it possible for it to run great and the valves be held open to long by being to tight? is it possible to be closing early and not have a loose rocker setting? distributor is new, what else could cause this type idle problem? using 93 octane as well and all lines are clean, fuel pressure is fine, oil pressure is fine, no smoke, etc.
any ideas
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Old 02-08-2006, 07:02:51 PM   #2
night rider
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Un stable idle sounds more like vac leak and or timing to me.

What port (timed or full) is your dist. vac advance hooked too?

Just cause the dist. is new means nothing really. I seen many bad new parts. The wights could be sticking in the dist.

If though the choke is wired up right are you 100% sure its opening at the same rate every time and not closeing back. I would un hook the hot lead, linkage and wire the choke open with a pc. of coat hanger or something just to test and see.

Valves too tight most of the times we'll cause a bad engine shutter. Real rough running cond. Lack of power, etc
1988 Camaro -
10.34:1 355, Brodix IK200 heads, 249/252@.050" .570"/.579" lift solid cam, holley 4150 HP 750, th-400, 3500 stall, ford 9" 3.89 gear

Vid clip of my 1988 camaro idling and reving.. New engine combo
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Old 02-08-2006, 07:13:17 PM   #3
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the dist vacuum advance is running to the Holley manifold full vacuum port on the left front of carb, timing is 10 BTC. Having thought to check choke position after warm up. anyway to tell if weights are sticking or if vac advance not working right? sprayed brake cleaner around intake to heads, to carb, etc. no idle difference. 18 isnt bad vacuum, but like i said it does have a bounce. 268 cam might cause a little lope, but the idle just feels off. powerwise it is good, although fixing this it should be better.
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