Valve lash on a 350!! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-18-2001, 09:15 AM
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Valve lash on a 350!!

I have a question about setting up valve lash on my 1990 K1500 w/350. I replaced the valve stem seals this past weekend and have two questions:

1) I tightened the #1 rocker nuts like the book said until the pushrod stopped turning. I then went 1 full turn tighter like the book said. When I tightened the other valves that you could with #1 at TDC, and came back later to #1, it was loose again. I thought I had forgotten to tighten it. Is this due to hydraulic pressure in the lifters?

2) I noticed when I started it up, it sounded slightly different and seemed to make less power. It didn't make any noise at all though. Could this be caused by me not having #1 at TDC when I tightened the rocker nuts? I had the distibutor lined up @ #1, but forgot to make sure the timing mark was at 0. It was probably around 4. Would this make enough difference to not allow the valves to open enough, thus producing less power?

Thanks!


Steve M
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post #2 of (permalink) Old 06-18-2001, 01:11 PM
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Re: Valve lash on a 350!!

I'm not a GURU at this, but I firmly believe the running the lash while it's running is the most for sure way to do it! You definatly need to have the timing mark on the crank at zero (unless your balancer has spun), otherwise you wont be at TDC..Take #1 plug out and hold your finger over the hole and ge5t somone to bump it over till you feel compression.Then turn the crank back till its at zero on the mark and you'll have her on tdc. It sounds like you have your valves too tight if it lost power. I run mine at a half turn so it'll spin up quicker..DOnt know if that really is the cause, but I can tell the difference on mine!!

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post #3 of (permalink) Old 06-18-2001, 02:20 PM
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Re: Valve lash on a 350!!

The stationary engine method works fine as long as you don't follow the book.I do them one at a time.You need to make sure that the lifter is on the base circle of the cam.You can do this by making sure that the other valve is at full lift then adjust the one that is close by rolling it between your fingers as you tighten the rocker nut down.As soon as you feel it start to drag on the push rod tighten it 1/2 turn to "preload" the lifter.Do it 16 times and put the valve covers on and start it up and let the lifters bleed and in about 5 minutes it should run quiet and smooth

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post #4 of (permalink) Old 06-18-2001, 10:23 PM
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Re: Valve lash on a 350!!

On my new 350 i turned them between 1/2 and 3/4 turns. When I first started it they chattered but quickly stopped. Small block chevys can be prone to cam problems, mostly 80's 305's, but anyway, I would try it again but dont turn them so far. You can do it with the engine running too, it makes a mess, but it is simple. Take off the valve cover, start the truck, back the nut off untill the rocker is chattering, then tighten it until it just quits making noise.

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post #5 of (permalink) Old 06-18-2001, 11:00 PM
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Re: Valve lash on a 350!!

I adjusted mine with motor running, I loosesnd till I got clatter then tigthend back up till the clater was gone and then another half turn, it worked fine for me and I havent had any clatter since, its seems to be faster then doing it one at a time with the motor dead.

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post #6 of (permalink) Old 01-03-2003, 09:15 AM
 
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Re: Valve lash on a 350!!

Kind of an old thread to bring up but i have some more questions on it. Im doing the Valves on mine right now.. i seem to be having somewaht the same problem as the frist post. i get all my valves adjusted then i go back back check them and some of the push rods spin now. i pre loaded them from bout 1/2 to 3/4 of a turn. Should everything be ok? Some of the push rods turn and some dont. Im just really paranoid and don't want to screw anything up.. or have to do it again for that matter [img]images/graemlins/smirk.gif[/img].. and if i go to re-adjust some of the loose ones do i need to back the nut all the way off. Even though its loose i don't really want to tighten it down more and risk getting it to tight.
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post #7 of (permalink) Old 01-03-2003, 09:20 AM
 
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Re: Valve lash on a 350!!

Might be a long shot but the last time I did my valves, I had to buy new rocker nuts. I got the best price at the dealer (amazing isn't it?) and the tech guy there told me that the rocker nuts were a one shot deal kinda thing.
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post #8 of (permalink) Old 01-03-2003, 10:14 AM
 
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Re: Valve lash on a 350!!

factory does it at 1/4 turn after 0 lash, thats the way i do mine and never had a problem. 1/2-3/4 turn, way too much, your valves wont close. you just need a little preload on the lifter (hydrolic only)
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post #9 of (permalink) Old 01-03-2003, 10:18 AM
 
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Re: Valve lash on a 350!!

so if i trun the engine over after i set them then its ok if the push rodes spin some?
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post #10 of (permalink) Old 01-03-2003, 10:57 AM
 
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Re: Valve lash on a 350!!

yes, the lifters are bleeding down, if you loosen them and let them sit, they will move back up. i adjust to zero by rattling the pushrod in the lifter cup, cause it isnt always easy to tell by turning, cause your torquing the rocker. you may have to revisit a lifter after your running, its pretty common
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