Valve lash help needed.

[batchik2]

i feel retarded here lol. i can get it running at WOT and its at like 1000-1500 rpms. the Vacume guage reads zero which leads me to believe valve lash isn't correct.



now when i bump the cylinder over to be lashed i stop right after the intake valve closes. this would mean its on its base circle, correct?



then i tighten the rocker just until zero lash (no play left in the pushrod). then another 1/4 turn.



am i doing this right?





BTW: its an old school 350 with a tbi intake. plane jane hydraulic flat tappet set up. any input is greatly appreciated.

[Scotty_S-15]

The safest and surest way is to set them with the engine running. Can't hardly mess that up. Back off until it ticks, slowly tighten until the click stops, and add your 1/4 turn or whatever.

.......... Regarding the base circle, the answer is no, just because the valve is closed doesn't mean its on the base circle. All cams are different, but for sure, after a valve closes, the cam continues to slowly back off the ramp. Some older GM Hi-Perf cams had relatively little base circle. That is, the duration of some of those cams was like 330 degrees, but only 215 degrees at .050.

[carkiller]

i agree with scotty. the best way to adjust a hydro cam is to do it running. almost impossible to get it wrong.

[Truckman91]

Wow, Im dissapointed Michael.....lol



EO-IC method is the one I use everyday.



When the Exhaust Valve just starts to open, adjust the intake valve on the same cylinder



(I personally do all the intakes first)



Then, When the intake vavle sets back on the seat, adjust the exhaust valve on the same cylinder.

[batchik2]

On 2007-06-09 17:06, SweetS10V8 wrote:

Wow, Im dissapointed Michael.....lol



EO-IC method is the one I use everyday.



When the Exhaust Valve just starts to open, adjust the intake valve on the same cylinder



(I personally do all the intakes first)



Then, When the intake vavle sets back on the seat, adjust the exhaust valve on the same cylinder.





as am i lol. they always brushed it at school but we never had to do it. thats why at the begining of the post i said "i feel retarded".



i just did that method a little bit ago. runs alot better but now i have to hunt down an idle problem.

[ZeroGravity58]

did you check for any vac* leaks? sounds like you may have one if it wont idle and is not pulling any vacuum.

[batchik2]

On 2007-06-09 23:49, ZeroGravity58 wrote:

did you check for any vac* leaks? sounds like you may have one if it wont idle and is not pulling any vacuum.





it sounds like it should be something major and obvious. maybe i AM over looking something simple. been known to happen before. lol

[batchik2]

this pos is driving me nuts. i can get it to run at like 3/4 throttle for a few seconds. and it will only run around 1000-1500 rpms. i still think its valve terrain related i just cant figure it out for the life of me. ive lashed and relashed these like 50 times. ive tried a couple different ways and the EO-IC method has had the best results. i KNOW the timing chain is on right and i KNOW the destributors dropped right. what are the other variables in this situation? bad lifter(s)?



<font size=1>[ This message was edited by: batchik2 on 2007-06-10 16:40 ]</font>

[stroker1]

If you are having questionable lash setting adjust them while the opposite valve is at max lift. Example when the intake is at max lift, adjust the exhaust. Then when exhaust of the same cylinder is at max lift, readjust/check the intake. Your cam will not have enough overlap to worry about if you do it this way. I'm with the other guys, you must have a tremendous vacumn leak. Is your carb sitting all the way down? Is your inatke gasket leaking? Is the base plate of the carb warped or has it been used on another engine and someone tightened it down wrong? I had a pipe plug screwed into my intake once at the back where the vacumn tree would normally be. It was sticking up too high and the carb bowl was sitting on it. Mine did the same. Would not idle for shit. BUT it made a loud sucking sound. Just for the heck of it cap off all the vacumn ports and try it again. How about your timing?



Try searching old posts on here for vacumn leaks, idle problems, etc. That might give you some good ideas.



Stroker1

[Scotty_S-15]

Can you check compression on at least a few cylinders? Good compression would be proof that the valves aren't too tight and hanging open. Regarding valves hanging open, remember, when in doubt, set them loose. Loose lash can't hurt anything, as opposed to setting them too tight.

........... A quick check for cam timing (timing chain) would be to pull driver's side valve cover, and slowly bar over the engine. As #1 cylinder crosses TDC, not compression stroke, but with both valves overlapping. Just as you cross TDC, both valves should be criss-crossing, one opening, the other closing, and both should have about the same lift at TDC. This isn't an accurate method, if for no other reason, different cams have different characteristics. But again, it's a good "ballpark" check.

............ Did you check to see if the timing mark is accurate? Did you try advancing the timing? Maybe it's just crazy retarded. I guess it hasn't run long enough to get a timing light on it, eh?

.......... And a maybe major vacuum leak like was mentioned? Like a plug missing from the intake manifold?





Heh, Stroker & me writing at the same time.

And like Stroker mentioned a carb vacuum leak. How about the carb gasket? You certainly wouldn't be the first guy to use a wrong gasket, creating a huge vacuum leak.

[batchik2]

its a TBI set up.



last night before i closed everything up over at the garage i poped the valve cover off and started to wiggle the rockers to see if anything changed since i lashed them earlyer.



a bunch of them were loose again. would this be a problem with the lifters?



... and i know the timing chain is on right and the dist. IS dropped right.



thanks for the help guys, its greatly appreciated.

[Scotty_S-15]

Oh yeah, you did say a TBI.

A few more thoughts:

* Timing chain marks have been known to be wrong. Saw it once myself.

* I know the dist. "dropped right in correctly", but that doesn't guarantee anything with ignition timing.

* Rockers loose again? Pressed in studs? Is it pulling out the studs? If so, there is something binding in the valve train. But again, loose rockers won't keep it from running. Overly tight rockers WILL keep it from running, and possibly cause damage.



Point is, given how poorly it (barely) runs, best to back to the basics.

[mzoomora]

If they are crimped nuts then switch to ply locks. The crimped nuts will lose their tightness after a while and back off.

[batchik2]

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On 2007-06-11 16:25, mzoomora wrote:

If they are crimped nuts then switch to ply locks. The crimped nuts will lose their tightness after a while and back off.

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thats a possibility. those nuts have been installed and removed a bunch of times. some of them do seem pretty easy to turn.



another thing that was brought to my attention was that the shortblock has been sitting assembled for a better part of 2 years now. a guy i work with recomended taking the lifters out and pumping them up with oil manually. good excuse to get rid of the stock tbi intake lol.



EDIT: ive checked every possible source for vacuum leaks and nothing seems out of place. and by now im sure id see carbon residue coming out of anything major that would cause this large of problem.