Valve adjustment on 1997 350 vortec suburban

Discussion in 'GM Powertrain' started by ahlberg, Jan 31, 2010.

  1. ahlberg

    ahlberg New Member

    Hi all,
    I have spent 3 weekends on trying to adjust the valves on my 1997 suburban 350 vortec. I have adjusted them 4 times with going to TDC #1 and adjusting the approprite valves. Then another 360 degrees with #6 at TDC and adjusting those valves. I removed the cap to make sure it is at the appropriate cylinder. I have done it from 1/2 turn to 3/4 turn to 1 turn. compared the haynes book with the internet .
    Every time I go back to check the valves they differ. Today I had no compression in 3 cylinders, which I have had before and would readjust all the valves. I backed off the valves on those cylinders and I would read 180 on those cylinders. I have read 180 on all cylinders with the valves backed off. I have not pulled the distributo since this problem occuredr, I have put a new cap and rotor and new plugs. Firing ordr is correct. Every time I go back to check the valve adjusment it seems like it has changed. This is a replacement crate engine from chevy. It seems like the lifters are not right for bleeding down. or it is the wrong harmonic balancer (it came with the engine).
    I heard a couple lifters knocking and wanted to do it right and adjust all the valves. What a nite mare the engine is trying to start but won't. I have spark and fuel. This is driving me crazy. The engine will not even start. No real backfires. I have been a aircraft mechanic in the Navy and race a few old muscle cars so I feel I am compatent. except for my spelling. PLEASE HELP !!!!!!!!!!!
  2. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    same as any hyd. lifter tighten till play goes away then back off 3/4 turn just make sure you dont calapse the lifter as you tighten
  3. ahlberg

    ahlberg New Member

    I have been getting all the play out then TIGHTENING between 1/2 and 1 turn. I was sure the book said tighten.
  4. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Oh sh!t your right my bad yes tighten till all plays gone then go 3/4 more my bad i was thinking one and typing the other but ya you can by clips that block the push rod oil holes to keep it cleaner while running but you can back them off till they click them go 3/4 more tight (thanks for waking me up to that)
  5. ahlberg

    ahlberg New Member

    Thanks for the reply. I think I am going to start from scratch and get TDC #1. The problem is I may have got the valves so far out of wack I can't tell if it's really on the compression stroke. But I was thinking I could tell by the push rod height if they are both at the same height and #6 push rods are at different heights then I know I'm on TDC #1.
    The engine won't even start so the clips are out for now. Do you or anyone else think I should back off on all the rocker arms and let the lifters bleed back overnight. Thanks all for the help.
  6. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    they need oil pressure to pump back up correctly or they will just have air in them back them off 1/2 turn hook up the battery charger and crank for a ten count go back through them and see if any tightened up. back those off half a turn and repeat till they all stay loose the internal spring and the oil pumping will top them out then you can start fresh
  7. ahlberg

    ahlberg New Member

    Sounds great I will follow yhat advice ! by the time I get off work its dark. My California garage is a east coast basement, full !!suburbans in the street. I will have worked on it by the end of the weekend. Can't wait for DST to be back. Trying to collect all the info before I hit it again. It's getting depressing but I have new hope. Dude (joking, california) Thank you for all the replys. The more info I have the better I feel about it. Thanks to all of you !!!!!!
  8. ahlberg

    ahlberg New Member

    Hi all,
    Well 6 weekends later the engine finally started today. The final answer in my case was bringing each cylinder to TDC and adjusting the valves. At the suggestion of a friend at work I divided the harmonic balancer into 4ths. I then brought each cylinder to TDC by lining up the next 1/4 with the timing mark on the timing cover. Following the firing order 1-8-4-3-6-5-7-2. I checked the compression and I had 180 in each cylinder. This was encourging. I attempted to start the engine and it started right up. I then backed each rocker arm nut off untill it started clacking. I then tightened the nut down untill it stopped clacking and turned the nut 1/2 turn in. It runs beautifully. Also those rocker arm clips to stop the oil from getting everywhere are priceless. They are fine at idle but when you rev it you will get oil on the exhaust manifold.
    I was adjusting the valves the way the book said and many articles on the Internet. In my opinion, do it the way I did above. I have not put the valve covers on yet. I go out and start it every couple hours as I am still in disbelief. Tomorrow when I get home and the engine is stone cold ( I will drive my other car) I will start it. If it's good then I'll button it up. Thank you guys for all your help and I hope this feedback will help someone else.
  9. Chapper

    Chapper New Member

    Hi Ahlberg. New poster going through similar valve adjustment issues (1999 vortec 5.7). When you were rotating the engine by hand what exactly did the rockers do for each cylinder as you hit tdc? Intake should open on the final stroke, then exhaust after the firing right? So as you hit the line on the dampener, intake opens, then exhaust opens after the line, right?

    The Chilton book seems to say the opposite, so I'm trying to fill in the blanks.

    When you rotate the engine by hand and are looking at the valves, there is a notch on the stock dampener that lines up with the v in the timing cover. This is the only notch/mark. The vehicle is bone stock. Not using the distributor for any indication, because it may have gone in 180 out. This mark should indicate TDC for piston 1, right? When I rotate the engine, with this spark plug out, I feel and hear the air, and see the intake open and exhaust open on either side of this mark. Sounds and logically means tdc right? Then I read the Chilton book.
    The Chilton book says "put your hands on the rockers and rotate the engine. When you feel/see no movement through the rotation this is tdc for piston 1. Then rotate it again and you will be at tdc for piston 6 and for the second adjustments. This flies in the face of everything I am seeing, feeling and thinking. Is this a Chilton mistake? Shouldn't the intake open during the final power stroke, then the spark fires, then exhaust opens right after tdc? This is definitely rockers moving???? Just want to get this right.

  10. xPosTech

    xPosTech Epic Member 5+ Years 1000 Posts

    He may not see this. You brought a 5 year old thread back to life.

    When on the compression stroke both valves are closed as the piston comes up toward TDC. If either valve was open means no compression. As piston passes TDC the plug fires the compressed air/fuel. The resultant fuel burn drives the piston down in the power stroke. Both valves are closed during this compression/plug fire/power stroke. As the piston passes BDC the exhaust valve opens and the rising piston pushes the burned mixture out of the cylinder. That is the exhaust stroke. As the piston passes TDC the exhaust valve closes and the intake valve opens. The piston falling from TDC toward BDC draws in a fresh air/fuel mixture in the intake stroke.

    This is a four stroke or four cycle simplified timing of the engine. Notice the valves in the compression/plug fire/power stroke. Both valves are closed almost a half revolution. That is the TDC to adjust them, not when almost any rotation of the crank will open one or the other. Also note that it takes two crankshaft revolutions for the four cycles.

    You should adjust them at TDC between compression and power.

    Did you understand that? You were one crankshaft revolution off.


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