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2000 Pontiac Grand Am No Compression

2000 ALL OTHER MAKES ALL OTHER MODELS
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TESTICUS1
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Blew a head gasket, which took the heads out. New heads (which have been shaved but not sure how much) new pushrods, supplied by the company that supplied the heads, put everything back together. cranks but no start. Standard troubleshooting, turns out no compression.
After a lot of hair pulling, decided to pull the rockers and pushrods, and what do ya know, compression.
Checked pushrods for length (against the old ones)
and they are the same length
My question is, what could cause the the valves not to close properly, killing my compression
Jan 25, 2007 at 9:37 AM
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MATHIASO
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https://images.2carpros.com/forum/automotive_pictures/46384_valves_2.jpg

there may be carbon build up between the valves and valve seat, check it out
Jan 26, 2007 at 2:08 AM
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TESTICUS1
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Thanks for the reply
Sorry for not being clearer, I only have compression when the pushrods and rockers are out but it's good and consisent compression. These heads have not seen any fire, carbon isn't an issue
It's acting like the pushrods are to long but a visual compared to the old ones say they are the same. Could anyone give me the specs on length, My Haynes manual only gives approx length (5 3/4" & 6")
The intake and exhaust pushrods are dirrerent length, so I tried switching them back and forth, no luck. Could any one give me the lay out as to which valve is which on the head, Haynes couldn't help me
Thanks for your time
Jan 26, 2007 at 4:21 AM
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MATHIASO
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did you adjust valve clearance?
Jan 26, 2007 at 11:24 PM
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TESTICUS1
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Sorry it took so long to get back. Unless I missed something in the Haynes, the only adjustment for the pushrod is the rocker torque spec, which I used. I assumed it uses hydraulic lifters. The vehicle is at a friends house and I don't have ready access to the book or the car
Jan 28, 2007 at 1:40 AM
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MATHIASO
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To obtain the correct hydraulic lifter ajustement remove the lash between the lifter and the pushrod, then depress the pushrod a specified distance into the lifter.Hydraulic lifter maintain a clearance of zero lash both hot and cold.In order for this to be done properly,the lifter plunger is adjusted to the middle of its travel.
Remove the slack amoung the lifter, pushrod,and rocker arm by slowly tightening the ajustement nut. Watch the lifter during this step.Do not tighten the adjuster so tight that it compresses the lifter.The slack is remove when the pushrod will no longer rotate.After the slack has been removed, tighten the adjustement nut one turn to postion the lifter plunger in the middle of the body.
Jan 29, 2007 at 2:37 AM
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Suggested Repair

Set hydraulic lifter preload correctly. Slowly tighten each rocker nut only until pushrod slack is gone and the pushrod no longer rotates, without compressing the lifter. Then tighten the nut one additional turn so the plunger sits mid-travel. Confirm intake and exhaust pushrods are in the correct positions.

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Conversation Summary

A 2000 Pontiac Grand Am 3.4L had a head gasket failure and received new shaved heads and new pushrods. It cranked but would not start and had no compression with the valvetrain installed, yet compression returned when the rockers and pushrods were removed. The pushrods matched the old lengths, and swapping intake and exhaust rods did not help. Carbon was ruled out because the heads had not been run. The expert explained that hydraulic lifters need zero lash: remove slack without collapsing the lifter, then tighten the adjuster one turn to center the plunger.

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