No compression when rockers tightened

Tiny
PCDJ64
  • 1998 BUICK CENTURY
  • 80,000 MILES

I just replaced gaskets in a 3100 vin M engine with roller style rockers.
the push rods are right where they originally where before it was taken apart, when the rockers are tightened to spec there is no compression at all in any cylinder, if I loosen then so they are just hand tight there is compression and it sounds normal turning over.
there are 2 sizes for the push rods, one size for intake and one size for exhaust.
the rockers all look identical and all are in good shape.
i have no clue what I am doing wrong, any help in this matter is greatly appreciated.

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Friday, June 8th, 2012 AT 12:02 AM

19 Replies

Tiny
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So you added roller rockers which it didnt have before?As far as I know when you use roller rockers you must use a roller cam as well.

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Friday, June 8th, 2012 AT 12:12 AM
Tiny
PCDJ64
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Original rockers are rollers, I only mention the type because some 3100 engines did not have them.

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Friday, June 8th, 2012 AT 12:14 AM
Tiny
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Alright it says intake push rods are marked orange and are shorter then the exhaust ones. The exhaust push rods are blue do you have in the correct spots?

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Friday, June 8th, 2012 AT 12:21 AM
Tiny
PCDJ64
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The intake and exhaust rods are where they were originally when it ran, the intake rods are a little shorter than the exhaust.

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Friday, June 8th, 2012 AT 12:32 AM
Tiny
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Please tell me exactly how and what torque you set the rocker arms too?

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Friday, June 8th, 2012 AT 12:41 AM
Tiny
PCDJ64
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Make sure the guides are lined up for the rockers to the head, tighten to 90in lb then I kept loosening until it got compression which was basically finger tight.

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Friday, June 8th, 2012 AT 12:51 AM
Tiny
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Alright I have step one tighten them to 124 inch pounds then step two additional 30 degrees.

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Friday, June 8th, 2012 AT 12:57 AM
Tiny
PCDJ64
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So at 90in lb I should have had compression, I have to have them literally only finger tight otherwise 0 compression.

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Friday, June 8th, 2012 AT 1:01 AM
Tiny
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How tight were they when you took the off?Why did you take it apart to just replace the rockers?

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Friday, June 8th, 2012 AT 1:11 AM
Tiny
PCDJ64
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Typical for the 3100 it had blown intake gaskets and the gaskets have guides in them for the push rods so you have to take them out.
I don't know how tight they were, they were on there pretty tight.
80 or 124 inch pounds both would give compression, it right now with them tight has no compression at all unless they are just barely on there.

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Friday, June 8th, 2012 AT 1:19 AM
Tiny
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Really makes no sense then if everything is right you should be able to torque it and 30 degrees and it should be good.

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Friday, June 8th, 2012 AT 1:35 AM
Tiny
PCDJ64
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The long rods go into the exhaust valve rockers, I wonder if I accidentally reversed one, I don't think it would be enough to kill the compression of the whole engine, just seems very strange.

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Friday, June 8th, 2012 AT 1:43 AM
Tiny
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It would only effect the cylinder that it was reversed on. But if the rods were reverse tightening them down to spec would loose compression like your getting.

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Friday, June 8th, 2012 AT 1:49 AM
Tiny
PCDJ64
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Push rods are in correct order, the remedy was to let the lifters sit and bleed out with the push rods tightened to 124 inch pounds, once that was done there was compression, apparently if the lifters expand with oil without the push rods they become solid until the oil is out of them where they can move again.

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Friday, June 8th, 2012 AT 11:34 PM
Tiny
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Ok did you torque them the additional 30 degrees?

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Friday, June 8th, 2012 AT 11:47 PM
Tiny
PCDJ64
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Yes, as close to 30 degrees as I could, they felt pretty tight.

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Saturday, June 9th, 2012 AT 12:08 AM
Tiny
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I have never seen a lifter do that on those engines.

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Saturday, June 9th, 2012 AT 12:18 AM
Tiny
PCDJ64
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Could be because of the anti freeze mixed with the oil, the mixture is harder to bleed out of the lifter than it is for just oil.
You take any of the lifers out and try as hard as you can to push them in and not one of them budges. What gave it away was the fact that whenever I would tighten a rocker the lifter had no give but the valve would move.

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Saturday, June 9th, 2012 AT 1:31 AM
Tiny
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Oh I see they were pretty much hydroloced that makes sense good catch you have a better view then I do though lol. Glad to hear you got it all figured out.

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Saturday, June 9th, 2012 AT 2:56 AM

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