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Engine rattle on down rev

losh1971

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Did you turn the engine over to tdc on the compression stroke of each cylinder before installing each pair?
I made sure the valves were fully closed before I tightened the bolts.
 

EYY

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If it is preload would the noise be constant even when revs are say 2k? As it is the noise goes away with some revs.
Not necessarily. If the cam is pounding the lifters at low rpm it'd sound pretty horrible.

For the sake of 20 mins, i'd definitely remove the rocker cover on passengers side. See if you can see anything suspect. Post pics of areas around the pushrod holes if there's any noticeable contact. Try to wriggle each pushrod - they should be firm and not rattle around freely.

You can also start the engine with the rocker cover removed - it's not too messy and sometimes means you can diagnose more easily.
 

losh1971

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I removed the passenger side this morning and couldn't see any problems, rockers and rods were tight. Maybe the issue is the drivers side. Just clarifying the noise could go away with some revs, or it should still be there?
 

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When I rebuilt an engine for the first time, I had a preload issue. The crow cam I used was ground on a smaller base circle which meant that preload was non existent and so it clacked like crazy at low rpm/no load but sounded okay when revved. Was only an old 202 - so I just filed a little off the rocker pedestals from then on it was silent. Not the right way to go about things though - should get the correct pushrod length to maintain correct rocker geometry.
 

losh1971

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I have just removed the drivers rocker cover and have the engine running. I can see all the rockers moving and there is no slop in them that I can feel. The noise definitely sounds like it's under the manifold. One of the push rods that sits under the thermo housing looks close to the edge of the bottom of the hole. Where as all the rest sit a decent amount above. I tried flipping the locating plate last night and it is in the best position as all the valves are being pressed on the dead centre.
Lex I just followed the instructions Mace sent me and it doesn't mention TDC. But I made sure the valves were fully closed. I can try again with them all on TDC.
 

losh1971

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Not the right way to go about things though - should get the correct pushrod length to maintain correct rocker geometry.

I am a bit suss that the very front push rod sits fairly close to the bottom of the hole.
 

losh1971

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Fair bummed about this, those rockers weren't cheap. And now I am off the road for probably two weeks.
 

losh1971

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Ok so the front most rod is close but I don't think it was touching. I say that because I still have some assembly lube on the bottom edge of the hole where it is sitting closer than I would like.
 

losh1971

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Just to add last night I did mention I had two leads swapped over and it did one miss fire before I shut it straight down. Is there anyway it could have shunted something to do with the chain and maybe damaged the tensioner?

I was reading about TC problems with the Buick and it does seem that the factory chains are fairly average. What I also read, and have noticed over the last 2 or 3 weeks that the power has dropped off slightly. Soon after fitting the CAI if I booted it, it would really come alive but not now, not so much. The new rockers certainly brought some power back but that was to be expected. I thought I was imagining that the power had dropped off but now I am not so sure. The other thread did say they noticed some power loss, when the chains were knackered.
 
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