Cold start knock question

[garyk1970]

Im working on a 87 gn....tuning,scanmaster install,etc....ive noticed if car sits a couple days, and when i start i hear a bottom end deep knock a couple of revolutions until oil pressure comes up....i changed oil,seen no copper...whats the fate of this engine? I know its hard to diagnose on the computer...tia

 

[turbo nasty]

Brand oil filter?

 

[garyk1970]

Mobile one before oil change ,and a Blue ac delco....oil filter could cause this?

 

[turbo nasty]

So it knocked with both filters?
Whats the oil psi fully heat soaked in gear idling?

 

[garyk1970]

Yep....thats why i changed the oil,added zinc....oil pressure hot in idle 25-30 psi...really good.when i changed oil, i did not fill filter.oil pump primed right away...

 

[getdowngranny]

Sounds like a rod knock in the making. Have you tried to put a load on it (powerbrake)? It will show itself sooner or later. Try using a thicker weight oil to see if it tames the knock. If you're lucky, it could be the flywheel. I once had a Chevy Tahoe 5.7 vortec that would do the same thing on cold start and I swore it was a rod knock but turned out to be a cracked flywheel.

 

[turbo nasty]

Balancer bolt loose and or key way worn from being loose, flywheel for cracks/ loose. As mentioned it could also be rod bearing dying.
Check the crank thrust as well

 

[TurboBuRick]

Comp roller lifters?

 

[NorEaster]

Mobile one before oil change ,and a Blue ac delco....oil filter could cause this?

I had a Mobil one that did that. Switched to a Napa (wix) and never heard it again.

 

[garyk1970]

Thanks guys...ill try these...

 

[PropaneDr]

I had a Mobil one that did that. Switched to a Napa (wix) and never heard it again.

im experiencing the same problem. car sat for 3 weeks. started it up this morning and rods were knocking for a few seconds and then went away. I am also using a Mobil 1 filter and the oil filter relocation kit. Is the mobil 1 filter a bad choice ? using 10w30 oil also. Had the oil pan off not long ago to replace the pan gasket. while under the car i had a real good look at the rod caps. I was able to move all of them side to side some. Im not really ready for a rebuild right now, engine is running fine and the knock goes away in a second or 2. Can i go with changing the bearings to an oversise bearing ? or just wait till it dies and rebuild the whole engine ?

 

[garyk1970]

The verdict is still out on the GN......hes gonna pull engne soon and check everything....