Engine Knock

[mdwatson]

Warmed my engine up this morning and everything sounded normal. Ran fine going to work and when I pulled up to go through gate I heard it knocking when I turned the radio down. I'm going to take it back to the shop that put the long block in but was wondering what y'all might think it is.

 

It's a 86 2.5L auto. The knock gets faster with rpms while giving it gas. Used a dowel rod to pin point the sound and it's extremely loud at the distributor cap. You can grab the cap and feel the knock through it and even through the wires. Not sure if the cap is acting as a echo chamber or not but when I put the dowel rod at the base of the distributor it's not as loud. Pulled cap and rotor and it looks fine.

[cruiser54]

Make sure the bolt is tight that holds the dizzy down.

[zagscrawler]

Can you hold the distributer and feel it when crankin it?  or just when its running?

[mdwatson]

Distributor was tight and didn't think to feel it when starting. Truck died and dizzy doesn't turn when trying to start. Hoping it's just broken and no other problems.

[zagscrawler]

ouch..  does it still sound like it has even compression when cranking it over or does it have an easy spot or fast turnover rate (faster then when it was before it died) when holding the key in start for a small period?  I'm assuming you mean my dizzy doesn't turn you pulled the cap and the rotor doesn't spin while cranking?

[Oyaji]

Have you done a compression test?. 

[mdwatson]

Yep pulled cap and it doesn't spin at all when trying to start. Motor does turn over but it is at a faster rate than before. It's at the shop now, I'm not looking forward to what the diagnosis is.

[zagscrawler]

oh man that's not good.  Are these motors noninterference? ive never asked.  

[Minuit]

Yep. 4.0s are non-interference. No danger of piston-on-valve action. I bet you probably screwed up your oil pump in some way since that's what turns the dizzy.

[zagscrawler]

I would like to think it was just the oil pump but isn't it driven off of the cam?  The fast spinning makes me think maybe broken timing chain or missing bolts in timing gears.... good to know about the clearance though I have always wondered. 

[carnuck]

Dist drives the oil pump If it was loose because someone forgot to tighten the bolts, it can drop down and seize the motor from no oil pressure. Dist gear can also be wiped out by a bad/loose oil pump.