Just tore down D16y8 that I rebuilt about a 100 miles ago. Reason Im tearing it back down? Got a weird metallic rap from top of block/head area only when engine is hot. Pulled crank out which looks perfect, bearing surfaces dont look bad. But on two of the bearing backside surface, they are stained brown in a couple of spots and rod surface also has same staining. Is this just oil? Number 1 has slight discoloration and number 3 has lots. During assembly, plastigauge showed rod bearing clearances between .0016 and .0015.



#3 rod showing discoloration

#1 rod

#2 rod looks fine

look at all the bearing surfaces after 100 miles plus idling.

 

did you applied assembly lube on the bearings during the installation? Looks like metal on metal damage...

 

Yes sir! Permetex engine lube on main and rod bearings and crank mating surfaces.

The brown discoloration in first two pics is of the back of the bearing that mates with the rod.

Last two pics show bearing surface that mates with crank. Does this look ok for 100 miles and lots of idle?

 

No, looks like you had junk under the bearings. Like oil or dust or something. Bearings get installed dry between bearing and rod end.

I pulled down a 300k mile D series that had zero wear on the bearings. Those bearings look bad.

 

Let me add two things here.

1.) The bearings were install into the rod cap and rod dry. Than i used engine assembly lube on bearing surface that contacts the crankshaft. All was done in a very clean environment and making sure nothing was between the bearing and rod/cap.

2. These bearings are DNJ brand sold by the machineshop. I know cheap **** bearings. They actually have light machined grooves in them. Also I want to point out the crankshaft surface is mirror finish still and not scored in any way.


So what are you guys thinking? If this was yours and your selling the car to your neighbor who you think will probably trash the car within 5 years. Im thinking investing in honda bearings of different assortment (black, brown, green) and getting clearance in middle of spec...

 

You will be about $300 in bearings at Honda for crank and rods on a D series.

Try some ACL bearings. They are less expensive and don't machine marks in them.

 

That's your problem right there. CHEAP bearings.

 

This.

 

Cool, ill order some ACL rod bearings. Makes no sense why bearings have machined grooves when they are just going to wear down and increase in clearance quicker.

I ended up taking the block, crank, and pistons back to the machine shop to get mic'd. Got a call back a few days later and he stated the piston to wall clearance was over the honda limit. I think he said it was like .004 and Honda spec was like .0025. He is going to purchase larger pistons (larger than +.030 over...) mic them and than send the block out to get machined correctly. Apparently he didnt do the machining cause his equipment only does larger bores such as Ford/Chevy/Dodge, etc. No extra charge to make it right so im happy.

So if the knocking noise was in fact piston slap, it would be the first I have ever heard of piston slap occurring when the engine is hot but not cold? Could the cyl walls expand more than the pistons would when hot?

 

Got everything back, reinstalled, and drove today. It's perfect finally. Problem was the machine shop overbored the block and I was hearing piston slap when it was hot. Selling the car this weekend to a neighbor and focusing on my mustang.