rod #3 nicked by oil pump drive shaft

[dreamweaver13]

I feel really stupid for just figuring this out. But I'm also so glad I caught it before reassembling my engine on the 2nd rebuild!

Shortly after I bought my supra 2 years ago I started to hear a knock that sounded like rod knock. I tore down the engine and all the bearings were in great condition. The only problem I found was my oil pump drive shaft collar had worn away more than 1/4 inch. I didn't think it through enough at the time and went ahead with my rebuild replacing all the bearings and seals and piston rings.

That rebuild ended poorly because of a large amount of blow-by. I think this was due to cylinders that were slightly too large for the std pistons - giving me a large ring end gap.

So I was about to install rod and piston #3 on my 2nd rebuild when I noticed a large gouge in the rod. Once noticing that, it didn't take me too long to figure out what had happened 2 years ago. I assembled the rod and installed the oil pump drive shaft. There isn't much clearance between the two. With my collar worn so much, the rod must have been hitting the end of the oil pump drive shaft. The weird thing is, the shaft doesn't look like it was hit.

So now I'm off to the machine shop with my rods. I have 2 extra sets of rods. Do I need to have a whole other set balanced, shot peened, and fit for ARP bolts, or can I just have him do one rod?

 

[Kai]

If i were you - i'd use your spare set of rods and have them shot peened and balanced as a group rather than pare down your existing set to match the nicked one - that rod is as good as junk my friend.

Far easier to just do it right and play it safe, sure, it may cost a bit more in the $$ department, but you'll be thankful when the engine decides NOT to eat itself

 

[Adjuster]

Your oil pump drive is SHOT!

That clearance on your retainer is way, way, way out of spec. (It's only supposed to be a few thousands... See the TSRM.)

That loose, you should have a ring of wear on your front cover from where the oil pump drive sprocket might have rubbed on it when the shaft pushed back far enough to hit your rod...

Get that oil pump drive issue fixed I'd hate to see you lose another rebuild.

One more thing. I never reccomend just hitting a worn engine with a hone, then throwing in new rings, and hoping your bore to piston clearance is still correct. It's easy to remove a few thousands while honing the bore, and that screws up your piston clearance, allows the piston to rock in the bore, and that ends your ring life very fast indeed. (Most likely they will not seal up, if ever, and will wear out quickly.) Best option is to bore your engine to your piston size, with proper clearance allowed for, then hone to spec, and then gap your rings, and you have the best chance of getting a good seal, and long life from the pistons and rings.

As you found out, at your cost, just rings and a hone, and your making a bad bet indeed.

Good luck with the next build.

 

[dreamweaver13]

thanks for your concern adjuster

That picture is from 2 years ago when I pulled out the shaft during rebuild #1. I just threw it in there so you would know what I was talking about. I have since replaced the collar and checked the shaft and it is straight.

And you're right about the rings not sealing and the bore being a few thou too big. That was a big mistake on my part, but if I hadn't made the mistake, I feel that I would have been worse off. I would have turned up the boost thinking my engine was in great condition and rod#3 would have failed catastrophically.

Right now, I'm inspecting my other 2 sets of connecting rods. They have a bit of surface rust and unknown mileage. I may just go for some eagle rods.

and 1 other thing: what could cause the oil pump drive shaft collar to wear so much?

 

[quake]

thanks for your concern adjuster

That picture is from 2 years ago when I pulled out the shaft during rebuild #1. I just threw it in there so you would know what I was talking about. I have since replaced the collar and checked the shaft and it is straight.

And you're right about the rings not sealing and the bore being a few thou too big. That was a big mistake on my part, but if I hadn't made the mistake, I feel that I would have been worse off. I would have turned up the boost thinking my engine was in great condition and rod#3 would have failed catastrophically.

Right now, I'm inspecting my other 2 sets of connecting rods. They have a bit of surface rust and unknown mileage. I may just go for some eagle rods.

and 1 other thing: what could cause the oil pump drive shaft collar to wear so much?

saw this at work a few weeks ago, the guy had done a rebuild and used a bolt on his oil pump drive gear that was too long. After driving he got rod knock or so he thought the rod was making contact with the shaft as adjuster said there is a spec for the collar.