spun #6 bearing twice... need advice

[mk3-4-me]

ok so last year i bought a motor from a guy on this forum. I got the engine and threw it in my 87. Drove it around untill the oil pump retainer bracket that holds the oil pump gear ground out somehow and caused it to lose oil and i got rod knock.

i pulled the motor and found out my #6 bearing spun.

You can see how my rod cap turned blue from the heat.

well i pulled it all apart and took stuff into a machine shop by me. I took the pistons/rods and crank in to get rebalanced and what ever else it needed. I told the machinist to resize the #6 rod but he said he mic'd it and it was within spec and didnt need resizing. But i insisted on him resizing it and he still said it didnt need it. I knew i should of got it resized to be safe but i was on a timeline and had to get everything back together.

So i put it all together, plastiguaged everyting and it all checked out. Got it running the end of last year and then i started to hear a slight RK again.

So i just pulled the motor 2 days ago and sure enough, my #6 rod again.


So im wondering if it was because i didnt get the #6 resized or if there is some other underlyin cause for it.

What do you guys think?

 

[Nick M]

Is the oil passage to the bearing clear?

 

[mk3-4-me]

I'll check when I get home. Is there a way to clean them all out?

 

[hvyman]

Brake clean and a air nozzle.

 

[Typhoon]

You reused the old rod. Once a rod cap changes colour, it should be considered junk.

 

[mk3-4-me]

No its not considered junk... It can still be resized back to spec. The blue was just from the heat.

 

[D.J.T.]

you can pay a machine shop to recondition your pistons & connecting rods along with the crank shaft so you get all the correct size bearings you'll need.

 

[NashMan]

I bet your rod is out of wack

the ware is uneven

good luck

 

[mk3-4-me]

Ya that's wat I'm guess/ hoping. I'm gettin it all remachined at a different shop.

So hopefully this build will last a bit longer. Lol

 

[CyFi6]

Pull all the allen plugs on the crank and clean out the galleys with a good bore brush and solvent. And definitely have that crank pin inspected it may be damaged again from the knock.

 

[Typhoon]

No its not considered junk... It can still be resized back to spec. The blue was just from the heat.

Yes the blue was "just" from heat. What do you think that "heat" did to the rod cap? Perhaps allowed it to elongate and ruin any chance of it providing the correct crush on the bearing shell perhaps?
Oh BTW, how did reusing that old rod work out for you? See the point yet?

 

[NashMan]

Yes the blue was "just" from heat. What do you think that "heat" did to the rod cap? Perhaps allowed it to elongate and ruin any chance of it providing the correct crush on the bearing shell perhaps?
Oh BTW, how did reusing that old rod work out for you? See the point yet?

this can be fixed with proper resizeing but it looks like was not done or done baldy

if it was from lack of il flow it would have happend pretty quick and wipe the baring all the way around

my qestion is what did the old baring look like ?

 

[TheMaxx]

Yeah blue= heat = ruined, If you insist on using that rod atleast have it cryo treated to try and maintain some strength in it.
Once a steel object has been overheated like that the temper, structure, and strength have all been changed and in this case I would consider that junk. I am no guru or engineer, and if there is someone who is and knows please correct me. However I would not chance wasting a new rebuild with a potentially weakened rod like that.

 

[IBoughtASupra]

I have a GTE rod if your interested in replacing the one that changed colors.

 

[mk3-4-me]

Well I've got a friend who works with me and he has so many stories of his 10 sec cars n 6 sec bikes that we talk about everyday. He gives me advice and says that he's reused rods after they turned blue from overheating. As long as it's been resized n balanced it should be fine. I know why it turns blue.

And I have eagles in here so I dnt have use for the stick rod. Thanks though!

And I spun another bearing because I started it up once and my motor gushed out 4 qts of oil and ran low. PO blocked off an oil line, which he shouldn't of, and it popped off causing the loss of oil.

I was jw if there's concern for it being the #6 again. I'm going to use a whole different crank and try m find 1 eagle rod to be safe as well. I'm remachined everything again so hopefully I won't have this prob again.

Thanks for the advice everyone.

 

[mk3-4-me]

And the bearing was pretty much all copper. Ill get a pic up when u get a chance,

 

[Zumtizzle]

I have a GTE rod if your interested in replacing the one that changed colors.

eagle rod...lol

 

[IBoughtASupra]

LOL! That was a fail. I didn't even realize it was an Eagle rod. Whoops.