ZCar Forum banner
1 - 20 of 20 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter · #1 ·
Hi, I just bought a 1981 280zx NA and when I took off the oil pan to look at the crankshaft I noticed it's blued around where the connecting rods and the crankshaft meet. Is this factory to harden the crank? Is it something I should worry about? I bought the car with the engine already out so I've never seen it run. The blue discoloration stops maybe like 1/8 to 3/16 inch from the connecting rod bearings. Odometer says 190k miles, engine looks like it was rebuilt by ATK North America not too long ago judging by the paint and ATK sticker on the block. Inside the engine looks clean too, not much oil sludge or anything like that. All help is appreciated
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #5 ·
Thanks for the replies, I'll measure it with plastigage and check the bearings/journals before I put the engine in the car. I opened it to check the cylinder walls and make sure nothing looked out of the ordinary/damaged. I don't know what made the previous owner take the engine out of the car before selling it to me, I think he said he was planning on restoring it.
 

·
Registered
Joined
·
214 Posts
If the crankshaft has been re-worked it will be stamped somewhere on one of the counter weights and the bearings will be marked if they are standard or undersize. If you are worried about it pull the crank out and have a shop look at it. May want to check it for cracks while its out for peace of mind. You may be able to contact the rebuild shop for information on the engine.
 

·
Administrator
1983 280ZX Turbo
Joined
·
2,459 Posts
Thanks for the replies, I'll measure it with plastigage and check the bearings/journals before I put the engine in the car. I opened it to check the cylinder walls and make sure nothing looked out of the ordinary/damaged. I don't know what made the previous owner take the engine out of the car before selling it to me, I think he said he was planning on restoring it.
Out of curiosity, how familiar are you with engines? It would be hard to see anything "out of the ordinary" unless you're very familiar with Z-car engines. If you are familiar with engines, I would expect that you're also familiar with Plastigage.

If you remove the main caps, do you know how to mark them, then orient the bearing caps correctly when re-installing and torque them? Putting the bearing caps back on incorrectly could possibly cause crankshaft damage.

I suggest that you are about to get in a lot deeper than you think. You may want to stop and think this over.

Regardless, I wouldn't put anything back together without using the manual step by step.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #8 ·
No I'm not familiar with these engines, I've only ever worked on v8s with my dad and this is something new haha. By out of the ordinary I meant like general damage. The previous owner suggested looking at the main bearings so I'm looking to check those and put it back together using the manuals I have
 

·
Administrator
1983 280ZX Turbo
Joined
·
2,459 Posts
No I'm not familiar with these engines, I've only ever worked on v8s with my dad and this is something new haha. By out of the ordinary I meant like general damage. The previous owner suggested looking at the main bearings so I'm looking to check those and put it back together using the manuals I have
OK, just make darn sure to mark EACH bearing cap before you remove it so it can go back in the right place and in the right orientation. Do not turn them 180 degrees. make sure you know which side is left and right and maintain that orientation. Of course, correct torque when installing is critical. It would also be a good idea to put some assembly lube on the bearing surfaces before re-installing the bearing caps.

Other than looking for sludge or broken parts in the pan, I still have no idea at all what you were looking for. If nothing's broken, there's nothing to see down there. If the engine had OK oil pressure while running, I certainly would not remove any bearing caps, I'd just put the pan back on.
 

·
Registered
Joined
·
1,286 Posts
Knock knock! Or spin the bearing. "The previous owner suggested looking at the main bearings." "I noticed it's blued around where the connecting rods and the crankshaft meet." I hope you got a good deal on it.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #12 ·
I've never seen the engine run since I bought the car with the engine/trans/front suspension removed (they dropped the engine and trans from the bottom). I'm gonna check the bearings and journals with plastigage and if it's all in spec I'll put it back together and put it in the car. Thanks for the tips about marking the bearings.
We're gonna be checking the compression too
 

·
Administrator
1983 280ZX Turbo
Joined
·
2,459 Posts
I've never seen the engine run since I bought the car with the engine/trans/front suspension removed (they dropped the engine and trans from the bottom). I'm gonna check the bearings and journals with plastigage and if it's all in spec I'll put it back together and put it in the car. Thanks for the tips about marking the bearings.
We're gonna be checking the compression too
You may be able to check compression with the pan off, as long as you only rotate it a few times. Otherwise you'll need to finish the bottom end and re-fill with oil before checking compression. If the previous owner thought you should check bearings, there's probably a reason.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #14 ·
Yes all I took off was the pan and I put it back on last weekend, we're gonna be hopefully mating the engine and trans this weekend and compression testing it, maybe tomorrow
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #15 ·
I emailed ATK support and asked them if they had any information on the serial number with no response, I was hoping they would have some info about what was done/when. Looks like full engine was rebuilt not long ago though
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #17 ·
update we checked the main bearings/journals with plastigage and they seem to be really new, gap is usually about .001-.0015". We're gonna test the oil pressure and compression tomorrow. so I guess the bluing is fine? crankshaft looked great too
 

·
Administrator
1983 280ZX Turbo
Joined
·
2,459 Posts
update we checked the main bearings/journals with plastigage and they seem to be really new, gap is usually about .001-.0015". We're gonna test the oil pressure and compression tomorrow. so I guess the bluing is fine? crankshaft looked great too
That's encouraging. Does the service manual give a gap spec?
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #20 ·
Yes we checked with the Hanes manual and it was well within spec, I think the numbers in that manual match what Dave said. We checked compression today and it was well within spec too, the engine seems totally fine and probably wasn't used much after it was rebuilt. We're gonna put in new gaskets to replace the ones we opened, new fuel hoses since mine are cracking, new injector o-rings and new timing chain guides since I heard those sometimes break.
 
1 - 20 of 20 Posts
Top