1978 280z Engine Rebuild project

[Zed Head]

Cool.  A broken crank bearing, damaged damper keyway on the crank nose, and a cracked piston.  Keep looking, there's probably more.  Looks like the PO kept driving when he should have stopped.

Looked back through the thread and see the title about 1978, and the comment about the spray bar instead of the oil holes in the cam lobes.  But, in picture number 1, you have square exhaust ports.  That's 1975-76 in the North American market.  That's not a 1978 280Z engine from around here.  You said you thought maybe it came from Japan, why?  I think that I've read that the square ports and even carburetors stuck around much longer in the Asia markets.  EFI and round ports with liners were emissions driven things.  The Aussies might know for sure about square ports 280Z's.

And we've all kind of overlooked the basics of getting the code from the side of the head.  It's probably an N42 (75-76), not an N47 (77-80).

Regardless, that engine is looking less and less like a good candidate for a rebuild.  Why chance it?

[Mark Maras]

  I agree with Zed Head. Engine was ran long after problems began and probably ran until it finally died. I don't know what good used engines cost in Texas but here in the NW they are a dime a dozen. Well maybe not that cheap but they are plentiful and can be purchased for $200.00- $500.00. If you start with a good used engine, you'll be able to refresh it for a lot less money (reusing pistons, rods, crank. cam. etc. and probably get a good balancer with it.) than using an engine that every part is in question including the block.  IMHO, Peace of mind is a big factor in this decision. You could throw a lot of money into this engine and still have those nagging doubts about its' longevity.

[Zed Head]

Just curious - what do the rod caps look like?  I've seen pictures of some that turn blue from overheating.  Sometimes it's the remains of the ones that blew a hole in the side of the block.

[txvepr]

I have secured a new crank, and by my meter measures it appears to be within spec of my Datsun motor rebuilding book.

The question I have is a chicken or egg type question.

Plastigauge. I understand how to do the measurements, but with the old bearings, and a new crankshaft, should I just buy all new bearings first? or do the measurements with the old bearings in there anyway? or what. Is what they would indicate with the original bearings not even relevent now with the new crank.

Make sense?

As to motors available, they are not a dime a dozen around here, Neither the dime nor the dozen. But I got the best deal I could get at this time.

According to Monroe's book, L28's built up to March 1977 had the oil spray bars. After they went to through the cam. And up to 1977 they had square ports. 

[Zed Head]

26 minutes ago, txvepr said:

According to Monroe's book, L28's built up to March 1977 had the oil spray bars. After they went to through the cam. And up to 1977 they had square ports. 

You have square so you're 77 or pre-77, right?

Regardless, you want to focus on the head and block codes.  N42 and N42 is probably what you have.  Exhaust manifolds or headers are designed for square or "round" (not really round but the liners are).  You don't want to buy 1978 (N47) exhaust manifold or headers for your square port head.

I think that you match the bearings to your crank measurements.  Then confirm that your measurements were good with plastigauge.  I'm not an engine builder though.  Carry on...

[siteunseen]

All you need to know about the head you can find out in 5 minutes.  Look above the front two plugs for the code N42 or N47, 1 minute.  Remove the valve cover and look at the valvetrain for a spray bar and holes in the cam, 4 minutes.  My early '77 that was built in 9/'76 has a N47 head with a spray bar and oiler cam, round exhaust ports with liners.

Nissan did some weird things between September 1976 and September 1977, it is often referred to as a "changeover year" to meet the USA's emission standards.

  

[Patcon]

If I were this deep into an engine, I would have the crank crack checked, polished and the assembly balanced. Before they polish they will mic it to see if it will be in spec after polishing, otherwise they will turn it. If it gets turned then you will need thicker bearings. Plastigage is not very exact but I use it because it gets you close if you use it properly. My machine shop normally helps with a lot of these details many times I get them to supply the bearings...

[txvepr]

Its been a while, having to take other paths thru the year, but I am finally back on track getting this block done. 

Block was honed, baked, and checked for true. Got the paint from MSA for the right color.

 

[txvepr]

I got the entire stainless steel bolt kit, gaskets, timing kit, clutch, etc... from ZCAR Depot. They are a great supplier and worked with me when we had a minor problem with the chain guide kit. See pic 

 

For some reason the left side chain guide was the wrong size, you can see the imprint the timing cover housing made when I tried to install it , the guide had too much flange sticking out. ZCAR Depot sent me the correct part right away and it's all good now.   My old one compared with the newer one below.

 

Edited December 18, 2016 by txvepr

[txvepr]

Chain guides in. Dizzy shaft timed...

Pumps on. 

[txvepr]

So this thing is giving me trouble. The oil pickup tube seems to stick out too far 'aft' and hits the oil pan so that I cannot align the screw holes for the bolts. It has been a long time since I removed this , but I don't remember it being jammed in there at the time. Is there any way this tube is a S130 version? Does anyone have a comparison photo of the 2 to show me? Thanks.

 

Edited December 18, 2016 by txvepr

[siteunseen]

Found this through google/images.  Maybe you can figure it out by comparing yours?

That Tom Monroe book is the best!

ZX and Z oil pickup comparison. ZX is on the left and is a bit longer to clear the baffles in the AZCar cast oil pan.

 

Edited December 18, 2016 by siteunseen