L28 Rebuild? Swap? Leave Alone?

[Ptero]

I've got a spare engine which came with the Z that I purchased several years back.  The spare was an engine that was used for "racing" but there were no details on the internals or what kind of racing.  I'm looking for a project on the Z and an excuse to crack open an engine to get some hands on learning.

 

Looking for opinions on what to do. (slow day at work)

-swap it in and see how it runs

-open it up to see if it's bone stock or not

-tear it down for no reason besides putting it all back together for fun and learning

 

Side note, currently have a running L28 in the car now and have never pulled an engine apart.

[Pop's Z]

Ptero,

 

You seem to have an itch to learn about rebuilds. So..."just do it". My 2 cents is to tear the spare motor down, figure out what's what with it as far as a "racing engine" goes, and do a complete rebuild. These motors are not complicated, parts are readily available, and there are several publications to advise you along your journey...Tom Monroe's "How to Rebuild Your Nissan & Datsun OHC Engine", and Frank Honsowetz's "How to Modify Your Nissan & Datsun  OHC Engine". These publications are readily available. Also there several members here who are Canadians, eh, who can help you with hands-on help if needed. "Blue", and "Zcars" are two of several of the Canadian Zedders.

 

You say you've never done this. Short story: When I was a younger guy I had a VW beetle on which I needed to have some work done. I was introduced to a book called "How to Fix Your VW for the Complete Idiot". With that book in hand and a factory service manual I learned how to do all my maintenance even to the point of successfully, completely rebuilding my motor. I didn't know doodely about mechanical stuff then. Since then I have successfully maintained a blue-water cruising sailboat and a twin diesel powerboat. I have done all the work on my Zed with the exception of paint and seat upholstery. So, if I can do it, so can you. We here on this site can help keep your chin up when the going gets rough, all these things you contemplate have been done previously by our members here. It's not rocket science. Good luck and keep us informed as to your progress.

 

Cheers, Mike

[Zed Head]

If the engine is complete enough you could hook it up on the garage floor and start it to see how it sounds.  Might tell you something about condition.  As far as tear-down, there are different levels.  You can learn a lot just by looking at spark plugs and the cam shaft, and the crankshaft.  If things look in good shape, you might decide to leave it alone and swap it in.  

 

I like to take things apart too, but things almost always break in progress.  And, even the simple stuff will cost you substantial money.  Head gasket, head bolts, intake/exhaust gaskets, etc.  Just offering the "don't do it" view.  You might end up with a pile of parts.

[siteunseen]

I'm on the side of "do it".  I bought that Tom Monroe book, read it about 3 times then rebuilt my 1st car motor all by myself and it turned out perfect.  One of the best feelings I've ever had, although there was a lot of anxiety and "while I'm this far why not do this...".  I could have easily done a good job for under $1,000 but I bought a new exhaust and header and a few other "while I'm this far why not do this...".

 

If you'll post some pictures you will get a lot more info/opinions.

 

Cliff

[rossiz]

my dad taught me some of the most important things about wrenching when i was a kid. i remember watching him work on an old automatic toaster to fix the little spring mechanism that makes the bread pop up when its done. he took it apart on the kitchen table, on the previous days newspaper and taught me that if you learn how to take something apart really carefully you can always put it back together correctly. 

• go slowly, take your time, think as you go. it's easy to get excited and rip things apart and wind up with a dizzying pile of parts. never trust your memory - take notes, take pictures, label things, keep them in piles of associated components.
• keep like fasteners together - in most cases they will serve the same purpose, and use an organizing system to keep track of where they came from (ziploc bags and a sharpie are perfect).
• look carefully at wear marks where one part meets another - this will give you clues as to how the parts go back together.
• think about what parts do - if you understand what a lock washer, compression washer, spacer, etc. does it makes it easier to know the order that these things go back on.
• a motor seems complicated as a whole, but when you break it down into systems it gets very logical. think of charging system, electrical accessories, ignition system, fuel system, lubrication, valve train, timing, etc. and it will make sense.
• ask questions, read up, get help when you feel that nagging doubt in your gut. when something doesn't seem right, it probably isn't. don't force parts together unless they're supposed to be, as in a press-fit component.
• when you're done and you have an "extra" part or two, never, ever throw it away and assume it's not needed. don't ask how i know this...

the advantage you have with a spare engine is that you have no urgency since your car is currently running. if you don't rush you'll be fine.

looking forward to the build thread!

[Ptero]

Wow, I wasn't expecting these well thought out responses.  Thanks everyone!  I'm leaning towards doing a tear down of the engine as I like learning new things.

 

I have both "How to Rebuild Your Nissan & Datsun OHC Engine", and Frank Honsowetz's "How to Modify Your Nissan & Datsun  OHC Engine".  I've flipped through them but at the time it was just theory as I wasn't working on an engine at the time.  I'll dig these out when I'm home.

 

The spare engine also has a 4 speed attached to it so I suppose I could pull the starter off my running car and do a compression test on this engine before I pull it apart.  I'd do a leak down test but I don't have the tool.

[madkaw]

Good thought on putting the starter on. It's about impossible to turn over by hand fast enough to do a good test . You should be able to tell somewhat the condition with a compression test. Might take note of the cam timing also.

[rossiz]

if that lump has been sitting for a while, be sure to pull the valve cover and pour some fresh oil over the cam & rockers to avoid damage from cranking dry...

[Ptero]

Took a bit of a closer look at the engine last night.  It's an L28 with an N42 head.  I managed to run a dry and wet compression test but the results were inconsistent at times.  I could test a cylinder 3 times in a row and each test would be a little higher than the last.

 

Ran a dry test twice.  Tested all cylinders and then tested them all again because I was seeing inconsistencies.

 

Cylinder #

1 - 105 dry, 120 dry, 130 wet

2 - 140 dry, 143 dry, 157 wet

3 - 122 dry, 120 dry, 145 wet

4 - 98 dry, 123 dry, 135 wet

5 - 40 dry, 60 dry, 75 wet

6 - 90 dry, 92 dry, 110 wet

 

Given the numbers I'm getting, I would say there are some issues that need to be looked at.

 

Any because everyone likes pictures...

 

 

 

 

 

[240260280z]

you could loosen all valve lashes quick and dirty (just back off the adjusters a full turn in ). This will make sure the valves seat at maximum and break off any carbon when you do another compression test. It will give you a better idea of what is going on.

[Zed Head]

You could have surface rust in the cylinders also, hindering sealing.  I was thinking that a spin would reveal any clanking or crunching, not really useful for a compression test on an old cold engine.  Plus that looks like newer reduction geared starter, they turn slow.  Did you prop the carbs open?  That can affect pressure readings.  Makes it harder to draw air in.

 

Also, you have a picture of the notch and groove but the damper marks aren't at zero.  And which block is it, N42 or F54?  Won't tell you for sure, but if it's F54 the PO might have left the flat-top pistons in (assuming it's an NA F54).  That would raise the CR.  

 

And, that looks like an L24 damper (multiple timing marks) with an L28 timing tab.  So the damper's not stock.  And it has a mechanical fuel pump, not stock for a US market L28.

 

You're going to take it apart anyway, I can tell.  Just a few things to think about.

[Ptero]

you could loosen all valve lashes quick and dirty (just back off the adjusters a full turn in ). This will make sure the valves seat at maximum and break off any carbon when you do another compression test. It will give you a better idea of what is going on.

 

I'll give that a shot and see if there is any change.

 

You could have surface rust in the cylinders also, hindering sealing.  I was thinking that a spin would reveal any clanking or crunching, not really useful for a compression test on an old cold engine.  Plus that looks like newer reduction geared starter, they turn slow.  Did you prop the carbs open?  That can affect pressure readings.  Makes it harder to draw air in.

 

Also, you have a picture of the notch and groove but the damper marks aren't at zero.  And which block is it, N42 or F54?  Won't tell you for sure, but if it's F54 the PO might have left the flat-top pistons in (assuming it's an NA F54).  That would raise the CR.  

 

And, that looks like an L24 damper (multiple timing marks) with an L28 timing tab.  So the damper's not stock.  And it has a mechanical fuel pump, not stock for a US market L28.

 

You're going to take it apart anyway, I can tell.  Just a few things to think about.

 

The intake is barely even attached so I'm pretty sure it has sufficient air but I'll double check.

 

The block is also N42.

 

Haha, yeah I'll probably take it apart but opinions and suggestions are always welcome from people who have done this all before.  Thanks for the extra info about the other parts!  I would have never known.