Short Block Health Check?

[ggzilla]

Nissan sells the original spec tri-metal rod bearings.

[datzenmike]

My old '68 dime was worn down in the rods and mains. It was a long time ago but I seem to remember it being a copper color? Were they copper? or have a copper layer under the babbitt?

[datsunaholic]

Babbit, copper, steel.  You REALLY don't want to be down to the steel.  Nearly every engine I've had apart had spots of copper showing, even as low as 75,000 miles on a factory engine.  Usually the upper shells on the rods and the lower shells (in the caps) of the mains, with most wear on the mains (which surprised me at the time).  But at 250,000, they weren't much worse.  I never did plastigage the old bearings to see how bad they were, but they weren't knocking or even have terminally bad oil pressure, but since I had 'em apart putting in new was a good idea.

[ggzilla]

Good idea? The new ones will look just the same after 1000 miles. If the clearances are right, don't fix what aint broke.

 

Datsun mains are not the tri-metal, so they will bed-in somewhat differently.

[datsunaholic]

I always replace bearings.  The 75,000 mile one wasn't knocking, but had run for at least 5 minutes with 3/4 gallon of water in the sump when the head gasket blew.  It was, total milkshake.  I had considered just doing a couple flushes, but then proceeded to drop the timing chain into the pan.  At that point, pulling the engine and just redoing everything seemed like a good idea,  and I had all summer to do it since I was just waiting for the days to report to boot camp wind down.  Since the truck was "dead" there wasn't anything I could do to make it worse.  So with nothing more than a Haynes manual I rebuilt the engine from the bearings up.  Learning experience.

 

I learned the art of measuring old parts much later.  The military taught me engine repair, but it taught me wrong.  Military almost always just replaced internal parts.  If it's apart, replace.  Mainly because 18, 19 year olds usually damage things taking them apart.  Working on WWII Allison V1710s taught me about tolerances and re-use.  Because when you can't get replacement parts, you HAVE to reuse.

[datzenmike]

Back in the '70s I figured the clearances were fine when factory built so replacing the bearings with new ones has to be better than the used ones in it. Today I would plastigage just to be safe but one time I could only afford bearings. My 521 mains were really worn down into the copper. It ran just fine but I removed the L16 from my retired dime and thought the mainsy were also worn, were slightly better. I used them.

[atkinson40]

I apologize in advance for my dumb questions.  I haven't pulled an engine before.

 

Found a new toy on CL for $50.  Carolina 3 ton.  Figure that should be enough to hoist engine and tranny.

 

 

Can I pull the engine and tranny out together?   I hate laying on my back lining them up. 

 

Pull the radiator and fan.  Unhook the muffler.  Unbolt the driveshaft and remove the tranny crossbar.  Remove the hood. 

 

Where do I hook on the motor?  Will I be able to lift it up and out and clear the front grill?

 

Thanks kevin

[hobbes_the_cat]

  Carolina 3 ton.  Figure that should be enough to hoist engine and tranny.  YES

 

 

 

Can I pull the engine and tranny out together?   I hate laying on my back lining them up.  YES

 

Pull the radiator and fan.  Unhook the muffler.  Unbolt the driveshaft and remove the tranny crossbar.  Remove the hood. 

 

Where do I hook on the motor? If your factory hooks are not there anymore I use a rear manifold stud and the ground bolt on the front of the head.  

Will I be able to lift it up and out and clear the front grill? YES but I pull the grill just in case it slips or bounces on the way out

[ggzilla]

Carolina 3-ton. Can pick up the entire truck weight. Of a Ford 3/4 ton. Which is good cause that's what often happens when you try to pull engine and tranny together. Just take it very slow, and be prepare to juggle the lift points (for engine and trans, usually you put the rope/chain farther back). You may have to raise the truck up if it is lowered.

[atkinson40]

The top rings have the number 50 stamped on it.  What does this mean please?  Thanks kevin

[datzenmike]

Could indicate that they are 0.5mm oversize if metric. 0.050" oversize if standard.

 

0.5mm would be about 0.020"

[ggzilla]

.50 stamped on the top of the piston means 0.50 mm oversize (there is no .050 inch oversize as that would be a custom piston). The L18 piston-to-bore clearance is .025-.045 clearance. The piston tolerance is -0.035 to +.015 mm diameter. Yet the difference between .020 inch and .50 mm is already .008 mm, so it will already be halfway out of spec if you fit inch pistons instead of metric. Might work, might not.

 

You can confirm the piston size by measuring the pistons with an inexpensive dial caliper which cost about $25.

[DanielC]

"The L18 piston-to-bore clearance is .025-.045 clearance."

I am pretty sure that is mm, not inches.

[ggzilla]

Yes, the factory dimensions are metric for L-series engines.

[Stoffregen Motorsports]

"The L18 piston-to-bore clearance is .025-.045 clearance."

I am pretty sure that is mm, not inches.

 

.025mm would be about .001"

.045mm would be about .0018"

 

Are you sure the top ring says .050? Sometimes they are marked as "top" or "up" so you know which side goes up. Sometimes simply with a dot.

 

What color are the top rings? Silver/chrome or black?

[datzenmike]

Piston to bore clearances are  0.001"- 0.018" on an L20B.

[atkinson40]

Thanks Everyone,

 

Ya'll are going to challenge my photography abilities taking images off shiny objects. :blush:

 

Ain't no period in front of the "50".  Nada,  Zip.  There's an "R" on the other side.

 

 

 

 

Thanks Kevin

[ggzilla]

Very good photo.

 

Does that caliper rear 3.365 inches? That is 85.471 mm ... which is an 85.5 (.50 oversize) piston less .029 mm tolerance. Within specification.

[atkinson40]

Very good photo.

 

Does that caliper rear 3.365 inches? That is 85.471 mm ... which is an 85.5 (.50 oversize) piston less .029 mm tolerance. Within specification.

 

Thanks GGzilla

 

I knew the degree in photography would be useful for something. :)

 

Yes the caliper does read 3.365 inches.  So the "50" on the ring must mean .50 oversize?

 

Thanks Kevin

[atkinson40]

Old engine is out.  Flipped it and see the following scape marks on the counter balance. 

 

I can't see where its hitting and I see similiar marks on other counter balances.

 

What did I do wrong when I put this one back together?  Don't want to do it again on the new engine. :blush:

 

 

This is the new engine L20B PCV tube hole that datsunaholic was talking about. 

 

Anybody have a picture of what it should look like so I can snag it on my next JY scavenger hunt?

 

 

Thanks Kevin

[ggzilla]

Scrape marks? Where do you see that?

 

 

The original reported symptoms were: "the 620 which has piss poor compression"

[datzenmike]

That's normal machining from the manufacturer.

 

 

 

This is also very interesting. The block is stamped on the left side while all North Am L series are just above the dipstick near the Starter. Newer Z series have this boss on the left side.

 

 

 

 

 

This is an L20B block vent pipe. The silvery rubber hose connects to the PCV valve.

[ggzilla]

So both old and replacment L18 motors are using the new block casting (same as Z-series engines). What are the chances of that?

 

Since L18 was only used in USA one year, but in Japan up into the 80s, it makes sense that most L18s here now are japan import motors.

[datzenmike]

I sure does. Used in Europe in the late 70s maybe into 80s. They were also made in South Africa in the 90s? but were strange looking. Different oil filter boss motor mount locations... can't find my picture of it. It was mentioned in a post from the guy from Portugal.

[atkinson40]

Scrape marks? Where do you see that?

 

 

The original reported symptoms were: "the 620 which has piss poor compression"

 

On the side of the big lobe sticking up.  Actually there are some shavings stuck to the edge that were not cleaned off after the machining. :no:  That's why I thought those striations were there because I didn't reassemble something correct.

 

Yes, this is the original 620/L18 with piss poor compression.  I measured the bore on what I thought was the worst bore and it measures 3.345".  My brain is hurting from going between metric and inches, but I only have inches micrometer.  I think this is within the .2mm wear limit?

 

I want to figure out why it had poor compression before I put the head on the other engine. The head was rebuilt by a reputable rebuider...I hope that's OK.

That's normal machining from the manufacturer.

 

 

 

This is also very interesting. The block is stamped on the left side while all North Am L series are just above the dipstick near the Starter. Newer Z series have this boss on the left side.

 

 

 

 

 

This is an L20B block vent pipe. The silvery rubber hose connects to the PCV valve.

 

Thanks Mike.  I might end up fabricating that if I can't find a JY score.  Kevin

 

My list is growing, need to wait for half price day at the JY:

 

1. Seats for the 620.  Bench makes my back ache.  Interweb search hasn't come up with anything obvious that will lean back far enough.  Just gonna have to measure distance from peddles to headrest while it's leaned back, and see if it will fit in the 620 space and I'll fit in the seat. I'm 6'1" and don't take well to sitting up straight.

 

2. A hitch that I can put on a camry or civic and mount a bike rack to.  I'm tired of that strap contraption that hooks to the trunk.