Short Block Health Check?

[atkinson40]

Camrys are both finally running sweet. 

 

Civic is up on tree stumps and I should be finished R&R rings and rod bearings over the next couple of weeks.

 

Finally maybe get time to get back to the 620 which has piss poor compression.

 

Friday it rained here so the JY is 25% off.  Perfect day for a field trip.  Pulled a short block that still had the cross hatch marks on the cylinders from being worked on.

 

Going to pull the pistons and check bores, pistons, rings and rod bearings.  Anything else I'm missing?

 

The block had an ATK rebuild sticker on it.  I've posted some images.  Looks like they were running Mexican gas from the looks of the tops of the pistons??

 

 

 

 

Can I use steel wool to clean up the cylinders.

 

Also in the first image there is a ??plug?? Right behind the alternator bracket.  My old motor doesn't have it.  Anybody know what this is?

 

Both motors are L18.  Is there any hickups using the head from the old motor on this L18?

 

Thanks Kevin

[datzenmike]

Probably a plug behind bracket for the front dip stick tube (not used) so look on the under inside to confirm.

 

Alternator bracket has three bolt to hold to block. Also oil filter boss usually does not have the 4 holes around it like that. I wonder if this is a JDM import motor?

 

No your L18 head (likely an A87) will be fine. Was there a head on this motor???? If JDM it may have had a closed chamber.

[ggzilla]

Worn out engines often have nice cross-hatches, so that does not mean much. More important is checking for a cylinder ridge. If your fingernail doesn't catch on the top of the cylinder that's good. If it does, time for a ridge-break, re-hone and new rings.

 

No need to pull the pistons to check any of that. You can measure the bores after rotating the piston down. You can remove the bearing caps and use Plastigauge to check the clearances. Do a visual on the top Ring gap. If it is within spec, chances are the rings are OK.

 

Any rust is bad. I would think steel wool would scratch the hone finish. Very fine sandpaper might work (cover the bottom of cylinder first, then use oil soaked rag afterward until it comes out clean). I think you will need to re-hone and new rings, but not sure. Few people sand the rust off without doing new rings, so there's little data -- it might work out just fine to sand it?

[Stoffregen Motorsports]

I know I'm being really strict here, but I used to be an engine builder, so...

 

There are a few things I see in the pics you posted. First off is the shiny polished spot about an inch down the bore. This is indicative of a very worn out ring set. The rust is/can be a problem and I would recommend buying the right hone so you can clean up the bore and give it a good cross hatch. Summit racing sells these hones for about $30. And if you're a car guy you will use this again, so it's worth it. http://www.summitracing.com/search/part-type/cylinder-hone-tools/cylinder-hone-tool-type/brush?keyword=hone

 

Honing will take care of the "shiny spot" but it may not take care of the rust. If the rust pits are deep enough (after you hone it) to feel with your fingernail then, technically, you should go have it power honed or bored, but that doesn't mean you need to. I wouldn't expect to see a ridge at the top of the bores as Nissan used a high nickel content in their casting which would make them far superior to something like a small Chevy block, and ridges are rare in a Nissan.

 

The rings could be shot, but a hone on the cylinders will revitalize the rings to an extent, by giving them something to bite on. The rings also could be stuck, by grit and grime that gather in the ring lands. If you don't plan on taking the pistons out, run the hone down the hone as far as you can. I use a rhythm of one second per down-up motion. In other words, with a battery powered drill on low speed, lube the bore with WD40 and run the hone down and up in the time it takes to say "one one thousand". That should give the proper cross hatch. Do this 10 or so times per bore.

 

You should pull a rod cap and look at a bearing to see if they are healthy. Try the number 3 rod as it gets the most abuse. Also you should deck the top of the block with sandpaper wrapped around a 1x2, using WD40, of course. And if you can, chase the head bolt holes and blow out the grit with air.

 

Now check that the block isn't cracked, usually around one of the center bolt holes. If it is, it can be fixed, but probably isn't worth it.

 

Another cleanup procedure that helps with old rings comes after you get it running. If you haven't pulled the pistons and cleaned behind the rings, you can do it by adding a quart of ATF to your oil. ATF contains detergents that will work the grit out. But it may smoke while the ATF is in the motor, so do it for 500 miles or so and then change it out. Be sure to use a new Fram filter too!!! (insert Fram joke here)

 

These are all "cheater" methods of getting a short block up and running quickly, and it's always a gamble that you could miss something, like a galley plug or a broken ring, etc. But if you're on a budget, I'd try this first.

[Stoffregen Motorsports]

It wouldn't let me post a pic, so if you don't know what a hone looks like, try the link.
http://i1007.photobucket.com/albums/af197/MattStoffregen/Datsun/Flex_Hone.jpg

 

fixed

[ggzilla]

This is a ball-hone. Ratsun is having problems with pics last few days - it depends on what methods you use. Some are broken others are not.

 

 

Ball-hone is superior to the traditional stone-hone I hear.

[atkinson40]

Probably a plug behind bracket for the front dip stick tube (not used) so look on the under inside to confirm.

 

Alternator bracket has three bolt to hold to block. Also oil filter boss usually does not have the 4 holes around it like that. I wonder if this is a JDM import motor?

 

No your L18 head (likely an A87) will be fine. Was there a head on this motor???? If JDM it may have had a closed chamber.

Thanks Mike

 

The plugged hole has threads on the under inside.

 

Dunno if it is a JDM motor.  It had a ATK rebuild sticker on it.

 

I found out about this motor from another 620 owner I meet at the swap meet.  He'd taken the head for his 620 and when I told him about my poor compression, he told me about this motor in the JY.

 

What is a closed chamber?  Thanks

 

Worn out engines often have nice cross-hatches, so that does not mean much. More important is checking for a cylinder ridge. If your fingernail doesn't catch on the top of the cylinder that's good. If it does, time for a ridge-break, re-hone and new rings.

 

No need to pull the pistons to check any of that. You can measure the bores after rotating the piston down. You can remove the bearing caps and use Plastigauge to check the clearances. Do a visual on the top Ring gap. If it is within spec, chances are the rings are OK.

 

Any rust is bad. I would think steel wool would scratch the hone finish. Very fine sandpaper might work (cover the bottom of cylinder first, then use oil soaked rag afterward until it comes out clean). I think you will need to re-hone and new rings, but not sure. Few people sand the rust off without doing new rings, so there's little data -- it might work out just fine to sand it?

 

Thanks GGzilla

 

I measured the bores to be 3.365".  Does this tell me anything?

 

There is no ridge at all. Nada,  Zip,

 

I used some "Bar Keepers Friend" to remove the rust.  I can't feel any pitting with my finger.  Bores still have a bit of staining, but no pits.

 

I'll check the ring gap and then pull the pistons to check the rings.  I want to make sure there's no rust on them.

[atkinson40]

I know I'm being really strict here, but I used to be an engine builder, so...

 

There are a few things I see in the pics you posted. First off is the shiny polished spot about an inch down the bore. This is indicative of a very worn out ring set. The rust is/can be a problem and I would recommend buying the right hone so you can clean up the bore and give it a good cross hatch. Summit racing sells these hones for about $30. And if you're a car guy you will use this again, so it's worth it. http://www.summitracing.com/search/part-type/cylinder-hone-tools/cylinder-hone-tool-type/brush?keyword=hone

 

Honing will take care of the "shiny spot" but it may not take care of the rust. If the rust pits are deep enough (after you hone it) to feel with your fingernail then, technically, you should go have it power honed or bored, but that doesn't mean you need to. I wouldn't expect to see a ridge at the top of the bores as Nissan used a high nickel content in their casting which would make them far superior to something like a small Chevy block, and ridges are rare in a Nissan.

 

The rings could be shot, but a hone on the cylinders will revitalize the rings to an extent, by giving them something to bite on. The rings also could be stuck, by grit and grime that gather in the ring lands. If you don't plan on taking the pistons out, run the hone down the hone as far as you can. I use a rhythm of one second per down-up motion. In other words, with a battery powered drill on low speed, lube the bore with WD40 and run the hone down and up in the time it takes to say "one one thousand". That should give the proper cross hatch. Do this 10 or so times per bore.

 

You should pull a rod cap and look at a bearing to see if they are healthy. Try the number 3 rod as it gets the most abuse. Also you should deck the top of the block with sandpaper wrapped around a 1x2, using WD40, of course. And if you can, chase the head bolt holes and blow out the grit with air.

 

Now check that the block isn't cracked, usually around one of the center bolt holes. If it is, it can be fixed, but probably isn't worth it.

 

Another cleanup procedure that helps with old rings comes after you get it running. If you haven't pulled the pistons and cleaned behind the rings, you can do it by adding a quart of ATF to your oil. ATF contains detergents that will work the grit out. But it may smoke while the ATF is in the motor, so do it for 500 miles or so and then change it out. Be sure to use a new Fram filter too!!! (insert Fram joke here)

 

These are all "cheater" methods of getting a short block up and running quickly, and it's always a gamble that you could miss something, like a galley plug or a broken ring, etc. But if you're on a budget, I'd try this first.

 

Thanks SM

 

I'll pull the pistons one by one and use your post as a guide.  Here are the cylinders after using "Bar Keeper's Friend"  to clean up the rust a bit.  No pits.

 

 

 

[ggzilla]

I measured the bores to be 3.365". Does this tell me anything?

------------

 

Nope. It requires more measurements than that, at very specific places. Any repair manual specific for an L20B will have the procedure. You want to check for out-of-round, for taper wear, and (if you are going to double-check the previous work) measure piston to bore clearance.

[atkinson40]

Took some more pics to see if it helps identify the engine,  When I removed the oil pan, I found a big ol' hunk of timing chain guide laying in the bottom.  I mean big.  Like four inches long.  Kinda chewed up.  So the guide somehow got chewed up and replaced w/o the oil pan being cleaned?  I dunno.

 

 

 

 

[ggzilla]

That's an L18 short block, without a doubt.

[atkinson40]

------------

 

Nope. It requires more measurements than that, at very specific places. Any repair manual specific for an L20B will have the procedure. You want to check for out-of-round, for taper wear, and (if you are going to double-check the previous work) measure piston to bore clearance.

 

 

Thanks GGzilla.

 

I'll follow the book.  I just thought maybe that measurement would tell if it's been over bored.  It seems a little big for the nominal and a bit small for the over bore given in the book.  The ridge was removed by someone.  You can see where it was removed.  I just don't know if it's been rebored,  Thanks kevin

[atkinson40]

That's an L18 short block, without a doubt.

 

 

Thanks GGzilla

 

Mike was saying something about holes in the oil filter mount and 2 vs 3 holes for the alternator bracket.  I thought some more pictures would help track down it's origin.  Thanks Kevin

[ggzilla]

3.365 inch = 85.24 mm. Remember all original specifications are in mm.

 

Stock L18 piston diameter is 85 mm (tolerance of about + or - .020 mm). Next oversize would be 85.5 mm, so you don't have that.

 

It might have custom pistons, because that is too large for the standard pistons. Or maybe they just honed it too far ... haha.

[datzenmike]

85mm bore can be L18 or L20B but from the look of the timing area it's an L18. The engine size is stamped on the block behind the dipstick tube.

 

The two bolt hole alternator mount is odd, the extra plugged dip stick hole, so is the oil filter boss and the block vent hole is usually to the side not upward. We had the L18 for just over a year around '74 but I still say this is a later 70s? casting of the L18 block perhaps for the 810/910 and imported in the '80s.

[Stoffregen Motorsports]

That must be an import motor, at least it's one I've never seen. It has the "L18" stamp on the angled boss in the middle, and the crank isn't fully counterweighted. I hate to say it, but the main reason I like the L18 is because they (normally) have a fully counterweighted crank. There goes half the reason I'd run one.

 

On the other hand, it looks like a pretty clean motor. I bet it doesn't need a thing.

[Stoffregen Motorsports]

Oh yeah, check the crank end play to make sure the center main bearing is ok. If it's more than .010" or so it's worn, but a really worn out thrust bearing would be in the "obvious" category. Your thrust clearance on the center main is important because it helps control the oil pressure and flow.

[atkinson40]

Thanks everyone.

 

I pulled the number three piston and measured the top of the piston above the top ring to be 3.345. 

 

I measured it below the rings around the middle of the piston to be 3.362.   Which is correct?

 

Also does this now tell me what it's been bored to?

 

I also popped the top ring and measured the end gap.  It was .018 in.  I think this is OK.

 

Thanks Kevin

 

PS:  What disadvantage is not having a "fully counterweighted crank"  and what is a "closed chamber".  Thanks Kevin

[DanielC]

Cold pistons are not round.  they expand more in one direction as they heat up.   I wold also be more concerned with the diameter below the ring lands.  Measure the piston diameter below the ring lands, 90 degrees to then piston pin.

 

I think .014 to .021 is a good gap for the top ring, .012 to .020 for the second ring, and .012 to .035 for the oil ring.

Check the ring gap just below the ridge on the top of the bore, and about 3.5 inches down in the cylinder and compare the difference.  About 1/3 of the difference is the amount of cylinder wall taper.

 

A fully counterweighted crankshaft is better at extremely high RPM.   Like continuous operating above 5000 RPM.

 

A closed chamber head gives you higher compression.  Can give you a little more power.  You may end up having to run premium gas.

[Stoffregen Motorsports]

Thanks everyone.

 

I pulled the number three piston and measured the top of the piston above the top ring to be 3.345. 

 

I measured it below the rings around the middle of the piston to be 3.362.   Which is correct?

 

Also does this now tell me what it's been bored to?

 

I also popped the top ring and measured the end gap.  It was .018 in.  I think this is OK.

 

Thanks Kevin

 

PS:  What disadvantage is not having a "fully counterweighted crank"  and what is a "closed chamber".  Thanks Kevin

The ring gap seems a bit large. A standard rule is .004" of gap for every inch of bore, so .004 x 3.345 = .0134" gap.

 

A "closed chamber" is referring to the shape and size of the combustion chamber in the cylinder head. They generally produce a higher compression ratio than "open chamber" heads. When used with the properly shaped piston, each style of combustion chamber has it's advantages, but for Datsun purposes, the closed chamber heads a generally more desirable because they (generally) also have larger valves and better ports...generally. Maybe someone else can post a pic of the two. For some reason, my Photobucket pics don't seem to be uploading lately.

 

The fully counterweighted crank helps the engine rev without excessive amounts of harmonic vibration. L-18's and L-20B's are the only 4 cylinder L's that came with fully counterweighted cranks.

 

85mm / 25.4 = 3.346" = standard bore

[datsunaholic]

That's a very late block. JDM, or Crate engine, based on a Z18 casting (you can see the boss where the NAPS-Z serial number would be).  You'll need an L20B PCV tube if it doesn't already have the tube, since a normal L18 one won't work.

[datzenmike]

An open chamber head is just that... it's open above the entire area of the piston top.

 

A closed chamber head has a combustion chamber that is smaller than the piston diameter and contains a quench or pinch area(s) where the piston at TDC is only the head gasket thickness away from the head surface. As the pistom approaches TDC the air trapped in this pinch area is violently squeazed out into the open part of the combustion chamber. This is beneficial as it promotes swirl and turbulence. This in turn homogenizes the air and fuel as it burns. A homogenized mixture burns more completely reducing lean (hot) and over rich (cool) areas in the combustion chamber.

 

All things equal, a closed chamber head will ping less than an open chamber head. Closed chamber heads don't alway have larger valves.

[atkinson40]

Thanks Everybody.

 

I found I was looking at the wrong set of numbers in the book for bore/piston size. :blush:

 

I now see that the L18 should be 3.35/3.345.  I think this engine may be OK. 

 

I need to perfect my measuring technique.  I'll measure multiple times to practice and satisfy myself it's all OK.

 

Rod bearings are cheap.  I'm just going to replace them.

 

Thanks  Kevin

[ggzilla]

I would measure the piston and the bore where the service manual indicates.

 

Rod bearings almost never wear out. They are only usually damaged by low oil. Measure them with $4 plastiguage. Don't fix what ain't broken.

[Stoffregen Motorsports]

I would measure the piston and the bore where the service manual indicates.

 

Rod bearings almost never wear out. They are only usually damaged by low oil. Measure them with $4 plastiguage. Don't fix what ain't broken.

 

If they are showhing the second or third layer, replace them. I see them a lot showing through to the second layer. Now days, it's hard to even find tri-metal bearings. Aluminum bearings suck.