Silky's L20B Goon Build

[Silky_Johnson]

Well Ratsun, it's time to start a build thread for my L20B bottom end rebuild (I think). Have I ever rebuilt an engine? No. Can I do it with the help of Ratsun? I'm 95% sure of it! The purpose of this thread is to:

 

1). Get good advice before I screw something up (for instance: "I would oil the $#!% out of that cam right before start up" - Hainz);

 

2). Provide good documentation (oics) of the process for future novices like myself (With these engines getting older and older, I figure more and more of us will eventually need to do some major work to the block unless we just start throwing away our L-series engines); and

 

3). Make a fool of myself by asking lots of dumb questions.

 

 

 

If you don't like to read, scroll down to my questions in bold below. I'm trying to be thorough and avoid miscommunications.

 

 

 

To start off, I have a 1971 510 Wagon. This is my car:

 

 

 

I have since taken off the windshield sticker. When I bought the car, it came with an L18, A87 Peanut head with a .480 lift cam, dual PHH40 Mikuni Carbs, stock exhaust manifold with a 2.25 pipe all the way back to a Flowmaster muffler, an early 280zx 5-speed transmission, and a roadster pressure plate. I have been fighting to get it to run better since I bought it, but I just can't get it to wake up like I think it should. A lot of guys hear what I have and are impressed, but it was running like doodoo. I wasn't impressed, and I was honestly surprised to see so many "good" modifications done.

 

To make a long story short, after researching here and trying everything possible to tune and correct ignition timing, fuel mixture, and so on, I decided to tear into the engine. I started with the head because it seemed easiest. I also needed to get a head gasket change under my belt. http://community.rat...ead-gasket/��If you don't want to waste your time, the result is that the head is good. In fact it's pretty dang good, with aftermarket springs, retainers, lash pads, etc. The only thing left on the head to do is to correct the wipe pattern, and then it's good to go.

 

Yes, I should have done a compression test before I ripped the head off, but I was lazy. I'm trying to avoid similar mishaps in the future by consulting Ratsun first. Anyway, I suspected low compression in the #1 cylinder of my L18, and since the head came back good, I assume that the block needs work. I thought I solved my problems by buying an L20B block to swap in.

 

 

QUESTIONS:

 

 

Is the block in need of a rebuild?

 

I was cleaning, painting, and getting the new L20B block ready when I decided to take a tip from Wayno. He says to try wiggling the pistons, because you should not be able to detect any movement. Justly, DatzenMike says that piston/block clearance is only .001-.002. I wiggled them, and the #1 cylinder has some substantial play. My guess is that I can wiggle it back and forth at least .015. At this point I'm assuming the cylinder is deformed. The piston wiggles front and back, but not side to side, so I think the cylinder is oval-shaped. Am I screwed? DatzenMike advised me to measure the cylinder, which I agree is the right first step. He gave good instructions to measure the cylinder for oval/egg-shaped wear, as well as taper in the cylinder.

 

I've been researching, and it looks like I need a micrometer to measure the cylinder? I have digital calipers, but I can't measure 3 inches down the cylinder with those. What should I buy? Or is there a cheap and dirty (Ratsun) way to do this.

 

 

Assuming the block needs a rebuild (I don't see how it wouldn't) where should I start?

 

I have been reading through the "How to Keep Your Datsun Alive" book, as it seems to be more thorough and easier to understand than others. Upon recommendation, I'll read through the others as well. My tentative plan, assuming that the block is bad and that it isn't too far gone, is to bore out the cylinders for either .030 or .020 oversize pistons. I plan on just replacing the pistons with otherwise stock L20B pistons to keep the compression ratio in a livable range for pump gas. I just want a good drivable motor.

 

From what I understand, I need to purchase pistons before I take the block to a machine shop so that the machinist can bore out the cylinders to exactly the size of each piston. Am I wrong?

 

 

Stripping the block for the machinist:

 

 

If someone wants to give me a step by step tutorial on what to do, have ats! From what I understand, I need to check main and rod bearing clearances with a plastigauge upon tear down. I understand how the plastigauge works, but I guess I'm not sure what I will do with the results. Is it possible that the old bearings will go right back in? Should I immediately toss out the old bearings and put new bearings in? Will the results of the plastigauge test tell me if I need oversize/undersize bearings to go back in? The reason I ask is because I need to know when and what bearing I need to buy, if any. I would like to start getting the block torn down soon so that I can get it to the machine shop.

 

Thanks to everyone for their advice. That is what this thread is for. I have recruited Laecaon for his in-person help if I need it. He will be handsomely rewarded with German brew. If Rustina510 wants to hang out, he can also have a drink or two.

[datsundash]

Wow, im so tired that I cant comprehend all of the questions. I can however help you with the machinist question. Strip the block sompletely BARE, everything goes, even the baffle and screen. Send the main caps with the block so the machinist can chuck the block in the mill for surfacing. be sure to label them so you can put them back in order.

[Sealik]

Not sure what you paid for the L20B.....but it sounds like it needs a 'little work'

That said....since you were boring and replacing the pistons, I would be tempted to find a Z22 block.

Bore to 89mm...Z24 or Ka pistons.......LZ23

There's no replacement for displacement...........

[bananahamuck]

Plastigage shows if there`s to much or not enough clearance ,, you only change bearing size if you machine crank..The bearings you have now should have marks on them labeled if they are over size or not..

 

I label and tag and ziplock bag everthing,, the less remembering i have to do the better off i am it seems.

 

i also have a spiral notebook to write all the readings down in also.. but i`m like you strickly garage builder no real machine shop experiance..

[Silky_Johnson]

Not sure what you paid for the L20B.....but it sounds like it needs a 'little work'

That said....since you were boring and replacing the pistons, I would be tempted to find a Z22 block.

Bore to 89mm...Z24 or Ka pistons.......LZ23

There's no replacement for displacement...........

 

Yeah, I didn't pay a lot for the L20B. No big deal there.

 

Yes, I am totally tempted to do a Frankenstein build, but I think that would put me over the edge on expenses. I need to work with what I've got and get my car running again. I already miss driving it too much!

 

To sum up my questions, I need to figure out if the block is bad (which I think is an unequivocal yes), and I need to know what I need to watch out for when I tear the block down. I don't want to run into any "you should've" situations later.

[Silky_Johnson]

Plastigage shows if there`s to much or not enough clearance ,, you only change bearing size if you machine crank..The bearings you have now should have marks on them labeled if they are over size or not..

 

I label and tag and ziplock bag everthing,, the less remembering i have to do the better off i am it seems.

 

i also have a spiral notebook to write all the readings down in also.. but i`m like you strickly garage builder no real machine shop experiance..

 

So here's where the dumb questions start. What do I do if the plastigauge shows too little or too much clearance?

 

Assuming I don't have to machine the crank, then I'll just go with whatever bearing sizes I find in there (probably standard). I'm just trying to get my ducks in a row before I start the tear down this weekend.

[Laecaon]

I checked all my bearings in my L18. All came back within the threshold for what was safe, but they were nearly worn out. I figured, new std unworn bearings had to have less clearance, and sure enough they tightened up the clearances, but still within acceptable.

 

Really, I think you should just get new bearings, they arent that expensive. But you do need to plastigauge to check to see if you need your crank machined, as you might have a taper on the journals which is not good.

 

I would find access to a FSM for the L20b so you can check specs, that is where I found what I needed to do to the L18.

 

I think olddatsuns.com has some FSM's you might find helpful.

[Silky_Johnson]

I think olddatsuns.com has some FSM's you might find helpful.

 

Good word. This is just pure gold: http://www.davidcmurphy.com/olddat/data/Model_L20b_Engine.pdf

[banzai510(hainz)]

Man thats a cool wagoon!!!!!!!!!!!

 

I usually just have the lower block dont by the machinist so you dont need to worry about plastic gage ect...

If the caps are not scared mostly likly stock bearing will be fine

[Draker]

This is what you need to do. If you are going to build an engine you are going to need some precision measuring tools.. micrometer, telescoping gauges, dial/electric bore gauge, plasti-gauges. You don't need all of them but you will need some. The other option is to take all your engine parts to a machine shop and have them do all the measuring have them tell you what you need done. Both options cost money but it will be up to you to determine what is more feasible with your budget.

 

You are going to need to fully disassemble the block and keep tabs on exactly where each part came from so that when you are putting it back together, all the parts return to the exact same place you removed it and in the same orientation.

 

Things you will need to measure:

-Uniformity of the block deck. Unless you've got a precision straight edge, I would let a machinist do this. Often it's free!

-You are going to need to check the block for cracks, again, machinist.

-You are going to need to measure the cylinder bores for multiple things including to see if they are too large or out of round. If there is a ring ridge, you will need to remove that with a ridge reamer. This is where the telescoping gauges and micrometers come into play. Also you are going to need a FSM to tell you what measurements are acceptable. You can also use a dial/electronic bore gauge for this. If you find that they are out of spec you will need to have them bored out and put oversize pistons in. You don't need to have the pistons as long as they are new or known good.

-Bearing clearances for crank and rods, plastigauges will tell you the clearances. These are good but are honestly not the most percision instrument for measuring. They work good though. Again you will need a FSM to tell you what is acceptable. Also you need to measure the thrust bearing clearance. After all you don't want that crank to walk around in the journals. If you find your bearing clearance to be excessive you but the crank journals are within spec, you can just get new bearings and then measure again.

 

There are a bunch more measurements you will need to take. You will need to measure absolutely everything. That's where the FSM comes into play. It will walk you though each step of the way telling you what are the acceptable limits. If you don't have the tools to measure everything, then it's probably best just to take the pieces to a machinist and pay them to measure the block, crank, pistons, rods. If you have access to the tools, then by all means measure away!

[Silky_Johnson]

Okay, the Factory Service Manual (FSM) is awesome. It eliminated a lot of the "stupid questions" part of my build thread. I studied it over and over again and dove into my build.

 

I decided to just overbore, so I ordered in new L20B .030'' oversize pistons, which is the biggest size I could get from Rockauto. I bought the Beck Arnley pistons and they came in an ancient looking box with a sticker saying "Made in Japan." That made me happy.

 

I got my courage up on Saturday to do the tear down. Once I got into it, it was no big deal. After memorizing the FSM, it was very easy to understand.

 

 

The plastigage worked well in my opinion.

 

 

 

That is a picture of the bearing clearance for the rod bearings. They are all about the same and within spec (if my calculations/methods are right). The tolerances for rod bearings are between .0010'' and .0022 on an L20B. Using the plastigage and torquing the bolts down to 40 lbs, they all came in at around .0015.

 

 

 

The bearings look good, and they're standard size, so new standard bearings are going back in.

 

The tolerances for main bearings are between .0008'' and .0024'' Based on the plastigage, again torqued down to 40 lbs, I came up with a little larger than .0020'', but not .0030'' across the board.

 

 

It looks like the mains are on the high side of spec, if not just slightly out. I'm going to throw new standard size main bearings in and measure the clearances when that happens. Jacob told me he ran into a similar situation with his L19 build, and he ended up putting new bearings in and new bearings brought him back down to spec. I'm hoping for and expecting the same result here.

 

So, by the end of Saturday, I got the block torn down for the machine shop. The picture shows the block without the main caps. I put the main caps back on before taking the block down to the shop, because they want them on there. The shop closed at 5:00 and I got there right before closing.

 

 

I even got the freeze plugs out.

 

 

 

 

For the freeze plugs, I watched a video on Youtube:

 

http://www.youtube.com/watch?v=Cru1X9hbZ20 This

 

This technique worked pretty well for all of the plugs except for the one at the front of the block. There isn't enough space behind the plug to pound it in, so I just worked at it. I ended up drilling a hole in the plug, rotating it, and some other things. I eventually worked the rim down on one side enough to bite onto it. At that point, it just pried out.

 

I ordered new bearings and freeze plugs from the machine shop for a decent price, and that way I don't have to wait for shipping. The guy at the shop said they get their stuff from "Rock" brand. He said it's Japanese stuff that they use in all of their import engine builds. I did a little research online, and it looks like Rock is the same as DNJ on Rockauto.com. I'm getting brass freeze plugs so they don't corrode.

 

All in all, I am very happy with the service of Clackamas Auto Parts in Oregon City (no, I don't work for them). They are boring and honing the cylinders for $20 per cylinder, pressing the piston pins into the rods for $10 per pin, and cleaning the block for $50. $170 for labor ain't bad, and they do good work. I'm picking up the block tonight, so assembly will begin this weekend. If anybody has any tips or tricks on engine assembly, feel free to chime in. I already know to use WAY TOO MUCH ENGINE ASSEMBLY GREASE. I saw that stressed in another thread. Likewise, I need to track down a piston ring compressor and ring pliers. The pliers seem so simple that even Harbor Freight should be able to make a functioning pair? Anybody have experience with these? I've heard bad things about the Harbor Freight ring compressors, so I think I'll stay away from those. The machine shop might let me borrow a ring compressor tool...

[Tristin]

I'm going to be watching this... I should be following along this path here soon (hopefully anyway).

[Sealik]

 

To sum up my questions, I need to figure out if the block is bad (which I think is an unequivocal yes), and I need to know what I need to watch out for when I tear the block down. I don't want to run into any "you should've" situations later.

 

I would be tempted to have the block magnafluxed

[Silky_Johnson]

I would be tempted to have the block magnafluxed

 

To look for cracks? I am on a pretty tight budget. How much should I expect to spend?

 

At first I thought you were joking, but then I looked it up. My mind went straight to flux capacitor... In a Datsun, you would only have to get that sucker up to 58 for time travel. Passed that point, the car would be shaking too much and the electrical connections for the 1.21 gigawatts wouldn't work. Another problem would be the PO's hack job of installing the flux capacitor...

[Sealik]

To look for cracks? I am on a pretty tight budget. How much should I expect to spend?

 

At first I thought you were joking, but then I looked it up. My mind went straight to flux capacitor... In a Datsun, you would only have to get that sucker up to 58 for time travel. Passed that point, the car would be shaking too much and the electrical connections for the 1.21 gigawatts wouldn't work. Another problem would be the PO's hack job of installing the flux capacitor...

 

58....????

That's it??? Hmmmmmm...thought it was a tad more. :D

 

Yes...to find cracks

I think it was around 60 bucks here to magnaflux the block.....can't find my bill

Talk to your machinist about that.....

Cheap 'insurance', especially if you don't know the history of the block???

[Eagle_Adam]

im also watching this thread, thanx for all the pics and questions!

[Silky_Johnson]

58....????

That's it??? Hmmmmmm...thought it was a tad more. :D

 

Haha! Actually my car shakes (shook) like a mofo during idle and low RPMs. The smoothest it ran was around 55 - 65 on the freeway. When I got above 75, the engine sounded like it was screaming at me, but that could be a result of the 2.25 exhaust with the Flowmaster. I'm hoping to eradicate the shakes with the new motor, but it could just be a lumpy cam... And as soon as I can financially recover from the engine build, I want to put a resonator in the exhaust to take the rasp out.

[Eagle_Adam]

ive ridden in some dattos with huge cams and they dont shake like your describing. - but thats for another thread :D

[banzai510(hainz)]

just look at the top center water passage hole . the 2 headbolt threads will be next to it(water passage in center) if not cracked most like good block.

 

I wouldnt even waited my time palstic gage the crank looked good already.

 

make sure to gap the rings.PS, I never dont this myself.

 

 

get rid of the flowmaster!

[jrock4224]

well shit i coulda just sold u the bare block for a hundered bucks....glad to see u are enjoying it...wheres the pyt shot

 

 

love the goon though....second fav color..

[Silky_Johnson]

get rid of the flowmaster!

 

I plan on it eventually. Gotta get the goon running first. What do you suggest in place of the Flowmaster? This is probably going to open up another Fram-inspired raging rant, but what's wrong with Flowmaster?

 

I'm good on gapping the rings. It seems like it will take a while, but easy nonetheless. I'll post pictures of the process for other newbs.

 

For cracks in the block, I already found two hairline cracks in the typical place around the middle head bolt hole, between the bolt hole and the two water passages. Typical. They are very, VERY small. I had to look pretty hard to see them after cleaning off the surface. JRock, did you find any oil in the coolant or vice versa when you pulled the engine? My inclination is to just run it and see if there's a problem. I found this quote from Mike:

 

Block cracks are over rated. It's not a crank or connecting rod. As long as there are no coolant leaks. A minor hairline indicates a stressed area has relieved itself just like an earthquake. Once relieved the area is seasoned. If a shop looks hard enough they'll find cracks on any block. Big deal, most cracked blocks are out there being driven daily with no problems at all. A good gasket, clean surfaces and proper torque procedure will cover it and you'll never have a problem with it.

[jrock4224]

no it was all good thats why i went ahead the vally and fluids all looked pretty good

[banzai510(hainz)]

YOu know I got a 80K milage block and it had a crack.

Im sure motor was fine.

But by block builder said replace it. I will assume he couldbt guareentee the block if soemthing happened.

 

It really comes down to you and do you spend the money boring out a block??????

 

some how flowmasters have tha anoying sound thru a 4 cylinder s with just a weber downdraft. Im sure its better if sidedrafts. Also the stock steel ones rot out from the inside vains. water/condensation collect right there.They make Satinless ones now cause of this.

The Cherokee kids have them and everyDeer in the woods hear them!!!!!

If you have already 2 or 2.25 inch pip I would find a stock type queit muffler that fits in the spot.

Mybe Off a Landrover discovery or whatever.newer car in the junkyard.

 

maybe try a resonator like you said if you think that will help.

[Silky_Johnson]

no it was all good thats why i went ahead the vally and fluids all looked pretty good

 

That's what I thought. I'm just going to button it all up and call it good.

[Laecaon]

I rented the autozone ring compressor, just make sure its tight, and put the piston in swiftly. I had to retry a few time on the first piston.

 

As for the ring tool, I just installed the rings by hand. Easy does it, and try to keep the rings level.

 

For motor assembly, I used STP oil additive. Its looks like honey, and is as slow to move as honey too. I honestly thing there are a ton of options for this. Part of my reason to do this was just to make sure there was a good amount of ZDDP in the oil, because I was only using some basic castrol for the first 50 miles.