My 1971 521

[d.p]

Can I measure it with a caliper?  Or a ruler? 

[Crashtd420]

Stock bore is 85.... I'm not sure what the 100 mark means but if it is bored over it could be 1.00mm which would make the bores 86.... or the 100 could be 2.5 mm making it 87.5..... 

Keep that in mind.... especially if you wanna hone and re ring or go up 1 more piston size...

[Crashtd420]

5 minutes ago, d.p said:

Can I measure it with a caliper?  Or a ruler? 

Caliper would be better

[banzai510(hainz)]

10 minutes ago, d.p said:

 

Not sure what you are asking here?  Marks left from the rings on the cylinder walls?   If that is what you are asking I can see them but can't feel them with my finger nail.    

 

Yes if you cant feel them then its OK

 

Durapro is sold in Austrialia  but is made in Japan Why nobody sells it here in USA is beyond me. Looks just like a Nissan gasket. They make a Graphite and a composition one also.

You can buy a Nissan gasket from the dealer or where ever But I don't know whats the size dia wise exactly and if you bore is oversize.  Maybe Im overacting.

 

 

Baz is like 75 years old, Don't know if he really even works there anymore. I got mine like 10-15years ago. He might give a deal if you buy multiple headgaskets plus you got to deal with shipping FEDEX and customs maybe.

 

The Nissan 87mm dried up years ago and only the 88.8mm is left.

 

Felpro front cover set are fine. and valvecover gaskets I love.

[wayno]

Just because you cannot feel something doesn't mean things are good to go, you have to look at other stuff also, I see vertical lines/scratches on 3 sides of the cylinder in this photo below, I cannot see the other 4th side, do you see any cross hatching between the vertical lines?

At first my guess of the ring lines was that the piston in that cylinder was in that spot for a long time, I see the same lines in the cylinder next to it in the same spot so expect these are #2 and #3 cylinders, do #1 and #4 cylinders have the same ring marks at the top of the cylinder like #2 and #3?

Everything appears to be black also, too me this means it was running really rich.

[d.p]

Bore is 85.89mm give or take at the top of the cylinder.  

 

Dunno what 1 and or 4 look like but the plugs were black when I pulled them.  Soot/carbon black not oil wet black.  Will take a closer look at the cylinder walls in a little bit. 

 

  

Edited July 26, 2019 by d.p

[Crashtd420]

37 minutes ago, d.p said:

Bore is 85.89mm give or take at the top of the cylinder.  

 

Dunno what 1 and or 4 look like but the plugs were black when I pulled them.  Soot/carbon black not oil wet black.  Will take a closer look at the cylinder walls in a little bit. 

 

  

So most likely thats1mm over bore pistons at 86mm then.... 

If you cant feel any of those mark you might be able to just hone and re ring.... just make sure those bores are not out of round.... 

 

You definitely gonna have to get some leaner jets in those carbs if you wanna run them....

[datzenmike]

Engine may have been run on short trips with the choke on or maybe idle a bit rich but not driven enough to burn it off. Valve guide seals may have rotted off or just worn out not controlling the oil going down the valve stems. Engine could have been over filled with oil even. Could be lots of things causing the black.

[d.p]

Doesn’t really matter why it’s like that. What matters is what I do now with it now.  

 

Tearing down the bottom end now and got the pistons out and all but the rear main cap.  I got the center one out using a timing cover bolt and leverage but the same trick for the rear just bent the timing cover bolt. The mfer will not give it up.  Anyone got a trick to it?? 

[d.p]

I got it out.  Ended up using a long ass crow bar to get the rear main out.  Got the bottom end torn apart and every cylinder has ring marks identical to 2 & 3 that I posted above.  I don't see any cross hatching but do see vertical lines but can't feel anything with my finger nail.  At this point I am going to take the head and the block to the machine shop and see what they say.  Crash says I should buy new bearings, can anyone recommend some?  

 

I measured a piston an it came out to 85.38MM give or take.  

 

 

 

 

Edited July 27, 2019 by d.p

[banzai510(hainz)]

OK I'm out of this thread.

This motor was most likey fine for the amount of use youll be driving it. maybe 2-3k a year if that.

A head gasket would have had this rolling .

Your going to get the bores cked and the builder will say new pistons cause it oblong otherwise we wont warenetee it ect........Otherwise you could have just bought a motor done.

this is going to be $800 on up.  The doing the head which most likely is fine also with the carbs

 

 

Clevite bearing are fine.  USA Japan are good. STD size fill be fine unless its gouged.  My 2 cranks were stock size and they had 200k miles on them

[datzenmike]

On 7/27/2019 at 1:39 PM, d.p said:

 

I measured a piston an it came out to 85.38MM give or take. 

 

You zero the caliper? 😄

 

It's VERY expensive to produce exactly 85mm pistons and a perfect 85.025mm bore without throwing away a lot of parts. Stock L20B pistons range from 84.985mm to 85.035mm and the block bore 85mm to 85.050mm. Pistons are measured and fitted to the measured bores to achieve the 0.001 to 0.025mm to 0.045mm or one to two thou. A smallish piston is mated to a matching 'smallish' bore. An 85.38mm piston would never fit a stock bore.

 

Nissan sells 0.5mm and 1.0mm oversize pistons. An 85.35mm piston is almost exactly a 0.015" oversize aftermarket. So it has been rebuilt before.

[d.p]

Dang Hainz don't take it personal.  And no I couldn't buy an engine for that much because there aren't any around here.  In the 3 years I have owned this truck I have see 2 L20bs for sale, one completely torn down for $300 and this one for $100.    And who cares how much I spend on it, its learning experience for me and I can afford it.   

 

Yes I zero'd out the caliper and just measured it again.  Pistons are stamped with '100' too, dunno what that means but I think Stoffgren mentioned something about that meaning it being bored 1mm over? 

 

[d.p]

I also measured #4 cylinder and it came out to 85.46mm give or take.  It's a bitch holding the caliper and trying to take a picture at the same time too.  

 

 

[banzai510(hainz)]

Yeah I just don't see a need for you to go thru with all this work. I remember the tensioner issue with your mechanic and it was a simple fix. Now your going full in on something that don't need to be done.

I bought a L16 for like 100 $ back in the day. Guy said it was bad. I installed it and it ran.It ran for 20K miles untill I ran it out of oil and then put oil in it and still ran It was a oil burner after that. I stripped the car down and I took the motor apart and find out the  main oil feed bearing was installedon the opposite side where the oil feed hole bearing was on the opposite side and it still ran. Also the also the head didn't have the water holes for the intake. In winter I would go in higher elevation places and the carb would freeze up. I couldn't figure it out till later. But otherwise motor was fine till I actually ran it out of oil then it was a 1 quart every 3 days motor till I pulled it

[Charlie69]

Buy you an inside micrometer.  You can not measure cylinder taper with your calipers.

[d.p]

Hainz, give it a rest man.  Me taking the head off my l16 was the first time I ever did anything to a motor that wasn't a bolt-on affair.  So I would say it went pretty well outside of the tensioner popping out and the shops incompetence.  My truck has been running great since then so I figure its a win regardless of how I got to this point.  And the engine is apart so we can talk about why I should have just ran it OR we can talk about the best way to put it back together, I prefer the latter.  

 

I looked at those inside micrometers on Amazon and they are $150.  Seems a lot to just measure the bore of a cylinder when I can have the machine shop do it for me.   Unless someone got a link to a cheaper one is it really necessary? 

 

 

[Stoffregen Motorsports]

Too many cooks in this kitchen.

 

If it were my engine, I would hone it with a ball hone, install new rings and bearings, have the head done and call it good.

 

The lines in the bores are probably nothing. If you can't feel them with your fingernail, there's almost no chance of them being a problem. If the piston skirts are not scuffed (like the engine was overheating and the piston aluminum started to melt), then those lines are likely nothing.

 

Clean the pistons with scotch brite and a ring land tool. Send the crank out to be mag'd and polished. Get a set of Hastings sprayed chrome rings and throw the thing together yourself.

 

I know, I'm just adding to the number of cooks in the kitchen, but I have also built a couple hundred of these engines. I earned the knowledge by actually doing, instead of bench racing.

[Greaser2]

Why chrome rings instead of moly?

[datzenmike]

Cast iron rings would be better for a 'hone and ring' job would it not? Chrome or molly for a re-bored block with exceptionally round, non taper bore with a perfect finish. I've used chrome rings on a 'hone and ring' rebuild and 15K later it was back to where it was before.

[mainer311]

4 hours ago, Stoffregen Motorsports said:

If it were my engine, I would hone it with a ball hone, install new rings and bearings, have the head done and call it good.

 

^-THIS. Except I would also get new pistons to be safe.

 

Also, if you can feel a ridge at the top of the bore, get yourself a ridge reamer and knock the ridge off before installing new rings and/or pistons.

 

I’ve always used cast iron rings.

[d.p]

 

Take me probably 7-10 years to get 15k on my truck.  

 

The book I bought said to use a ridge reamer before taking the pistons out but I couldn’t feel anything so I just pushed them out and they came out fine.  Why would I want to get new pistons?  I mean is it bad to reuse my existing ones if the cylinders will take them? 

 

Anyways engine builder can hot tank, hone and deck the block.  Will measure pistons vs cylinder to ensure clearances are right so I can reuse the pistons. Willing to disassemble head, clean it, mill if needed, valve job and reassemble the head for $450 all in.  

 

I would need to come up with rings and bearings.  I don’t know shit about what rings and or bearings to get or what not to get.   Assuming my block is 1mm over I would need rings to match that piston..so something like this in 1.00?  

 

https://apaengineering.net/HastingsCatalog/Home/partdetail/213

Edited July 30, 2019 by d.p

[d.p]

Oh and I took this pic of the wedge with the cover off, I thought it was cool because it never made sense to me before seeing it in person.

 

[mainer311]

If pistons are in good shape, you can reuse them. Hopefully you remembered to mark them 1 through 4. If not, try to figure out what cylinders they all came from.

 

Rings come oversized and will need to be filed for the correct ring gap.

[d.p]

12 minutes ago, mainer311 said:

If pistons are in good shape, you can reuse them. Hopefully you remembered to mark them 1 through 4. If not, try to figure out what cylinders they all came from.

 

Rings come oversized and will need to be filed for the correct ring gap.

 

Pistons and rods were already marked 1-4 in the right order.  Easy peezy lemon squeezy.  Ill talk to the machine shop

about rings and see what he says.