My 1971 521

[d.p]

Which would make sense because I charged the battery and my cig lighter voltage meter read 12.5 exactly. 
 

Still waiting on builder to measure everything so will wait to order rings.  

[Stoffregen Motorsports]

I spray the bores and the pistons with WD40 then drive 'em home.

[banzai510(hainz)]

well whats is the voltage while driving? 14 with nothing on.

If less than 13.5 while driving I say alternator is bad!

[d.p]

11 hours ago, banzai510(hainz) said:

well whats is the voltage while driving? 14 with nothing on.

If less than 13.5 while driving I say alternator is bad!

 

Yeah that's what I am saying its less than that, like hovering around 12 give or take. 

[banzai510(hainz)]

Yep its bad

[thisismatt]

I don't know why you want to settle on such a POS alternator in such a nice truck. If it's not putting out about 13.5 then it's not maintaining your battery

[d.p]

3 minutes ago, thisismatt said:

I don't know why you want to settle on such a POS alternator in such a nice truck. If it's not putting out about 13.5 then it's not maintaining your battery

 

I don't lol.  Will throw my original one back on until I can source another big boy alt.  

[datzenmike]

You need about 2 volts more than the battery from the alternator. Consider it a 2 volt 'push' putting current into it.

 

You used to be able to buy the brushes for the old style. I've pulled them out of bad alternators to keep a good one going. No one does that today, they buy a $45 POS from Oryliegh's.

 

[d.p]

The alternator that came on my truck when I bought it kept popping a fuse so I took it to one of those small alternator shops to have it serviced.  They charged me $45 and it still popped the fuses after.  So I went and bought one from Pep Boys or some shit and its lasted me 3 years.  Go figure? 

[banzai510(hainz)]

I remember that one popping fuses. I had a Alt that was popping my solid state volt regs.  I went to a another alt and put a Jap mechanical volt reg back in my 521. My Power selct Rockauto and JapanBosched mard VR still going strong for 2/ 3 yrs now

 

I love the new GM CS series alternators but they just too big for a 521. I stuck with the small stock size one

[thisismatt]

You can put in an alt from a d21, minivan, etc etc. Heck, I have an Eagle Talon alt in mine 😁

[d.p]

Can someone tell me if this is right?

 

On the 510 alternator  :

E ground black wire

A yellow wire goes to starter/battery

L shaped connector self explanatory

 

TIA

Edited September 23, 2019 by d.p

[d.p]

Ah fuck it I just threw my original alternator back on and no charge light.  

[mrbigtanker]

20 minutes ago, d.p said:

Ah fuck it I just threw my original alternator back on and no charge light.  

Funny how that happens. External regulated?

[d.p]

Yeah external.  I had a NOS external regulator that I tried swapping before going back to my original alt but no joy. I think that’s bigger alt is just bad.  
 

Fuck me for changing alternators on these trucks. Not fun at all. 

 

[mrbigtanker]

55 minutes ago, d.p said:

Yeah external.  I had a NOS external regulator that I tried swapping before going back to my original alt but no joy. I think that’s bigger alt is just bad.  
 

Fuck me for changing alternators on these trucks. Not fun at all. 

 

You should have no problem. Mine was a pain in the ass. 

[banzai510(hainz)]

Plug the T connector back in?

ck the fuse or reseat fuse 

[d.p]

Old alternator is back in. Voltage meter is reading around 14.x when driving around now.  13.x w/headlights on and a little less with the high beams. No ignition light either. 

 

[banzai510(hainz)]

Great you got it

[d.p]

Machine shop called with an update on my l20b and said he thinks the block would be fine with just a clean and bore.   Hasn't got to the head yet but did share his measurements on the bottom end.

Cylinders at 3.389

Pistons 3.385 - 3.386

 

He said standard 1mm over would be 3.386 and that it looks to him like it was bored .0003 over on purpose.  Is that typical?  

[mainer311]

I think you mean .003" clearance. Sounds perfectly fine to me, and highly depends on piston material/expansion. 

[datzenmike]

 

 

Nissan pistons are mass produced and range from 84.985mm to 85.035mm. Same with the bore. Nothing is perfect so a bore that is slightly oversize is matched with a slightly over size piston to get the correct side clearances. Less is thrown away. Always measure replacement pistons and bore and hone to match them as no two will be and exact oversize.

[d.p]

@mainer311 you're right I added an extra zero, my bad.  He did say the only thing he could do would be to go 1.5mm over but I told him I had no interest in that.  Pistons are cast if that helps.   He also said once he has everything done he can see about ordering piston rings for me as well.  But other than that he said the bottom end looked good.  

[datzenmike]

Maximum side clearance is 0.001" to 0.002" so 0.003" is already over. Honing will only make wider. I would go 1.5mm if there are over size pistons out there for this. Again measure the pistons and bore to match them to get the correct side clearances.

[d.p]

@datzenmike

 

Did you read what I originally posted? The cylinders mic'd at 3.389 and the pistons anywhere from 3.385 - 3.389 IIRC.  He also said that he thought it would all work fine.  I got no interest in going 1.5mm over either so if I can make what I have work I will.