Pretty in primer. A ‘69 521.

[datzenmike]

Closed chamber L head but what one? No coolant holes for the intake. W53 maybe?

[Slow Loris]

A87 that came on my L18 when I got my truck. (Not sure if they came together from birth but that’s how I got them) Just a little cleaner than last time I posted its picture. 

[datzenmike]

The A87 was used on all L18s but in open chamber design and with coolant holes for the intake. Probably was replaced in the late '70 early '80s with an import head which was cheaper than a valve job.

 

The A87 was the head used on the first year L20B which was only on the '74 610. For '75 all L20Bs uses the U67. For '78 and on all L20Bs used the W58 head.  

[Slow Loris]

My piston ring end gaps for top ring are all coming in too big. Whats that mean? I am working with 85.5mm fresh bores, cast iron rings, and seeing gaps at 0.024” whereas was expecting ideal gappage at 3.366 x 0.004 =0.0135”

 

 

Edited March 15 by Slow Loris

[datzenmike]

 Wrong rings

[Slow Loris]

Darn it rock auto. 

[Crashtd420]

On 3/14/2026 at 9:50 PM, Slow Loris said:

My piston ring end gaps for top ring are all coming in too big. Whats that mean? I am working with 85.5mm fresh bores, cast iron rings, and seeing gaps at 0.024” whereas was expecting ideal gappage at 3.366 x 0.004 =0.0135”

 

 

Out of curiosity...

What's you method for checking?

[Slow Loris]

Pushing ring down in bore with top of piston as squarely as I can, and feeler gauging the gap. How’s that sound? 

[Crashtd420]

11 hours ago, Slow Loris said:

Pushing ring down in bore with top of piston as squarely as I can, and feeler gauging the gap. How’s that sound? 

Sounds correct to me...

[Slow Loris]

Mmmk I’m checking my butt wipe err cam lobe wipe rocker arm geometry here and wondering what you see here:

 

 

is this kinda streakiness a sign that my valve lash is just a bit loose? Not quite as “wiped” as I was expecting…

[Slow Loris]

 

they look a little better after a few more revolutions I guess. Old rocker arm maybe?

[Slow Loris]

Never mind the ramen, this head bolt look ok to reuse?

[datzenmike]

In very general terms the bolt must be at least 1 to 1.5 times it's width in thread engagement. The damaged threads were likely not engaged into the block so were open to corrosion. Looks like you have plenty of engagement. 

[RoadRace]

14 hours ago, Slow Loris said:

 

they look a little better after a few more revolutions I guess. Old rocker arm maybe?

the flat spot on the rocker to the right is a concern, the pitting on the rocker to the left is also a concern. while the pattern on the right is closer to centered, the risk to damage the rocker pad and cam is there. 

[banzai510(hainz)]

looks like they will PASS to me. the right one has the line across it but alot do.

save this(its for  Pinto motor ut same set up. Mercedes also  datsun is 1.48(1.5ratio)

[Slow Loris]

7 hours ago, datzenmike said:

Looks like you have plenty of engagement. 

thank you glad to hear it, looked liked those ugly threads were not ever engaged so, that makes sense they were just hangin out.

 

7 hours ago, RoadRace said:

the pitting on the rocker

I see the pitting. To the extent that these rockers (and cam?) ought to be rehabbed or replaced?

 

It’s not a fancy or even reground cam in there, and not a performance build, but surely don’t want to eat it or be counterproductive to all the other work put into the motor.

 

3 hours ago, banzai510(hainz) said:

save this

got it thank you boss

 

 

 

[Slow Loris]

On 3/14/2026 at 8:25 PM, datzenmike said:

Wrong rings

well I ordered another set, same manufacturer and size, and they fit the same—gap too big, maybe a hair less at .023. So I think they sent me the right rings but still not as expected.

 

I could order the next size up, 030 and file them down to fit them in, but I don’t know if that would cause a weird fit around the piston, presumably the inner diameter will be getting bigger too? 
 

Or, run the big gap. According to how to rebuild your Datsun my 0.024 gap is ~.002 outside the maximum of the range provided for a stock bore. When you put it that way, Loris, it doesn’t seem like a big deal does it?

[datzenmike]

Ring gap too large could be the cylinder is larger than you think or the ring smaller than you think.

[Slow Loris]

So out of curiosity I checked a set of new std rings I had acquired (seems to be Hastings next size down from 020) and the gap was huge. So I think Hastings thinks these are correct.

 

Terms of the bore…well I gotta trust in my machinist that the cylinder is matched to the pistons I gave him so…

 

weird.

 

Would filing down a larger oversized ring be a bad idea do you think?

[RoadRace]

when buying a "file-fit" ring set, they typically come in .005" over. meaning if you have a .030" piston, and order a file-fit ring set, they will come in .035" as they are meant to be installed to your specs. while i agree that the .023" ring gap was a bit lofty, if the 2nd ring came in Ok, its not the end of the world. When running boost or nitrous, you're going to open it up to that anyway and its not going to cause any smoke or anything. 

Edited March 23 by RoadRace

[RoadRace]

On 3/16/2026 at 10:08 PM, Slow Loris said:

Pushing ring down in bore with top of piston as squarely as I can, and feeler gauging the gap. How’s that sound? 

also, while using the piston to square the ring for checking gap is good, its a bit clumsy and can lead to errors like thinking you've done it enough that you know its square. its not personal, its just being human, the piston method is good, but you can't make a visual check to verify its perfectly square because the ring is blinded by the piston.  I use a depth setting Vernier caliper locked at a pre-set height as measured from the deck. I can square the ring at multiple locations and physically pull the ring up to the stop - pushing it down isn't the problem, being able to pull it up to the stop is, and you can't do that with a piston, and you also have to keep pushing it down with the piston to make sure, and the piston wobbles at the top, the OD at the top can be smaller than the OD at the pin, depends on the piston - even though its impossible to make absolutely sure, and for consistency's sake, you'd like to check the ring gap a little closer to the top as you can see and feel what your doing better.

just my 2 cents....like I said previously, I'd run the extra ring gap so how critical can this be, right? But this is the method I use so I don't have to make those decisions...

Edited March 23 by RoadRace

[Slow Loris]

9 hours ago, RoadRace said:

  I use a depth setting Vernier caliper

Great idea! Just tried to do something similar squaring up the rear main seal but…squishy seal not work as good.

 

Yeah…I think regardless I’ve come to terms with just running the larger gap. Not interesting buying tons more rings I can’t return!
 

 

[Slow Loris]

On 3/20/2026 at 9:18 AM, RoadRace said:

the pitting

My machinist advised to ditch these rockers they looked bad enough.
 

Prob looking at resurfaced oem rockers as I see available various spots online, not sure if anyone in town is experienced with them per se.

 

Do I need to do anything to the cam? I’ll get it “looked at” for wear, at least.

 

I know the advice is if you replace the cam to replace the rockers, but if replacing rockers…how does the cam feel about that?

[datzenmike]

On 3/14/2026 at 6:50 PM, Slow Loris said:

My piston ring end gaps for top ring are all coming in too big. Whats that mean? I am working with 85.5mm fresh bores, cast iron rings, and seeing gaps at 0.024” whereas was expecting ideal gappage at 3.366 x 0.004 =0.0135”

 

 

 

3.366 x 0.004 =0.0135” You are gaped slightly above what's needed for racing blower or supercharger. Way too big. 

 

 

3.366 x 0.006 = 0.020" Racing nitrous or turbo

3.366 X 0.0072 = 0.024 This is the gap for racing blower or supercharger. 

 

 

If this is a race car, replace everything if you can afford it. If a daily driver, it's more than good enough. Polish the rockers yourself. 220 grit wet sand them on a piece of thick glass in the sink. 

 

 

 

From now on start using a racing oil with ZDDP above 1,000 PPM. Rotella T4 is good with 1,200 PPM 

[Slow Loris]

I guess the impression I got from machinist was that these rockers needed a lot more than a polishing?!

 

Yep been using T4 per your advice I read couple years ago, will keep doing it. Not many miles on the truck since I’ve had it, always had good oil pressure, can’t speak to its past. 

 

35 minutes ago, datzenmike said:

If this is a race car

Haha!

 

 

Race car yep.

 

36 minutes ago, datzenmike said:

You are gaped

Wish I knew what Hastings is up to with these gaps out of the box but here we are!