Datsun 521 Project - looking for engine advice

[RLDF]

Hey everyone,

I just took ownership of a 1970 521. I have two 1976 280z cars so the L series aren't a complete mystery to me but I am fairly new to doing deep engine work.

This truck has had literally every maintenance item ignored. I've gone through the brakes and shocks but I found my first big issue when I went to change the oil pan gasket. I found a mess of rubbery chunks and it turned out to be the timing chain tensioner:

 

 

After replacing the timing chain and rebuilding the carb I was able to get truck running pretty well and was able to bleed the brakes and go for a drive and realized there was a ton of white smoke. So I bit the bullet and decided to go for the headgasket change and see if anything else was out of place and that is where we are now. 

My concern now is that this appears to be a stock L16 but it has an open style A87 cylinder head. From my reading that should mean this thing has terrible compression and is not a good fit for this truck. The other mystery is that he intake ports appear to have been ported and very poorly pollished. Which makes even less sense considering the the stock L16 block and literally all the maintenance being wildly ignored.

 

Anyone have thoughts on what the best course of action would be given this combination of block and head? I'd like to just throw the headgasket in and just drive it a while and use it for truck things but I'm concerned if the power output is going to be enough.

 

 

[datzenmike]

 

Not even sure you have the stock engine. One, the pistons don't look like L16 pistons. Two, the block vent is not that used by the L16/18 but used by the later L20B. Three, the A87 head was used on the L18 engine and my guess is that it may be an L18. The L16/18 used the same length timing chain so if this is an L20B the chain won't fit the cam sprocket. The engine ID is on the upper block directly behind the dip stick handle. 

 

 

 

 

Someone may have sanded the intake slightly but it was never 'ported' as the openings would line up with the manifold gasket. As you can see there is a lot of material left. Never lay the head with valves pointing down. Lay on it's side.

 

 

 

Someone had the head off and didn't secure the tensioner first. It popped out and the chain rubbed new marks diagonally across the face.

 

 

 

What would I do?

 

Check that the head is absolutely flat. If not have it milled at a shop. Replace the valve seals now to eliminate them as an oil burning source. You have the old head gasket, does it have any blown out parts????? Is it blown between cylinders, or into a coolant hole? 

 

 

 

White smoke can be extreme oil burning. As you can see the exhaust valves are not tan color. Exhaust valves run very hot and burn off any deposits. If burning oil to the extreme they can make them black. Even the spark plug electrodes are black. Also they look oily. Use only NGK spark plugs and don't get them from Amazon, toooooo many counterfeits.

 

With a new head gasket on, get her running and you can assess much better if the rings are shot. If they are, you've only lost the cost of a head gasket and some hours work.

 

 

[RLDF]

57 minutes ago, datzenmike said:

 The engine ID is on the upper block directly behind the dip stick handle. 

 

 

The Block is indeed stamped L16 and pistons measure out at 83mm.


The head gasket I pulled off looks fine, no blown out sections, but there did seem to be coolant on the head bolts when I pulled them out. The head bolts also had a bunch of anti-sieze which I've seen stated before as not good.
 

 

[datzenmike]

Might be a later cast engine from the mid '70s when the block vent changed location. The different piston dish also bears this out. The L18 was still used into the '80s elsewhere in the world. This might be an import engine from Japan.

 

Open chamber A87 head on a small L16 produces a very anemic 7. 72 compression.

[Crashtd420]

11 hours ago, RLDF said:

57 minutes ago, datzenmike said:

 

The Block is indeed stamped L16 and pistons measure out at 83mm.


The head gasket I pulled off looks fine, no blown out sections, but there did seem to be coolant on the head bolts when I pulled them out. The head bolts also had a bunch of anti-sieze which I've seen stated before as not good.
 

 

My L16 had the same block vent... try looking under the distributor or possible behind the exhaust,  my guess is you'll find M 2 on the side of the block.. 

From what I was told these were later production replacement blocks..

Does the serial number match the tag on the firewall?

[datzenmike]

The Japanese Nissan Stanza used the L16 from '77 through '81.

 

 

Another feature of the later casting is the extra raised boss for the oil filter with four bolt holes around the edge.

 

[banzai510(hainz)]

On 3/30/2026 at 2:42 PM, RLDF said:

My concern now is that this appears to be a stock L16 but it has an open style A87 cylinder head. From my reading that should mean this thing has terrible compression and is not a good fit for this truck. The other mystery is that he intake ports appear to have been ported and very poorly pollished. Which makes even less sense considering the the stock L16 block and literally all the maintenance being wildly ignored.

its Match ported it fine.

 

Its a 521 for daily driving. the head will work fine. compression miniman concern .

You could have a SSS head but if still a stock car or DGV its still going to be nothing special. I know!!!!!!!!!!!!!!!!!!!

 

You running dual SUs????????????

[RLDF]

8 minutes ago, banzai510(hainz) said:

 

You running dual SUs????????????

 

It came with a Weber 32/36 which I was able to rebuild

[banzai510(hainz)]

I would just run what you have..

Most DGVs dont need rebuilding as nothing to rebuild. The accel pump tears and the needle valve . thats about it.

 

since its match ported a set of dual SUs would work good but most are junk know.

If you can find a used 38/38 would feel like a mid to high range improvment. On hills one has to clutch it alot. I went bac to a 32/36 for daily use.

Edited April 3 by banzai510(hainz)

[RLDF]

The carb rebuild was definitely worth it: 

 

 

 

 

I'm going to replace the valve seals and lap the valves a bit and gap everything and put it back together and see how it goes!

[banzai510(hainz)]

Wow never seen a accell pump look like that!!!!!!!!!!!!

 

On 521 or trucks swap out the fuel filter often. due to tank in wheel well. dirt gets past the fuel filler hose and trickles down in there with water and rust.

just changed mine and I do it yearly now. always dirty

https://www.ebay.com/itm/364270221424?_trkparms=itmf%3D1%26aid%3D1110006%26rkt%3D4%26mech%3D1%26algv%3DSimplAMLv11PairwiseFitmentPromotionV2WithCassiniQueryEmbRecallKatRecoCpcRecall%26pmt%3D1%26amclksrc%3DITM%26sd%3D267188124175%26sid%3DAQALAAAAEIkrIjVpAwBtbJtf1gxdlwI%3D%26itm%3D364270221424%26noa%3D0%26plcampt%3D0%3A153085335010%26algo%3DHOMESPLICE.SIM%26brand%3DWIX%26asc%3D20240415110138%26ao%3D1%26rk%3D2%26pid%3D101875%26b%3D1%26mehot%3Dnone%26lsid%3D100%26meid%3D8491edb6f7aa438d88c1b5cece72b6ae%26pg%3D2332490&_trksid=p2332490.c101875.m1851&itmprp=cksum%3A3642702214248491edb6f7aa438d88c1b5cece72b6ae|enc%3AAQALAAABMPz1TPr0HWFnlcVOSr5ki%2BmdHRGZMkQO69UwD%2FvZ%2BhzZekwesFH7FaqmLN5MRH4n9oocjuUgubMt99VoZgLTEbmwTbyVnmRfOi6r5wy0zFmqnZZR1RwwkVw0N31SMf5u%2FEJVd1NaCQ5vfYnu8AW6J3ed--shc29%2FbcQVWhrZy0mIwqYzqGchIzvzQ7vP2YWhgChdFDXjOnqcypUoWYmhXvm8kFsa7CZYRuUhoHk0xOU90ludo%2Bu9mveihTAt1VJKARaY9OXua3adJI%2BmCvixt%2B%2F7bRI3QSw%2FCnGPxcY%2BR4Y1LhjwuhjUzuhegWkRfxdgWbeyG4me8bEUkg3LNRrcjQb7TbEywCzR3VHkoHWsc6G1VeXhQT6jJS5li0VXj8rKHppIEnEaufdD0KE%2BziUdE58%3D|ampid%3APL_CLK|clp%3A2332490&itmmeta=01KNT0803XHNARY4E463PZ3B1V

Edited April 9 by banzai510(hainz)

[RLDF]

I've been working on lightly rebuilding the cylinder head and got the new valve seals installed and the valves lapped. Just need to do a pre install lash adjustment and I can throw the L16 back together and run it for a while.

 

 

 

I was also able to pickup a L20b from a 1980 4x4 pickup!

So I'll be working on rebuilding that while I drive the truck in it's current state.

 

 

[datzenmike]

Was it stored with air filter and hood off!

 

Keep intake and carburetor, put your exhaust manifold and oil pan on from the L16 and it will fit right on. I guess the L20B EI distributor is gone but your points L16 distributor will fit.

 

This will have a much different flywheel and clutch assembly than the L16. Keep the L20B flywheel and clutch and when removed from the transmission grab the release bearing collar on the clutch arm as it is matched to the L20B clutch. Your L16 collar won't work with this clutch.

 

There are two alignment dowels that fit the bolt holes in the block and head. They are the manifold side front and third one back. You can see the holes are larger. 

 

 

Set the cold lash to 0.008" intake and 0.010" exhaust. Recheck when hot, the clearance should expand to 0.010" intake and 0.012" exhaust.  

[NC85ST]

You’re going to like the l20 upgrade. 

[datzenmike]

I put a car L20B in my '71. Used the L16 oil pan and exhaust manifold and everything fell into place. Bit more torque and less down shifting. I liked it. 

[RLDF]

19 hours ago, datzenmike said:

Was it stored with air filter and hood off!

The filter was off but the hood was in place when we got there. Removed the hood for easier access.

I pulled the throw out bearing carrier thanks to your comment in another thread I found!

 

 

 

What did you guys do for the oil dip stick? is the L16 stick swappable?

[banzai510(hainz)]

just use the L16 oil picikup tube. oild pan and 521 engine mounts.

the L20 is a 225mm flywheels most likely so your going to have to use that sytem later or find a car 200mm clutch set up and t/o braring and sleeve. so take notice and labol the stuff what you take out the 720 and 521 not to mix up.

 

hi vol oil pump. the GOOD one

https://www.amazon.com/Hitachi-OUP0023-Oil-Pump/dp/B00T3MGEHO/ref=pd_ci_mcx_mh_mcx_views_1_image?pd_rd_w=fipHh&content-id=amzn1.sym.781fe6e1-9487-4a74-b81e-5a879e5ec273%3Aamzn1.symc.c3d5766d-b606-46b8-ab07-1d9d1da0638a&pf_rd_p=781fe6e1-9487-4a74-b81e-5a879e5ec273&pf_rd_r=93DJQ4N6EX6VXKZPGKQM&pd_rd_wg=eMvyB&pd_rd_r=0f1cb135-0cf9-4128-8e13-2225cfc983f0&pd_rd_i=B00T3MGEHO

 

MADE IN JAPAN water pump for 4 blade fan stock 510 and 521  or amazon or ebay

https://www.amazon.com/Aisin-WPN-032-Engine-Water-Pump/dp/B008EEZ3A6/ref=sr_1_1?crid=3EPNET25DRIXQ&dib=eyJ2IjoiMSJ9.r3axuzg-mSbi0wyLBCQAbQ.ogSkusytB-BiLWzdir5sPmeqkN8H3PaVRYLeERtFw0E&dib_tag=se&keywords=aisin+water+pump+wpn032&qid=1777405789&s=automotive&sprefix=aisin+water+pump+wpn032%2Cautomotive%2C174&sr=1-1