L18 torque specs and sequence

[racerx]

The books that I have is giving me different numbers for torqueing the L18 head.  So I need you guys help.  Can you pls. share your tech. expertise and let me know what the true torque specs are and the sequence and any other information that may help.

[banzai510(hainz)]

L16 is 40

I would do 45/50

 

 

Isnt this on olddatsuns.com tech section specs

[Draker]

follow the sequence for other L heads.  

[racerx]

Hainz, when you said 45/50, is that 1st and second or second and third time torqueing them.  Should I start at like 25lbs or something?

[banzai510(hainz)]

yes I do the 1st 20 then 40. then whats the spec is. I think 50 is OK.  Datzenmike might know off the top. But I know L16 is 40 which is a little light for me. but those are the early L motors that this was written for. mayb the bolt metal got better later.

 

I forgot the specs for a L18 but I make it a little tighter as my bolts have been strectched out a few times.

 

If you buy 280zx turbo bolts they can go to 60pounds.

 

just hope they don't break.

[DanielC]

When torquing head, or manifolds, you have to realize the specific instructions are written for an auto shop.  One of the concerns in an auto shop is beating the flat rate.  It does not hurt to add more steps to torquing a cylinder head.  Put the cylinder head bolts in "finger tight.  Then with one had on a ratchet, maybe even the weak (left) hand.  Then go to 20 ft/lbs, and recheck that.  Then 30 ft.lbs, recheck, 45 ft/lbs, recheck, and finally 10 ft/lbs or so  below the final torque,  recheck, and the final torque, and recheck that.  After the engine has been warmed up, ran and cooled down, recheck the torque.  Check it again in about 100 miles.  Recheck at the next oil change.  By now, everything should have settled into place, and you will not need to recheck as often, but I think Nissan still recommended a head bolt check every 12,000 miles.

 

Before you even put the head on, chase the threads in the head bolt holes.  Clean them out again, and then follow the directions on what lube to use on the head bolts. 

 

Make sure both the head, and the block are flat.  Make sure both are absolutely clean.

 

If at all possible get Nissan gaskets.  I believe individual gaskets are available, and would rather use the Nissan gaskets on the head, and manifolds, and keep those gaskets from a gasket kit for a possible repair.

 

Near the bottom of this page,

http://www.davidcmurphy.com/olddat/620tech.htm

you can find a PDF version of the Nissan L-16. L-18 factory service manual.

 

If you are asking about torque, and sequence, you need to download this manual.

[Doctor510]

L18 is 60 lb ft in three steps

[scooter]

Throw those old bolts out, get 280zx bolts and go to 60 pounds or get some head studs. I think why people have issues is re using 40 year old bolts regardless of the gasket. They are yielding and not giving proper clamp force regardless of torque.

 

I've had no problems with fel pro headgaskets.

[datzenmike]

The bolts are reusable if not damaged. They are not the 'torque to yield' bolts used today which stretch and are not considered safe to reuse.

 

The sequence for bolting down an L head is...

 

R A D

7.....8

3.....4

1.....2

5.....6

9...10

 

Torque in this order to 20 pounds. Start again same order and increase to 40. One last time same order to 60 and done.

[Stoffregen Motorsports]

This is rather funny, because with all the L motors under my belt, I can't honestly say I remember what a stock L-16 bolt torque is. That's because we always ditched them for the stronger head bolts like the turbo bolts mentioned above. Torque on the turbo bolt is 56#.

 

Almost as important as the torque spec is the re-torque after a few heat cycles.

[banzai510(hainz)]

One of the best aftermarket gaskets is the Durapro Gaskets soldout of Australia( they made in Japan Graphite and 87mm bore size.

 

Baz at Datsport has them and I think StewardWilkeson or something like that. Or if you a Tourist at the local Aussie parts store.

 

Felpro is so so in My opinion. Maybe best on a 83mm L16