L series heads variations | The Z Club of Great Britain

L series heads variations

Discussion in 'S30 (240Z,260Z,280Z) Engine' started by smileyinside, Jul 16, 2017.

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    Here's the text minus photos:

    Hey everyone, I've been researching the various engine heads available to us and thought I'd make a sticky on the topic. I should mention that all of this information I have collected is second hand from forums and websites and there may be one or two errors.

    Here is a useful graph pulled from HybridZ that compares flow rates on various heads:
    The E30 is the head from the L24 off a 240k/C210 Skyline and also the Japanese Fairlady 2.0L L6. It is often asked if it is worth using in a Z because of its ability to generate a high compression ratio. Popular opinion is that the E30 stock valves are too small, which results in a lack of flow. It is possible to spend money altering the ports and bigger valves to take advantage of the CR increase, however it is far cheaper and easier to obtain a later E88 for this purpose. This is because the later (260) E88 has larger ports (same size as the N42) and valves. This head has a high quench design. The E30 has 37 cc chambers.

    E30 Head Pics:
    The E31 is a sought after head that came on the early 240z. It has chambers designed for high quench, but with smaller valves than 260 and 280 heads. Since only 10,000 were made not many will be left that haven’t already been collected and used for racing. The chambers are 42cc, the intake ports are 35mm and it had bronze seats from factory. The E31 used an externally oiled cam via a 'spray bar'.


    The E88 head came on the late 240z (71-73) and the early 260z (74). The versions on the 240 and 260 were slightly different.

    The 240 E88 had a closed chamber design similar to the E31 Head and smaller valves than the 260 version. This variant had a 47 cc chamber. It also used an externally oiled cam like the E31.

    E88 240 Spec:
    The 260 E88 was an open chamber design which meant less compressions for emissions control reasons. This variant had the 47 cc chamber and the large ‘Ex valve’ inserted. There were no quench pads on this head.

    E88 260 Spec:
    I read this on hybridz from a single source: there exists a 3rd type of E88 variant, which came on the early 240zs and was identical to the E31 except for the E88 casting code.

    It has been said that the E88 head has the advantage of being a ‘bolt on’ increase to CR on any L28, and that they are more plentiful than the popular P90. The E88 head has the same cc size as the N42 and N47 heads.

    E88 - Late EFI head

    This cylinder head was designed for fuel injected L-series engines and was fitted to MR30 skylines, it's kidney shape combustion chamber is similar to that used in the P90 and 05L heads, a good cylinder head for high compression N/A engines but sadly becoming less common now that these Skyline's are no longer readily accessible in Junk Yards.

    The N42 head came on the later 260z. It is popular because it is more widely available than the P90, and has a good compromise of compression and flow characteristics. It is often recommended that the head is shaved to improve the CR. It is also known for its square exhaust ports.

    The N42 heads have hardened steel seats so it can run unleaded petrol. The head was used on fully dished pistons which meant that there was no quench in the design. It has been stated by some forum members that if you run and L28 with flat top pistons with an N42 head and standard petrol that you may experience some knocking. It has also been said that the N42 is the preferable head for high compression NA motor because it already has large ports, BUT the chambers need modification for higher compression, better flame burn & better quench. The N42 had 44mm intake and 38mm exhaust.

    This thread on Hybridz shows a fairly in depth process of custom cylinder head building an N42 NA race project head: http://forums.hybrid...ad.php?t=108398

    N42 Head Pics:
    The N47 head came on the 280zx & MR30 Skyline (Aus Del. Model) and has the same specifications as the N42 except that it has ex liners cast in it. Ex liners heat up while the motor is running and burn off excess hydrocarbons in the exhaust. Some feel that these liners reduce the flow. This head had hardened steel seats so it could run unleaded petrol. Like the N42, if placed on a flat top L28 the motor compression is in the mid 10s. The intake runners on this motor are set up for fuel injectors.

    N47 Head Pics:
    The P79 head came on flat top piston L28s which are F54 blocks. It has a 53cc chamber and if used with dished pistons compressions drops to 7.8:1. For this reason flat top pistons are recommended. The exhaust ports and liners are identical to the N47 and it has an internally oiled cam. The chamber is a high quench design, and has been said to reduce detonation if used with the flat top pistons.

    Some people have said that with the P series heads that unless you are using a complete F54 block then they aren’t worth the development costs to get good compression for it to be used in an N/A engine.

    There appears to be 2 versions of this cylinder head, a round port version (found in North American markets) and a square port version found in Japanese Domestic Market and possibly other export markets.

    The P90 head has the same characteristics as the P79, however it has non-linered square exhaust ports. The P90 and P90a are said to be the best flowing heads (out of the box) due to their turbo origins.

    The P90 is popular because it is the L28ET head and has the largest combustion chamber of all the L6 heads. This head is popular for turbo setups but is also used for N/A. The P90 has an internally oiled Cam, nearly straight exhaust runners, high quench/swirl chambers and steel valve seats to run unleaded octane fuel (ULP).

    The P90 has straighter exhaust runners because of its deeper chamber and these are said to aid the flow. The intake runners are lined up with the valve bowls better in the P90 because of the deeper chamber, which straightens out the short-side radius 'bump' which is more pronounced on other heads. This is an improvement because the N42/N47 heads have a sharper bend as the runner transitions which hinders the flow slightly more (due to increased turbulence) than the P90. It has a 44mm intake and 37mm exhaust with a chamber volume of 54cc.

    Chamber measurements,
    Length( along head) 86.9m
    Width,( from arc at spark plug direct across) 64.3mm
    Depth at deepest ( base of spark plug boss) 16.6mm

    P90 Head Pics:
    The P90a is another turbo head which has been found in two variations. One variation has the solid lifter style which is exactly like the P90 and the other one has hydraulic lifters. Apart from the lifters the P90a has the same specifications as the P90 head. These hydraulic lifters make the engine almost silent. However, replacement lifters no longer exist for this head, making it very expensive to recondition.

    This head came on the L28ET. It has a 53.6 cc chamber, 44mm intake valves and 35mm exhaust valves. It has square exhaust ports.

    The 05L head came on the L20 ET in the 1980 skyline in Japan. It has 29mm intake ports. Exhaust ports are 36mm x 27.5 wide and the center ports are a little bit wider at 33.8mm than the rest of the exhaust ports. The intake valves are 38mm and the exhaust are 34mm. The 05L has square exhaust ports. Port runner shapes on both (P90 and 05L) heads are the same i.e the short side radius hump is not present on the O5L.

    Chamber measurements:
    Length( along head) 84.1mm
    Width,( from arc at spark plug direct across) 52.4mm
    Depth at deepest ( base of spark plug boss) 13.5mm

    The 05L head is considered by some to be a blank slate. It has small chambers (37cc) and small valves and ports which you can always make larger or reshape. For a race car build it is normal to weld up the combustion chambers for higher compression, port the intake and increase the valve seat size. The 05L is a great option because it does not require the combustion chambers to be welded (for certain racing categories you can only remove and not add material to a head) given it's small size to start with, which means unlike the P90 you aren’t decking the head for higher compression and the cam to crank distance isn't altered.

    Un-shrouding the valves on this head would increase chamber size slightly and make for a good engine head on a big displacement L-series build 2.8-3.1 ltr engine.

    05L head on left hand side of photo, P90 for comparison on right hand side.

    Note: The 05L has a more shallow combustion chamber than the deeper P90.

    Again 05L on left hand side and P90 on right hand side.

    Note: The small port sizes on the 05L
    The Y70 head came on the L20a ET on Japanese models. It has round exhaust ports with liners. The intake ports are 30mm, the intake valves are 38mm and the exhaust valves are 33mm

    Y70 Head Pics:
    Big thanks to Lurch and all the guys on Hybridz for being a wealth of information.

    http://forums.hybrid...30 intake valve

    Competition Heads
    LY Cylinder Head - Part no. 11042-E4622
    Nissan actually made a few variations of this cylinder head over the years, Early rally LY24, early circuit LY24, mid-term LY26 and later LY28 ( LY29 ), used mostly in Japanese Circuit racing. Originally designed with the East African Safari in mind, but never actually used in this event. It was however used in the Southern Cross Rally. (See Ross Dunkerton). These cylinder heads were designed to be used with fuel injection system.

    The LY head was a cross flow, single overhead camshaft with 2 valves per cylinder. No doubt the evolution of this head was to go on and become the Nissan RB30 power plant..


    'The Safari Head' Part No. 11041-E4621
    Info posted by HS30-H here.
    As seen in the FIA homologation papers for the H(L)S30 ( FIA 3023 / JAF GT-010 ). Internally at Nissan it was nicknamed the 'Safari' head, even though it was never used in anger on the E.A. Safari Rally. Essentially it was a 6 cylinder version of the 4-cyl FIA head, and was always intended to be used with Nissan's race 'ECGI' electronic injection system with triple side-draught throttle bodies.
    You can see some details of the head on the homologation papers ( amendment 5/5V ). Compression ratio was intended to be 11.0:1 with a 36.2cc chamber. The heads were individually sand cast ( stock heads were die cast ) and the architecture was completely different to that of any of the stock production heads. The inletmanifold was used as a log to join the cooling passages together, and the cooling properties eliminated any hot spots / cool spots.

    Assembled on an L24-base, capacity upped to around 2500cc within the rules, with the option E4621 narrow-journal high strength crank, narrow journal rods, 8-bolt 7kg flywheel and the full ECGI injection setup, it was given the internal reference code 'LR24-ERY'. They were used in Japanese circuit racing in late 1971 through 1973 in cars like the Omori 'spider' car in my forum avatar, sometimes alongside LY24-ERY

    15 Nov 2009
    The E88 also existed in EFI-form and was used in the MR30 (with dished pistons).
    The E31 and early E88's used an externally oiled cam (via a 'spray-bar').
    There is also a P99 L28ET head.
    All heads except the N47 and P79 used the square exhaust ports (without liners).
    The L28 N42 block is more common then the F54

    In Australia the 'common' models are 240Z E31/E88, 260Z E88, 280ZX N42, R30 E88, R30 N47. You will not see many F54 blocks, P79 or P90(a) heads. One of the most accurate calculators out there for L6 engine specifications is called 'lengine' and was a Sydney Z club product back in the mid '90's. It's not perfect (e.g. it doesn't know about the big end size issue with late L20A rods), but it's still a damn good tool. I'll dig up a copy and post it up.
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