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:
E30
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:
E31
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'.
E88
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.
N42
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.hybridz.org/showthread.php?t=108398N42 Head Pics:
N47
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:
P79
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.
P90
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 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 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’. This is an improvement because the N42/N47 heads have a sharper bend as the runner transitions which hinders the flow slightly more than the P90. It has a 44mm intake and 35mm exhaust with a chamber volume of 53cc.
The information below about improving the P90 performance in an NA setup is taken from
http://datsunzgarage.com/: In NA setups to improve the CR on a P90 it is best to shave of ~.08” from the deck, insert the 75-80 valves which have .08” longer stems, put up cam tower by .08” and to shim up the spring bases by .08”.
Some consider the N42 better for N/A because not quite so much work/money is needed to improve its CR by the same amount.
P90 Head Pics:
P90a
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.
P99
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.
O5L
The 05L head came on the L20 ET in the 1980 skyline in Japan, like the Y70. It has 28mm intake ports and I have conflicting information about if it came with liners. The intake valves are 38mm and the exhaust are 33mm. The 05L has square exhaust ports.
The 05L head is considered by some to be a ‘blank slate’. It has small chambers and small valves and ports which you can always make larger or reshape. For a race build it is normal to weld up the combustion chambers, hog the intake ports and increase the valve seat size. The 05L is a great option because it does not require the combustion chambers to be welded, meaning you aren’t decking the head and the cam to crank distance isn’t altered.
Y70
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.
Sources:
http://www.zspecialties.com/http://datsunzgarage.com/engine/http://forums.hybridz.org/showthread.php?t=104420&highlight=E30+intake+valve
