What would be the best head I have for a L28ET

[Noddle]

Hi,

 

Hopefully sometime soon I will be building a L28 to replace my Turboed N/A L24

 

my issue is that I have 3 heads to choose from, a E30, a N47 (MN47), and a N42

 

I don't have a lot of money to spend, so replacing the valves in the head is not a option for me at the moment.

 

The E30 has very small valves which i assume would be a negative point.

The N47 I believe has slightly smaller vales than the N42, but it has the closed chamber design (like a P90)

The N42 has the larger valves, but has a open chamber design.

 

What I was planing, unless some one has a good reason why not to,

 

is run a L28, with dished piston, with a standard N47 head with some minor head work,

this would include some work on the intake port to remove the casting marks, blend the port onto the valve seats and un-shroud the valves. i would be running a N/A "A" Cam as I am now with my L24

 

Engine management will be,

Megasquirt II, ( msextra )

EDIS,

440cc injectors,

standard headgasket, arp head bolts and arp rod bolts,

3 inch exhaust,

Intercooler

T3/4 Turbo, the same as what on my L24, fuel will be E10 ( 95ish octane )

 

Can anyone see why this would not work with good results ?

 

thanks for any input

 

Nigel

[B00STDZ]

I would use the n42... or try to find a p90

[Noddle]

I would use the n42... or try to find a p90

 

A N47 would be more like a P90 (turbo head), than a N42, and when I unshroud the valves, it will remove a few more cc's from the chamber size.

[Pyro]

the n42 and n47 has the same chambers and valves.

the n47 has round exhaust ports and liners, the n42 has square exhaust ports and no liners.

the n47 uses internally oil cam (oil comes out of the cam lobe), and the N42 uses a spray bar.

 

so, if you want to use the 240 cam then you will be required to use the N42 head with the spray bar.

 

with stock dished piston, the compression should be 8.3:1 which will work fine for low to moderate boost (7 to 10) on pump gas and fairly high boost with e85.

 

The P90 and P79 have the bigger heart shaped chambers.

Edited October 13, 2010 by Pyro

[Noddle]

the n42 and n47 has the same chambers and valves.

I disagree. the dirty one is a N42,the clean ish one is a N47, the N42 has a steep right around the combustion chamber, the N47 does not.

 

the 3rd picture is a P90

 

Nigel

Edited October 13, 2010 by Noddle

[Pyro]

the N47 head you have is not from a 280/280zx L28 (1977 -80).

 

what you have is a N47 from a L24 maxima

Edited October 14, 2010 by Pyro

[BRAAP]

As Pyro stated, that is the Maxima N47, aka MN47. It is nothing like the P90 or P79 heads, chamber is much different offering more squish than the P90 and P79, also has shallow chambers with the same length valves as the E31, E88, N42 and Z car N47 head. P79 and P90 use much shorter length valves length due to their deeper chambers. Also has smaller intake valves, as you already stated, and smaller intake runners with very pronounced "D" shape starting approx 1" in from the manifold mating surface.

 

I would NOT use the MN47 head on a Turbo L28 with any off the shelf pistons! Even with dished pistons, the compression ratio will be too high and it will detonate, popping your head gasket or worse. Unshrouding the valves will only removes 2cc if done correctly, 3cc if you take it too far or start to remove some of the squish pad, (at that point, just use the N42, it already has larger intake valves, larger intake runner and no liners in the exhaust), and that is still not enough to drop the comp ratio down to safe boostable levels. If you are going to have custom forged pistons manufactured, you could have them made with a "D" dish to match the chamber of the N47 making use of the squish and get the comp ratio down to a boostable level, not a cheap option, cause you'll want the larger intake valve, extensive intake port porting, etc. to get the most out of it.

 

Don't despair, that head does have value to the N/A crowd, and easily worth a straight-across trade for a good P90 head, (at least here in the states), which if this were my project, is what I would do if I had that head and were building a Boosted L28.

[Noddle]

As Pyro stated, that is the Maxima N47, aka MN47. It is nothing like the P90 or P79 heads, chamber is much different offering more squish than the P90 and P79, also has shallow chambers with the same length valves as the E31, E88, N42 and Z car N47 head. P79 and P90 use much shorter length valves length due to their deeper chambers. Also has smaller intake valves, as you already stated, and smaller intake runners with very pronounced "D" shape starting approx 1" in from the manifold mating surface.

 

I would NOT use the MN47 head on a Turbo L28 with any off the shelf pistons! Even with dished pistons, the compression ratio will be too high and it will detonate, popping your head gasket or worse. Unshrouding the valves will only removes 2cc if done correctly, 3cc if you take it too far or start to remove some of the squish pad, (at that point, just use the N42, it already has larger intake valves, larger intake runner and no liners in the exhaust), and that is still not enough to drop the comp ratio down to safe boostable levels. If you are going to have custom forged pistons manufactured, you could have them made with a "D" dish to match the chamber of the N47 making use of the squish and get the comp ratio down to a boostable level, not a cheap option, cause you'll want the larger intake valve, extensive intake port porting, etc. to get the most out of it.

 

Don't despair, that head does have value to the N/A crowd, and easily worth a straight-across trade for a good P90 head, (at least here in the states), which if this were my project, is what I would do if I had that head and were building a Boosted L28.

 

 

Sorry about the confusion of the N47 , MN47, this head was off a MR30 L24e Skyline, and they all have this head ( N47 ), well the ones I have seen.

My problem is that i have never seen any P90 heads, I did hear that some of Nissan Patrols had P90's, I will need to look into this more.

 

thank you for your input.

 

Nigel

Edited October 15, 2010 by Noddle

[Tony D]

N42.

P90=A lot of hype for not much real world benefit.

 

Non-US N42's can have radically different combustion chamber shapes, up to including the N47 style closed-chamber depending on what market they were used in originally.

 

You want a 'best' here's one: O5L from late model L20A Turbo.

 

Then hog the ports, change the valves, and CNC the combustion chamber to match. No welding on ANYTHING required. From a 'base starting point' the only real thing you have to do is buy and have installed the larger valve seats from and N42 and use the standard larger valves, which apparently you have already.

 

Seats and installation and then start cutting.