head swap question

[cj71z]

So I adjusted the valves the other day and now they're really loud(clack, clack), figure I have too much play from this old head and probably need to tighten it up w/ new lash pads. I also know I need new stem seals, seats and guides because they're originals. Now to my question...I'm looking to buy a rebuilt head so I can swap it because I don't have alot of time for a machine shop. So I was thinking about either the E88 or a N42. I have the orig. L24 which still has great compression, so I figure the bottom end can still go a while longer. Has anyone ever used a N42 on a L24? I know the E88 is a bolt on replacement, but I'm looking for a little more performance and I figure that the larger valves of the N42 will help out.

[agemeansnothing]

Yes my brother had a N42 on his L24 in his 260Z, it worked great there really nothing to worry about with N42's. I have one except on a 280Z. But you could really rebiuild your head I had a shop tell me they wanted $250 to do everything. He said about 4 days to do it just giving you options. Ian

[cj71z]

Thanks for the response, how does the L24 feel with the N42? Little better performance, more power? I know it won't be alot of money, but I found a rebuilt one for around 250$. Since I'm planning on going the F54/N42 route in the future I'd figure I would pick up the head and use it for a while instead of putting money into the E31.

[Nigel1943]

Be careful here. If I remember rightly there are at least two types of N42 heads, one with small valves and one with the larger valves which I believe will foul the cylinder bores on an L24. Someone else may be able to confirm this as I'm not 100% certain. Anyway, I see you have an E31 head which I personally would refurbish as it is one of the best performing heads with it's kidney shape combustion chambers.

[kinfish]

Reportedly, there is a tolerance stack-up problem installing 35 mm dia exhaust valves (stock is 33 mm) in an E-31 head and then mating to a 2400 cc block. Not sure if it also applies to E-88, N-42, etc heads.

The larger valves can contact the rim of the cylinder causing damage ..... bent valves? I had my E-31 rebuilt by a machine shop that works exclusively on racing and classic engines and they updated it with the larger exhaust valves. The solution is to notch the rim of the block to provide additional clearance. Process is documented in one of the engine books on the market. Problem does not exist with larger blocks.

[agemeansnothing]

It works like va charm but, I do not know which kind it is ( small or large valves), but he just bought a E31 an is replacing his N42.

[zguitar71]

You will have to eyebrow the cylinders on the 240 block to accomidate the larger valves of the N-42. The compression will go down which could hurt the performance even with the larger valves.

[Walter Moore]

Now you guys have me worried.

I had my E31 rebuilt a while back, and had all the valves replaced. All that I could get were the 44mm intake and 35mm exaust. I haven't been able to start it yet, but it turns over just fine. (It is an otherwise stock L24)

Would I be able to tell if I had a problem just by cranking it over with a rachet? I have done that several times to keep it from rusting up while I was finishing the rest of the car. I never noticed any problem that would have indicated an internal collision.

[cj71z]

Thanks for the info everyone. So it looks like the best bolt on replacement is the E88 or else get my E31 rebuilt. I don't really want to lose performance, I am curious about the gains of the larger valves. From the looks of it my compression would drop from the low 9's to the high 8's using either the E88 or the N42. What kind of difference would this really make in the drivers seat?

[Arne]

For street driving, I would think the compression will help more than the larger valves. The valves will help mostly at high RPM, while the compression helps everywhere.

[Ksteve]

I put an N42 head on my L24 and yes you do need to notch the block at the top of the cylinder bores. I did a thread search under "notch block" and found some useful information/advice from Jmortensen and Pfred (thanks guys!).

After doing some careful measurements I used a teardrop carbide bit in a variable speed drill to make the cuts into the rim of the bore. How much to cut depends on how deep your valves will protrude into the bore at max lift (what cam? head shaved? gasket thickness?)

I am using a Datsun OEM "A" cam with a 1mm Felpro gasket. The cuts I made were about 2mm wide by 3mm deep by 2cm long and the engine is running great with no interference problems. You do have to be cautious about going too wide (beyond the edge of the head gasket) or too deep (within 1mm of the top piston ring max height).

As a side note, I measured the position and size of the existing valve releifs in the L24 pistons and compared it to the N42 valves and they did not even line up due to the wider valves. When I assembled the head and block and rotated to check the clearances the valves had good clearance with the top of the pistons even without the valve releifs.

I hope this helps. Im not saying this is the best route to go but I already had the good L24 block in the car and a freshly rebuilt N42 head.

Good luck with whatever you decide on.

Steve