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I live in Nar Nar Goon Use to rally a Yellow and red 260 2 seater

Thought I would do up a hot street car for sunday drives etc

So I recently bought a 240 absolute basket case from Brisbane $700.00 Chassis 330 matching numbers

Posted

Why do want the P90 head specifically???

 

In my experience, unless your planning to put a hair dryer on, the N42 can give better results for a lot less work.

 

I had a P90 head on my first race motor but we had to take a fair bit off it to get the compression we wanted and then a fair bit of work to getthe porting to suit as well. At the time I was running L28 out to 2.9 running standard injection and using the standard L28 computer with a couple of tricks to double pulse the injectors for more fuel.

 

My last L29 used an N42 head with better results for less dollars and this head is now on my stroker L31. Now a story in it's own right. The spec for that motor was L28 out to 2.9 with N42 head, standard single butterfly log of 280ZX and Haltech F9 computer. Good for about 130-140 hp at the wheels with points dizzy, but more importantly plenty of torque to pull out of corners.

 

One big advantage of the N42 head is that they are a lot easier to find and need less work to get flowing nicely.

Posted

Current plans are 2.8L ,P90 with tripple 45mm webers, 74 Deg cam.10.5:1 etc

As for the head casting I have had good experiance with the P90 Big valves large ports and compresion can easily be alltered by changing piston shape.but this is not set in stone as it is early days, Just chasing up some parts

Havn't used the N42 before how do they compare?

Posted

My engine builder and a couple of others found that the N42 head was a better unit for a higher compression NA motor, and can be made to work quite well with not a lot of work.

 

The motor that my current head was built for originally had a P90 head, but we found with what I wanted and the budget available to me the N42 was a better head and needed less work to get the flow and susbequent torque I was after.

 

I now have a few N42 heads as spare as they are also a lot easier to get a hold of than the P90 head.

 

 

Posted

true, but when you machine 120thou ( 4mm) off the face, and introduce some angle milling here and there,somewhat grossly oversized valves, you end up with a head of equivalency to the n42, better quench and flame path flow, and the superior port runners compared to the inl/exh flows on a n42, You cannot use the stock timing chain guides, look at kameari's solution, I have a couple of their setups avail for sale, and better to consider a vernier type cam gear or a multi hole, if you must.

 

Other option, is to go for a lower rpm torquier motor,

my thing, i just rev the tits off it to run with the group S guys, and I have to use a 14"  diam rim

Posted

true, but when you machine 120thou ( 4mm) off the face, and introduce some angle milling here and there,somewhat grossly oversized valves, you end up with a head of equivalency to the n42, better quench and flame path flow, and the superior port runners compared to the inl/exh flows on a n42, You cannot use the stock timing chain guides, look at kameari's solution, I have a couple of their setups avail for sale, and better to consider a vernier type cam gear or a multi hole, if you must.

 

Other option, is to go for a lower rpm torquier motor,

my thing, i just rev the tits off it to run with the group S guys, and I have to use a 14"  diam rim

 

So a lot of work for not a lot of gain...... ;D

 

I still reckon for ease of build and availability the N42 is the way to go for a good torquey NA L28, L29 or L31.

Posted

Matt yes you are right, little gain for a lot of effort, but, as I am constricted by GroupS rules, I did a lot of flow bench testing, bear in mind it is all through a "stocK"  throttle body and at 28**cc after all the work, I have found that the P90 does do a better job ---- in my application.

What doesnt help is that some other GroupS Zeds are running HS8 SU carbs (pommy 2" off Rover/triumphs etc) however, the CAMS elegibility guys are clamping down, which is upsetting them, but at least I am staying with them.

The whole injection thing is a real bastard to work with within the CAMS rules.

As an aside, the Porsches are given the OK to run 8"rear rims and 7" front rims, but they never sold them like that, It was a"FactoryApproved Alternative" for them.

Shit we had Sumitomo mk63 calipers, vented rotors, disc brake arse end, and 8" front and 10" rear rims, ALL IN OUR HOMO papers, but CAMS wont allow it, likewise, CAMS wont allow the 240Z in GroupSb even though they were sold from September 1969 somewhere in the world.

My 280Z was NOT sold in Aussie, but they allow it, so why not a 240 in Sb insted of putting them in Sc.

I know why, cos CAMS already got a scare when the first original Datsun sports car, the Datsun Sports 2000 absolutely blitzed the Group Sb ranks.

 

Well thats my little whinge and rant.

Nuff Said.

Posted

Use a modern injection system like Motech and hide it somewhere and show the scrutineers the standard computer if they ask, plus you know most of the tricks to the L28 computer computer anyway.......

 

I know when you're chasing big horsepower with plenty of restrictions it becomes expensive.

 

I know who's motor would owe them the least in dollars and I wouldn't be that far behind in power, especially on a kW/$ basis. Only problem I have is the car is pretty much a circuit racing orphan now, though will be intersting to see how far John Siddons is in front of me at Noosa.

 

Plus you forgot all the fibreglass bits that are homologated for the Z for both standard and ZG panels ;D

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