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Some questons on N/A buildup


Guest GreenZ

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Guest GreenZ

I've been reading here for the past couple months about building N/A engines. I want to get more hp from my tired engine, need more info on the N42 head/zx flat top piston combo. I have a good N42 head, but an older block (1977). Would it be safe to put the zx pistons in that block? What cam should I run? Would I be able to retain the stock fuel injection in my car? What work should I have done to the head? What about porting/polishing? I plan to use the car on the street; it must still pass emissions and I want it to look fairly original. I have invested a lot of money in the rest of the car already, it looks great, but its slow as hell. Any advice you guys can give me would be helpful. Thanks.

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You can put the pistons in your block, but if you mix and match engine parts, it would be a good idea to have the engine balanced when you get the machine work done. It was make a nice difference in smoothness.

 

I would run a mild cam, there is a Schneider for sale on Ebay right now that is a nice street cam. You can also get it from MSA, it is the 274 duration, .480 lift.

 

Add a nice header and exhaust and you should be good to go.

 

The N42, just have a nice 3 angle valve job done and go from there.

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Guest Al 260Z

Recommend freshening for old block, including inspection, hone cyl bores, new rings and bearings. Very likely no cyl boring or crank grinding req'd. Balancing is great, but more $$. New OEM balancer recommended. Check for timing chain stretch per FSM. On my 250k mi overhaul, I found no chain stretch so I just replaced the guides and tensioner.

 

If you need to pass smog, you'll have to stay away from too radical of a cam, cause you won't be able to get to idle at required rpm with sufficiently lean idle mixture.

 

Beware of the PING monster if you start pushing up CR. Big cam helps with ping at higher CR. Best have an expert lined up to help you out of trouble if you go this route.

 

You'll get more HPs without concern about ping or smog with turbo TB and cold air intake... worth checking into. Port matching head & manifolds highly recommended, also unplugging stock exhaust via upgrade to 2-1/4" to 2-1/2". Don't believe smogger will fail you as long as you keep a cat cvtr in place.

 

Later,

Al

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Guest GreenZ

Should I have the intake manifold worked on? Extrude honed? How much should I be looking at spending? I was thinking about headers and a 2 1/4 inch exhaust is already on the car with flowmaster muffler and high flow cat. thanks

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For a budget build up like this I've described a way to use your '77 280Z dished pistons but have the tops shaved down until they become flat tops with a reduced compression ht, using L24 rods which improves rod/stroke ratio and along with an N42 head, makes almost 10:1 compression, and in the process a method of assembly of the piston/rod units into the engine in such a way that the engine is far more balanced than random assembly order would provide. Try to find it by search, probably in the L6 forum. If you can't find it, I'll provide particulars.

 

Forget about extrude-honing your manifold at this point and porting and polishing, your money could be much better spent. Once you've increased compression, cam and headers come next and when the compression goes up, you'll have to enrichen fuel supply. Minor modifications can be done at first, but as you increase horsepower, you will need more & more fuel. DAW

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Daw

 

How do you recommend the fuel supply be enrichened? Adjustable regulator or fudging the temperature sensor?

 

I'm in the midst of building the "new" engine. Low mileage N54 shortblock with a N42 head, three angle seats blending/pocket porting and manifold matching with 240sx TB, cold air, header with duals and a "Mitchamore" cam,

 

Part Number 918-268

Intake Exhaust

Duration @ .050 .222 .222

Valve Lift .430 .430

Hot Valve Lash .010 .010

 

The enrichening component, while considered has been put off, but now that you mention it, any input would be appreciated.

ecp48

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Anyone know how much more the turbo injectors flow than the stock 280 N/A?

 

Possibly the larger injectors would give enough without going to the adjustable Fuel Regulator. Or would they be overkill? I know on 5.0 Mustangs, they don't recommend stepping up the injectors untill the engine is severely modified, unlike what I am planning.

 

ecp48

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Guest GreenZ

hey ecp48,

let me know how your engine works out for you. I have not yet decided what cam to use in my new motor. What kind of hp are you expecting to get? I want my car to at least be able to spin the tires, which is something it cannot even do right now, except when it rains :roll: . BTW, the compression on my current motor is around 135 on all cylinders. What should it be?

Jason

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You need to give particulars on your engine before anyone can give you an idea of what the compression should be. Most service manuals like a haynes will give you that information. My turbo engine has 145 to 150 psi.

 

Really that number is pretty useless, the main thing you want to check is even compression across the cylinders. Different guages will give you different results.

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Do things one step at a time. If you do the rising-rate fpr, that may be enough. Only if you still need more fuel do you need to go on to other enrichenning measures, and then only according to how much more you need re which to use. DAW

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Guest GreenZ

Lockjaw,

the engine is totally stock, 135 psi across all cylinders. Valves were adjusted not too long ago, maybe 5,000 miles or so. Went and tested my 83 ZXT, it had 140 on five cylinders, and 138 on the other. I would think the N/A should have more compression than the turbo.

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