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Maxima head performance update

278 Views 9 Replies 4 Participants Last post by  AZIN

for those of you that have been following this motor build, she's finally in and tearing up the streets of Arizona.

I was keeping my expectations low, so I wouldn't be dissapointed. Wow! This motor is much better than I ever expected. I have driven many Zs and many very fast Porsches, Vettes, Audis, etc. This car will either take them or keep with any of your basic 13-14 second cars. NO DISSAPOINTMENTS.

The build:

Early 260z body

F54 bottom end, rehoned, new rings and bearings

Maxima N47 head with AZ ZCar comp valves, mild port and polish

AZ Zcar cam, headers, 2-1/2" exhaust

390 rear, early 5 speed
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I forgot to mention that I'm running the hated dual Webers amd they are apparently making gobs of power-- not even really tuned, yet.

And the chamber volume of these heads is about 40cc which makes for just under 11:1 with a Felpro gasket. I'm running about 12 degrees advance with no ping on a tank of half regular topped off with premium.



EDIT: Blue is blind :)

Post Edited (Oct 25, 7:29pm)
Nice report!

What is compression?

I haven't put the guage on it yet, so I don't know psi numbers, maybe later this week. According to the Lengine calculator, it is at 10.99:1.

How many miles should it take to break this in and how should I be driving it during break in? I know there are lots of theories out there, but those of you that have experience with these engines, what's yours?

put it on a dyno and go your local 1/4mile track and amaze us.
Break in, what is that??

I personally have no self control. A cam break in is about all I can handle. After that, I have a habbit of doing heavy burn outs in the driveway. So, I don't do break in's and I haven't had any problems. But I'm sure others on this forum will have various opinions.

What are your cam specs and what does your ignition timing look like (initial, and total)
I don't know for sure the cam specs, because when I bought this from Dave at AZ Zcar several years ago, it was sitting on his shelf and he couldn't remember either. But, with my calipers I figured out that the lift is about 460-- don't know how to effectively measure duration with calipers.

I have the timing set at about 10 initial right now. I know this is a dumb question, but how do you set and measure total?

Also, if any of you know DGVs, I have a very small flat spot at about 1/4 throttle just as I start to ease into it. It stutters ever so lightly then as I mash past it, it takes off and snarls like a tiger. Any ideas on this transition hesitation? I'm thinking that either the idle jets are too small or large, but really don't know, that's why I'm asking.

Also, I ran it through emissions yesterday and hydrocarbons and COs were were within specs on everything but idle HCs were high. Here it was reading 700 HCs when spec to pass is 400.


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With a lift of 0.460" I bet the cam is about 270 degrees. You really can't measure the duration with calipers. You need a degree wheel and a dial indicator and it is still a pain to measure duration on a datsun engine, especially one that is not on an engine stand. So don't worry about it.

Bigger cams like more initial timing. 20 degrees initial would be good for your setup. It would help low end responce and reduce emissions. However, it is important not to over time the engine at higher rpms. A timing light with a degree knob or a balancer that is degreed is needed to see how high the timing goes when the engine is reving. For a Z, it is better to have a timing light with a degree knob. So, you need to rev up the engine to about 4000 rpm and use the timing light to see where the timing mark stops advancing and that is the total timing.

Normally , Z's have about 18 degrees of mechanical advance in the distributor. If you set the timing to 20 initial then you will get 38 total, which is about right. But the vacuum advance will increase that by another 10 or 15 degrees which would be too much if you use 20 initial. So, in cases like this, I weld up the advance slot in the distributor to reduce the mechancial advance to 8 or 9 degrees. But that is kind of a complicated proceedure.

Try this. Set the timing to 20 degrees inital and disconnect the vacuum advance and see how it runs. This maybe all you need.

Sorry I can't help you with thoses carbs. But more inital timing may help.

Good luck.
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I will try advancing the timing. I always thought one would reduce emissions by retarding timing some-- no?

I'm not running any vacuum advance as it isn't working on my distributor, anyways. So, about 20 degrees and let her rip. I'll see what happens and report.

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