My N42 head

[Guest norm[T12SDSUD]]

Hey 2003Z with a P90 head you may just want to go ahead and get some flat tops and still shave it at least .040" which will still leave you well below 10:1 CR. I think a .080" head shave on a P90 with flat tops will put you just over 10:1 CR.

[JMortensen]

I've got a P90 and dished pistons, running NA. You think shaving is a more cost effective way than changing the pistons to motorsports pistons? I can get the set of those for around $350.

Not addressed to me, but especially if you have an N47 or N42 hanging around, modding the P head is way easier than swapping pistons. Here's the details on the mods necessary (thank you Darrel for finding that site): http://www.geocities.com/zgarage2001/head.html

 

You don't even need to mess with lash pads. Just use the longer N valves instead. Shimming the cam towers is the hardest part. That's 20 minutes worth of work.

[Dan Baldwin]

'']Hey Dan ,are your pistons domed or flat top?

 

KA24E pistons machined flat, with valve reliefs.

[Guest norm[T12SDSUD]]

Are you running the triples now Dan?

 

Also did you ever make it back out to the 1/4 mile with the 255 whp setup?

[Dan Baldwin]

Yes, 3x2 45mm SKRacing carbs w/ 38 or 39mm venturis.

 

Haven't been back to the drags. When I went a few years back, ran a 13.5 at 106.5, then 103, then 101, then 97. Fuel pressure was all over the place, clogged filter.

[JessZ]

First, as Jon mentioned Norm, Stephen is not worried about replacing the seats; his problem with the head is that attaining that .035" qunch distance you mentioned will prove difficult with the flat tops. Stephen asked me why not use the dished pistons I have, as they are all in order. From what I've learned on this site, until this last post, and what I told Stephen, is that the flat tops are the way to go.

Norm you also mentioned doing a .080" shave on the head and dished pistons, thanks for the advice, and thanks to all others who chimed in on the dished pistons option. Jon the web addy you gave up about the P-series heads was great, thanks again.

 

One more thing here please. About shaving the N42 head and dished piston option, which shave is it the the head:.070", 080", or .090"? And about the head gasket: 1mm or 2mm?

[Guest norm[T12SDSUD]]

The machine shop will charge for every .040" shaved.

So, if you use the dished pistons and shave it .080" you will be right about 9.8:1 CR with the stock 1.2mm gasket which is perfect for 91 octane gas.

 

You will need to buy 4 .015" shim packs for the cam towers.

You could buy 5 packs, but raising them .060" will be enough to offset the chain slack. If your chain and guides are new you can get by with just putting 3 packs on for .045"

 

You may need to shave a little metal off the top of the cam towers to keep your valve cover from hitting them if you raise your cam towers a total of .060"

[JMortensen]

Norm, if you only shim the towers up .060 do you run into issues with the wipe pattern? I'd rather buy another set of shims than have to mess with the lash pads.

 

Nevermind, I just realized you're going to have to mess with the lash pads anyway, which would be the advantage to doing the P head instead.

[katman]

Your machinist is going to kill way more power with his substandard valve job than you're going to lose in quench and combustion chamber shape. Just my HO. By the time somebody who knows Z heads properly locates the valves, cuts all the right angles, blueprints the spring seat pressure, and fairs the casting to the seats, you got $1500 in the valve job alone. Worry about how you're going to get the most out of your tune, not your quench. Again, just my HO. Like Norm says, a good healthy shave on an N42 makes the chamber look a hole lot better.

[JessZ]

The LENGINE calculator seems to be crunching out reasonable numbers for what I'm thinking of doing (don't know how accurate it is taking into account the variables). This coupled with Dan Baldwin's post and my spinning head, I feel that I just need to commit. Jon's advice with the larger duration cam is going to happen, now it's the head work. ahhh I don't know. I just want fun and reliable; this is probably why I stuck with the stock L24 for so long. It seemed so easy about a year ago, now that the engines at the shop waiting I'm stumped; too many oppinions for me.

[Dan Baldwin]

I say go with yer original plan: N42 unshaved or lightly shaved, flat-top pistons, Nissan head gasket. DONE. 9.8+:1 CR, with a cam, no problemo. Fun and reliable.

 

FWIW, the LEngine calculator does OK, but doesn't correctly account for shaving dished pistons. Definitely need to double check it.

[Guest norm[T12SDSUD]]

Hey, Dan is probably right.

He has been able to run without pinging where others have not.

 

With a longer duration cam that will reduce the tendency to detonate or ping.

 

Also it's a heck of a lot simpler to do.

 

 

Later,Norm

[JMortensen]

I wouldn't do it, but that's just my $.02.

[JessZ]

Well tomorrow I will just order up the flat tops and call it good. As for the head, I'll have the cam custom ground to the appropriate valve train. Jon I know you're all for running the full advance on the timing. I'll just add the octane booster and give the distributor a flip when I'm at the track kickin' some azz. I'm looking forward to posting some vids when the car's back together--don't hold your breath.

[AK-Z]

since this is kinda on the same subject.

 

I have a N42 and a N47.

 

Obviously the N42 head was already described and suggestionsm made.

 

My question is how is the N47 in terms of pinging? Would you mill it down 0.06-0.08 like the n42 head, or is it fine? Or should I just try to find a p90 or a p79 head?

[Dan Baldwin]

With a cam, I bet you won't have to retard timing at all.

If you do, I'll buy you a shot of tequila next time I'm in San Luis Obispo:)

 

FWIW, I ran my 3.1 with a stock N42 head shaved ~.010", stock cam, and 2mm head gasket, ~10.3:1 CR, at 35deg advance, with no pinging for years.

[Dan Baldwin]

AK-Z,

N47 supposedly has the same chambers as the N42. But the ZCCNewEngland club car has a 9.8:1 CR flat-top/N47 build that has to run with timing retarded to 26deg on pump gas. Still makes very good power, though (164rwhp). With a mild cam, power should go up a goodly amount due to moving the torque curve up AND the ability to run more advance.

 

I don't know if I see the purpose in shaving that much out of an N-head and then running dished pistons to make the CR reasonable. That is what Norm did with his 2.9, but I think it was more from working with what he had available to MAXIMUM effect rather than some master scheme:)

[AK-Z]

Oh sorry I ment milled down 0.006-0.008.

[Guest norm[T12SDSUD]]

Yeah Dan is right. The main reason I set mine up like that was because I had been told the N42 pinged badly with flat tops. Since I had the dished pistons already I could shave the head and raise CR to 9.6:1 on the old 2.8L I ran.

 

When I got stroker crank though it worked out good though as I ended up at 10.6:1 CR while running two headgaskets and only had to shave the pistons .015" for proper head clearance.

[2003z]

Not addressed to me' date=' but especially if you have an N47 or N42 hanging around, modding the P head is way easier than swapping pistons. Here's the details on the mods necessary (thank you Darrel for finding that site): http://www.geocities.com/zgarage2001/head.html

 

You don't even need to mess with lash pads. Just use the longer N valves instead. Shimming the cam towers is the hardest part. That's 20 minutes worth of work.

No N head lying around. I have read that before, and he said it wouldn't be worth it for dished pistons. Maybe pistons and headwork? I can get the domed motorsport pistons for cost, or real close to it at least.