N47 head L28

[JessZ]

I've seen Jim claim that the MN47 head yields too much compression for a California pump gas flat top L28. Is the MN47 head the same head that came on the N42 280z block? By using the Lengine caluclator the N47 flat top L28 yields a 10.08:1 ratio, which from what I've gather will make a fine daily driver motor.

Is this a mistake for me to grab the flat top block and put this N47 head (that came off a N42 block) together? Should I just hold out for the N42 head?

I see people disagreeing about what head is the "right" head for a 10:1 L28 daily driver, but agreeing that both heads flow very well. Am I confused that the MN47 and the N47 head are the same head?

It seems that once I think I have a good combo in mind, I read more and just get more confused.

Is my '71 series II E88 head a good choice for a daily driver on a L28 flat top?

Thanks guys...

[JMortensen]

The MN47 is 39cc combustion chamber IIRC. Plug that into the calc and see what comes up. I think you meant me (Jon, not Jim) but I will state again for the record that I think it would be a very bad idea to try to run an 11.5:1 or whatever compression L series engine on CA 91. CA gas is the worst in the country. And as I've said before, you might be able to get it to run by putting in a big cam and cranking the timing back a LOT, but you'd probably make more power with a 10:1 compression engine and having all the advance that the engine can use. And for the record no, I haven't tried it myself, but my ~11:1 L28/E31 combo required 95 octane in CA to run total advance in the mid 30's.

[JessZ]

Jon sorry for the "Jim." I value your advice, so thanks again. I guess I'll go for it then. The N47, which actually comes with the N42 block, but adding the flat tops won't be a problem, right?

And Daw you mentioned, "I think I'll be better off with the .460" 270/280 cam I'm putting in." Is this combo going to yield a solid street motor?

[JessZ]

so I learned that I can't have the N47 head ported. the N42 head seems like the best bet here?

[JMortensen]

No problem on the Jim thing. I'm sure a lot of people think I'm Jim Ortensen. Dumb me for choosing that screen name.

 

I think that is the same camshaft that Bastaad525 had on that same build basically. He lives in SoCal, and was running your crap gas. He said he had to crank the timing on his engine down to about 25 degrees total to avoid pinging, and IIRC that was with a N42/N42 flattop setup, so basically the same thing you're talking about. My comment at the time was that I'd rather have a 9.5:1 engine running 35 degrees advance than a 10.5:1 engine running 25 total.

 

That is the MSA cam you guys are talking about, right? In Bastaad's case with CA gas, it was too small. The problem is that if you go bigger than that then you have to deal with coil bind on the valve springs and get different valve stem seals (search Jessz, lots of info on that stuff). If you were going to pick a cam from MSA, I'd recommend the Stage IV. Really though I'd rather have a cam reground, and for 10.x:1 on CA pump gas with SU's I'd look for something in the .490/280 to .490/290 range. Can't go too much more lift than that or else the pistons start hitting the valves, but those should be safe. Also look for threads about wiped out cam lobes to see why you might want to avoid Schneider cams.

[zeiss150]

Just to add my experiance (which pales in compairison to the other guy's on this site)but... I have an F54 block (pretty much the same thing as your N42 block it just has different cooling) and I rebuilt it with a 20 thousandths over bore and FLAT TOP pistons. I was going to be running an N42 head (Z head not the Maxima head) I would have had over 10:1 CR and I was worried about blowing up my engine with crappy 91 oct. california gas (stupid pollotics). So I decided to use a 2mm HKS head gasket which would lower my CR to a usable 9.2:1 CR, and on top of that I put in an MSA schnider 460 270 cam with performance valve train to prevent valve float at high RPMs. Long story short I have a bitch'n SU powered, non-detonating, honda killing, G35 embarassing, 240Z. The throttel is super jumpy and on a rainy day like today, I lost traction just giving a little more throttle then usual. I love my NA rocket ... But... I'm going turbo... more power .....MORE POWER. Horse Power = haroin. so now I need to take my engine apart and put in dished pistons to get my CR to a usable turbo 8.3:1 CR. The moral to this story is ... build your engine for TURBO applications ... cause we all wind up there eventually.

 

Just my 2 cents ... I hope it was worth more than 2 cents.

 

 

P.S. N42 head = 280 Z MN42 head = "maxima" <----- the M is for

 

P.P.S. There is a thread on here about the NM42 head that is about 100 pages long that will confuse the crap out of you... but its fun to read if you have a few day's...

 

P.P.P.S. Dont even get people started about the P90 head... ok I'll stop typing now.

[JessZ]

I PM'ed you with some questions and comments.

[zeiss150]

answers to your questions are on the way!

[Guest Lisa-Adam]

Well, this guy's page is usually a really good guide to the spectrum of Datsun L series heads:

http://www.geocities.com/zgarage2001/z.html

and he says the N47 has the diamond-shaped exhaust ports.

I just last week took my intake and exhaust manifolds off of my '78 L28 in preparation for getting the block cleaned for a rebuild. It does indeed have the exhaust "liners", and by year also should be an N47, but I remember looking at them and thinking "square", as opposed to diamond. I'll look again tonight as I have to get the left side freeze plugs out next anyway.

Given you've got a '71, I'd say you're looking at a different exhaust setup. Of course, if your donor L28 comes with an exhaust manifold or a decent header, then you're all set. As long as you're going to all this trouble, though, it sure is a good time to put on a really nice exhaust... aside from the money, of course.

good luck,

[z-ya]

The engine I currently run in my track car is a rebuilt 78' L28 (N42 block and N47 head), with ITM +0.5mm flat top pistons. Stock head gasket. Head was milled just a little to flatten it out in a few spots. CR is in the 9.9 - 10.0 range. The rotating assembly was balanced. The intake ports were matched to the intake manifold, and a very light port cleanup was done (budget racer). It has a mild road race CompCams camshaft in it.

 

It makes 180WHP and runs fine on pump 93 octane with a total ignition advance of 28 deg. This is my reliable "spare" motor that I am using full time now since I had a piston melting problem in my supercharged motor....

 

The reason for using the N47 head was mainly that I had it, and I have a nice round port header. Again, this is a budget racer.

 

Pete

[Dat260]

The engine I currently run in my track car is a rebuilt 78' L28 (N42 block and N47 head), with ITM +0.5mm flat top pistons. Stock head gasket. Head was milled just a little to flatten it out in a few spots. CR is in the 9.9 - 10.0 range. The rotating assembly was balanced. The intake ports were matched to the intake manifold, and a very light port cleanup was done (budget racer). It has a mild road race CompCams camshaft in it.

 

It makes 180WHP and runs fine on pump 93 octane with a total ignition advance of 28 deg. This is my reliable "spare" motor that I am using full time now since I had a piston melting problem in my supercharged motor....

 

The reason for using the N47 head was mainly that I had it, and I have a nice round port header. Again, this is a budget racer.

 

Pete

 

Hi Pete,

That is pretty good, 180whp. I read a lot of post about engines with a lot more engine work then yours and still produce under 200whp. It gives me hope for my build. Arizona pistons w/240 con/rods, 40dcoe, headers, bigger valves but do not know what cam to use, yet. I'll be happy if I break 200whp with my parts.

Cheers,

[z-ya]

I've had good luck with the ITM pistons for NA applications. They are a heck of a lot cheaper than the Arizona Z forged ones. If you don't plan on going turbo, use the money you would save using cast pistons on head work.

[D1CNAR]

i have a 260 with a l28 block with flat tops with a stock cam and a n47 head ported and shaved with trip webber 40's and a msd ignition ran on pump gas that i drive daily and i beat the hell out of my buddies car with a cam and a n42 head with the same block , my other car is a l28 with an e88 head with round tops and that is a screamer too ive done about all the swaps possible the only head not worth much is the p79

[Guest datsfast260]

I have a stock P79 flat top block with a P79 head shaved .110 with an Isky stage 3 type 2 cam, 6 into 1 header, and jetted SU carbs. I'm at 12.5:1 CR and running Cam2 110 octane with 390 posi. I'm running 193hp at rear wheels. I put shims under my cam towers and valve springs. I also added the longer 280 valves which are tulip shaped and thinner lash pads.

[D1CNAR]

the e88 n 42 or n 47 are all awsome choices have done all of them for a stock bolt up of a stock head if your goin to have it machined go with the p79 head it is by far the best flowing head the only thing that kills it is the chamber volume have the head worked shaved maybe even welded and your good to go 193 hp is nothing to the ground for that work something seems wrong there

[FlatBlack]

the e88 n 42 or n 47 are all awsome choices have done all of them for a stock bolt up of a stock head if your goin to have it machined go with the p79 head it is by far the best flowing head the only thing that kills it is the chamber volume have the head worked shaved maybe even welded and your good to go 193 hp is nothing to the ground for that work something seems wrong there

 

 

I lost you at "e88 n 42"

 

You are throwing around some big claims up there if I read that right. Claims that don't agree with other members who have done high comp builds and that have way better grammar than you.

[Zmanco]

FYI, I too ran with flat top pistons (ITM .030 over) and N42 head and moderate cam for 10.3 CR and had detonation issues on 91 premium (that's the best we have), even at our altitude here in Colorado. I'm running megasquirt so in the end backed off the timing in the 4k - 5k rpm range by almost 10 degrees. Boy could I feel the torque fall off as it passed through that range compared to the cool days when I could run more advance. As Jon and others said, I think running a lower CR and being able to run full advance would be a better combination.

 

And like zeis150, I too am going turbo - power really is addictive

[z-ya]

the e88 n 42 or n 47 are all awsome choices have done all of them for a stock bolt up of a stock head if your goin to have it machined go with the p79 head it is by far the best flowing head the only thing that kills it is the chamber volume have the head worked shaved maybe even welded and your good to go 193 hp is nothing to the ground for that work something seems wrong there

 

Complete sentences, correct spelling, and punctuation, would make it much easier to understand what you are trying to say.

[D1CNAR]

For thouse of you who can't figure it out, i apolagize for the typing. I have tried pretty much every combination of heads and the best stock bolt up head is the "N42" or the "E88". If you intend to have the head machined the "p79 is by far the best choice the flow is uncomparable to the others. the only down side of the stock "p79" head is the chamber size witch results in low compression. Check out some flow charts online. and for the record dont be a dick if your looking for advice

[z-ya]

What about the P90? Since the combustion chamber is the same as the P79, and it has square exhaust ports like the N42 and E88. And why the E88? Why not an E31? It is the choice of many an SCCA champion.

 

Maybe a little searching and learning is in order