heads

[Guest buds260z]

I would like to know wath is the best head for my flat top piston f54 block I

have a 268 cam and a set of 32/36 dvg webers it was all free !!!

[1 fast z]

MN47!!!!

 

 

 

Nuff said.

[BRAAP]

It depends on what you plan to use this engine for. If it is going to be a mild race head and you will be using race gas or at least Av gas, the Maxima N-47, as mentioned by "1fastZ", is an AWESOME head, though you will want to have the larger intake valve seat and valves installed. Comp ratio with an L-28 running Flat tops that come above the deck .025” or so at TDC with the Maxima N-47 yields above 12:1 compression. Not real pump gas friendly, but a great performer. If this is going to be a street car that will run pump gas, then I would lean more towards the P-79 or P90 heads.

 

If you want a more technical reply to your question, I urge you to read all three pages of this thread, as myself and a few others went into depth about Datsun L-series heads for use in performance applications.

 

http://forums.hybridz.org/showthread.php?t=104420

 

Regards,

[1 fast z]

The MN47 head, will yeild 11.3-1, on a stock flat top block, with a felpro head gasket. I run this setup on one of my cars, and have many customers that also run this same exact setup, with the heads I have setup for them. If TUNED right, you will have NO detonation problem, especially if you bleed off the static compression with a hotter cam. Alot of people are affraid of 11-1 on L series, but there is NO need to be. The MN head has the HIGHEST quench head that is availible, without mods, and that GREATLY reduces detonation.

[JMortensen]

What kind of gas do you have out there in AZ 1 fast z? Cause in CA that sucker will ping regardless of how it's tuned. Oxygenated 91 octane is not the same as some other states with "real" 93 octane.

[JMortensen]

Also, the guy has a 260 cam and a pair of DGV's. He didn't say I'm building an all out race motor, money is no object, what should I use. Search and there are many threads about the different heads and their pros and cons.

 

For a street car on 91 pump gas easiest thing to do is get an N42. Not as easy but better is to get a P90 and shave it and put N42 valves in it.

 

If you're going racing I like the MN42. But if you aren't it's going to be more of a headache to get ready since you'll need to install bigger valves and seats, etc.

[1 fast z]

I port the MN47 for guys all the time. I get great flow numbers with STOCK valves. PORT velocity is a direct relationship upon TORQUE. So if you can get GREAT flow with a smaller valve, the motor will produce LOTS more torque then a larger valve with the same flow. I got about 210 CFM at .600" lift, at 25" of water for a pressure. I will say it one more time, the MN47 is the BEST bang for the buck, by far.

[JMortensen]

I will go so far as to say that for a guy in CA who doesn't want to spend money on AV Gas or other high octane fuel the MN47 would be the WORST head possible, by far.

[JMortensen]

More compression and ping info: http://forums.hybridz.org/showthread.php?t=102568

[BRAAP]

First off, 1fast Z, it appears that you have some valuable experience in the field of exotic Datsun building and it is quite possible that you have been able to get the Maxima N-47 to work on a flat-top L-28. I don’t want you to think I’m discrediting your work or abilities, though I do question your giving that advice on the forum without qualifying that advice. Honestly, just how many other Maxima N-47 flat-top L-28 combos have you heard of that work with NO issues on pump gas? I’m not talking about “grease ball Bubba” who makes these claims because his engine barely started with this combo, but honest, proven, legitimate claims that it works? I’ve been around, and building performance Datsuns for quite a few years now, your claim as to this combo working on pump gas is the only one I’ve heard of and if you are getting this combo to work on pump gas, you probably should make it clearer to the forum readers that not just any ole Maxima N-47 with any ole cam and carbs/EFI will work. At least 50% of the readers are newbies that wouldn’t understand this and would just take your advice at face value and go out put a Maxima N-47 head on their flat-top L-28 only to have it detonate itself to death. I now that is not what you would want. Let them know that they should use your modified version of the Maxima N-47, what ever minimum intake valve closure point is needed, ign timing parameters, etc.

 

Now here is why the rest of us won’t run pump gas through our flat-top L-28’s with the Maxima N-47 head…

If the combustion process is ideal, i.e.fuel mixture is ideal, and the ignition timing is ideal with race gas AND pump gas at the same timing settings, and not overly radical cam timing, i.e. using a STREETABLE cam, then dynamic compression could be low enough at low RPM to run on pump gas, but once the RPMs rise and the engine is “on the cam”, then dynamic compression rises and once it rises to a certain point, (if the engine is properly tuned and dialed in with a good combination of cam, intake tract, and exhaust tract), it’s VE will be greater than it was stock and therefore will be more prone to detonation as there is more cylinder pressure before the ignition process is initiated. I have been pretty successful in Datsun L-series builds and I also specialize in exotic Datsun L-series head work, (extensive porting, chamber reshaping, 5 angle valve seats using Sunnen VSC seat cutters exclusively, etc), but I find it rather hard to believe that the L-28 flat top-Max N-47 head combo doesn’t detonate or ping to some degree on pump gas unless the timing is backed way off from ideal or even backed off from stock settings. I would be interested in reading what a knock sensor records on this combo running pump gas and with ideal ign timing, not backed off. (No guys, I will not volunteer my engine for such a test, LOL). My personal F-prepared track car 240 Z is powered by a flat-top L-28 with one of my “super-whiz-bang” Maxima N-47 heads, I run Av gas through it to keep the denotation demons from breaking my rings. Detonation can happen even mildly, inaudible, and over extended periods of this inaudible detonation, a major reduction in engine life is the result, i.e. hammered rings and rod bearings evidenced by the top compression rings with a step on the top and bottom, and the bearings tend to squish out. At moderate levels of detonation, broken rings and severely hammered rod bearings are the result and at the extreme end, which is usually audible detonation, burnt pistons, broken rings, and again squished out rod bearings. As a performance engine builder, I’ve seen many a customer bring many a hammered street engines through the shop to have us fix their mistakes, and detonation from too high a static comp ratio is just one of those mistakes many engine builders make and almost every single one of them say they never heard it pinging or detonating! In that statement, if you are able to get the Maxima head on a Flat top L-28 to work on Pump gas with a street cam and without backing out the ign timing, then we should not assume that any Joe Blow that wants the ideal set up should be able to just bolt on a Maxima N-47 head to his Flat Top L-28 bottom end and have it live for 100,000 miles of street driving on pump gas.

I’m not saying with complete confidence that this combo can’t be run on pump gas and that you haven’t been able to do this yourself, but you must admit, the odds are definitely against it working for “Joe Blow” without some of your special customized head work and meeting certain tuning parameters….

[JMortensen]

^^^What he said.^^^

[Gollum]

Hmm when I first read this post I thought for sure it wouldn't get any replies.

 

To back up what braap said...

 

http://www.streetrodstuff.com/Articles/Engine/Detonation/

 

detonation can be very hard to notice and under a mild engine builds unoticable until the engine is pushed hard. Like BRAAP mentioned, you might be fine under low RPM, but higher RPM and on pump gas you'll most likelly have SOME form of detonation. But if you're not getting very much HP/CI then the motor can usually take it, as long as it's not sustained.

 

And I must just be a plain fool to not believe that a 11.1 compression non corss flow 2v motor won't detonate on CA spec 91 octane. There are plenty of vehicles that will detonate on CA gas from facotory, but have knock sensors to retard the timing. With an old L series motor you're gonna run into problems. You'll NEED a programable ECU and some dyno tuning time just in hopes to get it to run on 91 octane.

 

To just assume bolting on a MN47 head on a flat top L28 will be fine and dandy, is just plain wishful thinking.

 

But I still believe it's perfectly doable. Just takes more care that most people will realise.

[1 fast z]

On my setup, I run Megasquirt, so yes, I do have some more tuning advatages over others. I run 36 Full at 2000 RPM with my setup as well. NO ping, and I have pulled apart the motor, before, to verify this, no broken rings, ring lands, bearings perfect, etc. If you just tune the car to run a little "fat" then it will work perfectly. Now if you run 11+to one on a open chamber head, such as the N42, N47, NON-early E88, etc. You WILL see ping with that much compression. QUENCH is the key here. The next key is that you need to run no more than .030" piston to head clearence, to obtain this quench therory. When that piston comes up there, and smashes all that charge and pushes it torawads that spark plug, and attomizes that charge well, you will DEFFINITLY reduce detonation. With an ALLUMINUM head, such as L series, the heat gets dissapated alot quicker than with that of an IRON head, and you can generally run a point more compression with an alluminum head for that reason, and people run 10.5-1 ALL day on Iron heads. Another easy way, is to just run more duration on your cam, that will help BIG time on detonation. I run a 270-280 adv cam on my setup.

[JMortensen]

Just for reference I have an L28/E31 combo with ~11:1 and polished chambers. I run 44 Mikunis which run in the high 12:1 air/fuel range under WOT (according to a narrow band O2), I have a .490/280 cam, and in CA and here in WA I have to have at least 95 octane in order to run full timing advance in the mid 30's. No point in having the compression if you have to back the timing way off, which is what I read about lots of people doing.

 

I've been probably the BIGGEST proponent of quench here, had it out with Dan Baldwin a couple times. I think the quality of the gas you're using makes a HUGE difference, and I think that quench is important but can't overcome the crappy gas some parts of the country have.

[1 fast z]

Yea, you cant tell ANYTHING from a narrow band, so you could be at 14-1, or 10-1, who knows. WIDE band, is the only way to make sure what the ratio is. A E31 does NOT have as high of quench as a MN47 head though, so your loosing some there. I went from a 9.8-1 Flat top, and ZN47 head, and had ping, then kept everything else constant, then went to a 11-1 HIGH quench setup, and got rid of the ping. QUENCH, ill say it again, QUENCH is the key here. Again, this is just my opinion, no one has to follow, doesnt matter to me, Im just tying to shed some of my experience and light on the issue.

[Mack]

great, now I get sucked into this thread......

 

How many guys are runnig a Maxima N47 (P47 ) with flat tops in a street motor on pump gas?

 

ME.

 

Been running it for over a year now, DELIVERING PIZZAS. probably have in excess of 20K on this set-up. I did do some mild porting. had the valves unshrouded out to the fire ring. blended the exhaust bowl area into the liner and took out some rough edged casting marks on the intake runner. I am running a 260Z "C" stamp camshaft (256 duration, same lift as other L engines) Im running STOCK 280ZX FI, and boy, does it suck. I took the injector bumps out of the intake manifold and put a 60MM TB and ported it to match. and I have a cat back 2.5" mandrel bent exhaust.

 

I set my timing for about 12 to 15 degrees initial, i run pump gas all day long. I DO get ping, only AFTER about 3500 to 4000RPM which is when the poor flapper door AFM is maxed out and the computer swithces to an RPM/fuel curve. It hits like a switch every time, right at 3500 to 4000rpm, depending on ambient air temp. If you dig around the forum, you will find that the stock AFM's and therefore the a/f ratios go to crap at this point.

 

Now, I can run mid-grade gas and it runs fine for highway cruising and around town. No ping unless its over about 75* ambient. no ping whatsoever on the highway, just flat out cruising.

 

this is the ticket. I took it to a dyno for fun, again only having the mods listed in here..... I dont have the chart, but it put down a peak of 141rwhp.... at only 4100rpm. the reason I didnt go higher was because I had a bad igntion control unit. It wouldnt let me rev past about 4500RPM. it was screwing the tiing up past that point. Now, look around at dynos of stock L28's and you will find that they put down about 95rwhp at this point (4100RPM) so, clearly this set-up is worth something.

 

If I had Megasquirt or even 300ZX EFI with a MAF, I almost garauntee you it wouldnt ping. Hell, if I even had an adj. fuel pressure regulator, I could probably cure it.

 

edit: screw you. I still refuse to call it an MN47, its a P47 to me, lol!! j/k!

[Gollum]

Like I had said, there's gonna be ping issues unless you're using an aftermarket FI system.

 

That's the sum of 'my' previous post. So even as you've show, it's nothing close to a bolt on power adder. Such a recomendation needs more explaination than 1 fast z's origonal post, unless you like to deal with ping issues.

[1 fast z]

What the hell is a P47??? No one knows what the heck that is, so stop, freakin saying it!!! LOL. Everyone knows, its MN47!

[1 fast z]

I know that my customers use DCOE's with the MN47 setup, and run on pump gas, with NO ping. LIke I said, it doesnt make one bit of difference to me which head you guys use, I am just shedding some light.

[JMortensen]

great' date=' now I get sucked into this thread......

 

How many guys are runnig a Maxima N47 (P47 ) with flat tops in a street motor on pump gas?

 

ME.

 

Been running it for over a year now, DELIVERING PIZZAS. probably have in excess of 20K on this set-up. I did do some mild porting. had the valves unshrouded out to the fire ring. blended the exhaust bowl area into the liner and took out some rough edged casting marks on the intake runner. I am running a 260Z "C" stamp camshaft (256 duration, same lift as other L engines) Im running STOCK 280ZX FI, and boy, does it suck. I took the injector bumps out of the intake manifold and put a 60MM TB and ported it to match. and I have a cat back 2.5" mandrel bent exhaust.

 

I set my timing for about 12 to 15 degrees initial, i run pump gas all day long. I DO get ping, only AFTER about 3500 to 4000RPM which is when the poor flapper door AFM is maxed out and the computer swithces to an RPM/fuel curve. It hits like a switch every time, right at 3500 to 4000rpm, depending on ambient air temp. If you dig around the forum, you will find that the stock AFM's and therefore the a/f ratios go to crap at this point.

 

Now, I can run mid-grade gas and it runs fine for highway cruising and around town. No ping unless its over about 75* ambient. no ping whatsoever on the highway, just flat out cruising.

 

this is the ticket. I took it to a dyno for fun, again only having the mods listed in here..... I dont have the chart, but it put down a peak of 141rwhp.... at only 4100rpm. the reason I didnt go higher was because I had a bad igntion control unit. It wouldnt let me rev past about 4500RPM. it was screwing the tiing up past that point. Now, look around at dynos of stock L28's and you will find that they put down about 95rwhp at this point (4100RPM) so, clearly this set-up is worth something.

 

If I had Megasquirt or even 300ZX EFI with a MAF, I almost garauntee you it wouldnt ping. Hell, if I even had an adj. fuel pressure regulator, I could probably cure it.[/quote']

That's supposed to be an ENDORSEMENT? I would HATE to have to drive such a hamstrung engine on the street. No ping unless it's over 75º or 3500 rpm! Even here in Seattle that means that there's months when I wouldn't be comfortable driving it just due to the weather being too warm. Then there's the 3500 rpm thing. Limited to 3500 rpm = SUCK ***. I'd rather have a P79 or P90 and 8.5:1 compression running 35º total advance than have 11:1 compression and not be able to go past 3500 rpm or drive when its 80º outside. I guarantee you my old engine at 8.3:1 which revved to 7000 rpm and didn't ping on 87 no matter how hot it was would WHIP THE POO out of your hamstrung high compression motor.

 

All I can tell you Mack is that you need to get a hold of some high octane gas and see what that engine is actually capable of. It'll blow you away. Be careful though, because if you find out what your engine is actually capable of, you'll HAVE to buy the high octane gas from then on out.