heads

[z-ya]

I run my F54/N47 combo with a stock cam and no port/pollish all day on pump gas. I scoped it on the dyno just to be sure it wasn't pinging. I've go the total advance set to 26deg. 165WHP and 175WT. Very bullet proof and streetable. I run northeast 93 octane or better in it.

[JMortensen]

I know we've talked about yours before too Pete, but you should try some high octane gas too and see what that last 10 or so degrees of timing would do for the whp. Or just get a bigger cam.

[JMortensen]

I'm going to shut up now. Maybe BRAAP will keep the argument going, but I think I've said all I need to say, and it doesn't seem to be making a dent.

[BlackBeaut]

Put of interest for us people of Non-US origin, has anyone got any pics of the MN47 chambers, maybe some comparison with the other common heads, E88s, N42s, P90s etc.

 

I know in the UK we did get a Maxima with an L24 engine, but I've no idea what the head is on that. I've also got an L28 that came out of an '87 Patrol which is an N42/F54 combo, that head has FI cutouts on the inlet, so is this head of better design than the '70s N42, or what?

 

Cheers,

Rob

[RacnJsn95]

I've read of AT LEAST 4 or 5 guys on zcar.com that run the Maxima N47 head on a flattop engine, and have no problem with ping. I'm going to stick one on my new engine once I get it done, not that it matters to anyone, I'm just a regular guy.

[Mack]

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.

 

I should have clarified. I dont get ping UNLESS I am over 90% throttle. I can go 3/4 thorttle and take it to redline and its fine. I can shove it in 5th gear, go up a hill and mash the throttle and it wont let out a peep ntil the RPM's get to 3500. And the thing about the temperature,..... the temperature only affects what RPM it starts to ping at in the 3500 to 4000 range. Im thinking it has something to do with the density of the air and how much you need to move through the flapper door to get it wide open.

 

oh, and I doubt your 8.3:1 engine would make a 1980ZX 2+2 run low 15's in the 1/4 mile.

 

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.

 

I do need to get some high octane gas, but that would be a bandaid. I NEED megasquirt. that would be the proper way to do it.

 

It was stated in this guys original post that he was running webers (albeit DGV's, not DCOE's) that would probably run a little richer than the STOCK EFI. You can just slap a P47 on a flat top block and it will run, it will be quicker than a stock motor by far. you will deal with ping only under WOT (or close to it) unless you go megasquirt or 300ZX stuff.

 

Hey, Ive been using my car for pizza delivery for about 20K miles, plus towing trailers, boats, motorcycles, cross country trips. My engine runs like a champ. nice and smooth. good oil pressure, seemingly good compression (havent checked it), when it cranks over, its very even. I have a 1978 for van with a 460 in it that is NOT so even tho, lol!! the point im trying to make is that I have not broken any ring lands or mashed any rod bearings from my pinging.

[Mack]

oh yeah, BLACKBEAUT...

 

here is the pic you requested......

 

 

the maxima N47 is on the left, a regular 280Z/ZX N47 is on the right. the chamber CC's out to be right around the 39cc mark. very nice quench area.... hope this pic helps!

[Pyro]

FYI, The reason the quench design is less prone to detonation is not because it is just quenching. The quenching effective makes the flame travel faster and therefore requires less ignition timing advance to complete the burn. So, less timing prevents detonation without reducing power. But I'm not sure how much less the MN47 requires compared to the Old N42. On small block chevys, the fastburns need about 6 degrees less than the old style heads.

[JMortensen]

I think this was pretty much addressed to me, so I'll respond.

I should have clarified. I dont get ping UNLESS I am over 90% throttle. I can go 3/4 thorttle and take it to redline and its fine. I can shove it in 5th gear, go up a hill and mash the throttle and it wont let out a peep ntil the RPM's get to 3500. And the thing about the temperature,..... the temperature only affects what RPM it starts to ping at in the 3500 to 4000 range. Im thinking it has something to do with the density of the air and how much you need to move through the flapper door to get it wide open.

Again, this is a GOOD thing???

oh, and I doubt your 8.3:1 engine would make a 1980ZX 2+2 run low 15's in the 1/4 mile.

With my HORRIBLY slipping clutch it ran the quarter in 15.5 at 108 according to the gtech with a vehicle weight of 2635 lbs. When you knock a couple mph off and do the old trap speed to hp equation comes out around 250whp. Still think it couldn't get your ZX into the low 15's? Maybe not without the new clutch...

I do need to get some high octane gas, but that would be a bandaid. I NEED megasquirt. that would be the proper way to do it.

I'm betting not. I think you'd have to run super rich to keep from pinging with MS on your setup. If you stepped up to 95 or so in the octane, I'd bet you could run a good ratio in the low 13:1's and run all the timing you needed to maximize performance.

It was stated in this guys original post that he was running webers (albeit DGV's, not DCOE's) that would probably run a little richer than the STOCK EFI. You can just slap a P47 on a flat top block and it will run, it will be quicker than a stock motor by far. you will deal with ping only under WOT (or close to it) unless you go megasquirt or 300ZX stuff.

I bet if you slapped a shaved P90 on a flat top block and could run a proper amount of advance without pinging it would be faster.

Hey, Ive been using my car for pizza delivery for about 20K miles, plus towing trailers, boats, motorcycles, cross country trips. My engine runs like a champ. nice and smooth. good oil pressure, seemingly good compression (havent checked it), when it cranks over, its very even. I have a 1978 for van with a 460 in it that is NOT so even tho, lol!! the point im trying to make is that I have not broken any ring lands or mashed any rod bearings from my pinging.

Still sounds sucky to me. "I haven't broken any ring lands" is not something to be bragging about IMO.

[1 fast z]

Your car ran 15.5 at 108? HMMMMMMMM, those numbers dont jive at ALL. For the reason that 108 is easily in the 12's, and 15.5, is around 85 MPH or so, give or take. You have some problems there. And let me say this again, I run 11.3 ON my Megasquirted DAILY driver, and I dont mean pussy footing around, anyone who knows me (lots of people on the board) KNOWS that I drive VERY hard, 7k, DAILY, and NO detonation. You can take a N42 head, or any other open chamber head, and you take a closed chamber head such as the MN47, you can run about .5-.6-1 more compression, with the same amount of timing. Once again, QUENCH!!!

[JMortensen]

Your car ran 15.5 at 108? HMMMMMMMM, those numbers dont jive at ALL. For the reason that 108 is easily in the 12's, and 15.5, is around 85 MPH or so, give or take. You have some problems there. And let me say this again, I run 11.3 ON my Megasquirted DAILY driver, and I dont mean pussy footing around, anyone who knows me (lots of people on the board) KNOWS that I drive VERY hard, 7k, DAILY, and NO detonation. You can take a N42 head, or any other open chamber head, and you take a closed chamber head such as the MN47, you can run about .5-.6-1 more compression, with the same amount of timing. Once again, QUENCH!!!

I had just installed my Mikunis when I did that 1/4 run and was running a stock clutch. The stock clutch was starting to be too weak for the old engine with SU's, and it wasn't anywhere close to holding down the power with the triples. I know the numbers don't jive, but that's because of the clutch.

 

One more time, QUENCH is great, but octane is going to be necessary for anyone who lives in a state with 91.

[Mack]

Jmortensen>>>>>>Look, I dont know why you are getting into a pissing contest with me about this head. I run it, have been running it for quite some time and my engine survives to this day. Someone on this board asked if there was anyone out there running this, I said it was me.

 

The ONLY bad thing about the car is the crappy EFI. Megasquirt.....That woudl take care of my problems. Putting the car in 5th and lugging it up a hill SHOULD produce tons of ping if it were a compression/poor chamber design related ping. but, since its an EFI/bad tuning related ping, it DOES NOT ping at low RPM's only when the ECU goes into its little AFM-maxed-out-tirade and goes lean. STOCK ENGINES go lean at this point, like in the 14's AFR's under WOT. thats not good. the reason they do not ping is because of 2 factors. the air flwo isnt there and the compression isnt high enough to ping on a 14:1 AFR. OPTIMUM AFR's for performance on an N/A engine are somewhere in the 12.5 ~ 13.0 range.

 

So, J mortensen, you are telling me that you had a car that put down 250RWHP with 8.3:1 compression?!?! thats not even close to right, unless you have some MAJOR headwork. either that or you are running a 3.1 or 3.2L. Ive NEVER seen a dyno for an L28 that put down even CLOSE to 250rwhp with a 8.3:1: compression ratio. Me thinks your G-tech is fouled. How would a shaved P90 run any better than a maxima head? unless you are shaving it less than .080", but I ASSUME you are talking about "the mod"? It would run worse. less compression = less power.

 

I bet if I put mikunis on my car it would scream too. However, I am running a stock L26 cam, stock intake manifold and stock exhaust manifold. put all these stck parts on your 8.3:1 motor and it would be in my rear view by the end of first gear.

 

 

BOTTOM LINE.... you can slap a P47 () on an F54 flat top block and have a decent little screamer if you can live with a little ping under WOT. A better set up would be megasquirt to tune the ping out of it. an even better set up would be a cutsom intake manifold (cough*1 fast Z's* cough) and megasquirt. The stock EFI system and manifold both suck. oh yeah, a cam would be nice too. thts my next upgrade. somethign with more than .410" of lift and a lil more duration than 256*, lol!!

[JMortensen]

Jmortensen>>>>>>Look, I dont know why you are getting into a pissing contest with me about this head. I run it, have been running it for quite some time and my engine survives to this day. Someone on this board asked if there was anyone out there running this, I said it was me.

Because I think you and 1 fast z are misleading people. Not intentionally, not with malice, but I think you are.

The ONLY bad thing about the car is the crappy EFI. Megasquirt.....That woudl take care of my problems. Putting the car in 5th and lugging it up a hill SHOULD produce tons of ping if it were a compression/poor chamber design related ping. but, since its an EFI/bad tuning related ping, it DOES NOT ping at low RPM's only when the ECU goes into its little AFM-maxed-out-tirade and goes lean. STOCK ENGINES go lean at this point, like in the 14's AFR's under WOT. thats not good. the reason they do not ping is because of 2 factors. the air flwo isnt there and the compression isnt high enough to ping on a 14:1 AFR. OPTIMUM AFR's for performance on an N/A engine are somewhere in the 12.5 ~ 13.0 range.

I guess we'll see if the engine pings after you get MS installed. Until then I can only go on what you're telling me, which is that it pings at high rpms. FWIW I've always tried for 13.2:1 on my NA engine. I think the 12.5 is a turbo thing, adds a little bigger safety margin cause they need it.

So, J mortensen, you are telling me that you had a car that put down 250RWHP with 8.3:1 compression?!?! thats not even close to right, unless you have some MAJOR headwork. either that or you are running a 3.1 or 3.2L. Ive NEVER seen a dyno for an L28 that put down even CLOSE to 250rwhp with a 8.3:1: compression ratio. Me thinks your G-tech is fouled. How would a shaved P90 run any better than a maxima head? unless you are shaving it less than .080", but I ASSUME you are talking about "the mod"? It would run worse. less compression = less power.

It wasn't my Gtech. A friend borrowed it when he found out I was ready to install the triples. He had it for 3 days, we got to use it on the last day because I was working out linkage and other crap. When I finally got all that working, the clutch was way beyond unable to deal with the increased hp. We did the test anyway just for kicks. This was the original gtech setup which reads fast on the trap speed (or so I hear). I figure it was probably good for 105 mph corrected, and probably would have been higher had the damn clutch not slipped so much. It was probably still slipping a bit 2 or 3 seconds into 3rd and 4th gear. I do have a lot of headwork done, and I have the larger cam. This video was taken a couple days after we did that test. I had just installed the ACT clutch at this point: http://videos.streetfire.net/player.aspx?fileid=3B512F0F-8AD1-4DAB-BD8E-0AE1768FB642

 

Compression does NOT equal power!

Compression does NOT equal power!

Compression does NOT equal power!

Compression does NOT equal power!

Compression does NOT equal power!

 

From the other thread I linked to earlier:

interesting you mentioned that. You know' date=' once when I dynoed that setup, my friend was along with his Z, and he had a VERY similiar motor setup. We dynoed back to back. Our power outputs were within like 5hp.

 

The big difference, is that he was running dished pistons, and I THINK a different head as well, not 100% sure that was like 4 years ago. But at any rate, I remember that his motor was much lower compression than mine, about 9:1 if I remember right. But otherwise our mods were almost identical, including almost identical cam specs, identical header, very similiar exhaust... almost everything.

 

BUT, he was running like 13 or 14 degrees BTDC at idle vs. my 8 degrees.

 

We were both VERY surprised when his dyno came out so close to mine, as we both expected mine to be significantly higher with my much higher compression. That was one of the first times it really hit me just how much power is really hidden away in timing advance. Sure there may have been other things contributing there, but it sure seems to me the timing advance was the most significant difference in our setups other than his being much lower comp.[/quote']

See what I mean? Bastaad was running a point and a half more compression than his friend but they were within 5 hp on the dyno. Depending on what ignition system his friend was running even he sounds like he might not have been running enough timing.

I bet if I put mikunis on my car it would scream too. However, I am running a stock L26 cam, stock intake manifold and stock exhaust manifold. put all these stck parts on your 8.3:1 motor and it would be in my rear view by the end of first gear.

Not necessarily. Probably, but not necessarily.

BOTTOM LINE.... you can slap a P47 () on an F54 flat top block and have a decent little screamer if you can live with a little ping under WOT. A better set up would be megasquirt to tune the ping out of it. an even better set up would be a cutsom intake manifold (cough*1 fast Z's* cough) and megasquirt. The stock EFI system and manifold both suck. oh yeah, a cam would be nice too. thts my next upgrade. somethign with more than .410" of lift and a lil more duration than 256*, lol!!

In the long run your engine probably won't like pinging at WOT. It may not have caused any serious damage YET, but it will if you keep it running like that and run it at WOT all the time. A big nasty cam would help you out a LOT. Aftermarket EFI would help A LOT.

 

That is the reason why I keep arguing. Because you really SHOULD have those things to run this high compression engine on pump gas. If you don't, then you shouldn't be doing it, and you shouldn't be telling other people to do it IMO.

 

I LOVE the MN47 head. If I were going to build another L head for racing, that would be it for sure. Key words "for racing".

[1 fast z]

YES COMPRESSION IS A DIRECT REALTIONSHIP UPON POWER IN TORQUE!!!!

 

 

 

Dang what has this come to. NO you cannot compare two DIFFERENT motors, and say, "well, his motor is the same as mine, except for the compression, there are MANY different factors to be played. The compression basicly just shifts up both curves.

 

 

 

 

How are we missleading people???? I am saying that my setup with MS, just like MACKS would be if he were running it works GREAT. I never dynoed my car, but I ran 13.9, at 101, with a weight of 2950lbs, not bad if you ask me.

[JMortensen]

YES COMPRESSION IS A DIRECT REALTIONSHIP UPON POWER IN TORQUE!!!!

NO IT ISN'T!!!! As Bastaad said, the engines in his example were pretty well identical except for the compression but the lower compression engine that could have an appropriate amount of advance made more power.

 

Another example: my old engine vs my new engine. I agree that my 11:1 engine makes more power than my 8.3:1 engine did. A lot more. BUT if I have to run 91 it won't stop pinging until the advance is set to 5º at idle. When it is running with the distributor set that way with only 22º total advance, it makes WAY LESS power than the old 8.3:1 did.

 

The only way to get the new motor to run the right amount of advance without pinging is to run 95 octane. I think you guys are setting people up to build motors that will require 95 octane or better to run without pinging, while running total advance in the mid 30s. I say that because of my own experience, and the experience of other people on this board. It's not just my opinion.

 

I already tried to bow out of this argument once. This time I mean it. I'm gone.

[BRAAP]

I think Jmortension was referring to the fact that a bump in compression ratio isn’t going to yield significant power gains in of itself and that compression ratio alone is not an attribute to build an engine around, but yet the compression ratio is one facet that is modified to make the most out of a particular combination of chamber shape, cam specs, useable RPM range, etc.

With that said, yes, raising the compression ratio will increase torque and power, pretty much linearly across the power band, but not a whole lot, in fact, (depending on how much of a bump in compression was made), it would be somewhat difficult to FEEL with our “butt dyno” but a chassis Dyno would show this increase and if the driver is consistent enough, it might even show up in the ¼ mi MPH.

Now depending on how radical the engine components that are being utilized are, will dictate how much of an advantage that bump in compression is worth. The more radical the set up, i.e. bumpy cam, huge ports, etc, the higher the percentage of gain a raise in compression ratio will be vs an engine that is mild such as a stock engine. There are several other factors that more compression will help or could hinder, but that is not the scope of this thread and I really don’t have time this week for another novel, (i.e. the thread “big and nasty headwork”. http://forums.hybridz.org/showthread.php?t=104420 )

In short, higher compression does compliment big cams, big ports, etc.

It is a fine balancing act, but when all the parts are balanced to each other from many aspects, the combination will be a robust one that performs a little better than your garden variety performance engine that the builder just “threw” cool parts at.

 

1fastZ, those are respectable numbers, 13.9 @ 101 for 2950 lbs Z. Nice work.

 

 

As an aside, where the heck did this “P-47” crap come from? The last time I checked, the head was cast with an “N47”, no “P” anywhere. Though I can see where someone who hasn’t really studied the head from a design standpoint might call the MN47 a “P” series due to the fact that the chamber does resemble the P-79 and P-90 chambers in generic outline shape only. If you look closely, the P series heads and the Maxima N-47 chambers are not shaped the same. Plug bosses are different, chamber wall shape, etc. I personally feel that the “P” designation on the P-79 and P-90 heads references the entire design as a whole, not only with the newly designed chamber, but also the shorter valves and revised ports with their sharper short side radius etc. The Maxima N-47 has the standard valve length and port shapes, etc. of the Z car N-47. From several aspects in the heads design, the Maxima N-47 resembles the early heads “way more” than it does the newer P-series. Sorry guys, but it is cast “N47” and being as it does resemble the “N” series MUCH more than the “P” series, it only makes since to call it what it is, the Maxima N-47 or MN47 for short. Or how bout call it the N47-A, (beings as the “A” suffix seems to denote hydraulic lifters on the P90 head’s) maybe designate it the N47-B, or N47-M?

Or you could just keep on calling it a P47 and the rest of us will just chuckle at you every time we see the “P47” in a post, LOL

[1 fast z]

"As an aside, where the heck did this “P-47†crap come from? The last time I checked, the head was cast with an “N47â€, no “P†anywhere. Though I can see where someone who hasn’t really studied the head from a design standpoint might call the MN47 a “P†series due to the fact that the chamber does resemble the P-79 and P-90 chambers in generic outline shape only. If you look closely, the P series heads and the Maxima N-47 chambers are not shaped the same. Plug bosses are different, chamber wall shape, etc. I personally feel that the “P†designation on the P-79 and P-90 heads references the entire design as a whole, not only with the newly designed chamber, but also the shorter valves and revised ports with their sharper short side radius etc. The Maxima N-47 has the standard valve length and port shapes, etc. of the Z car N-47. From several aspects in the heads design, the Maxima N-47 resembles the early heads “way more†than it does the newer P-series. Sorry guys, but it is cast “N47†and being as it does resemble the “N†series MUCH more than the “P†series, it only makes since to call it what it is, the Maxima N-47 or MN47 for short. Or you could just keep on calling it a P47 and the rest of us will just chuckle at you every time we see the “P47â€, LOL"

 

 

 

I am soooo cracking up right now over all of this, hahahahaaha. YOU LOST MACK. (mack and I have argued over this for a year, lol.)

[Gollum]

How are we missleading people???? I am saying that my setup with MS, just like MACKS would be if he were running it works GREAT. I never dynoed my car, but I ran 13.9, at 101, with a weight of 2950lbs, not bad if you ask me.

 

 

 

 

MN47!!!!

 

 

 

Nuff said.

 

 

I personally never said it couldn't be done or was a bad idea. I just stated that more information needed to be given' date=' EXPECIALLY to people where 91 octane is the best avaible. Some very careful consideration needs to be taken for say, someone like me who lives in CA. Running this head might end up being more expensive for the power than just buying a L28ET from a junkyard, or even using the stock head and having it ported and putting a larger cam in. There are lots of options to consider. The MN47 seems like a GREAT option, if you can run 93 in it and be fine where you live. This isn't an option for many people. This is my only argument. That just giving people a head recomendation without any type of disclaimer seems rude to me.

 

And I don't think anyone took notice of the link I posted, so I'll post some parts that apply here.

 

One thing to understand is that detonation is not necessarily destructive. Many engines run under light levels of detonation, even moderate levels. Some engines can sustain very long periods of heavy detonation without incurring any damage. If you've driven a car that has a lot of spark advance on the freeway, you'll hear it pinging. It can run that way for thousands and thousands of miles. Detonation is not necessarily destructive. It's not an optimum situation but it is not a guaranteed instant failure. The higher the specific output (HP/in3) of the engine, the greater the sensitivity to detonation. An engine that is making 0.5 HP/in3 or less can sustain moderate levels of detonation without any damage; but an engine that is making 1.5 HP/in3, if it detonates, it will probably be damaged fairly quickly, here I mean within minutes.

 

Production engines are optimized for the type or grade of fuel that the marketplace desires or offers. Engine designers use the term called MBT ( Minimum spark for Best Torque) for efficiency and maximum power; it is desirable to operate at MBT at all times. For example, let's pick a specific engine operating point, 4000 RPM, WOT, 98 kPa MAP. At that operating point with the engine on the dynamometer and using non-knocking fuel, we adjust the spark advance. There is going to be a point where the power is the greatest. Less spark than that, the power falls off, more spark advance than that, you don't get any additional power.

 

Now our engine was initially designed for premium fuel and was calibrated for 20 degrees of spark advance. Suppose we put regular fuel in the engine and it spark knocks at 20 degrees? We back off the timing down to 10 degrees to get the detonation to stop. It doesn't detonate any more, but with 10 degrees of spark retard, the engine is not optimized anymore. The engine now suffers about a 5-6 percent loss in torque output. That's an unacceptable situation. To optimize for regular fuel engine designers will lower the compression ratio to allow an increase in the spark advance to MBT. The result, typically, is only a 1-2 percent torque loss by lowering the compression. This is a better trade-off. Engine test data determines how much compression an engine can have and run at the optimum spark advance.

 

For emphasis, the design compression ratio is adjusted to maximize efficiency/power on the available fuel. Many times in the aftermarket the opposite occurs. A compression ratio is "picked" and the end user tries to find good enough fuel and/or retards the spark to live with the situation...or suffers engine damage due to detonation.

 

So why do you say that higher compression is always better again 1 fast z? In theory you're right, and I agree with you, but if I have to run 91 octane there are other factors to consider.

 

Now, has anyone considered a high profile head gasket to bring the compression down .5 or so? That seems like a great idea for people running a MN47 on lower octanes.

[1 fast z]

"Now, has anyone considered a high profile head gasket to bring the compression down .5 or so? That seems like a great idea for people running a MN47 on lower octanes."

 

 

 

 

Ok, you are loosing nearly ALL quench by doing this, if you read what I stated above, I say that you need about .030" to get MAXIMUM quench effect. Doing what you say will decrease compression, but will also decrease quench, and more than likely you will have the SAME amount of detonation, for the reason that you lost all of your quench.

[Gollum]

Well, lowering the compression would lower the burn temperature and temp within the chamber, wich are the two things that create detonation. Maybe I'm just stupid.

 

I understand quench is good. But you make it sound like you achieve all the quench from the compression (stating that lowering the compression .5 will ruin the quench) instead of the actual chamber design.

 

So if .5 will loose "nearly ALL quench" how do low compression motors not detonate themselves to death? I'm not knocking you down, I just want to understand your philosophies on the subject.