heads

[Mack]

a high quench head in and of itself is not less prone to detonation, but a high quench head and motor designed to take advantage of it IS less prone to detonation, and not just because of the timing factor/flame travel factor.

 

A motor that is designed for it has .035" or less clearance between the top of the piston and the quench pad on the head. HERE is a good article on Quench.

 

jsut a small exerpt

 

In a running engine, the .035" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, reduce detonation and increase power. Take note, on the exhaust cycle, some cooling of the piston occurs due to the closeness to the water cooled head.

 

EDIT: hoov100, are you running a Maxima N47 or just a regular Z/ZX N47 head? they are NOT the same! nor are they even close! lol

[hoov100]

just a regular old n.o.s n47

[Lockjaw]

Your car ran 15.5 at 108?

 

You need to get your Gtech checked.

 

I would like to weigh in on this subject. My friends and I took a p79 and milled it 110 thousandths, and ran a nice big crower in it, and it required a little octane boost with 93 octane gas.

 

Now I don't know about the CC's of this head versus the Maxima head, but I would bet on needing some good timing control to keep detonation at bay.

 

The bottom line is running that head on a flat top engine is not the thing to do for someone who is not very versed in Z engines, and tuning them. Run a p79 or p90 milled about 75 or the N42 and be safe.

[BRAAP]

Actually, I moved back to MN now. The E31 has a different comustion chamber design than an MN47 (you win 1 fast Z). While the E31 is high quench, its not as much of a quench design as an MN47 (ugh, it hurts everytime I type it, J/K), its just basically a small chamber. Or at least this is what I remember My E31 head looking like before I sold it. I still have on, but its on a car right now. bone stock early early 71.

 

 

Mack,

You are not interpreting your feelings correctly. Your feelings were correct in calling the Maxima N-47 what it TRULY is, the MN-47. With its same valve length as the Z N-47, same exact intake and exhaust port as the Z N-47, etc.

 

“Da Nile” is not just river in Egypt you know, LOL..

 

On a serious note, the E-31 chamber is slightly different from the MN-47 head. The MN-47 head has a much more efficient design from the standpoint of the burn process. For example, just look at the late model VORTEC heads from GM with the spark plug way close to the middle of the combustion chamber, a nice SMALL high squish combustion chamber etc. This is not a direct exact comparison, but was used to illustrate how the newer cylinder head, (aka “the new kid on the block”), has brought more power potential to the table vs the old technology. The Maxima N-47 head has leaps and bound more technological design in the combustion chamber and port design and especially shape, than the E-31 ever thought of having.

 

“Mack” Daddy, (LMAO), you’ve come along way baby in realizing that the MN-47 head is “DA” head of choice for nice N/A warm-mild-semi wild street/mild race L-series 6 cylinder heads….

 

BOOYAaaa… The MN-47….

 

 

(In my best Darth Vader impersonation...)

 

Mack… Come over to the dark side… Young Jedi…

...The Dark side is more powerful than you can ever imagine….. LOL

[Silent]

question.

 

is there a way to tell on the outside ofthe head, if it is a z head or maxima head?

 

another note

108 mph is good for mid 12's under severe traction {ie dead hook} i have seen 11's out of 108 mph {very very well set up mustang}

 

1/4 mile time does not equate to how fast a car is. show me mph, then i'lltell you if i want to runyou or not. but at 108, thats a negative. me running 14.0 @ 98 on a bone stock head with piddly crap done doesn't have the balls to hang.

 

 

due to me being on this board, im being swayed away fromthe e31, and early e88{which i have a couple of} more towards the n42 and n47{which is in my car} BRAAP makes very good points, and yet i understand it. odd? naaa

 

i have seen over 250cfm out of a e88 head, does it make it pump gas friendly? not likely. just because one person can do it,doesn't mean the rest of people on this boardwill runout and try it and have the EXACT same success. me? im not going to try it. or am i already? not sure. can't look at the bottom of the head while it's onthe block.

 

think for a second. would you want someone to follow oyur exact footsteps and jump on the mn47 bandwagon because you said it would work perfectly without detonation? hell i ping at 38 degrees full advance. does this mean i will build someone the exact same set up? nope. the set up is not perfect by anymeans. does thi also meani can build another dsm to trap 108 mph with just bolt ons and a few hours with a die grinder? not likely. EVERY CAR IS DIFFERENT. take that into account when giving advice. please, for thelove of the z if anything else.

 

im done mindless babbling. kickme later

 

BRAAP, i'll be contacting you shortly about stuff

[BRAAP]

Silent,

The MN-47 has a cylinder head temp sensor port on the pass side of the head near the block to head interface, directly behind and below the #5 spark plug, (just like the P-79 and P-90 heads, but don’t think for second, Mack, that this feature in of itself makes it a P47 head.. LOL). The Z car N-47 does not have this provision as that particular EFI sensor is in the thermostat housing on the Z car variants.

 

I agree. The ¼ mile MPH is a much better indicator of power being produced, not ET, (knowing the vehicle weight as well, one can get a ball park HP calculation), and ET is primarily an indication of traction “and” the drivers ability to shift at the correct times etc, (it is amazing at how bad you can botch a run with a missed shift, etc, but yet your MPH will still be really close to your good run MPH). 60’ ft times are an indication of the vehicles traction out of the hole.

 

I’ll be keeping on eye on my PM box here at Hybrid and my E-mail for your post…

[POSTM]

I have pulled three MN-47 heads and have a Maxima motor in my Z.

All of these MN-47 heads have an opening for mechanical Fuel pump that is blocked off with a plate. On the ZN-47 there is no hole in the casting. When you go to the pick-n-pull you would have to pull the valve cover or pull power steering pump to clearly see the difference. I have read that some of the early MN-47 heads have different combustion chambers, but I have not found one yet. And a bit off topic I would not recommend putting a Maxima motor in your Z even if you get it for free.

It was a plumbing nightmare.

 

Chuck

[Guest norm[T12SDSUD]]

Ah Detonation.... our friendly neighborhood pyscho!!

After successfully running a 10.7:1 CR setup for three years I decided to try running an 11.6:1 setup twice. It ran great for a month each time until it a warm day and high load 3rd gear pulls and then pooey..broken ringlands.

 

I rebuilt it the third time at 11.3:1 CR and it ran great for three months until I took it to the track. Top of third pulling past 6500 rpm boomie 4 piston ringlands let go at one time!!

Rebuilt it back to 10.7:1 CR again and it ran great for over a year and a half and then while running full throttle up a mountain 3rd gear again above 6500 rpm on a day over 90 degrees and kablooey....broke ringland on #6.

 

Basically, once you get over 10.5:1 CR with carbs and your chambers start building up carbon and you have no knock sensor then you are just a bad tank of gas or lean out away from a rebuild. When your headers and exhaust are so loud you can't hear the pinging ....you'll know what just happened once you let off the gas and see the smoke cloud!

 

I do like the looks of the MN47. My N42 is shaved .070" so it is almost a closed chamber shape now, but almost isn't close enough.I can't back my timing off below 36 degrees or she misses at high rpm so I just have to watch the high load full throttle situations.

If someone is running triples it can probably supply the fuel necessary to hold off detonation under certain circumstnaces ,but I believe my past troubles are probably due to the limiting factors of my SU setup.The last time could also have been due to a bad distributor as there was some play in the old distributor.Also I had just installed larger headers the week before so one of my theories is it was allowing more air to get in the chambers but maybe the SU's just couldn't provide the fuel.

Anyway,I'm building it back up once again now this winter so I really need to get some sort of exhaust analyzer this time around to see if she is going way lean above 6500 rpm.

 

 

 

 

Later,Norm

[hoov100]

i have been running MN-47 at 11:5 C/R using EFI with BIG injectors and have been driving up and down twice a day highway 74 (look it up to see what im talking aobut) for the past three years and have never had a problem that bad at a high load, but i am using a completely different fuel system.

[Guest norm[T12SDSUD]]

Yeah a properly setup EFI system with HUGE injectors is definitely a benefit.

I used to drive the Hell out of my car at the track at least every other week with as many as 44 runs in one night one time, but usually at least 20 runs on an average night. Could be 30 year old cast pistons that are abused like Hell don't take kindly to the slightest fuel or timing imbalance! haha

 

later,Norm

[Mack]

I have a ZX N47 from 1980 that had the cylinder head temp sensor in the same spot as the P series heads. there is no definitive way to tell if it is a Maxima N47 other than if the block says L24E, chances are it would NOT be a regular Z/ZX N47. they have bigger intake valves and will not fit on an L24e;s bore without eyebrowing they cylinders. and thats an aweful lot of trouble to go through to have a crappy L24E. the fuel pump cut out thing is a good way to tell, and its not like its exactly hard to pull a valve cover on these motors, lol!

 

hell, Ive got a system down to where I can pull a head, strip all teh intake and exhaust stuff off of it and be ready to roll out of the U pull It yard in about 45 minutes. Ive done it a few times....

 

On teh detonation note..... I think a megasquirt and a spork manifold would take care of it. The stock FI intake really does suck .......... as well as the stock computer.

[Wondering Nomad]

 

hell' date=' Ive got a system down to where I can pull a head, strip all teh intake and exhaust stuff off of it and be ready to roll out of the U pull It yard in about 45 minutes. Ive done it a few times....

 

[/quote']

 

 

Would you mind expanding on that process? There's a MN47 head at my local yard and I'd like to get it on Thursday if it's still there.

[POSTM]

When I go to the pick-n-pull, I pull the head with both manifold attached. Loosen cam bolt with a hammer on an open end wrench, remove exhaust, P/S pump, and idler cut water lines and wiring. Pull head bolts. Now you can get at all the manifold bolts. Takes me longer than 45 min but I’m old and slow. Chuck

[Mack]

what I do is this....

 

 

I start by removing the exhaust downpipe thingy from teh manifold (3 bolts). should be easy because most yards cut the cat out. then I use a hacksaw and cut the wiring harness (how many have you guys EVER pulled?) cut the coolant lines, vaccuum lines, fuel lines, anything that is attached to the engine and is rubber. then I take off the powerstering pump, which is easy once you get the tension off the belt, or just cut the belt. then I take teh valve cover off, loosen the cam bolt, remove sprocket, let chain drop. start loosening head bolts. remove all those. then you can flip the head/manifolds up a little and get the PCV valve hose, then remove head+manifolds as an assembly, get it out on the ground and set it on its side with the manifolds sticking up. then its easy to get at all the manifold bolts and heat sheilds. all you need is an extension, a 12mm and a 14mm, and a Ujoint type wobble.

 

oh yeah, it helps to be strong, lol!

[The Revelation]

i was wondering if it is cool to run a turbo with an MN47 head? currently have an '83zx motor in my '72 240z the motor has p90 heads. (Im sure this question is dumb but this is my first car that i can actually work on) Im curious if a p90 would be better because its turbo induction or would the MN47 be better, from what ive been reading 1fastz says that he drives around town at 7000rpms daily and has no detonation, does that mean that your car dosent overheat? cause i really want to make a turbo car out of this and the last thing im looking for is a blown-up engine.

[BRAAP]

Uh, that link is NOT an N-47 head. That is an N-42 head, came on the ’75 and ’76 280 Z. Note the square exhaust ports and spray bar cam oiling. Only very few N-47 head had the spray bar, (early ’77 models), and the N-47 is round exhaust port with the liner, not square.

If you guys want pictures of heads, just ask. I have a few assorted examples of the following castings in my inventory, late E-88, N-42, a couple ZN-47, at least one of not three MN-47 heads, and at least one if not two P-90 heads.

[spacecase70]

I think i will stick with my N42/ N42 setup, too much controversy on this head. sorry to dig up a grave

[HowlerMonkey]

I run a turbo on the MN47 head but it is part of the stock L24e setup.

 

Running stock boost it does well and has been for 30k miles.

 

Damn the port shape........I have no leaks.

[Dan Baldwin]

Again, the compression doesn't just bleed off at LOW rpms. It does it at ALL rpms. And again, you'd make a lot more power with the bigger cam, even though it is "bleeding compression".

 

Been absent awhile, but I gotta say, I do not think big cams "bleed off compression at ALL rpms". My understanding is that volumetric efficiencies of greater than 100% are possible with big cams at elevated rpm. My 3.1 went from 189 lb-ft of torque with the stock cam (at 10.35:1 CR) to 210 lb-ft (same CR) with a 290/.490" Schneider cam, to 220 lb-ft with a Sunbelt 310/.550" cam (at 11:1).

 

When you "get on the cam" with high lift cam profiles, you go from losing a ton of v.e. at lower rpm to GAINING v.e. at higher rpm. The engine will aspirate its actual displacement (even more!). Which means you are not "bleeding off compression" at higher rpm. The risk of detonation isn't as high at elevated rpm because detonation requires 1) load and 2) TIME. At high rpm, there simply isn't enough time for detonation to occur.

 

This is not to say that high-rpm detonation (which is more difficult to detect) can't be a problem. It has wrecked plenty of engines!

 

But I disagree with the idea that big cams in a well-developed engine build will "bleed off compression" at all rpm. They sacrifice low-rpm v.e. for high-rpm v.e. Which also allows for higher compression ratios. Win/win, if higher-rpm power is your goal!

[z-ya]

Welcome back Dan!