Newbie seeking advice - what is the best L engine/head combo

[Mack]

hrmmm, can I throw a monkey wrench into the mix? what about a maxima N47? it has a 40cc combustion chamber and also the quench area shape of the P series heads? what will THAT do on a street motor? epsecially if I put a "C" stamp 256 degree camshaft in it and bolt the sucker onto a flat top block and give it bigger intake valves?

 

McAdam

[TimZ]

The other advantage to the P head that I haven't been able to verify is the height of the intake ports. We didn't even get into this yet, and I almost don't want to, but supposedly the intake ports are located higher on the P90 which makes for a longer short side radius. I'm sure I don't have to explain the benefits of that to you.

 

Damnit - now you've sucked ME into this mess....

 

This is simply not true. The intake ports are in exactly the same place on both heads, as evidenced by my ability to use a P-series manifold gasket on my n42 head (yes that's right - I use an N42 on a high boost TURBO setup with no problems - granted it's modified a bit... )

 

So, given that the valve sits 0.100" HIGHER in the head on the P-series, the P-series has the smaller short side radius.

 

Geez , guys, as far as I can see Dan is the one that is voicing the apparently heretical opinion that there are more options that just the P-series, not the other way around. HE'S ONLY SAID EXACTLY THAT IN ALMOST EVERY FREAKING POST. Get over it.

 

Oh - and ALL of my dyno numbers were on 94 octane pump gas, not 100+ race gas.

[Guest steves280]

Interesting reading. I just went through this, I have all sorts of free heads to choose from so that wasn't an issue. Engine is an 82 ZX with a P79/flat tops. I went with shaving the P79 .080, using some N47 valves and also believe quench is a good thing.

 

Haven't done a bunch of hypo 4 stroke stuff but have done a tons of 2 stoke race engine tuning and on them, no quench equals detonation given the same CR/advance/fuel. Also even without detonation, the tighter quench heads made more power. I tested this on an air cooled alcohol racing 2 stroke (super easy to swap heads), tried 4 different cuts with the same CR on a test day and the tightest/widest quench (obviously as the quench band gets wider the chamber must be deeper to keep the same CR) had the best lap times. The only problem was centralized overheating of the piston crown if the chamber to piston surface area is too small and too centalized. I don't think that's an issue with these Zcar heads.

 

The only coment I was going to make is: what's this about $$$$ to do this mod? I paid $50 to have the head cut .080 and the shims were another $75. Given people are talking about heads being ported by Sunbelt etc as examples, $125 doesn't seem like a lot of cash to lay out.

[JMortensen]

This is simply not true. The intake ports are in exactly the same place on both heads, as evidenced by my ability to use a P-series manifold gasket on my n42 head (yes that's right - I use an N42 on a high boost TURBO setup with no problems - granted it's modified a bit... )

 

Did you measure from the bottom of the head to the top of the intake port? Cause I wasn't talking about the relation of the intake and the exhaust. Theoretically you'd want both higher, and that's what I thought you got (kinda misspoke about intake without also saying exhaust). This port thing I'm really not sure of, so I don't really want to argue it too much, but a friend of mine told me that as a reason why he used a P90, and he had about 20 L series heads. I **assume** that he measured and I think he said he did, but I'm not absolutely sure.

 

Geez , guys, as far as I can see Dan is the one that is voicing the apparently heretical opinion that there are more options that just the P-series, not the other way around. HE'S ONLY SAID EXACTLY THAT IN ALMOST EVERY FREAKING POST. Get over it.

 

I thought I was pretty much the only one arguing. Dan and I are both stubborn, so it might still be a few more posts. If you can't deal, don't read it. I can say that there have been a few interesting posts on the IZCC list about this...

 

hrmmm, can I throw a monkey wrench into the mix? what about a maxima N47? it has a 40cc combustion chamber and also the quench area shape of the P series heads?

 

Because it has the L24 bore it has the smaller valves. So in order to take full advantage you'd need to install the bigger valves and unshroud just like the E31. Don't know that I've heard of anyone going that far with the Max N47.

[DAW]

Maybe it's just a wash between the open chamber and closed chamber heads.

 

BTW, I'm selling several E31, early E88, late E88, N42 and N47 (L28) heads . Look for them on e-Bay. Also some sets of L28 rods.

 

There are two kinds of problems: there are problems; and there are personal problems. DAW

[Mack]

Because it has the L24 bore it has the smaller valves. So in order to take full advantage you'd need to install the bigger valves and unshroud just like the E31. Don't know that I've heard of anyone going that far with the Max N47.

 

Actually, I have gone that far, I just havent bolted it on yet. The head had the larger exhaust valves, but was lacking on the intakes. so, I put my 280ZX N47 intakes in it and had both intake and exhaust unshrouded all the way out to the fire ring (traced on the head from the head gasket) I also cleaned up the bowls above the valves extensively with a trusty dremel. cleaned up some of the bumpy casting marks on the intake runners and I obviously couldnt do much to the exhaust ports.

 

all said and done, I have about $255 into the head. $30 for the head from the J/Y, about $150 for machine shop work. $25 was for the 260Z "C" stamp cam and another $50 for dremel tools and sand paper. I just hope it will still run on pump gas. calculating a compression ratio of about 10.7 ~ 11 to 1. sounds like it should, as norm is running even higher on the crappy N47 280zx head (sorry, couldnt resist)

 

hopefully, I will get to bolt it on this week sometime, as I have had this damn head sitting in my garage since the beginning of summer.

 

Mack

[DAW]

In previous posts, I spelled out the advantages of using the Maxima N47 small cc, closed-chamber f.i. head and that the cam, intake valves springs (and 280Z intake valves if you want to go with larger valves, exhaust valves are the same dia. as L28E already). It makes an excellent choice of heads, especially for retrofitting an L24 240Z from carbs to f.i., using unleaded fuel, and increasing the c.r. (not over the E31 or early E88, but from mid-'72-on). On a Maxima L24E (with slightly dished pistons, maybe 5cc) the head yields 8.9:1. On a flat-top L24 240Z shortblock (use mid-'72-on for the 9mm rod bolts vs 8mm) it should be right where you want it for street/autocross performance on a budget.

 

With some chamber work, it's a good choice for larger displacement (up to about 2.9L) engines but with flat-top pistons you have to watch that you don't end up with too high a c.r. for the cast pistons. With large-cc dish-tops (like '75-'79 L28E) you lose some of the closed-chamber design benefits. The chamber volume increase due to unshrouding chamber work can add some needed volume in these larger engines.

 

BTW, McAdam, I think you might need to reconsider the 280ZX valves you've put into that head and use 280Z valves instead.

 

This info may be useful to a newbie who's searching (as in SEARCH) for a way to hybrid-ize the L24 in his 240Z to increase performance and mpg while he builds a more serious performance engine or plans out his engine transplant. And this type of info is likely more valuable to him than the ill-mannered pissing matches that develop here on this site. I've allowed myself to get sucked in to this in the past but I'd rather distance myself from it now. It's inherent when people are passionate about what they've built with blood, sweat, and tears, but I see respect for others' ideas (and collaborative brain-storming of innovative ideas) on other sites. A good site affords mutual trust and respect that allows a member to present a reasonably sound idea or concept and get other points of view, not be denegrated. It's getting to be a PITA to present an idea, to a newbie for example, as is the topic of this initial post because of all the back-biting going on.

 

Some of the worst offenders don't even contribute to the site, but they rant here showcasing their personality disorders, wasting everyone's time. DAW

[Mack]

BTW, McAdam, I think you might need to reconsider the 280ZX valves you've put into that head and use 280Z valves instead.

 

what are the advantages of 280Z valves over the ZX valves? I thought all N47 headed L28E motors with dished pistons were the same? the machinist was the ones that used my 280ZX N47 valves in the maxima N47 head. he said that they were the same length, diameter stem and everything, just the 280zx ones had a bigger diameter head.

 

hope to have it up and running soooooooon, lol

 

McAdam

[JMortensen]

I'm guessing that DAW thought you were using the P head valves which are shorter and would have been a shimming nightmare.

 

Couple questions for you Mack:

1. What was your chamber volume when you were all done unshrouding the valves?

2. Forget 2. I re-read DAW's post.

3. Would it have been easier in retrospect to run a P79 that was shaved since it already has the big valves in it?

 

On another subject, this has been bugging me:

I use an N42 on a high boost TURBO setup with no problems - granted it's modified a bit...

Unless you're running flat tops Tim you're not getting the benefit of the quench anyway, so that is not a very good argument for an N42, plus you say you've modded the head, which pretty much throws it all out the window.

[Mack]

to clear up some stuff, i had originally brought in my 280ZX N47 head to a machine shop, because the motor had blown the headgasket. they found out that it was warped .018" and that many of the coolant passages were corroded. they gave me a ridiculious quote to repair it, including shaving top and bottom and welding coolant passages, at which point it ws decided to use this head for parts and purchase a maxima N47 that was in far better shape. After i purchased the N47 max head, I ran across a running 82 parts car for $200. So, naturally I bought that and this is more of a project than a make it run so I can drive it thing.

 

Couple questions for you Mack:

1. What was your chamber volume when you were all done unshrouding the valves?

 

I havent the foggiest on chamber voulme, stock is 40cc, i know they didnt take out THAT much when they unshrouded. Id say its close to 42cc or so, Ill ry and measure it with a graduated cylinder sometime soon.

 

2. Looks like DAW thinks you already have the big valves in there. I thought that was impossible, and that you'd have the smaller intake at least. What's the story there?

 

the head was pulled from a 1983 nissan/datsun maxima/810. It had large exhaust valves already and the tops of the bores were nothced to allow this. The machine shop machined the valve seats and installed the 280ZX N47 intake valves for me.

 

 

3. Would it have been easier in retrospect to run a P79 that was shaved since it already has the big valves in it?

 

I beleive that it would have been more costly to run the shaved head, because I would have had to find cam tower shims and pay for the extreme shaving of the head, as well as measure and purchase new lash pads. All they really had to do to this Maxima head was unshroud and install larger intake valves. it will still run stock lash pads, not require shimming and it still has a smaller chamber volume than the .080" shaved head.

 

McAdam

[DAW]

The N47 Maxima head has a heart-shaped closed chamber like the P79/P90 but it does not have the raised roof and attending shorter-length valves. It has the same dia. exhaust valve head as L26-L28 but the intakes are the same dia. as L24-L26 intakes so L28 intakes/seats can be substituted for better breathing. The intake valve spring on the Maxima head is weaker than the other L6 heads and the cam sucks.

 

Unless the 280ZX valves are from a '79 L28E, they are going to be too short by .100" which will decrease the rocker arm ratio and put the wipe pattern off of the valve end (leading edge) of the rocker which meets the rotating cam lobe first (unless you use huge lash pads). Even with any valve spring shims removed, the effective spring tension is going to be high and coil stacking a high probability with any significant cam profile.

 

BTW, speaking of L-series valve length, has anyone tried using a reground (smaller base circle) performance cam in an uncut P79/P90 head (with raised-top pistons for n/a or dished-top for turbo) and installed a set of 280Z L28 valves (.100" longer) to get around buying 16 lash pads? Stock lash pads that I've checked are usually around .160" thick and pads go up to .330". The shorter valves would yield an effective pad thickness of .280". Is anyone as cheap as I am? (I have both sets of valves available to use). DAW

[DAW]

Addendum: oops! in the last paragraph above, I meant to say the longer (I said shorter by mistake) 280Z L28 valves will increase the effective lash pad thickness. DAW

[Mack]

the valves came out of my 1980 stock 280zx motor with the N4 on it. the machine shop said they were a spot on match for the maxima valves, with the exception of being bigger in diameter. they said they were the same length as well, as that was one of my concerns. Ill have to look into the springs on the maxima head.

 

i did no know it was weaker. but, will that really matter with a stock-ish cam? hrmmm, food for thought. stock max cam is what, 240 degrees? 260Z "C" stamp cam is 256, but same lift. will the weaker springs have adverse affects with this cam?

 

good question on the cam and valves, about trying to skirt the cost of 16 new lash pads. I dont see why it wouldnt work? way to think OUTSIDE the box, lol

 

McAdam

[DAW]

With a 1980 ZX and N series head, you're OK with sourcing those L28 valves. Length is equivelant to the Maxima L24E valves. When you said you used 280ZX valves I just assumed you mean't the more plentiful F54 280ZX engine with the P47/P90 head as your valve source.

 

I was thinking about what I said about using the shorter valves where longer valves belong and I think I had it wrong about the rocker arm ratio direction. I guess it would actually act like it had a super thin lash pad in place and increase the effective ratio while moving the wipe pattern towards the pivot, not the valve. Regardless, the coils would bind.

 

Good luck and I'm interested to see the results, it looks like a good formula to me. DAW

[gramercyjam]

My head only takes 12 lash pads. They are about $3.00 each. But if you don't need different ones with a longer valve, why buy them.

 

Something that effects lash pad selection (besides cam, shaving, shims, ...) is when you put in larger seats and valves, the effective length of the valve stem will change from what was in there (at least mine do) due to the valves sitting prouder in the chambers.

[DAW]

Thanks John, you're right 12v; not 16v. I'm working on a 2.3 16v engine for my '82 230CE euro-spec MB to replace the 2.3 8v and I'm working on an AQ 171 Volvo Penta crankshaft, rods, pistons, and 16v head for a stroker build for my son's Volvo 242 (no driver's license yet, but a car)and I guess I've got 16-valve on the brain.

 

I thought that lash pads cost more than that and times 12, 24, or 36 to get the right ones would add up.

 

Prouder? What the hell does that mean? DAW

[Dan Baldwin]

A good site affords mutual trust and respect that allows a member to present a reasonably sound idea or concept and get other points of view, not be denegrated. It's getting to be a PITA to present an idea, to a newbie for example, as is the topic of this initial post because of all the back-biting going on.

 

Check out my first response in this thread, I didn't start it

You've given as much denigration as you've taken, DAW, callin' me a flat-earther and all (see "stroker experts" thread: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=36580&start=0 ).

I been denigrated!

 

Some of the worst offenders don't even contribute to the site, but they rant here showcasing their personality disorders, wasting everyone's time. DAW

 

Whom EXACTLY are you talkin' about here?

 

When and if I feel I have something to contribute, I contribute.

I do admit this particular post is mostly "wasting everyone's time", though...

[DAW]

I'm referring to whoever the shoe fits.

 

By "contributing to the site" I was referring to "Contributing Members." While not a criteria to participate, there seems to be an inordinate amount of disruption and counter-productivity to this site by malcontent members who drag the site down rather than support it.

 

I visit many other technically based sites (various technologies) and I don't see the prevelance of personal conflict that often overwhelms this site. I've been sucked in before and am a guilty party at times but I acknowledge it and have tried to reform.

 

I believe something that could benefit HybridZ is if admin would select and flag/rename with keywords particularly long and controversial topic discussions, and place them into an archive or "library" that can be browsed rather than the needle-in-the haystack Search approach. Very often key concepts are discussed in a thread that are salient to the topic but not in the title. If the searching member were selecting specific words in an answer to his question he wouldn't have the question in the first place.

 

Topics such as "N vs P" could be contributed to in a structured "technical article" format for the reference library, cross-referenced with other L6 performance topics, and broken down into a "data, tests, etc." section and a "personal experience/opinion" section which are listed in pro and con categories. The back-biting commentaries have to be extracted/edited out. BTW, I couldn't present this type of idea in an admin forum thread because I don't see a way to communicate by presenting such a topic unless you post onto an appropriate old-topic thread already initiated by admin. I might be missing a way to do it.

 

As for you, Dan, you have a wealth of knowledge and experience and I've learned a lot from you, but speaking honestly and candidly, I think you have an aggressive, inflexible, know-it-all approach to presenting your point of view that doesn't serve you well. I've noticed a trend on the site wherein a member posts a topic and other members just send PMs rather than take the risk of posting and becoming fodder for disrespectful members. My $0.02. DAW

 

P.S. admin: ban me if you want for speaking up, I won't miss this.

[DAW]

Ok, I'll respond to my own post...I see how to present the archive/library idea of edited posts with cross-referencing, by doing it on Site-Support forum and I'll put it there. DAW

[gramercyjam]

Prouder? What the hell does that mean? DAW

 

used this way by machinests and fabricators I suppose (see bold) .....

 

from webster.com

 

 

Main Entry: proud

Pronunciation: 'praud

Function: adjective

Etymology: Middle English, from Old English prud, probably from Old French prod, prud, prou capable, good, valiant, from Late Latin prode advantage, advantageous, back-formation from Latin prodesse to be advantageous, from pro-, prod- for, in favor + esse to be -- more at PRO-, IS

1 : feeling or showing pride: as a : having or displaying excessive self-esteem b : much pleased : EXULTANT c : having proper self-respect

2 a : marked by stateliness : MAGNIFICENT b : giving reason for pride : GLORIOUS <the proudest moment in her life>

3 : VIGOROUS, SPIRITED <a proud steed>

4 chiefly British : raised above a surrounding area <a proud design on a stamp>