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

[Guest swither2]

Hello all, I just bought my first Z. It is a 72 240 with E88 head. I picked it up yesterday and already want to modify it. I would like to start with bolt on mods for more horsepower. Therfore, I would like to keep an L engine and a bolt on head. I just had the SU carbs adjusted by a reputable shop and they said the head looks like it has just been rebuilt. I would appreciate any advice and approximate HP to go along with the mod.

 

For example, get an L28 from a 77 280Z and bolt the E88 head in place with manifold and carbs form ...

 

I cannot find where other sites have this topic covered. I apologize if I am wasting anyones time in rehashing old topics. A simple link to this kind of info would be greatly appreciated.

 

I appreciate any advice anyone cares to give. I already have an early trans am with a 455 ci engine, so a V8 swap does not appeal to me at this time.

 

Thanks all

[johnc]

http://hybridz.org/nuke/index.php?name=PNphpBB2&file=search

 

Type in "N42", "P90" and then hit enter.

[Guest bastaad525]

yeah TONS of info to be had in the searches here, many many posts have come and gone with just this kind of info. But... I'm bored and gots nuthin else to do so....

 

 

Best L6 motor option hands down is L28 Turbo I know not QUITE what you were looking for, but it's the truth. Having gone the exact same route you are about to go, spending lots of money and time building up an N/A L28 for the street, in the end I didn't quite meet my power goals and ended up with a car that could barely keep up with or beat the current batch of 'hot compacts', let alone taking on any real muscle cars... forget it. I ended up building a 10.5:1 compression, .060 overbored L28 (making it officially a 2.9L), with an N42 head, flat top pistons, mild cam, mild headwork, rebuild Ztherapy SU's with SM needles, open air filter, 3-2-1 headers into 2.5" mandrel exhaust thru a straight thru muffler, lightened flywheel, 6 puck clutch, 5 speed and 3.9 differential. Asides from building a monster stroker motor, swapping up to tripple carbs or to good EFI, and lastly doing some heavy duty ($$$) headwork, this was about the epitome of what can be done with an N/A motor. The last few options could have netted me quite a bit more power, sure, but all would have been expensive, piled on to the over $3000 I had already sunk into that drivetrain. All that three grand got me was 0-60mph in about 6.5 seconds, and a 1/4 mile in 14.8. Decent, but hardly fast. This was in my current '72 240 which weighed just over 2300lbs at the time (weighed at an equipment rental place). The car put down just over 170hp and 170ft lbs to the wheels when I dyno tuned it. As I said... I could have made more if I had spent another couple hundred to over a grand investing in tripples or more extensive headwork, maybe a bit over 200hp to the wheels, but that'd be close to $5000 invested. In the end I was pretty dissapointed, expecting a much faster car. Losing to mildly fixed up hondas and clapped out 5.0's wasn't fun.

 

I suggest canning that idea altogther, saving up and just doing a turbo swap right off the bat. You'll spend less and get more in return, in the long run. For less money invested overall you can end up with a setup very similiar to what I"m running now. A bone stock turbo swap with simple additions like an I/C, better fuel pump and bigger injectors (which can all be had cheap if you don't mind going used), upping the boost to the 12-15psi range, will get you close to 250hp at the wheels, possibly even more. On top of that torque will be even higher... well over 100ft lbs more than what I was putting down with my N/A setup. With a total invested very close to what I had invested in my N/A setup (note, what I DID have invested, not what I was projecting for if I had gone tripples or what have you, as I never did those upgrades), I've now got a car that will run 0-60 in estimated 5 seconds flat, and a low 13 second quarter mile, about 1.5 seconds faster in the 1/4! I also get better gas mileage and better around town driveability.

 

I'm sure your reply will be something to the effect of "yeah that sounds good, but I really just want to do what I can with the N/A - SU setup for now" and that's fine... I think many of us have given that exact same response. But many of us also did carry thru and go on to build those N/A setups and many of us were not happy with the results and ended up going turbo aftewards. So... just think about it you could save yourself lots of time and money... if I could do it all over again I would have skipped the N/A buildup altogether and would have an even faster turbo, probably with an upgraded T3/04 turbo, programmable EFI, LSD and the works!! With a turbo setup the sky is really the limit (and your checkbook of course).

[johnc]

B525,

 

I don't know why your 240Z built up with that engine wasn't MUCH faster. I had a 1970 240Z that weighed 2260 lbs with a 4 speed and a 3.54 rear. The engine was built to BSP specs: N42 block and head, 1mm overbore, stock engine internals (cam, pistons, etc.), SU carbs, Nissan Comp header, MSD, 9.5 to 1 CR. It repeatedly dyno'd 162 to 165hp at the rear wheels. That car ran a 13.9 at Carlsbad and a 14 flat at Bakersfield the only two times (and only two runs) I drag raced it and had a 135mph top speed.

 

A friend with a similarly built 1971 240Z was only .2 behind my car at the same two drag events.

[e_racer1999]

^^ya that did bewilder me for a moment....

 

anyway, it does kind of depent on what you want to do with your car. if you want to drag race it, then you are going to want to go balls to the wall and go for either a turbo swap or a full set up. if you want to do SCCA or ITS, you need to see what you can get away with. i am in a similar situation as you and i am just going to be building an N47 L28 (ripping out the exhaust sleeves) with slightly domed pistons, cam, 6-1 header to 2.5 and SUs. that's fine for me. if you want more power, i suggest checking out a 3.0 or 3.1 set up..... just my $.02

[Guest bastaad525]

B525' date='

 

I don't know why your 240Z built up with that engine wasn't MUCH faster. I had a 1970 240Z that weighed 2260 lbs with a 4 speed and a 3.54 rear. The engine was built to BSP specs: N42 block and head, 1mm overbore, stock engine internals (cam, pistons, etc.), SU carbs, Nissan Comp header, MSD, 9.5 to 1 CR. It repeatedly dyno'd 162 to 165hp at the rear wheels. That car ran a 13.9 at Carlsbad and a 14 flat at Bakersfield the only two times (and only two runs) I drag raced it and had a 135mph top speed.

 

A friend with a similarly built 1971 240Z was only .2 behind my car at the same two drag events.[/quote']

 

I think we've had this conversation before. I won't hesitate to say I wasn't really driving it the greatest having only been to the track one time and getting in two runs, spinning the tires all thru first and half of second gear, and getting a horrible 60 foot time, I forget what it was now. I do know a few other things that probably weren't helping my time, for instance that the power on that motor didn't carry up as high as it should have, it seemed to fall flat after about 5000rpm, though I would shift at about 6500. Given the cam was rated to pull to 6000-7000rpm, I never did figure this out, but was blaming the SU's. Then there was my tires... 195/70/14's on stock N/A ZX rims, bought off the bargain rack at Just Tires for $25 a pop... not exactly the grippiest things on earth. And the gearing sucked, the 3.9 diff combined with the late 70's 280z 5 speed sucked, with way too short 1st and 2nd gear (contributing more to the wheelspin) and then way too tall third, but not tall enough to cross the traps so necessitating a shift to 4th. With better tires and gearing alone, I think I'd have been more like low 14's, but who's to say? I too have a couple friends who have/have had very similiar setups at the time, one who accompanied me to the track that night and only ran .1 faster. Almost exact same setup, differences as I recall were 1) I was running an ACT clutch and light flywheel vs. his stock, 2) he had 3.7 LSD, 3) his motor was not overbored, just stock 2.8, 4) slightly different cam specs (his was the MSA mild cam). Oh and he had better tires on the ZXT turbo wheels, so a little wider as well, and I outweighed him by about 100lbs, me personally, dont know what his car weighed but his was a '73.

 

I seem to remember everyone thinking my times were just about right for my setup, power and weight, which would have been about 2350lbs or more, given I do remember going with a full tank of gas (weighed at 2320lbs with about a 1/4 tank).

 

Other than that my best guess is that I was just not driving it well. Also, John I'm assuming you must be a light guy? 13.9 is pretty damn quick for 165hp in a 2260 lb car if I guess you at 150lbs even, or is 2260 with you in it? I will mention also that at the time I raced I weighed about 300lbs, so total weight would have been close to 2700lbs. I will say that until you came along I'd only heard of one other guy who ran 13's on a very similiar setup and that was Bryan Little. Whereas I've talked to plenty of guys in the 14's.

 

At any rate, it wasn't fast enough for me, and the car is much more fun as it is now. And given the chance to do it over I would just do the turbo from the start.

[johnc]

Then there was my tires... 195/70/14's on stock N/A ZX rims, bought off the bargain rack at Just Tires for $25 a pop... not exactly the grippiest things on earth.

 

I think that was your problem. My car was running 225/50-15 Yoko A008IIs and I got just a medium chirp with a 3,500 rpm launch while slipping the clutch a bit. I also speed shifted (engine had a rev limiter) and I cut a pretty good light.

[Dan Baldwin]

swither2,

IMO, best easiest bet is a N/A F54 bottom end from a 80+(?) 280ZX non-turbo, which has flat-top pistons, and either use your '72 E88, or an N42 or N47 head from a 280Z (same cc size as the '72 E88, but bigger valves), or shave the F54's P79 head ~.080", shim the cam towers, and use the earlier slightly longer 280Z valves. 2.8 liters and ~10:1 CR, should give 15-20% more torque and power than the L24.

 

 

ACK! Don't think I'd do this, word on the street is the exhaust flow on the linered heads is not much if any "worse" than the square port heads, you just can't port it. Ripping out the liners is reportedly equivalent to massively overporting, => poor exhaust scavenging at low-mid rpms. My info IS 2nd or 3rd hand, just do some more research afore you go butchering that N47.

[z-ya]

As you were there to witness it Dan, the F54-flattop/N47 engine I built for our club race car put 164HP to the wheels. The head is completely stock, including the cam. The exhast liners are still in there. It also has a round port 6:1 header, and 60mm TB. The only porting that was done was to the intake to match the intake runners to the head, and to match the TB to the manifold. The motor has been rock solid reliable so far. Here is a dyno plot:

 

http://www.zccne.org/events-2004/dyno-2004/bad-dog.jpg

 

Pete

[Dan Baldwin]

Oh yeah, I was there....

OK, 2x 1st hand info on the stock N47 being A-OK

Sounded SWEEEEEET, too as I recall

 

As you were there to witness it Dan' date=' the F54-flattop/N47 engine I built for our club race car put 164HP to the wheels. The head is completely stock, including the cam. The exhast liners are still in there. It also has a round port 6:1 header, and 60mm TB. The only porting that was done was to the intake to match the intake runners to the head, and to match the TB to the manifold. The motor has been rock solid reliable so far. Here is a dyno plot:

 

http://www.zccne.org/events-2004/dyno-2004/bad-dog.jpg

 

Pete[/quote']

[Guest bastaad525]

IF I were ever going to build another N/A motor, I would go with a P79/P90 head and shave it and shim the cam towers. The argument for the P79/90 head vs. the N42/N47 is HUGE, and if you do a search you'll find days worth of reading material. I've read most of it, and the arguments for the P90 being the better head are just too strong.

 

#1 it was the last L6 head Nissan designed, meaning Nissan had a lot of experience on the other heads and knew better what they were doing.

 

#2 this head is designed for the turbo engine. Some say that means it flows better... makes sense to me

 

#3 it has the better 'heart shaped' chambers, vs. the N42's round chambers, which is better for fighting detonation and for 'swirling' the air fuel mix better.

 

 

However, you can make good power on just about any Z head, really. N42 works just fine as well and doesn't need to be modded like if you do if you want to run the P90 with decent compression. Then again, Norm the infamous guy with the N/A Z that run's 12's in the 1/4 mile, does run an N42, but he runs it modified in the same way you'd mod the P90... shaved significantly... the best of both worlds? Either head works fine and don't even worry about the exhaust liners if you choose a P79 or N47.

 

 

Seriously if you wanna go N/A take a free day sit and do a search and read read read as much as your eyes can take.

[Dan Baldwin]

I've read most of it, and the arguments for the P90 being the better head are just too strong.

 

And ALL of those arguments are solely supported by SPECULATION rather than HARD DYNO NUMBERS OR TRACK RESULTS.

 

#1 it was the last L6 head Nissan designed, meaning Nissan had a lot of experience on the other heads and knew better what they were doing.

 

By this logic a 1976 L82 Corvette has MUCH better-performing heads than a 1970 LT-1. Point#1 provides zero support to the P-head performance superiority theory.

 

#2 this head is designed for the turbo engine. Some say that means it flows better... makes sense to me

 

If these heads are "designed" for a turbo, that in no wise indicates superior performance for an NA application, the argument could just as easily be made that SINCE they are (supposedly) DESIGNED for a turbo that they are deficient in NA apps. Please note that I am NOT making this argument, only saying it *could* be made! Point#2: zero evidence.

 

#3 it has the better 'heart shaped' chambers, vs. the N42's round chambers, which is better for fighting detonation and for 'swirling' the air fuel mix better.

 

What is important is not which LOOKS more like a "high-performance" combustion chamber, it is which ACTUALLY PERFORMS better. "Heart-shaped combustion chambers" does NOT necessarily imply "better performance. FWIW, I didn't have any noticeable detonation problems running ~10.5:1 CR with a STOCK N42 head and STOCK cam at ~35deg advance (though I DID experience detonation with that setup when I ignorantly tried to run 18deg initial advance with a stock distributor, which gave me ~43deg total advance!). Currently I'm at 11:1 CR with mostly stock N42 chambers (shaved maybe .020", mild reshaping, chambers still very much "open"), and running PUMP GAS. Dyno'd 255rwhp last year (only 238 this year, gotta find out why...). NOT TOO SHABBY.

point #3: no evidence

 

I'm not saying the same setup with a P90 would make LESS, or MORE power. Just saying that if there is SCIENTIFIC eveidence of P-head superiority out there, I have not seen it.

 

Then again, Norm the infamous guy with the N/A Z that run's 12's in the 1/4 mile, does run an N42, but he runs it modified in the same way you'd mod the P90... shaved significantly... the best of both worlds?

 

I *think* Norm's head is shaved ~.040", I *believe* he has said this makes it more of a "closed-chamber". But it certainly didn't make it a P-head! P79/90 have to be shaved ~.080" for decent compression on a NA motor. But you can't ascribe Norm's performance to his N42 being "modded like you would mod a P90"! Is all or most of this inherent P90/79 performance advantage in the modification (serious shavage) required to make it a viable NA head?!

 

Either head works fine and don't even worry about the exhaust liners if you choose a P79 or N47.?

 

Agreed.

 

Seriously if you wanna go N/A take a free day sit and do a search and read read read as much as your eyes can take.

 

Just be sure you can separate HARD EVIDENCE from unsupported SPECULATION!

 

Dan "I'm NOT saying the N-heads are 'better'!" Baldwin

[Tim240z]

OH NO...not again.....

[Guest bastaad525]

yep and there are all the good counter points 'FOR' the N42. Really there hasnt' been any hard evidence provided to say the P90 flows better or would make more power at the same compression level. But I will say a few more things.

 

 

If I remember right Norm actually did shave his like .70-.80. I also remember some mention that at least part of the reason he did this was to make the chambers 'less open' or, that is to say, more like the P90's chambers.

 

 

Secondly, when I rebuilt my motor with the N42 and flattops and raised the compression up to 10.3:1, then stuck it back in, I had MAJOR detonation problems on the stock EFI, and that setup always ran rich for an N/A, but on the dyno we had to get it down to a high 12:1 air/fuel ratio, via use of an adjustable FPR, to make it go away. This was with initial timing retarded 2 degrees from stock, on CA 91 octane fuel.

 

When I stuck that same motor in my 240z and went from stock ZX efi to SU's, the problem came back, I had to adjust the SU's so rich that the car ran like a dog in normal driving, and was getting 12 mpg's, to make the ping go away. The problem was finally solved when I upgraded the cam and retuned, for some reason the hotter cam allowed me to lean the mixture way back out but never heard a ping again.

 

About your logic on the Corvette heads, remember as well how bad emmissions regulations became from 1970 to 1976... maybe I'm wrong in guessing that might partially explain why the earlier head performed better there? But you are still right, just because the P90 came later, doesn't mean 100% certainly that it performs better. Why has no one done a flow-test on these two heads yet???

 

And you are absolutely right, that saying that because the heads are designed for the turbo motor, that this indicates superior performance to the N42. As a matter of fact, it's well known to be quite the opposite. In their stock forms, the P90, being designed for the turbo motor and giving a much lower compression ratio, of course it will not give as good of performance as the N42. But shave the head, bring compression up, and then what? Alas... we may never really know, eh?

 

But that brings up an interesting question haven't seen touched on before... what about the P90 cam?? I dont' know for a fact, but I think it's fair to assume that the turbo cams specs might be different from the N/A cams specs. So this could possibly be more of a detriment to an N/A setups performance. Something else that would be good to know the facts on.

 

Now, on the heart shaped combustion chambers... man I wish I had links to all the material I've read on this subject... a lot of it not even Z related. I've had read sooooo much on this though, and have so many times seen it suggested, or rather, proposed as fact, that in a two valve head, a heart shaped chamber is better than an open chamber. Something about better quench area, and the better mixing of the air fuel mixture. I've seen this mentioned too many times to think there's nothing to it. Okay so I don't have the facts to back it up, but it seems like one of those things that is almost universally agreed on in the performance world, so I have to think there's something to it.

 

 

But in the end we did both make the same point, and that is, whichever head he would go with, he'd be fine, and would make good power either way (assuming I haven't talked him into a turbo setup... then again, it looks like he may not even be coming back ). All I said is, if *I* were ever going to build another N/A motor (which I never ever will), I would definately go with a shaved P90.

[johnc]

Some say that means it flows better... makes sense to me

 

According to Sunbelt, the P90 and the N42 heads both flow the same in stock form. And, in stock form, both heads are very good and the only thing that should make a person choose between one of the other is desired compression ratio. So, for a turbo application, P90. For a normally aspirated applicaiton, N42 - amazing how Nissan figured that out umpteen years ago.

 

Now, if you start talking about modifying the heads (shaving, porting, etc.) then the head choice is meaningless. Both need basically the same porting and polishing and the desired quench is most often achieved through piston selection.

[JMortensen]

Secondly, when I rebuilt my motor with the N42 and flattops and raised the compression up to 10.3:1, then stuck it back in, I had MAJOR detonation problems on the stock EFI, and that setup always ran rich for an N/A, but on the dyno we had to get it down to a high 12:1 air/fuel ratio, via use of an adjustable FPR, to make it go away. This was with initial timing retarded 2 degrees from stock, on CA 91 octane fuel.

 

This was my experience in bolting an E31 onto an L28 with flat tops too. I am beginning to think that our pinging problems have more to do with CA's crap gas then anything else. I mean my chambers are polished and I still had severe pinging unless I ran drastically retarded timing which is a good way to warp exhaust valves and lose buttloads of hp. I found that I needed to mix gas to get about 95 octane to stop the pinging in my case.

 

According to Sunbelt, the P90 and the N42 heads both flow the same in stock form. And, in stock form, both heads are very good and the only thing that should make a person choose between one of the other is desired compression ratio. So, for a turbo application, P90. For a normally aspirated applicaiton, N42 - amazing how Nissan figured that out umpteen years ago.

 

If Nissan had it "figured out" then why did they bother with the P79? They could have just left it alone and let the N42 go for another 4 years. How come L4 guys all covet the small chamber heads (similar to P90)?

 

I agree with John when he talks about HIS N42. Like when we were arguing this last time and you said that you had your pistons machined to provide quench on your N42. That makes sense to me. But for the average guy who wants to slap a head on a block with flat tops, run pump gas, and get the best result, I don't think you can beat the P90 shaved .080.

 

By this logic a 1976 L82 Corvette has MUCH better-performing heads than a 1970 LT-1. Point#1 provides zero support to the P-head performance superiority theory.

 

Dan's argument turns against him here. You're trying to convince us that the '76 head is better than an '81 head. '76 was right in the heart of the crappiest smog years in history, and that's when the N42 came about. Not that '81 was much better, but the '81 certainly looks a hell of a lot more like the '70.

 

I am going to adopt Dan's approach on the closed chamber heads though because I like the way it puts the onus on someone else to do something: show me an open chamber L engine that makes the SAME power with flat tops and the same compression ratio as a closed chamber, high quench and I'll be convinced. Until that happens I'll keep with the engine builders and promote what is commonly considered the preferable design: the closed chamber high quench area head.

[Dan Baldwin]

Bastaad,

Much appreciated you didn't take my post personally!

 

I can appreciate your trepidation about the N42 if you had the problems you mention. I never had such probs. Despite the fact that I was running LEAN up top with the SUs. Enough so that the car would begin to overheat after a few laps at speed on warmer days. With the 3x2s (only semi-tuned, still a little lean up top at 13.2 - 13.8:1), no overheating, at ~240-250rwhp, with a stock replacement 3-row 260z radiator, and no oil cooler

 

Heart-shaped vs. open chambers:

Remember that VW commercial years ago about the boxy Golf actually being more aerodynamic than a swoopy Porsche 928? I think it's the same thing here. There's just way too much subtle stuff going on to categorically say that chambers of THIS general shape are always better than chambers of THAT general shape.

 

In the end we DID make the same point, but I'm never above arguing

 

Ditto what John said. If I were turboing, I'd definitely go P90. For NA, N42. Shaved P90 should get you to pretty much the same place, but with more effort. My engine builder had a helluva time getting my engine to 11:1 with the N42, I wonder if it would've even been possible with a P90.

[johnc]

I agree with John when he talks about HIS N42. Like when we were arguing this last time and you said that you had your pistons machined to provide quench on your N42. That makes sense to me. But for the average guy who wants to slap a head on a block with flat tops, run pump gas, and get the best result, I don't think you can beat the P90 shaved .080.

 

In the above example, a modified P90 is "probably" better then a stock N42, and I agree. But, now we're talking about comparing apples to oranges. Again, stock N42 to stock P90 the choice comes down to application. Comparing modified N42 and P90 heads you can't say one modified N42 is better then another modified P90 unless the mods are identical. And even then, is this for a NA or a Turbo application?

 

I'm no saying either head is better (or for that matter the E88, E31, N47, P79). I don't care which one is better. What I'm trying to say is that NO ONE can say which head is better without knowing the application, mods necessary, usage, etc. Head selection cannot be done in isolation based on a 3 digit code and Internet expertise.

[JMortensen]

In the above example, a modified P90 is "probably" better then a stock N42, and I agree. But, now we're talking about comparing apples to oranges. Again, stock N42 to stock P90 the choice comes down to application.

 

Total agreement here too. Wow. Agreement...

[Tony D]

Just an observation to throw in:

IN 1986, RS Okinawa was running 444RWHP as recorded on a Bosch Eddy-Current Dyno in a N42 head, N42 Blocked Twin Turbo setup in a 75 Fairlady Z. This engine utilized Blowthrough Carburetion, and when asking the Owner about it, was simply told "It's what's available". There were no P90's available in the JDM market!

"Best" is totally subjective dependent on the market! EMISSIONS is what drove head design for the US market.

THe N42 was available with several different chamber configurations outside the USA. And was available FAR longer than in the USA. I have several 77 and 79 N42 heads I harvested in Japan. Some with monster Porting and Welded Combustion Chambers...

 

Anyway, remember "performance" was not necessarily the decision to be made. "Performance within required emissions parameters" is the actual phrase that should be used.

 

I agree with the comparison made earlier using the smog choked 76 Vette and the LT1. No comparison when going for a performance application.

 

When it comes down to it, "what's available" is what you will work with. I wouldn't waste any effort nor would I fret about percieved advantages or drawbacks to this head or that. Unless you are running for a national championship, a land speed record, or some serious competition I would go with what you have within reason.

 

One of the worst things a new person can do with a new car project is spend a lot of money on what everybody tells him he "needs", leaving little else for improving the other parts of the vehcile. Like John C says, 160hp on STOCK parts. My EFI L28 in a 2+2 dynoed at 147, runs a 15.30 with my 335# holding it back, and CONFOUNDS those who look at it.

 

You don't need a lot of speed parts. Optimimze what you already have first, learn to drive it well, and optimize handling and control and LASTLY, add horsepower.

 

Though when I was young and stupid (a comment on myself, not anyone else) I build stupid horsepower into ill handling vehicles. I have MUCH more fun now with something that handles the power I HAVE, and can still build stupid power if I want to go crazy...

 

(Bonneville 2006/7 204+mph anyone? The check book is getting warmed up now... )