Mild Mods for the L24

[Xnke]

Before you all go on about how I should drop the L24 and spend money on getting an L28 and a turbo, (which is not what I'm after) please read the following goals.

 

1. I want to work with the L24 block, E88 head, and E88 intake manifold, dual SUs.

2. I want to be able to run 87 or 89 octane gas. (87 is cheaper on the college wallet, and leaves more money to buy parts. 89 is the "good stuff", while 93 octane around here is just too expensive for me.)

3. I am not going to be living on the track. This will be a fully street-ready, comfortable car. There WILL be A/C on this car, I'm not a total masochist, it gets hot in the summer.

4. There is no minimum horsepower. However, I'd like to shoot for 180, as bone stock it pushes 150hp.

ANND.....

5. Shitty fuel economy will not be tolerated. 20Mpg minimum!

 

Now, given that I've searched all over and found very little on this, I think I've got a decent post. I'm still restoring the body, and so I'm not going to be ready for engine work for some time. That gives me time to plan and save.

 

Here are some of my ideas so far:

1. a reasonable bore, maybe 1-1.5mm over stock.

2. L26 or L28 crank. lotsa people don't need them when they build a stroker, and I'm sure i can get a good one for not a lot of money.

3. Electronic ignition. I've got a Holley unit that came with it, but it's got some bugs, and needs to be cleaned and set up. Other than that, it's in good shape.

4 Head work. I'm handy with a rotary handpiece, and have access to a flow bench. I'm a competent machinist (I've patterned, cast, machined, and assembled a complete model inline-6 gas engine, and it does run pretty good.)

5. possibly a different cam. I don't know much about this.

 

As you can see, I'm new to working with auto engines. I'm also a college student, so progress is slow, but steady. Money is hard to find, but I understand that you don't want the best you can afford, you want the best you can get. Does anyone have any ideas or suggestions on what they would do, given that what I'm trying to do is rather unknown territory?

[hoov100]

"blow through carb, intercooled turbo"

[JMortensen]

I know you said an L28ET swap is not for you. Fair enough. But why not put a stock L28 block under that E88 head and SU's. Should get you close to your 200 bhp goal with maybe a cam, header and exhaust. The way I see it you're going to spend A LOT more money building the L24 into a stroker than you would just finding an L28 with dished pistons and building it.

[BRAAP]

First off welcome to HybridZ.

 

So you don’t want an L-28, but what you proposed is essentially building one, well close any how. If you are planning to use the L-26/L-28 crank, over bore the L-24 block 1.5mm, why not just bore it another 1.5mm? Then it would exactly be an L-28. So why bother paying the money for new oversize pistons, machine work to over bore, when you can find a suitable L-28 engine, if it is in good condition, just kiss hone the cylinders, re ring, new bearings etc, and it will be FAR less expensive than this L-27. If money is an issue, don’t spend money on things you may not need. The machinist is going t to charge you to over bore the engine. Those pistons for the over bore cost money. If you want an L-24, leave it an L-24.

 

The ONLY reason I would even consider your proposal is if you wanted to keep a numbers matching block in your car and you wanted more displacement, and you don’t mind throwing money at something that wont get any closer to your goal than what already exists for far less. If are dead set on staying L-24, then leave it an L-24, don’t build an L-27 or L-28 unless you are attached to that particular L-24 block for whatever reason.

 

Mileage and A/C are your requirements.

 

My suggestion is to go find yourself a running L-28 with the EFI and electronic ignition. Bolt that in your car. Install quality ignition components and fine tune the ignition advance. Then fine tune the EFI and 25-30 MPG and 170-190 crank HP is totally realistic. Even the L-24 with the SU carbs is capable of 28+ MPG if you keep your foot out it.

 

L-28 testimony...

My personal 280-Z, with a BONE stock L-28 short block, barely over 8;1 compression, (low octane friendly), was getting an honest mile post to mile post 28-30 MPG, (installed dual 2” exhaust vs the previous dual 1 ¾” and mileage dropped from a solid 30 to 28 on the freeway), a little head work, Cyclone header and dual exhaust, finely tuned stock EFI with the stock cam, lightened flywheel, recurved ignition advance, quality plug wires, plugs and coil, cap and rotor. That 2900 lb 280 (2900 lbs with half tank of gas and driver), ran 0-60 MPH in 5.7 seconds, and the 1/4 mile in 14.4 seconds @ 97 MPH.

[z-ya]

I built an 8.7:1 L28 for my Wife's 280Z. It is an all stock P79 motor (flat top pistons, P79 head) except for +1mm overbore. It makes excellent midrange torque, and is really fun to drive. She gets 30mpg average, and she has a heavy foot. It needed just some minor adjustments to the 78' EFI, and the timing is set to factory spec. It runs fine on 87 without detonation.

[Xnke]

Very good points, all around. I see the homebrew-L27 vs L28 money argument, and understand that. Even if I am doing the machinework myself, it's still gonna cost money to get the pistons and pins, so I agree on this point. The only reason I considered it is that this block probably will need boring anyway, as the PO ran with no air filter for some amount of time, and when I got it the dry compression test ran 82-85-85-75-90-92. Ick.

 

(For those who wonder how I came up with the numbers: the CA18XXX engines use a 84.5mm piston, and from all references I can find, it's got a 38mm pin height, making it essentially a drop-in replacement for the L24. The L-26 crank came from all the folks who'll be dropping the LD28 crank in, leaving lots of stock out there. See, I was kinda thinking. The fact that the L24 made more horsepower than the L26 or L28 also had me a little swayed.)

 

EFI is out of the question, I already will be reworking the wiring harness in this car, and don't need anymore complications. Besides, I think the dual SUs are pretty sweet myself. And like you said, they are capable of good mileage too.

 

Exhaust work is in. I'm a good welder, according to my instructor at school, and welding coke cans with a torch is my specialty. (Not at the rims, mind you, but actually slashing the can up and welding it back together.) Having access to a good pipe bender, and a CNC plasma cutter machine up at the school makes a custom header simple, as long as I'm buying the material.

 

So, what are we left with? lesse....

 

Find a solid L28, -400$ (5-7 paychecks)

sell off the uneeded head and EFI intake, +200$ or so

sell the extra L28 electronic distributor, I've already got one. +30$

sell the worn L24 block, ???$

 

So, that's about 200$ to buy the new block, pistons, ect. (playing fast and loose with the numbers here.)

 

Considering that the headwork cost should be minimal, (as if that even applies here, minimal is still costly) what kinds of things should I search for here as far as E-88 modifications?

 

Thanks for the warning guys, had I not found this forum, I could have wasted a lot of money. Guess i better start looking for that L28...

[CantZme]

from what i understand, the e88 will likely bring compression up higher than 10:1? someone correct me if i'm wrong:rolleyesg... wouldn't it be a better idea to just pick up an l28 with flattops and a p79 and just port that head instead? the p79 is the stock head(no quench issues here), i think it flows better and you'll keep compression down as well(87 octane baby!). with the money you save, get a mild cam and you should EASILY be able to reach your goal with some fine ignition and EFI tuning. then again, that's just my .02 cents...

 

-Adam

[CantZme]

oops, i missed the "no EFI"...my bad:mrgreen:

[Tony D]

Wrong assumption here:

"The fact that the L24 made more horsepower than the L26 or L28 also had me a little swayed."

 

That is t he basis of you arguemnt or logic behind the reasoning, then you need to know that statement is false from the get-go!

 

Using the latest rating methodology, the L24 produced about 115-120hp, the L26 120-125, and the L28 130-135hp. Current day rear-wheel dynos will confirm this is the real case.

 

The Ratings systems changed along the way. At each step, the Z-Car needed more and more HP to cope with it's growing corpulence, and each successive engine had more HP that it's predecessor, mainly through more low-end torque for drivability. I have a stock L28 that honestly rear-wheel dynos to 147HP, gets 22mph towing an 800# trailer behind it at 80mph and with three people in the thing with 3.90 rear gearing, and runs consistent 15.30-50's in the 1/4 mile in 110 degree heat. Most L24's in stock form are lucky to spin the dyno wheels to 120hp.

 

If you are basing your logic for staying away from an L28 Transplant because you think it has less HP than an L24, you may want to rethink it.

 

An L24 can make horsepower, but for economy you want torque and gearing. It's how GM 3.8L V6's pull 38mpg in a boat whereas our little featherweight cars run and are lucky to get close to half that (or at least 66% of it during steady state cruise...)

 

I see you already have come to the conclusion that hte L28 may be a better course, but I'd caution against doing work for the sake of doing it. The L28 should bolt right in and give you near the numbers you want right out of the box without any work whatsoever. Take the money, save for as long as it's running troublefree, and do your headwork to hop it up after you have run it for a while. Better get used to the different driving technique of the L28 and maybe spend that money on a five speed transmission rather than adding expense to a head that may work well right out of the box!

 

My example engine above is still in the factory guise at 225+K miles. I put it in with 186K on the clock, and it's still running strong. You could save a lot of money in that timeframe---allowing you to do some more substantial renovations along the lines of your goals, rather than adding expense off the bat with something you may not even need to do!

 

Horsepower comes in detail, not bolt on parts or trick machining. That same car above...when I got it, it had Triple Webers, Headers, and didn't run. A quick distributor and transistor igniton swap got it fired and running reliably. A trip to the dyno had a dissapointing 86 HP to the rear wheels. Make no mistake though, it felt fast but it only produced 86HP. Some ignition wires got that to 90 rather easily. Long story short, I wasn't willing to spend the time to rejet the Webers---I sold them to someone for $650. Recouped the purchase price of the car, and put me $350 into profit as it stood! Sold the header for $25, so that got me to $375 in the black for the purchase of the car. Stuck on a complete EFI system from a 76 that I had laying around (take off from the Bonneville Car) paid $45 for a K&N Air Filter Element for the stock housing, and did a 60mm T/B modification (call it 'bought from MSA' but I'm still the cost of Polyurethane Bushings ahead at this point). That engine, the same engine, spun the same dyno to 147 to the rear wheels!!!

 

The cold air system I had on there, got taken off for noise issues, but there was no noticable result in the Dyno. The same 2.5" crush-bent exhaust from the headers was still on the car, better than stock I guess.

 

Point being I took off all the 'bolt on speed parts' and ended up almost doubling the available horsepower to the rear wheels. It didn't feel as fast, it didn't sound fast at all---it was very very quiet. Quieter than a stock 280Z to be honest. But it flies, and the numbers didn't lie!

 

So think long and hard about 'changing things' when the real power comes from details, and not gimmicks!

 

And yes, mine runs fine on 87 octane, and true to my form, found that it digested Sunoco 84 Octane "Sub-Regular" available during a trip through Michigan several years ago! Stock works, when you start performance tuning, you have to be ready for the trade-offs and compromises that will result.

[Xnke]

well, this all makes sense. Time to look for a L28...thanks guys!

[Daeron]

wisdom seems to dictate that you nickel and dime your suspension and steering up to snuff.

 

Visit the FAQ sub forum, and read through the hyperlinked table of contents. Check the stickies in all the sub forums that are appropriate to your vehicle, including electrical, fuel delivery etc.. read through all that and sponge up what you can. Make an appointment to read through it all again in a month when you have been reading about these cars for a while.

 

By the time you read through them all the third time, between the constant reiteration of points deemed worthy of highlighting by the forum as a whole, and your daily reading of issues and questions that come up, you begin to get the idea.

 

You've had a few rather well informed people give you rather well informed answers to your rather well informed (for a newb) questions, and I see you already taking them to heart and at face value; you should go a long way here.

[Xnke]

Ok, so i've thought up something that i can do now to improve performance, and that can transfer to the L28 block later: Triple SUs.

 

I've already got three SUs, the two on the car already, and an extra rear carb. Time to put those welding skills to good use!

 

Seriously, I've seen many of these cars with triple carburetors. Mikunis, Webers, Dellortos, Solex, but only two with triple SUs. I hear that they don't work so well due to the L-XX series firing order, but I think that got debunked somewhere on the boards here.

 

Any Thoughts on this? I know it can possibly improve flow, but there are many other things to do before it makes much of a difference.

[JMortensen]

Ok, so i've thought up something that i can do now to improve performance, and that can transfer to the L28 block later: Triple SUs.

 

I've already got three SUs, the two on the car already, and an extra rear carb. Time to put those welding skills to good use!

 

Seriously, I've seen many of these cars with triple carburetors. Mikunis, Webers, Dellortos, Solex, but only two with triple SUs. I hear that they don't work so well due to the L-XX series firing order, but I think that got debunked somewhere on the boards here.

 

Any Thoughts on this? I know it can possibly improve flow, but there are many other things to do before it makes much of a difference.

Search here and at classiczcars.com and you'll find the discussions you're looking for. No need to rehash the whole issue again.

[dhayes5]

I have a '72 that is probably an 8 out of 10, 99.5% rust free 240Z 82k original miles. I have had this car for 10 years and have rebuilt the suspension (all new poly, shocks, NOS euro springs, factory bolts etc. etc.), added a ZXb (close ratio 5-speed) and R200 3.90 rear end, toyota 4 piston calipers up front, pertronix ignition and Accel Super Coil, and MSA 2.5" exhaust (which was added before the R200 and now barely clears the R200 - more on that later) with stock L24 exhaust manifold.

 

I have tuned this car by following the Z-Therapy video (i.e. checked cam timing [now on third mark), valve clearance hot, ignition timing at 10BTDC, then carbs). Also found out that ATF is way too thin for the dashpots and am now running 10-30 in them (summer).

 

I would like to get the most out of this setup first and have it in the best state of tune possible. Then, perhaps look at another cam etc. I am looking for input on the following and any other suggestions from people who have a similar setup:

 

1. Will my cam timing being set on the 3rd mark, meaning the chain is stretched but still able to be adjusted out, cause issues (i.e. if I replace the timing chain and put it back to the 1st mark or 2nd as some people have suggested for more torque)?

 

2. In terms of cams, has anyone had experience putting the "C" cam (this was suggested by Robello Racing) in this engine? So far I cannot find any posts that tell me the different cam profiles for stock Nissan L6 camshafts (I have heard there is an A and a C).

 

3. I have read the stock manifold is very good unless you do some major changes to this engine in terms of flow, is this your experience -- even if going to the "C" cam? Keep in mind I have pretty low backpressure with that 2.5" exhaust.

 

4. What would be the effect of adding SM needles to this (my current) setup?

 

I typically drive the car between 2-4k rpm (will accelerate to 5-5.5k if I get on it). The 5-speed helped the mileage as the car tacs about 3.9k at 75mph in 5th for cruising.

Edited September 17, 2011 by dhayes5

[Tony D]

Can we combine this with the 200HP thread now, just to save space?

[Z Greek]

Xnke

I like the idea of stock L28 for you. Bolt your SU's on, and let her rip. I don't know about other parts of the country, but out here in Spokane, you can get an L28 complete for $150 at our pull and save wrecking yard (including alternator, and A/C pump if the car was so equipped). You have to invest a couple of hours of time to get it out, but I find it kind of fun out there. There seems to be about 1-2 280Z, or ZX that come in every month (and Spokane is NOT a large city). You have to watch inventory, and be quick to get out there. You can grab a 5-speed for another $50 if you are quick enough! If you want to play with your 240 block with 260-280 crank, I have a 280 crank you can have, but freight across the country would probably be more than you can find one in your neck of the woods. The free crank goes for anyone, it's just taking up space standing up next to the 'fridge in my shop.

One comment you made I found interesting. You said you are new to this working on cars game, but that you could do your own machine work? Quality machine work is the bargain of the universe. Even if just re-ringing, you can have your block honed on a Sunnen machine for around $100 (I find Nissan blocks to be very hard, and by the time you run a hand hone long enough to end up with a decent cross-hatch, you no longer have a round, straight cylinder). A decent quality valve job can generally be had for $125-$150 plus parts. L-series cranks are tough as hell, and a quick polish is likely all you will need. Unless you want to spend a couple hundred grand to equip an automotive machine shop, let the pro's handle that part. Assembling an engine is fun, and ANYONE can do it. Buy a couple of books, be slow and methodical, and keep it CLEAN, CLEAN, CLEAN.

As far as fuel. Detonation will destroy an engine quicker than anything. Contrary to some folks believe, there is NO detrimental effect to high octane fuel. You will not "burn a hole in a piston," running even racing gas in a stock engine, just the opposite. Think about your comment that you are on a budget, and premium fuel is out of your price range. 10,000 miles a year is LOT of driving in one of our cars. At 20 mpg, you would burn 500 gallons a year. Premium is, what, $.50 more per gallon? That is $250/YEAR. That is $5/WEEK. Just sayin', don't short yourself from running optimal ignition timing with the false economy of running rot-gut fuel.

Good luck, have fun, and Enjoy the Ride!

[Tony D]

"Think about your comment that you are on a budget, and premium fuel is out of your price range. 10,000 miles a year is LOT of driving in one of our cars. At 20 mpg, you would burn 500 gallons a year. Premium is, what, $.50 more per gallon? That is $250/YEAR. That is $5/WEEK. Just sayin', don't short yourself from running optimal ignition timing with the false economy of running rot-gut fuel."

 

OOOOH! I'm going to add that one to my Oil Consumption Rant, I'd never thought through the math on the Premium Fuel!

 

Then again, I wouldn't say 10K miles a year is a 'lot' on these cars---I'm gone 233 days a year past three years now (180 days 'out' comes Sept 24th this year...) and managed to put 7000 miles on my DUALLY (which I'd expected to put MAYBE 3000 on in a year) and the Z? Last year the insurance audit showed around 14K for the 18 weeks I was in town...Driving it 100 miles daily to work and back for the days I'm in the office (396-500 miles a week), and usually 400+ on a weekend...

 

Lets just say 'for me' if I was in town more, my mileage would be considerably more than 10K miles a year. When I worked a local job and didn't have a company vehicle I was putting 26K a year on my Turbo 240 and that was only driving 22 miles each way, or 44% of the mileage I drive daily now!!! That was 'only' 500 miles a week total. But then again there was a time when gas was .89 cents a gallon, so 17mpg from the 140 wasn't that objectionable considering the performance.

 

BTW, this is a 'necropost'...look at the original post date. That is why I said we should combine it with the 200HP N/A post!

Edited September 17, 2011 by Tony D

[Z Greek]

"Think about your comment that you are on a budget, and premium fuel is out of your price range. 10,000 miles a year is LOT of driving in one of our cars. At 20 mpg, you would burn 500 gallons a year. Premium is, what, $.50 more per gallon? That is $250/YEAR. That is $5/WEEK. Just sayin', don't short yourself from running optimal ignition timing with the false economy of running rot-gut fuel."

 

OOOOH! I'm going to add that one to my Oil Consumption Rant, I'd never thought through the math on the Premium Fuel!

 

Then again, I wouldn't say 10K miles a year is a 'lot' on these cars---I'm gone 233 days a year past three years now (180 days 'out' comes Sept 24th this year...) and managed to put 7000 miles on my DUALLY (which I'd expected to put MAYBE 3000 on in a year) and the Z? Last year the insurance audit showed around 14K for the 18 weeks I was in town...Driving it 100 miles daily to work and back for the days I'm in the office (396-500 miles a week), and usually 400+ on a weekend...

 

Lets just say 'for me' if I was in town more, my mileage would be considerably more than 10K miles a year. When I worked a local job and didn't have a company vehicle I was putting 26K a year on my Turbo 240 and that was only driving 22 miles each way, or 44% of the mileage I drive daily now!!! That was 'only' 500 miles a week total. But then again there was a time when gas was .89 cents a gallon, so 17mpg from the 140 wasn't that objectionable considering the performance.

 

BTW, this is a 'necropost'...look at the original post date. That is why I said we should combine it with the 200HP N/A post!

[Z Greek]

Oh, I see what you mean about the original post date, I thought this was new this week! Obviously I am new at this forum stuff (and I am pretty old, so I need my 13 year-old's help anyway!), but I am having fun reading, and occasionally chiming in. Thanks for putting up with me! Haven't heard of the term "necropost," but I have figured out the meaning.

[Tony D]

If you've ever read my rants on 'oil consumption' you will see we both have a similar outlook on expenditures regarding consumable items like gas and oil. You can buy a LOT of oil for $3500---and chances are it will take you 10+ years to spend it, even at a quart every 500 miles!

 

I like to say 'great minds think alike'---I just never thought of the Premium Fuel in that manner. I think Consumer's Union is fluoridating my water and contaminating my precious bodily fluids...