If you want more engine performance/power, IMHO an L28 swap makes more sense than modding the L24.
which carbs/cam for E31 head on an L24 stock block?
I am looking into understanding my options for upgrading my SU carbs, E31 head for more performance. Carbs, cam and head work I am considering now, block work would need to happen later.
Here is what I am considering:
Is this a good cam/carb combo for a stock L24?
Is there a different cam I should consider?
Are there other things I should/could have done to the head, while I am at it?
As far as the block goes, I think my options are overboring and performance high compression pistons. I heard that I can take my existing 9:1 C/R to 11:1.
Here is what I am considering:
[li]port & polish head[/li]
[li]triple Webers, 40 DCOE: http://www.thezstore.com/page/TZS/PROD/PFFC03/11-2990[/li]
[li]performance cam - stage III: http://www.thezstore.com/page/TZS/PROD/PEM01/10-2003, although I would get the kit which comes with:
[li]Schneider Performance Spring & Retainer Kit[/li]
[li]New Rocker Arm Set[/li]
[li]New Lash Pad Set[/li]
[li]Schneider Installation Cam Lube[/li]
[li]Schneider Formula 2 Additive[/li]
[li]Cam Tower Blockoff Plate Kit[/li]
Is this a good cam/carb combo for a stock L24?
Is there a different cam I should consider?
Are there other things I should/could have done to the head, while I am at it?
As far as the block goes, I think my options are overboring and performance high compression pistons. I heard that I can take my existing 9:1 C/R to 11:1.
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With the triples you would def need head work and compression to make them work. If I were in your shoes ztherapy SU massaged and needled and maybe a mild cam.
It may not make sense in one way, but I have been thinking hard about it for the past couple of hours and I decided that the engine and head that came off the line in that Z have to stay with her. Any nip and tuck is fine though.
I looked around and I am open to twin turbos like this guy is talking about: http://www.classiczcars.com/forums/...0Z-need-advice&p=241743&viewfull=1#post241743
Is that something worth looking into deeper?
I looked around and I am open to twin turbos like this guy is talking about: http://www.classiczcars.com/forums/...0Z-need-advice&p=241743&viewfull=1#post241743
Is that something worth looking into deeper?
Are you working on a Series 1 or a later 240Z? Unless its a series 1, I would consider the car more valuable if it had an L28.
What is your end goal you have in mind? What about a rough budget to work with? The guys on here have seen just about everything you can do to these cars, and almost all of them will agree with Dan, the L28 is simply more cost effective.
From what I've read over the past two years (not just the past few hours) is that the SU's are fine for any engine a normal guy like you or I would want to drive on the street.
I spoke to the guys at Rebello Racing regarding SU carbs on my L28 I'm building with a ported and polished N42 head, and they claimed that I would be fine with stock SU's. I'm going to keep my SU carbs on my new engine until I find a pair of "metro turbo" carbs from the UK so I can do a blow through turbo.
You can easily put in an L28 rotating assembly in your block and retain your factory block and head.
What is your end goal you have in mind? What about a rough budget to work with? The guys on here have seen just about everything you can do to these cars, and almost all of them will agree with Dan, the L28 is simply more cost effective.
From what I've read over the past two years (not just the past few hours) is that the SU's are fine for any engine a normal guy like you or I would want to drive on the street.
I spoke to the guys at Rebello Racing regarding SU carbs on my L28 I'm building with a ported and polished N42 head, and they claimed that I would be fine with stock SU's. I'm going to keep my SU carbs on my new engine until I find a pair of "metro turbo" carbs from the UK so I can do a blow through turbo.
You can easily put in an L28 rotating assembly in your block and retain your factory block and head.
I don't know. It's a 1970 240z, VIN HLS-30-03177, prod date: 4/1970 (based on sequential ordering in http://zhome.com/IZCC/ZRegisters/classic.htm). Valuable to me means more than the monetary value, so I may still consider modifying it. It is definitely something to consider, though.MX500 said:Are you working on a Series 1 or a later 240Z? Unless its a series 1, I would consider the car more valuable if it had an L28.
I want to keep the same block and head.
This is pure planning. I must let the dust settle from all the changes I have already committed to (ship the car, shipping tranny and diff and parts, rebuild tranny, swap tranny and R200 diff) and see where I stand. I am planning on it being a daily driver, but I have also found several raceways with club racing and instruction. This greatly interests me.What is your end goal you have in mind? What about a rough budget to work with? The guys on here have seen just about everything you can do to these cars, and almost all of them will agree with Dan, the L28 is simply more cost effective.
That said, I want to estimate the amount and cost of work to be done and the cost of parts to squeeze the most power from my L24/E31 that I possibly can, while still having decent mileage (~20 mph), passing state inspection, and not running the risk of blowing her up. Then I can plan the financials.
Does this mean what I think it means? Putting an L28 crank and connecting rods into the L24? I read of a mention of this.You can easily put in an L28 rotating assembly in your block and retain your factory block and head.
I figure this twin sequential turbo idea is a route taking me to spending a little money: custom manifolds, turbos, triple weber 40 DCOE carbs, new cam/valve train/L28 valves, port&polish&bore bigger ports for L28 valves in head, nick block for valve clearance, overbore block, swap L28 crank/conn rods, new performance pistons, water pump, oil pump, fuel pump/rails, and ECU. flywheel? clutch?.
Couldn't I use these things called ECU maps to generate a fuel-saving daily driver map and a max power map? Somehow hook them up to a toggle?
What's the ballpark on that setup: C/R? HP/Torque? Cost?
if you put the rods and crank from a L28 in the L24 you get a factory L26. Even though you said many times that you wanted to keep the original L24 and not swap in a L28, I knew they would try and make your project their project . They want to live out what they want to do and you foot the bill and labor. There is nothing wrong with keeping the number matching L24 in the car. The L24 revs harder than a L28. If you look at race cars you see triple mikuni carbs, you may want to look into that. Dont let them bully you into changing your original plan, and realize that some people that will comment here on your post can barely keep their stock z in running condition. Get info from credible sources and talk to race shops like rebello or whoever. I understand that more displacement is desireable to a lot of folks but if I had a series 1 240 I would be keeping the number matching motor too. Good luck
wow a blow through turbo, very 1974 tech. I thought that mild gain died off when the EFI meteor hit.MX500 said:Are you working on a Series 1 or a later 240Z? Unless its a series 1, I would consider the car more valuable if it had an L28.
What is your end goal you have in mind? What about a rough budget to work with? The guys on here have seen just about everything you can do to these cars, and almost all of them will agree with Dan, the L28 is simply more cost effective.
From what I've read over the past two years (not just the past few hours) is that the SU's are fine for any engine a normal guy like you or I would want to drive on the street.
I spoke to the guys at Rebello Racing regarding SU carbs on my L28 I'm building with a ported and polished N42 head, and they claimed that I would be fine with stock SU's. I'm going to keep my SU carbs on my new engine until I find a pair of "metro turbo" carbs from the UK so I can do a blow through turbo.
You can easily put in an L28 rotating assembly in your block and retain your factory block and head.
I totally understand that dropping an L28 in is the price/performance winner, hands down. Even though it will cost more and perform less, I have to go the route of seeing how much I can safely get out of my block and head. I am not sure I can give a rational explanation for why this is. I can live with the irrational. 
What does this mean?heroe said:The L24 revs harder than a L28.
Here's my options worksheet. What do you guys suggest? Could you help me guesstimate the HP and MPG entries in the table? And sanity check the cost. Thanks.
Requirements:
Details:
Option 1: stay with what I have. Stock engine and SU carbs, tuned
Option 2: triple Webers (Mikunis)
Option 3: Head work (perf cam – stage I/II/III) + Option 2
Option 4: Head work (L28 valves) + Option 3
Option 5: block work: overbored + perf pistons + L28 crank and rods + Option 4
Option 6: Twin turbo + Option 5 (http://www.classiczcars.com/forums/...0Z-need-advice&p=241743&viewfull=1#post241743)
Requirements:
- Use numbers matching L24 block and E31 head
- Get 20 mph city
- Pass state inspection
- Low risk of blowing it up
- Affordability
- Maximize HP and torque
| Option | HP | MPG | Total Cost | Parts Cost | Labor Cost |
| 1: stock | 151 | 21 | $200.00 | $0.00 | $200.00 |
| 2: carbs | ?? | ?? | $2154.80 | $1754.80 | $400.00 |
| 3: cam | ?? | ?? | $3554.75 | $2854.75 | $700.00 |
| 4: valves | ?? | ?? | $4132.07 | $3132.07 | $1000.00 |
| 5: block | ?? | ?? | $5249.80 | $3749.80 | $1500.00 |
| 6: turbo | ?? | ?? | $7000+++ | $5000.00+++ | $2000.00+++ |
Details:
Option 1: stay with what I have. Stock engine and SU carbs, tuned
- Labor: dyno+tune
Option 2: triple Webers (Mikunis)
[o]Triple Weber kit - 40 DCOE: $1499.95 (http://www.thezstore.com/page/TZS/PROD/PFFC03/11-2990)
[o]Triple Mikunis 40: $??
[o]Air cleaners: $254.85 (http://www.thezstore.com/page/TZS/PROD/PFFC03/11-3026)
Option 3: Head work (perf cam – stage I/II/III) + Option 2
[o]Cam kit: $899.95 (http://www.thezstore.com/page/TZS/PROD/PEM01/10-2000)
[o]Other head parts; gaskets..: $200
[o]Option 2 parts: $1754.80
Option 4: Head work (L28 valves) + Option 3
[o]L28 valves (12 count): $277.32 (http://www.raceeng.com/p-4131-nissan-l28-comp-plus-valve45mm.aspx)
[o]Option 3 parts: $2854.75
Option 5: block work: overbored + perf pistons + L28 crank and rods + Option 4
[o]Z Car Turbo and High Compression N/A Performance Engine Rebuild Package: $ 1995 (http://www.racetep.com/xmasspecials.html#dat)
[o]Electronic fuel pump: ?? - No idea
[o]ECU: ?? - No idea
[o]Option 4 parts: $1754.80 minus duplicates.
Option 6: Twin turbo + Option 5 (http://www.classiczcars.com/forums/...0Z-need-advice&p=241743&viewfull=1#post241743)
[o]Twin Turbos: ?? - No idea
[o]Custom intake manifold: ?? - No idea
[o]Custom exhaust manifold: ?? - No idea
[o]Option 5 parts: $3749.80
In considering options, I really ought to include the L28 swap that Dan advises. I could pull the L24 and keep it stock in the shed, in case I decide to sell at some future date.
Requirements:
Requirements:
- Use numbers matching L24 block and E31 head (or L28 swap)
- Get 20 mph city
- Pass state inspection
- Low risk of blowing it up
- Affordability
- Maximize HP and torque
| Option | HP | MPG | Total Cost | Parts Cost | Labor Cost |
| 1: L24 stock | 151 | 21 | $200.00 | $0.00 | $200.00 |
| 2: L24 carbs | ?? | ?? | $2154.80 | $1754.80 | $400.00 |
| 3: L24 cam | ?? | ?? | $3554.75 | $2854.75 | $700.00 |
| 4: L24 valves | ?? | ?? | $4132.07 | $3132.07 | $1000.00 |
| 5: L24 block | ?? | ?? | $5249.80 | $3749.80 | $1500.00 |
| 6: L24 turbo | ?? | ?? | $7000+++ | $5000.00+++ | $2000.00+++ |
| 7: L28 swap | ?? | ?? | $?? | $?? | $?? |
| 8: L28 swap + carbs/cam/valves | ?? | ?? | $?? | $?? | $?? |
| 9: L28 Turbo swap | ?? | ?? | $?? | $?? | $?? |
Take your stock motor out, and put in a 2.8 motor from an 81-83 ZX. (Will have flat pistons already) Put the e-31 head from your stock motor on the l-28. Put S-M needles in your SU-s if the head is stock, use triple 40's and a header if you have head work done and run a hotter cam.
Thanks, ghosttanker, that sounds simple enough. I'll look for an engine and use the stock head for now. What kind of C/R and HP would this setup give me?theghosttanker said:Take your stock motor out, and put in a 2.8 motor from an 81-83 ZX. (Will have flat pistons already) Put the e-31 head from your stock motor on the l-28. Put S-M needles in your SU-s if the head is stock, use triple 40's and a header if you have head work done and run a hotter cam.
If its not bored-10:1, 10.3:1 with 1mm head gasket. If you are going with the l28, swap in a 280z tach, because it has a lower redline, and will work with electronic ignition upgrades.
total horsepower depends on the headwork, carburetion, and cam, as well as the exhaust, and tuning and tweaking skills.Properly set up, this combination can get you a little over 200 hp without too much hassle. It's hard to pull more than about 180hp through stock SU's.
In terms of head work....if you get a 81-83 NA motor, it will have a p-79 head, which already has hardened valve seats and larger valves than the e-31. It has larger chambers than the e-31 though, so the e-31 gives a higher compression ratio. You can raise the p-79 CR by having the head shaved and by using longer valves and shims under the cam towers. You can also modify a p-90 head the same way; these heads come off the turbo motor, which has dished pistons. The p-79 and p-90 head have a more modern shaped combustion chamber and can handle higher CR with less detonation problems.
The decision is a toss up, determined in my mind mostly by access to parts and availability, and cost of machine work. I personally run a stock 83 block with a shaved/shimmed/ ported, polished and slightly worked in the bowls and valve seat area, p-90 head with a stage 3 cam and headers. I know from experience this will run over 200 hp with triples although right now I'm working on a custom manifold for a megasquirt EFI system. I run this combination because I got a great deal on a 83 motor with a p-79 head, and then got a great deal on a p-90 head. If I had a e-31 head instead, I might have used it. But maybe not....I do my own porting, polishing and bowl work, and my own head building and setup, so the only machine work I pay for is the shaving of the head and the valve job. For me it's way cheaper to get a good deal on a p-90 and modify it than to have a machine shop install larger valve seats into an e-31. However, I hear that it's become very difficult to find the right valves for the p-90 conversion.
So in the end it comes down to what you have, what you can find, and how much headwork and setup you can do yourself, and how good a machine shop you can find. I would recommend you start easy. Port match and polish your e-31 head yourself, put it on a stock 81-83 short block with a stage2 cam and your SU's, and run it. Future upgrades would be headers and triples.....but you will be pretty happy with the e-31/l-28 combo, which should be getting you close to 180 hp.
In terms of head work....if you get a 81-83 NA motor, it will have a p-79 head, which already has hardened valve seats and larger valves than the e-31. It has larger chambers than the e-31 though, so the e-31 gives a higher compression ratio. You can raise the p-79 CR by having the head shaved and by using longer valves and shims under the cam towers. You can also modify a p-90 head the same way; these heads come off the turbo motor, which has dished pistons. The p-79 and p-90 head have a more modern shaped combustion chamber and can handle higher CR with less detonation problems.
The decision is a toss up, determined in my mind mostly by access to parts and availability, and cost of machine work. I personally run a stock 83 block with a shaved/shimmed/ ported, polished and slightly worked in the bowls and valve seat area, p-90 head with a stage 3 cam and headers. I know from experience this will run over 200 hp with triples although right now I'm working on a custom manifold for a megasquirt EFI system. I run this combination because I got a great deal on a 83 motor with a p-79 head, and then got a great deal on a p-90 head. If I had a e-31 head instead, I might have used it. But maybe not....I do my own porting, polishing and bowl work, and my own head building and setup, so the only machine work I pay for is the shaving of the head and the valve job. For me it's way cheaper to get a good deal on a p-90 and modify it than to have a machine shop install larger valve seats into an e-31. However, I hear that it's become very difficult to find the right valves for the p-90 conversion.
So in the end it comes down to what you have, what you can find, and how much headwork and setup you can do yourself, and how good a machine shop you can find. I would recommend you start easy. Port match and polish your e-31 head yourself, put it on a stock 81-83 short block with a stage2 cam and your SU's, and run it. Future upgrades would be headers and triples.....but you will be pretty happy with the e-31/l-28 combo, which should be getting you close to 180 hp.
Thanks heroe and ghosttanker, you have given me lots to think about. I have a few questions I hope you can help me answer and I must apologize in advance, because I am going to have to create another table! Many options!
I have the opportunity now to decide what engine to drop in. I am getting the car in about 3 weeks and for a short period of time I can work on the Z and drive my current Rabbit, but then I will sell my Rabbit and use the Z as a daily driver. I don't want to do this work after it is my daily driver. So I am putting myself under this pressure to build as much as I can now.
I have no machine shop, garage, automotive tools (phillips head and a hammer! no sockets!), chock blocks, micrometer, etc. It has been over 20 years since I turned a wrench and even then I had variable success on the couple of engines I tried to rebuild (Audi 200 4 bangers) - first one blew a head gasket in Austria at 2 AM. The tranny I rebuilt worked well, though. I want a professional job done, since it is to be my daily driver. I'll have to pay for that.
I see now that it may be better to keep the e-31/L24 stock and in storage, along with the 4-spd and the R180 diff. This way, it can be restored to stock. I have read and you have mentioned that the e-31 head is valuable, as it has higher compression. I think it is already port&polished, it would just need the cam. But I think I should look into the p-79 or p-90.
A few questions:
Doesn't compression also dictate horsepower?
What is a reasonable upper limit to compression for street driving?
What is the most horsepower a L28 can deliver, with that reasonable compression, and what would need done?
Would a p-90 with its turbo be a good direction for max horsepower or is a turbo a big headache?
What is the story on these longer valves? It sounds like you are saying that whether I go with the e-31, p-79 or p-90 I need these longer valves.
I have a little money to spend and I found an L28 with a p-79. Since a) my car is completely restored/rebuilt and b) it's a daily driver so I am concerned about reliability, then I am considering whether to rebuild the engine. This takes me down a merry path because if I rebuild the engine, why not take the opportunity to overbore and put high compression pistons in? And if I do that, I really need to do head work, install better valves (which do I need and where could I get them?), a stage II/III cam, and invest in triple Webers! $$$
So decision matrix time:
Option 1 is your recommendation, ghosttanker. Option 6 is kind of where I was headed in my mind and just do the whole thing!
A few more questions I hope you can help me answer, so I can completely understand my options:
What's a rough idea of the compression and horsepower for these options?
Which options should I just eliminate as bad price/performance?
Given that I can overbore and get HP pistons for a particular compression, what overbore and compression should I get, if I go there?
Given some money to spend now, what would you recommend?
Thank you
I have the opportunity now to decide what engine to drop in. I am getting the car in about 3 weeks and for a short period of time I can work on the Z and drive my current Rabbit, but then I will sell my Rabbit and use the Z as a daily driver. I don't want to do this work after it is my daily driver. So I am putting myself under this pressure to build as much as I can now.
I have no machine shop, garage, automotive tools (phillips head and a hammer! no sockets!), chock blocks, micrometer, etc. It has been over 20 years since I turned a wrench and even then I had variable success on the couple of engines I tried to rebuild (Audi 200 4 bangers) - first one blew a head gasket in Austria at 2 AM. The tranny I rebuilt worked well, though. I want a professional job done, since it is to be my daily driver. I'll have to pay for that.
I see now that it may be better to keep the e-31/L24 stock and in storage, along with the 4-spd and the R180 diff. This way, it can be restored to stock. I have read and you have mentioned that the e-31 head is valuable, as it has higher compression. I think it is already port&polished, it would just need the cam. But I think I should look into the p-79 or p-90.
A few questions:
Doesn't compression also dictate horsepower?
What is a reasonable upper limit to compression for street driving?
What is the most horsepower a L28 can deliver, with that reasonable compression, and what would need done?
Would a p-90 with its turbo be a good direction for max horsepower or is a turbo a big headache?
What is the story on these longer valves? It sounds like you are saying that whether I go with the e-31, p-79 or p-90 I need these longer valves.
I have a little money to spend and I found an L28 with a p-79. Since a) my car is completely restored/rebuilt and b) it's a daily driver so I am concerned about reliability, then I am considering whether to rebuild the engine. This takes me down a merry path because if I rebuild the engine, why not take the opportunity to overbore and put high compression pistons in? And if I do that, I really need to do head work, install better valves (which do I need and where could I get them?), a stage II/III cam, and invest in triple Webers! $$$
So decision matrix time:
| Option | block | head | compression | horsepower | turbo | overbore | pistons | rods | valves | cam | carbs |
| 1 | stock F54 | worked E31 | 10:1 | 180 | no | no | stock | stock | stock | stage 2 | SU |
| 2 | stock F54 | stock P79 | ?? | ?? | no | no | stock | stock | stock | stage 2 | SU |
| 3 | stock F54 | worked P79 | ?? | ?? | no | no | stock | stock | long | stage 2/3 | triple Webers |
| 4 | rebuilt F54 | worked P79 | ?? | ?? | no | no | stock | stock | long | stage 2/3 | triple Webers |
| 5 | rebuilt F54 | worked P79 | ?? | ?? | no | yes | HP | stock | long | stage 2/3 | triple Webers |
| 6 | rebuilt F54 | worked P79 | ?? | ?? | no | yes | HP | HP | long | stage 2/3 | triple Webers |
| 7 | rebuilt F54 | worked P90 | ?? | ?? | yes | yes | HP | HP | long | stage 2/3 | triple Webers |
Option 1 is your recommendation, ghosttanker. Option 6 is kind of where I was headed in my mind and just do the whole thing!
A few more questions I hope you can help me answer, so I can completely understand my options:
What's a rough idea of the compression and horsepower for these options?
Which options should I just eliminate as bad price/performance?
Given that I can overbore and get HP pistons for a particular compression, what overbore and compression should I get, if I go there?
Given some money to spend now, what would you recommend?
Thank you
option 6, I would guesstimate 190-200, thats a 3.0 bore, cam, headwork, header. Most builds top out at 210 Hp. I have seen people pull out 300+ hp out of a na L28, and if you wanted to just buy a motor like that shipped to your door, you would pay 8-12k plus shipping. As for turbo, its not a pain, just a different driving feel. A stock L28et is 180 hp I think? Turbo is less expensive to reach hp goals. You can program your cars driving personality, turbo is a whole other direction. Compression is generall agreed 12:1 tops for NA motors on pump gas. I run about 10:1 on a mild overbore and its fine as a daily fun car. Turbo you would be 8:1 maybe stock? Im reading up still myself. My problem is like the peanut butter but no bread thing, cereal but no milk. Which z body to go what direction. Which one to sell. with one car, you got it made. With one I would go with mostly stock, reliable and good longevity with logical upgrades like aluminum radiator, modern fuseblock, flame thrower headlights etc. For a daily my cut off for a commuter car would be about 250 hp. Because I cant resist pushing the envelope once in a while. This may vary by person.
Wow, I guess I was expecting more hp. I really don't have a good sense how much extra horsepower is involved in going from 150 to 180 or to 200. I was kinda thinking 250-300 was the target. But, 180 is a 20% increase and 200 is a 33% increase. I suppose that's a lot of extra power. $8k+ is out of my league.
What kind of bore for 3.0? I am seeing (86, 86.5, 87, 88mm bore) and (9-1, 10-1, 11-1, 12-1 comp ratio) on: http://www.importperformanceparts.net/imports/pek-nissan.html
You said your cutoff would be 250 hp for a daily. What would it take for you to reach that number with a F54 and P-79?
"with one car, you got it made" lol! If you only had just my troubles!
Thanks, heroe
What kind of bore for 3.0? I am seeing (86, 86.5, 87, 88mm bore) and (9-1, 10-1, 11-1, 12-1 comp ratio) on: http://www.importperformanceparts.net/imports/pek-nissan.html
You said your cutoff would be 250 hp for a daily. What would it take for you to reach that number with a F54 and P-79?
"with one car, you got it made" lol! If you only had just my troubles!
Thanks, heroe
Only that there is a persistent myth that the L24 is inherently "revvier" than the L28. Plenty of L28s that rev to 7500 and beyond, pulling way harder than an L24 in the process.reefedjib said:What does this mean?heroe said:The L24 revs harder than a L28.
Though I'm not entirely clear on what revving *harder* even means!
Anything say above 210 hp on a na is going to be too pricey then. I would say 250 hp na L28 by a good builder would be 6-7k. At 250 hp most stock parts are inadequate and you spend more by making the car high horsepower ready. Subframe connectors, wider wheels, flares, suspension, brakes, whatnot. You gotta do the math yourself. Its your money. Im not even a good estimator, I dont have that life. I work on garbage all day long, daydreaming about bleeding the clutch hydrolics on my new 82. I wish I worked on z cars for 30 years. Those are credible
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