L26 refresh - thought I'd share the results
Posted 20 May 2008 - 11:25 AM
I have recently refreshed the near stock L26 fitted to my 76 260 coupe and thought I'd share the results just in case any others wanted to go down this path.
The engine was started out basically stock with only mods being removal of the air pump and EGR, installation of 240 carbs, HM headers into 2 1/4 exhaust and a 240 A grind cam shaft and 280 trany ign, (all of which I installed 18 years ago), this engine span up freely and made around 88 rwkw -up from the standard 76 rwkw of a "stock L26) at around 5800 rpm but seriously lacked any torque (due to low 8.3:1 comp) .....so made lots of noise but no "shove" in the back.
With the refresh I wanted to retain the original block and keep the car as "standard" as possible but at the same time extract some extra welly so I decided to go down the path of upping the compression by installing flat tops and making it breath with bigger inlet valves.
The engine was stripped down and found to be in excellent condition for its 250,000 hard km with the bores only requiring a light hone, the crank was spotless and all bearing journals still standard size.
The head was cleaned up, ported and CC'd by Chris Wood who also installed stainless valve seats and 280zx inlet valves, Chris also lightened the fly wheel and the crank and I then had the crank and fly wheel balanced. New standard bore 83mm flat top pistons were sourced from Lindsay Drife (rare as rocking horse poo!) and the engine reassembled with all new timing gear, bearings and a new turbo 280zx oil pump.
BTW - The flat tops produced a comp ratio of aprox. 10:1 so premium pump fuel would be fine (98 RON)
The only missing link was the cam shaft, Wades had new billet cams on back order so we reinstalled the 240 A grind cam and refitted the engine. After a thousand kms on the fresh engine it was time to run it up on the dyno, the engine was making a mountain of torque up to 4000 rpm (40% more than the standard engine) but ran out of puff after 5000 rpm. The dyno results confirmed that the engine was horribly asthmatic with this standard 240 cam struggling to 98 rwkw, but making an enormous amount of low end torque (it felt like driving a turbo diesel !) and desperately in need of some lift and duration, hitting 5500 rpm was like hitting a rev limiter with the engine dying suddenly from lack of air ! The engine is beautifully smooth to drive pulls like a train up to 4000 however just needs more air to breath ......
Well having waited 12 months for an internal oiling billet cam shaft, I had a 70/30 grind prepped by Camtech which 230 deg duration and .450 lift (very close to the standard Roadster grind) , I did not want to go overboard with a huge cam as I wanted a nice streetable engine that can still handle a/c and idle nicely and not sacrifice low down torque for top end power. Trial fitting the new cam we were pleased to find that the cam/lobe wipe is perfect and I can retain the standard lash pads, the rocker arms were sent off to Wades for resurfacing (to match the new cam) .
The new camshaft was installed and dialed in last night with the help of Lou Mondello, the valves springs checked for binding and found to be fine for reuse) the rocker arms will be back from Wades today so final assembly and run in will be completed tonight. After run in it will be time to run it up on the dyno for a mixture tune and some power runs.....
We anticipate around 110 rwkw at 6300 rpm on the standard 240 carbs (without any loss of low end torque)........any more will be a bonus.
Anyway for those intersted in a nice streetable L26 refresh this may be the path to follow.
Stay tuned for dyno results
Posted 20 May 2008 - 11:31 AM
Posted 20 May 2008 - 11:59 AM
Posted 20 May 2008 - 12:12 PM
I have not run the engine as yet but is should make a big difference
My engine has large valves, hi comp at 10:1 and should work well making power to around 6300 rpm. ......I should have some preliminary results tomorrow after the first dyno run tonight.
Rather than regrind an old cam I wanted a fresh billet which took some time to source.
Go to the Camtech site for L series cam specs (and they have billets in stock)........price for billet cam with 712 grind was around $360 plus freight
What spec is your engine and the existing cam ?
Posted 20 May 2008 - 01:30 PM
Before I go ringing engine rebuilders around Brisbane & to give me some idea whether I'm getting reasonable value for money, can readers just give me some sort of ballpark figures for engine rebuilding so I can form some idea of budget? I don't want to go crazy, just freshen the motor for more mileage, but hobby car not daily driver. So I suppose I would keep my early 260 pretty much standard, with perhaps a bit of head work to suit unleaded & perhaps a small increase in compression so as to be closer to a 240 in spec if that makes any sense.
I already have had a set of 240z carbs rebuilt, & bought new headers. The rest is unknown territory.
Any advice & cost ranges would be very much appreciated.
Posted 20 May 2008 - 02:01 PM
I also considered an L28, however like you wanted to keep matching numbers, the L28s are also less willing to rev and can be agricultural unless lots of $$$ are spent (IMHO)
My refresh ended up around $3.5K which included the following
Engine block hot tank and light hone
New standard bore L24 flat top pistons
Cylinder head work including new 280zx inlet valves, new stainless valve seats, porting and combustion chamber CCing.
Fly wheel lightening and crank balancing
All new replacement timing gear,chain guides etc, new 280zx hi vol oil pump.
I basically renewed every item I could.......apart from new parts most money was spent on the head work and flywheel machining and balancing of the flywheel crank and rods.
I also sourced all the parts from a wholesaler so got very cheap prices. My mate who specialises in Roadster race engines also assisted me quite a bit with the reassembly.
I would expect the same build would be around $5k if I had an engine builder do all the work. ......the end result is a fresh engine better than new, nicely balanced, smooth revving and a great tractable street drive.
The final $$ come down to what you want done and how bad the starting point is, if you have a stock untouched L26 that has not been butchered, it can be transformed into a great thing.
Posted 20 May 2008 - 03:24 PM
L28 f54 turbo block + n42 head (replacing the current l24 )
They did exactly the same as Alan's except i didnt go for flat top pistons And the cylinder porting/cc'ing which is a stage 2 "whip the head off and get it done " thing.( I also needed some linishing on my crank ) Think around 1 K less than Alan's price and you'd be on the money.They also itemised the quote which was super handy.
They also re-assembled the whole head (I had already disassembled the head and block was already dissassembled ) !! Also supplied everything I need to put it together( rings gaskets etc ).
Only change from Alan's setup is I am running dellortos with almost certain boosty efi thingy ( designing the intake and all that in my spare time ) in the future ( hence the lower compression ).
Agree exactly with what Alan said lastly. Be sure to put aside 3 - 4 grand for the build and be ready. The guys at torque team are FAST I mean 4 days and it was done ready to pick up.
- Simestime likes this
Posted 20 May 2008 - 04:21 PM
The engine is already stripped down & quite clean so Torqueteam should be able to assess it quite quickly & accurately which always helps with quoting. Fantastic.
260Coupe, what's with the 280zx high volume oil pump? Sounds like a damn fine idea, is it easily available & how do I visually tell the difference from a standard one?
Posted 20 May 2008 - 04:51 PM
Posted 21 May 2008 - 08:54 AM
Ok- installed the resurfaced rocker arms and dialled in the cam and ran it in last night.
Did some preliminary mixture runs on the dyno and the power figures were excellent, torque was building from 3000 and peaked at 5500 rpm, Kw at 5000 was comparable to the previous standard 240 cam at 5000 (peaked at 96/97 at 5K) but then climbed away to 105+ at 6000 rpm.!!!
This was looking promising.......After retiming (18 deg static) and checking tappet clearances we made several runs to check cruise mix and hi and low end and found SR needles to be just about perfect............we then hit 111+ rwkw at 6000 rpm with power still on the way up with little loss of torque (power and torque usually head in opposite directions ..at high rpm torque heads south while power increases)
The engine combo has proved to be a cracker, torque builds to 2500 and stays flat all the way to 5500 and peak power will be around 6400 rpm at around 115 rwkw or just over 150 rwhp in the old money (we only went to 6000rpm continuous on the dyno due to the fresh cam and rockers but on the road it pulls easily to 6500 with no power loss !)
Tractability on the road is perfect, idle is a little lopey (but should be fine to run aircon) small throttle input provides instant response and the engine spins up easily and just after 4000 rpm it really rockets up to 6500!!! Low down torque is equal if not better than any comparable L28 (smoother and more linear delivery) and drivability on the road is outstanding (I drove it to work in trafic this morning)
In short I can highly recommend this combination over the standard L28 converstions, the only issue I see is the problem of standard 83mm flat tops being very hard to find. (lucky I have a spare set )
Anyway for all of you L26 drivers, pay no heed to any "expert" how says you can't make an L26 get up and go.
Posted 21 May 2008 - 01:14 PM
Posted 21 May 2008 - 01:25 PM
As my engine was unmolested it was a joy to work on, with standard cylinder head thickness and valve heights etc, all the assembly was very straight forward, no need to thick lash pads or shimming cam towers............the whole combo works perfectly
I have driven many a Zed with an L28 fitted and most drive like dogs unless big $$$ is spent on sorting them out so my advice is stick with the L26, add some compresson and some breathing and it will perform favorably with any well sorted L28
If you need any help or more details on the work performed let me know.
Posted 21 May 2008 - 01:34 PM
I'm still debating whether to go down a similar NA build path, or keep the turbo setup that I currently have for my L26.
Posted 21 May 2008 - 03:14 PM
Yep to go from a stock 100 rwhp (approx 76 kw's) from bog standard Zed to a 50% gain in HP (110 + rwkw or approx 150 rw hp) and 40% increase in torque is a good result considering I have retained the original engine capacity and normal aspiration (no turbo).
Posted 21 May 2008 - 06:43 PM
Posted 23 May 2008 - 08:30 AM
My 260 is a very early one, with E88 head. From looking through the Forum I get the impression that the N42 is the head to go for, as it has bigger valves??. I happen to have one to hand, so presume better to spend the money on that?
I don't want to up the compression too high - say, 9.0 to 9.5:1 or so, like a 240, in lieu of the stock 260 which as I recall is around 8.3:1 or so. So I won't go chasing flat-top pistons which are rare anyway, & which gave you 10:1, but is there a choice or range of 'dished' pistons, as in different dish depths, to choose from?
Sorry for all the questions but I want to get the direction clear & correct so I can brief Torqueteam accurately (& not be completely ignorant).
With the 240 having a shorter stroke so faster revving, how come 240 owners don't bore their existing engines out with 280 pistons which are 3mm wider, & up the cylinder capacity that way (would make for roughtly around 2550cc I think), rather than going for the 280 motors with the longer slower stroke? Or is it just that there's no substitute for cubes?
Posted 23 May 2008 - 09:14 AM
Check the Capacity of the N42 combustion chamber and compare it to the E88 to calculate the comp ratio. (you may find you are going back wards) Larger inlet valves can easily be installed into the E88 head. Also check the head thickness and choose the one that is closest to standard thickness .
I'm not sure if there are any 83mm dished pistons available apart from the standard 260z pistons, you can obtain a little less comp with flat tops by opening up the combustion chamber, maybe talk to the guys at Torque team to find out what options are avialable to you.
L24s do not have the cylinder side wall thickness to bore out to 87mm hence most go for an L28 block as they are readily available (most are Jap taxi 280C engines or from Nissan patrols). very few actually came out of 280zx's as most have very lazy cams installed and done a million km's.
You are correct in the "capacity = HP" to a point but IMHO it is a very crude way of going about things (often referred to as "brute force and ignorance")...... I think I have proved that the same, if not more power can be made from the L26 and deliver it more smoothly and accross a better rpm range.
Posted 23 May 2008 - 09:24 AM
hey fuzzy you should go na and sell me your turbo setup lol
I'm tempted, love the idea of a bit of an NA build, but also love a turbo build . My turbo setup is a bit old and needs a bit of work to get it back up to scratch, the turbo needs a rebuild or new turbo (hard to turn turbine, even by hand) and rebuilt carbi. See my intro post if you want to check out how the previous owner hooked the turbo up. Has to go back to NA for RWC anyway but then we shall see what I do, but that is a fair way off at the moment Actually, I should get off my butt and make a project thread..
Posted 23 May 2008 - 01:40 PM
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