L26 with E88 and head timeline - pistons

[Pedro]

Hi,

 

i was reading through the following head timeline to try and work out my performance head options.

 

http://www.viczcar.com/forum/index.php?topic=6012.0

 

My question is:

 

My L26 was freshly rebuild to factory specifications (a number of years ago now but lo mileage since)

The car is a 12/75 260z

It was the orginal matching numbers motor and its first rebuild (car still has original wet legs!)

The car was issued with a L26 and E88 head combo (note above build date)

according to the above chart this would suggest on a std rebuild that flattop pistons went in.

 

Something tells me that many L26s around this time have dished pistons though.

Basically Whether it has dished or flattop will change the head route i take.

 

anyone know which is more likely? or a way to find out? (cheaply easily)

cheers,

Peter

 

[dat2kman]

Pull out a spark plug, use a borescope camera, Snap on sell them, a visual will tell you if dish or flat.

The dish is shallow at 7 cc's.

Other method, use small thin screwdriver, with piston down about half way, gently feel for a "rise" on the edge, the raised edge is only about 4 or 5 mm wide, and it is a gradual "lift" as you slowly slide screwdriver tip about, gently.

 

I take it you want to keep the rebuilt bottom end as it is, but look at a better head, or work your existing head?

 

What are you leaning towards re head?

 

 

[Pedro]

Ideally, the block is rebuilt and matching #s and in the engine bay so would like to use it.

 

Basically i want some more compression and cam wise would like to get her to rev to 6500-7000. 6500 would be fine, 7k would be amazing. Right now it runs out of breathe at the normal 5.8-6k for an L26;

 

If its already got flattops in then that is a good start - head wise i figured i would match the 83mm bore with the head only because my understanding is this is probably my best bet. I have read the L24E had a head with a peanut shape to it, "e88" specific to the L24E? ideally if that bolts on and gets my compression to 9.5 or so, then i can simply select a cam and i am going to be able to achieve my goal fairly easily.

 

If it has dished pistons i dont know what to do. there would be the option of putting in flattops ($$$), or head shaving and the like to get to 9.5:1; The head on it is the E88 (12/1975) so i figure this isnt ideal for quench. 

 

Aim will be around 9.5-10:1 so its streetable and not too grumpy, can hold idle. i always run 98 octane.

[dat2kman]

Let us know what pistons you have first!

Leave bottom end alone, it will be fine.

There are a few heads around, i have a nice welded up chamber head that will up your comp nicely, even more so with flatties.

At least you keep the matched numbets!

[d3c0y]

I've got a race port E88 for sale too, it's a bare head but has megga dollars spent on the ports. Message Peter MC26 for details on it.

 

There are pics of it in my build thread too 39mm wide intake ports.

[Roberto]

according to the above chart this would suggest on a std rebuild that flattop pistons went in.

Something tells me that many L26s around this time have dished pistons though.

Basically Whether it has dished or flattop will change the head route i take.

anyone know which is more likely? or a way to find out? (cheaply easily)

cheers,

Peter

 

Hi Peter.  The standard L26 pistons are slightly dished.  Not as much dish as the L28 dished pistons, but not flat like L24's either.  If it was a standard reco. it probably hasn't got new flattops in it.  Do what Dat2kman suggests to confirm.

 

Standard you have 8.3 to 1 compression and with flattops you will only get 9.3 to 1 compression.  If your aim it to get to 9.5 to 10 then some shaving will also be needed.  Would you consider L28?

 

 

 

 

[Pedro]

hey roberto/all,

 

i like the idea of a L28 but am trying to avoid 'hanging' my L26 in the shed since its been nicely rebuilt.

 

I dont really have the room. And power wise, i think w can get enough poke out of the 26. for me anyway.

 

I will try and work out the piston type, but i dont have the tool to take the photo so not sure what i am going to do on that one.

 

screw driver test i guess. I am going to softly keep researching assuming dished.

[peter mc]

just remove the plug and get the piston near tdc and look throw the plug hole you will see the top and see if its flat or dish

 

 

[260Coupe]

I refreshed my L26 a few years back with flat tops and power went from 80 to around 110 rwkw on standard 240 carbs and on a standard 240 A grind cam with the only head work being 280 valves........so yes flat tops are certainly worth the effort if you want to retain the orginal L26

 

I have a set of genuine 83mm flat tops in std size if you need them PM me .

 

cheers

 

Al.

 

[Pedro]

options everywhere;

 

there are 3 real options for me now (the way i see it); i have settled on (roughly) a 72 degree cam to get desired RPM, so 9:5 CR will be required to run it minimum according to the specs.

 

- Flatops

- head (high quench) L series head, 39cc-44cc chamber. Some porting

- 72 degree cam

 

- leave dished pistions

- heavily shaved and ported head down to 35cc

- 72 degree cam

 

- leave dished pistions

- head (high quench) late E88 efi head, 39cc. Some porting, maybe some shaving to get CR. (given dished pistons). 

- 72 degree cam

 

long term not really sure which of the above 3 options are best. 

[d3c0y]

If the compression is good i wouldnt even bother taking the head off it - that's a pain and especially changing pistons.

 

If i were you i would just do the following:

Get a cam that matches the power band you want

Stick a set of triple 40mm carbs on it

Put a CDI ignition on it (MSD/Crane HI6 etc).

 

You could have all that for $2k and you will make more power than stuffing around with heads and pistons.

[Pedro]

In answering your query:

 

I could be wrong but i didn't think any decent cam (capable of lifting rpm to 6500) would be effective at 8.3 CR. (possibly reduce power).

 

Also, i could be wrong but i didnt thing fuel supply (hitachi's) was much of an issue with only 2.6 litres and a 72 degree cam.

 

I have a ZX electronic dizzy and Crane hot coil and figured spark was of no real issue there at the power levels we are talking about.

 

Hence the need/want to raise the CR, so i can get use out of any cam upgrade and the engine will produce the desirable rpms ~ 6500. 

 

The only way i am aware of doing this is FLATTOP pistons or, head choice/shaving, which is why i presented these ideas. 

 

Going from 8.3 to 9.5 and getting a medium/hot street cam will transform the car on hitachi carbys (from my understanding).

 

Triples are nice but overkill until the other engine items are sorted (from what i have read). The stock L26 couldnt even handle 100mm of carbys (2" sus) let alone 120mm + of triples.

[260Coupe]

IMHO - avoid shaving the head to increase comp - this creates more problems than it is worth with piston/ valve clearance and you also need to look at shimming the cam towers to maintain timing chain tension .............it all gets very messy.

A 72 deg cam in a stock L26 will just make it a pain in the @ss to drive on the road, it will move the modest HP you have further up the revs and create a big hole below 3500 rpm (I know I tested a 72 on my stock L26 on the dyno and in the car........it was horrible.......you had to drive it hard in every gear just to keep up with traffic............making lots of noise and going nowhere make you look like an dill!)

 

Up the compression with flat tops and do it properly .

The best combo I found (if you want to retain your L26)  with power that is still pleasant to drive is flat tops, 240 A grind cam, elec ignition, 240 carbs and a proper dyno tune. As I said early you should be looking at around 110 rwkw  (40% up from stock rwkw).

This type of mod is relatively inexpensive as you are only swapping pistons and a cam.............head work can be big $$$ so unless you want a big giggawaht street racer kepp it simple.

 

Al.

 

[Pedro]

cheers for the advice, cams is one thing where i am still learning and real world experience goes a long way.

 

i am printing this thread now, so far its been a wealth of info for me!

 

sounds like the 240a is more sensible for most of my driving.

[d3c0y]

I guess it depends if you are doing the labour yourself or not in regard to modifying the head. As long as you shim up the cam towers the amount you take off it's a very comon practise.

People have taken up to a max of 2mm off the head.

 

L24s with triple 44 mikunis pick up something like up to 40hp at the crank so an L26 will definitely benefit.

The cam you are talking about is a very mild cam. You aren't talking about running something with massive overlap or any of that and there are plenty of cams out there designed to run in the setup you have already got.

 

http://www.thezstore.com/page/TZS/PROD/PEM01/10-2001

 

Look at this cam from MSA:

Description:

Grind: 17030. Lift(In/Ex): .460/.460. Duration(In/Ex): 260/260. Characteristics: Moderate idle, good power 1500-5000 RPM. That will probably let the engine rev up to 6500rpm no an L26.

 

Or the next step up:

Description:

Grind: 17033. Lift(In/Ex): .480/.480. Duration(In/Ex): 274/274. Characteristics: Good idle, power range 2000-6000 RPM. Great slalom grind, works well with stock carbs or triple Webers.

 

More safe RPM + better flow = more power.

 

The best combo I found (if you want to retain your L26)  with power that is still pleasant to drive is flat tops, 240 A grind cam, elec ignition, 240 carbs and a proper dyno tune. As I said early you should be looking at around 110

 

L26/E88 'C' grind cam is apparently the most 'agressive' of the standard cams but is by no means sporty.

 

A big hole below 3500rpm sounds more like a 74works or a tuning issue? If you want lots of low down torque just put an L28 in, it's a small capacity engine you are going to have to rev it a bit. I have driven L24s with cams in them and it's not like you rev them up to 4000rpm to keep up in traffic or anything crazy like that? I think you are making it sound a lot worse than it really is. I guess it's different for different people.

[Pedro]

After much consideration, i have decided at this stage to build Dat2k's e30 head on my dished pistons.

 

head mods will probably be limited to a bit of porting and cleanup, possibly some bigger valves (depending whats in there).

 

I am thus far settling on a 68 degree cam, the exact specs to be determined. It is a street driven zed so should be good for 'most' of my driving.

 

CR will be somewhere in the 9.5-9.9 range depending on gaskets and precise head cc (~ 35cc).

 

I hope to not backpedal and end up with flattops... but like any zed project - anything can happen!

 

cheers for the advice all, When i get to the next step i will provide an update!