Ok guys..
there's lots of talk about whats the best block to have, whats the best head etc....
Whats your opinion???
In Australia we got F54 blocks everywhere. Apparently there the best to use. There is also a turbo F54 block, which i think can only be indentified by the pistons it runs.. Low compression for turbo..
But in any case, im sure all F54 blocks r turbo strong. Knowing Nissan.

Has anyone done any mods and found out what NOt to do???
I've heard of people using 2.4L deisel cranks, and 240 rods in a 280..


At the moment im running a 2.6L block with a E88 head. Stage 1 camshaft. Twin carbs. small amount of cam lump at idle.
Power drops off at 6500 rpm. anything over 7000 is a waisting fuel.
Standard 2.6L engine does about 5500rpm max power.

I do know the first gen 2.4 motors r no good as Nissan had probs themselves stopping the thing vibarating apart at high rpm. BRE had this problem too and were getting about 2 - 3 races out of a crank before it had to be restraightened. Problem was an out of balance crank shaft. I think they fixed it for the later 2.4 engines. All 2.6L and later engines had a fully counterweighted crankshaft. Problem solved.

Apparently the Late 280 Turbo heads r the best to use, as nissan revised the flow chambers for more breathing for the turbo.

Even the BRE boys did extensive head flow testing with all sort of technics. eg - Multi cut seats - boring and polishing.
Even after all this research they found the Datsun Heads flow is soo good, the only thing to do really is match port your intake and exhaust manifolds.
They did multi angle cutting of the seats for excellent combustion seals but found this pounded the seats pretty bad. All good for a race engine. no good for the street.

So all in all, the BRE race heads didnt get too much reshaping of the basic design. Big valves, big cam and alot of combustion chamber valve releiving..
Ever seen a Nissan heads combustion chamber?? of course you have...
Notice how the valves sit really close to the chamber side walls..
Lots of gains can be made by giving your valves as much room as possible. Theres usually plenty of meat there befor you get to the Head gasket. Use it!!!
Good idea too after this to CC your head. Making sure each combustion chamber has an equal Volume. Goes along way to making your engine more balanced. And if each cylinder is doing equal work then its gonna last longer and giv you an extra horse or 2..
Running multi carbs makes all these thing crucial. You can have 1 carby running a bit off and think, Damn carby is stuffed. But it could actually be a dud cylinder, broken valve train..
I usually run tripple webbers which means everything needs to be as balanced as possible.

Well the F54 is the same block, turbo, or N/A, just different pistons. The block has more internal structual strenght, siamesed cylynders as one of the stong points. The N42 head is the popular one to modify to add to the F54, with flat tops, this gives you 10 to 4 compression. I believe the E88 gives the same compression as well, and the E88 on the 260 has larger valves. There should be plenty of 260's there, they made those until 78 in the land down under. Then there is an E80 head and the Y70 head if you could ever find one, sorta rare, I think 1970 Z's only. The P90 turbo head is also good, and most likely if you are doing turbo charge, should use this one, for it has increase flow. Then I think somewhere's out there, there is a crossflow head, exhaust manifold on the right side of the engine, and intake on the left side. I'm working on a F54, flattops, with the N42 head. with attached a ZX 5-speed and 4:11 rear end, and keep the carbs.

Our member Bryan Little has covered all this in his website, "DATSUN Z GARAGE". On our homepage, press the link on the left margin to get into his GARAGE. Then select the head/block discussion.

Also, I have several manuals and reference books about these head/block combinations which I will gladly share, but I just sat down for the first time in about 5 hours and I'm too lazy to get back up and find the books just now.

By the way ~ the 1971 240 car I'm thinking of parting out has an E88 head and four-screw round-top carbs.

Yep. the P90 head is the turbo head. The later the head is th emore combustion chamber CC's it has.
eg. early heads (high compression) later heads (low compression)

TYhese other heads your talking about i have not seen yet.. We get E31 E88 N42 P90. Thats about it. Rare hear to find one with exhaust liners.

And that Z garage site is awesome. Heaps of good info. And from someone who's done it all too.... Theres not substitute for experience.
The info on the heads and compressions is great also.

I'm gettin together a F54 block which will be standard ( rebuilt ). And put a P90 head on it. Stage 3 cam (35/75) . Im just a little worried about not having enough compression to get the benefits of the Triple webbers

Does anyone know what the compression on a standard L series engine should be????
I've got an old tired 2.6 and im getting 150psi on each cylinder...
(Pounds per square inch)
so what should it be and what would be tooo much????
should it be 180ish???
and about 250psi max high comp....

is there a formula to get psi converted to compression eg
- 180psi = 8.8 to 1....?????

YES! I have the formula and will look it up as soon as possible. Bryan also figured this out but I don't recall how he posted it in the Z GARAGE site.

Are your compression readings wet or dry? It's useful to take a dry reading first, then squirt a bit of oil into each cylinder immediately before re-testing that cylinder, to test your rings. Take careful notes ~ if you're like me you will not remember all 12 readings!

Differences of 20psi in each cylinder indicate blowby and time for new rings. As you no doubt know, one or two vastly lower cylinder readings (compared to their neighbors) indicate bad news ~ usually a gasket or a bad valve(s).

yeah i got that Frank...
Didnt do a wet test as the compression was too low. Im guessing there's too much blow by now and it needs new rings..

The formula i use for testing engines is...
if theres more than 10% difference between any cylinders then she's stuffed. or.
if its more than 10% down from factory settings then its a good idea to rebuild tooo.

Hey Pete!

OK, what I have is the calculation for Compression Ratio.

We first have to know the engine's CLEARANCE VOLUME (CV). That requires knowing the total volume of all the combustion chambers ~ that's done by "CC-ing" an engine. It determines the amount of air space left in the combustion chamber when the piston is at Top Dead Center. We add the CV of each cylinder to get the total.

Then we have to know the Swept Volume (SV) of the engine. This is simply the TECHNICALLY ACCURATE displacement of the engine (not rounded off to the nearest big number to sound good for sales). It's the accurate volume of each cylinder, added together. (We can't use the engine's "sales size" to determine this. For example, the 2.4L engine actually only displaces 2393cc, not 2400cc. The 2.6L is actually a 2565cc and the 2.8L is a 2753cc).

When we know these two quantities, the formula is:

Compression Ratio = (SV/CV) +1


Now that I re-read your question, I don't think I know the exact answer:

"Can we determine the CR by the cylinder PSI?"

A "leaky" engine (worn rings, bad valve seats) designed for Hi Compression could have the same PSI as a lower compression engine in good shape. They could both give 180psi, (for example), but the condition of the "leaky" engine would prevent it from developing the (say), 300psi it was designed to have. So just by throwing a compression tester on both engines and getting the same psi readings, you might be misled to believe they were both designed to give the same CR. (Did I say that right? Does that make sense?)

Your question about compression figures for the L series engines:
The 2.4L ("L24") in good shape should show 180psi
The 2.8L ("L28") in good shape should show 140psi *IF IT IS A TURBO*

I'm looking for the rest of the specifications. Get back to you when I find them.

BY THE WAY ~ I recommend a link from Melbourne called the ZShop.Net. It has some useful info (and pictures of some blonde birds) and a few phone numbers if you don't mind calling Victoria.

hahahahaha
Makes perfect sense Frank.
Going by your figures my old 2.6L with 150psi is probably still got some life in her. All the cylinders read the same. 150. not too shabby for a block that i have no knowledge of its history.
Some - one did a bad valve and cam job on it though. None of my wipe patterns r central or corresponding. Clicks a little more than it should. I tightened the gap up a little and that shut it up a bit.
And now my crappy 260 emission carbies r spitting fuel out the air intake.
Probably a sticky float that i cant even get to with those stupid inhouse float chambers.. grrrrrrrrrrr...
gotta love the 240 carbs.

Can I mail you a pair?

yep.. those multi carbs can be a real pain sometimes. Theres nothin' like a single barrel carb for ease. But, a Z needs to breathe. I personnally like the earlier carbs as they are easy to maintain. And they've actually got a mixture screw you can use. yay..
Have also used stromberg su's on a Z but found the Hitachi ones to be even better. I beleive also you can get different size su's. eg. 1 and half inch, 2 inch..????
I think the Jaguar V12 (1975) has 2 inch stromberg su's.
would be interesting to see if bigger su's would do any good on a Z.
I had the standerd 260 emission carbs on me 2.6L. Then put 3 x 42mm webers on it. Basically there was NO horsepower increase. The engine reved alot better and further but that was it. Great sound too!!!!!
So even though i put huge carbs on it compared to what it had, there was no increased horses. But. Now she'd be able to handle a really thirsty cam;)

I've got a set of triple Weber DCOE40s with 30mm venturi which I'm thinking of putting on my L24 this winter (your summer, Pete), but I still have to figure out what to do with all the hot-water plumbing that warms the SUs. The Webers don't have any provision for water heating so I have to close it off somehow. My cam is not hot ~ only slightly warmer than stock, so I have to be careful not to over-carburate. E-31 head with slightly higher than stock compression (shaved 0.10") and less than 2,000 miles since rebuild. Should be a falrly nice performer with good dependability by the time I ever get it done.

sounds great Frank...
If u need help with the set up let me know. I've got heaps of info on jetting for Z. Usually a pretty stock Z engine will take either 30mm or 32mm chokes. I pretty hot street Z would use about a 36 or 38mm choke.
So really the biggest you'll need is 45mm webbers.
My Z with a stage 1 cam ran a 30mm choke.
I think 40 and 42 mm webbers take a 36 or 38mm choke maximum.
The 45 gives you a little more.
Bloody expensive to get new jets or chokes if your sizes r wrong as you need to buy 6 of each.
Your water inlets will have to be blocked.
Disconnecting these gives you like maybe 1 horsepower. And makes it a pig when its cold.

so really it doesnt matter how big your webbers are. What ever your choke size is that determins how much breathing it can do.
Small chokes makes it zippy down low but cant breathe up high..
Big chokes breathe up high but make it boggy at low rpm.

If u need some settings let me know.. i'll try find a few variations you can try. Or. you might even be set-up for it already.
Bloody webber maniac here.
About the only prob you'll have with them is getting them all synced..
Each carby must operate in sync with the rest. If you think the twins can be a handle full try 3 of em.
One big myth about webbers is that they go out of tune. THIS IS FALSE>>
They go out of sync with each other making the car run as if a carby is out of tune. Webbers have 1 mixture screw for each cylinder and these things do not turn them selves.....
Each cylinder had its own set of jets and venturies. 2 cylinders per weber.
These must be all the same.
Next is a lot of time synchronising all your linkages so that they all operate at the same time...
Even Z's will do it with twin carbs. They m,ust open at the same time..
If your car sounds like its out of tune its probably the linkages wearing over time.

There a pretty thirsty carb but they can only suck in as much air as the engine lets it. so keep your vaccum up and throttle short and you can get really got mielage out of em.
They can tend to suffer from fuel build up too..If your gonna run webbers you gotta drive it like its got webbers. If you putt putt around they'll fuel up and most times to clean em out they just need a good revn...

In short. - Webbers r great but you need to keep on top of em checking them at least once a month if its a daily drive car.
Standard twin carbs r great for trouble free motoring. Check these about once every 3 months.

Mate, I'm under there every DAY! I love having my old car back and just fiddling with the engine is most of the fun for me. I owned the same car for 12-1/2 yrs (25 yrs ago) and I was fairly proficient with it then. But it's been totally rebuilt during the 24yrs we've been apart so a lot is new now. I've always admired Weber setups, mainly for the mid-range performance but also for the cashe they impart to the car (and NOTHING ELSE sounds like them). Admittedly, this is the first set I have ever been able to afford so I will be starting at Ground Zero and making all the mistakes as I learn (I never learned anything by succeeding ~ mistakes taught me everything I know about life). (And about women).

I take seriously your words about them being warm-weather carbs. But I have been so intent on mounting them that I'm sure I will tolerate whatever small aggravations I have to endure to have them on. I have been studying which water hoses have to be re-routed and it doesn't look overly complicated, but I'll save the hook-up after I remove it, in case I decide to remount the SUs later.

I'm missing the Idle Jet Holder screw on one Weber, which I will order over the winter. They were tuned and running right on the 260 they came off of before I got them, so I don't want to mess around with them much and put them out of sync. A basic external clean-up and new strainers should do the trick for now. When I get ready to mount them and try them, I will refer to you and probably ask advice as I step along.

Good to know you're an authority on these. This Club is a Blessing to me ~ somebody knows something about everything I need. I'll let you know when I get ready to put them on.

no probs Frank...
nice set up...about the warm weather thing. i used to have problems with my 260 carbs.if i sat for too long on a hot day she'd cough and splutter till i got goin. strange fenomena this is.. whats even stranger is the remedy.
I dont run air cleaners on my engine so if its gonna suck hot air this would be the worst case cenario. All i did was put a heat shield on it.
Peice of aloominum about 20cm wide and about 60cm long. Just this crude peice of metal between your exhaust and carbs doesz it. As soon as i put this on all my carb problems vanished. I think its like vapour lock.
the exhaust basically heats your fuel up and heats the intake air. Even with the 260 emission carbs have a small heat tray beaneath the float, no good.. i was astonished. It ran like it neede a good tune. crazy
Dont start buying any jets or things for it yet..
i'll start a new thread and giv u a starting point.

manifold too...here you can get this crappy LYNX manifold for webbers.
its sooo small ..crap...
the ones i use are made by warner-ford. They've been around for ages
and r nice and chunky. The ports match up to the webers and head pretty close. Just somethin to watch for..
Its hard to tell witch one you've got there..
Also the one you've got looks like it has a balance bar on the manifold.
Balance bars r great for multi carb engines as it helps to even out the vacuum of each ventury. great for a street car. No horsepower to gained by not having it...(no brainer)

one more thing. Apparently running your fuel line into a fuel block with three outlets is the best way to go. The main reason is so that you make all of your fuel lines to each carby the SAME length.
This is what the experts say. But, is it crucial for a street car???
My Z ran fine with all the original gear eg, fuel pump, fuel lines. etc/.

Hmmmmm.......well, as you can see, none of my fuel lines match the others. But if I set the regulator to 3 or 4 psi, that pressure is the same everywhere along the line, no? The Webers have no fuel return line like the SUs have, so the fuel would run to the float needles and hang there maintaining 3-4psi as it is used. In actuality, I realize fuel doesn't move in a stop-go fashion while the engine's running ~ it flows constantly, sometimes faster than other times depending upon engine speed.

These Webers came off a 260 with a hot cam. The engine was under-carburated with them (30mm venturi). I'm hoping my 240 with the slightly warmer than stock cam (I don't have grind numbers for the cam) will max-out on these Webers without over-carbing the engine.

This will be a fun project and it will be interesting to see what kind of performance I get with these. If I am not happy with them, I can return to the dependability and flexibility of the excellent 4-screw round-top SUs.

Tell me what you think of this arrangement:
(No, this is not mine. It's another member's car. He made the set up hmslf).