Just in "theory" Alfa Romeo made a straight 8 cylinder
engine using 2 alfa engine in the 1930s, other car
companies also did this in some form or other.

There is a 3 cylinder all alloy HR10 and HR12 and
just wondering what it would be the best way to tie
2 together to make a lightweight engine for a 240z?

Its just for chatting but someone could be interested? :)

Id love a straight 8 using 2 A10s or A12s but weight
of all alloy 3 cylinders and the smoothness of a 6
is hard to beat.

2 Suzuki capacino engines for a 1320cc tt v6..... Enough said

There's a reason they stopped making straight 8s years ago you know :)

the longer the cranks, the more they can flex.

If you run 2 3 cylinder motors inline, you don't get the same result as a regular inline 6 - the crank journal clocking won't be the same, and instead of the 1 5 3 6 2 4 firing order (which evenly spaces things front to rear, and keeps it somewhat of a smooth running motor, no secondary imbalance) - you'll have 2 3 cylinders one after the other, and they are both inherently unbalanced motors.

It's not quite the same thing, but it's also why most v8s (outside of race only stuff) have 90 degree cranks and not 180 degree cranks (the 180 cranks, or 'flat' cranks make each bank of cylinders fire like a 4 cylinder engine, so better exhaust tuning to be had vs 90 deg ones, but they have a big secondary imbalance issue then. so pretty much all production v8s use 90 degree crank phasing. It means the firing order is uneven - they don't alternate from one bank or row of cylinders to the other - they instead go left right left left right left right right, and repeat - so you get 2 exhaust pulses in a row from one bank, then nothing for a little while. THis '2 in a row' exhaust pulses is actually what gives production v8s their distinctive thumping sound . Flat cranked v8s sound a lot different.

It's not quite the same thing, but 2 3cyl motors inline is asking for a rough vibrating driving experience. With very little benefit.

TO keep it datto related - despite there being some great inline 6s out there from nissan, you really need to look at a v6, which is shorter and weighs less for the same capacity as an inline 6 (perhaps a vg30 rather than a rb30 for instance). Yes the v6s have harmonics and vibration issues, but they are pretty well taken care of with balance shafts (in other words I'm saying look only at v6s that have balance shafts in their design,

Haha! but where are talking split cranked S6 or S8
wouldnt that make a difference to flexing?

Thanks John was wondering is offsetting the cranks at 180
degrees or other angle could bring back the 1 5 3 6 2 4
firing order to bring back the smoothness?
eg. halve of 360 is 180 and 6s fire at every 60 degrees
like most 3 cylinders which are 1-3-2 so the maths done
my handful of neurons in! but am I wrong?

A basic NA HR12 is under 140 pounds x 2 = 125kg
or almost 80kgs lighter than an L24

I also see these ugly little suzuki G10a engines in
swifts and they are used in all kinds of things even
one boosted with 230hp in a porsche!! out of all things.
128 lbs each x 2 would give a 2 liter with 180hp+ NA
in mild tune knowing they make 90hp worked

I dunno if they're alloy or not, but the VQ30(?) is a mean as engine. A mate of a mate has one in a something or other SX nissan. The engine is internally standard, and it's pumping out 400+hp. They sound pretty sweet.

there is a smorgasboard of awesome engines that will easily fit into a 240z engine bay

bolting 2 engines together to me seems crazy, even if its only in theory or for discussion

just take the engine of choice (you choose your level of awesomeness), install and your away

Yeah its a bit of a brain fart but my ultimate
datsun is the one I did with the kb10 I photoshoped
with 10inches extended front end and chopped lower
roofline, 99.5 inch wheelbase and longer engine
bay will allow an inline six.

I must say there is only 1 v6 I like....
Its from TAPerformance, an all alloy OHV v6,
simple, pushrods, light, cheap and compact.
Problem is its over 2 liters and not Nissan.

So would prefer if the balancing can be solved
using offset crank at 180 degrees, waiting on
Jmac to put me straight on this one.

Am I the only one to want an all alloy 2 litre
6 cylinder with 6 x Keihin flatsliders and a
spaghetti F1 style exhaust?

It appears so D, rest of is are happy using stuff already out there, sometimes no point reinventing the wheel

Absolutely

just theory though

If they can meld ford and Holden v8 blocks for v8 #OOPS#tercars any thing is possible