New engine build

Hi Poeple

I am quite new to this group so please be kind !

I am planning on building my first engine. I have read loads on the net
on how to ... performance this ... lightened fly wheel etc etc.

A few times I have come across the statement " but dont do this if its
going in a bus" !

So my question is this - what would be a good design, from carb though
to exhaust for my new engine.

I want not so much power/speed but tough reliable cruising at 70 - 80
MPH. Good MPG would be high on my list to.

I have read that a "square engine" ( stroke equal to bore ) is good for
fuel econ. Small inlet is good for busses ? Keep your flyweel heavy
(180) etc.

I will be using a spare 1300 dual port as my donar.

Any good sites I might have missed ( for bus engines ).
I would prefer type 1 as there doesnt seem to be that much info on type 4 )

Ta

Rich

64 1600 split bus daily driver , 68 1300 bay bus, 78 2000 bay bus, 70
1200-70 1300 71 1300 and 72 1300 bugs.