Right.....there may be a really simple answer to this, but I'm a bit puzzled......

On a "normal" in line engine build-up you can fit the crankshaft, then when you are fitting the pistons/rods, you can fit the conrods to the pistons, fit the rings, and then use a piston ring compressor to enable fitment of the pistons down the bores.
You can then access the big end bearings to fit the half shells and bolt it all up.

However.......I am perplexed as to how you do the build of a horizontally opposed engine.

You can do the same procedure as above for two of the cylinders (one side of the engine), but then how do you do the opposing pistons?
Maybe I'm missing something really obvious here but......... whichever way I think of doing it, the two halves of the crankcase have to come together at some point, and I am assuming (always bad......and maybe this is where I'm wrong) that there isn't enough gap between the case halves to access the big ends and still have all four pistons in their bores.

If this is the case, the gudgeon pins must be fitted to two of the pistons after the crankcase halves are together? If so, how the hell do you line up the conrod and piston/little end bearing in order to get the gudgeon pins in?

The simple solution is a plugged access hole for putting the pins in, but the alignment is baffling me a bit.

Like I say.....there is probably a really simple answer that will have me going "ohhhhhh..of course".

Might be handy information to know if I ever fancy building myself a 2.33 litre 500bhp lump. ......or maybe I'll just get a Westfield!! lol

 

Marty.
If you can get a look at the March issue of Japanese Performance, there is an article in there where Scoobyclinic have done a strip and rebuild guide, your question is answered there.
Keith.

 

Scooby powered Westfield !

LOL

 

Marty there are plugged access ports as youi say, you simply build the crank/rods/bearings and then assemble in the two c/case halves...........

pistons now ready to be fitted.........

alyn

 

I kind of guessed that access ports may be the solution, but I wondered how you line the little end and the hole in the piston up if you can't access the conrod?

And........a Scooby powered Westfield.......nooooooo.....Hayabusa powered........yessssssss!! Neil Booth's 550bhp Westy is a bit insane like!!!

 

Sorry to hijack, but a question I've always wondered is, with the flat 4 set up, why do the bottom of the piston rings never wear out if the pistons are moving side to side instead of up and down?

 

I guess you are suggesting that the weight of the piston is pressing down on the bore?

If you're not having a laugh, the answer is that the rings are "sprung" into the bore, so the forces are pretty equal all the way round, the weight of the piston is negligible.

Once the engine is started, the pistons are flying up and down the bores anywhere between 600 and 8000 times per minute, so the lateral forces (the pistons wanting to fly out sideways) combined with the piston ring centralising forces will be keeping the pistons central in the bores.

That's my take on things anyway.