1879cc

[Beastofthesoutheast]

Here’s my question I’m planing a build my first complete one. I’ve done the research and watched many videos. I’m pretty sure I can do it. Now my question I plan on using my 88mm thick walls in this build one reason where I live there’s no machine shop close and the think walls are better at handling the heat. I’m going to use a 78mm crank shaft. Not sure yet if I need a line bore yet but I want to use clearance piston rods. There’s a lot of contradicting info out there. One says use short rods n others say use longer. So I’m confused about this I know there are A pistons n B pistons I’m pretty sure the 88s are A pistons. What length rod will be the best. I’m not looking for a hot rod engine just something with more power when I need it. I’m sure the stock rods won’t work cause they aren’t clearance but will 5.4 or 5.5 inch rods will work? Also will that cause me to need to get cut to fit push rods or will the stock ones work ? Thanks I appreciate the advice in advance.

[bugguy1967]

You might run into some cylinder clearance issues with a 78mm and such a small bore. Also, the 88 pistons are designed for 69mm strokes, so you'll need about .150"-worth of spacers with 5.325" rods. Not a good combo, IMO.

Do a 74, 5.325" rods, and 88s or send your case out and get the work done. It probably needs some work anyway.
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[Wreck]

I don't think this is a good type of engine for a novice builder . As Tabari mentioned with a 78mm crank and 5.4" rods you will need 4.5mm of cylinder spacers . That then brings into issues with tinware fit etc .

I was looking at some pistons from KB 88mm with a 1.24" compression height and a more modern ring pack .
The cylinders may need honing to suit the 88mm pistons , also the pins are 21mm so the small end of the rod will need re bushing .

[Alstrup]

I agree. "everything" doesnt fit.
A 74 x 88 with 5,325" rods will be fairly easy to put together and most things will fit, or close to.
'There was no mentioning of the rest of the engine, but a well built 1800 engine can soon outperform a sloppyu built 1900 cc engine.
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[anthax]

Go 90,5 cylinders and b height pistons with that 78mm crank.
I used standard length rods (5,394?) 5,4" rods.

More or less stock width engine.

[Beastofthesoutheast]

I’ve heard of people n seen on videos where they would measure n cut the excess length off the piston skirt so it will clear the crank n all. Is that the issue you guys are talking about ?

[Alstrup]

Yes. But as mentioned, thats only half of it. You will need custom PR tubes and modify half of your cool tin. Your exhaust wohnt fit anymore etc etc. Everything is possible, but there are several downsides by doing it that way.

I have built my fair share of odd combo engines in my time, mostly for gaining knowledge in finding the really good combo´s andsiphon out the lesser desireable ones. I have found that when using A pistons there is a "point of no return" at 76 mm stroke. More stroke than that, and you do not gain what you should due to the internal relations.
It is always a bummer to have to reuse something when you wanna build a larger engine. It almost always ends up in a less efficient set up.
If you want/need to reuse the 88´s, fair enough, but then stay with 74 max 76 mm stroke and get it built right.
If the case needs to be sent out for a line bore it would be easy to get the case cut for larger cylinders and then build a 1776 or a 1904 depending on what the rest of your parts stash suggests.
don´t get me wrong. I generally like mini strokers, but they are not as easy to get good power out of as people think.
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[Beastofthesoutheast]

Ok thanks again.

[BFB]

Yep, just cut about 1/4” off the bottom of some stock pistons today to clear from hitting the 78.4 crank…
I’ll have to clearance the cylinders too.
So yeh, if your not ready to put an engine together, take it apart to clearance stuff then put the engine together, take it apart to clearance stuff then put the engine together, take it apart to clearance stuff then put the engine together, take it apart to clearance stuff then …. You probably shouldn’t try it.
I enjoy the shit out of it though
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[johnnyvw164]

First build and no machine shop nearby...I personally would not choose to build such an "oddball" combination. Can it be done? Sure. But as others here have mentioned there's a lot of measuring, cutting etc that will need to be done. Easy button would be a 1776 or 1915...stock crank (or get a c/w one if you need a new one) and either 90.5 or 94 mm P&C. You can either buy everything you need off the shelf, or ship parts to a shop that does these all day long.