No paper gasket between case and barrels + RTV Silicone sealant...?

If you took it off the combustion chamber for calc, you'd have to add 1.3mm to the deck. Same result. You can only loose that 7.5cc it by machining it off.

 

What if I just wish it off, will that work? Think my mind is a strong enough abrasive

 

Word of caution.
If you do decide to get 90.5 or 92 P&C's, do it before you do anything else, the cylinders might not be the same length as you current ones. In that case you would need to recalculate any depth machining plans for the case/heads.

 

Have you considered a Scooby conversion?

 

All this trouble and expense eh?
I can't stand it psychologically without getting something positive out of the process. For me that equates to a noticeably better engine be it a 135HP 2020 racy type one...

... or my stump pulling 2,4L type-4.

When you get down to it, all that machining and replacement parts - the cost is not all that different but the result certainly is!

 

Makes sense! Would the best approach be accuretly measuring the length of my current cylinders, then measuring the length of the 90.5's so I can compare the difference and calculate deck height of the new cylinders without being able to fit them in the case? Although, that approach assumes the pistons would be the same height installed on the rods, which I guess they may not be... hmmm

 

Ooh curveball. I haven't nah, and I quite enjoy learning about and working on the aircooled engine so I'm happy sticking to my type 1 for now I think each to their own though init!

 

Yes, I would do exactly that. If you have a vernier calliper you can check the piston pin height very easily but it should be bang on, it's the cylinder lengths that differ. e.g. my type-4 104mm cylinders were about 3mm longer than stock. You might find 90.5 and 92mm are a little bit longer too. The manufacturers are actually trying to do you a favour, they know you'll be opening up the case and heads and allow a bit so you can clean up the mating surfaces at the same time.

3mm longer like mine were though is flippin stupid in my opinion. I run mine with 3.75mm deck to get the compression down low enough for my stock cam, which is actually mental but works. It's the area between 1.5mm and 3.5mm that's troublesome.

 

I hear what you're saying. Beautiful engines btw!
If I'd known what I know now, who knows what option I'd be looking to pursue! I do have nearly all the parts I need right now though, so it's not too big a hassle to have a bit more machine work to finish things off. I'm also content with a smaller capacity, and the 1776 upgrade makes sense if I'd need to have machine work done to the case anyways.
My case is in great condition, is full flowed tapped, got a solid stock crank and with the W100 cam, feel like it could be a solid build. Wouldn't want to have to sell/get rid of all that for a new setup I guess!

 

With a high lift cam your effective dynamic cr will be lower again..

Take it your calcs are based on flat pistons . any dish makes that cr even lower..

You'd need to reduce your chamber to about 45cc to get that to a cr of 8, dont know how much head that would need skimming but might neec to worty about valve lift at that point.


Sorry there were only two posts on this when i typed.. might have been overtaken.


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Don't risk anything silicone. You'll have worms.

Invest in a tube of Curil T, thin, smelly and good. Or the strange brown stuff (Wellseal?). Permatex prob fine, assuming it's not silicone.

 

Ace, thanks so much for the tip!

 

I think your just making all this up to make me feel inadequate,

 

Eh?