So I just found that my Bug motor is a 1600. Do I need to have machining done to the block to go bigger than 1641? And if I do whats involved? I would like to build up a motor around the 2L mark(bigger is better)

Yes, for bigger cylinders, 90.5 or 94mm gives 1776 and 1915 and both require machining to the case to fit into the case. For more displacement/options, a larger crankshaft can also be used with nearly any cylinder size, so many combinations are possible, each with differing pro's and con's, but basically speaking, up to 78mm stroke crankshaft requires little internal case clearancing. 78x90.5 gives 2007cc and this is a very strong combo, or 78x94 gives 2165cc which is also quite common. These days, over 2.5 liters is possible, (bigger is better) but heaps of work just getting everything inside the case .

As Matt said above, if your machining for the barrels you might as well go a bigger crank.
I prefer 2007, but that's just me.

I too am looking at this option - going bigger.....

Is there somewhere that we can read all this? or do i have to read through every thread that talks bout engines?

I have enough knowledge to do an engine build, but it is all the numbers and sizes that i dont know.

Sorry to snipe this thread, but it seemed like the best place to ask.

On this subject, usually on average how much does it cost to get a stripped case machined to 94mm and all bored appropriately for fresh bearings? (well i guess line boring is the only sort you could do without including the crank)??

Thanks mate, thats tops !

It costs alittle more but it's worth thinking about getting a new case that's already bored for 94s.

Atleast then you're not dealing an old worn case that's been through god only knows what in the last 40 odd years.

I noticed a few weeks back George is now selling new genuine Brazilian blocks bored out to 94mm by Stan for bit over $800.
Stan decks the cases properly which is something you really gotta do when boring for 94s as most of the original sealing ledge is knocked out.

Yep. If I was building a new engine I'd be going with a new case.

The thing with mag cases is they will crack, it's just a matter of when. And after they've done a million of so heat cycles over 40 years they are a lot closer to this point.

These are good,

http://www.cbperformance.com/catalog.asp?ProductID=185 


And Alloy is even better,

http://www.cbperformance.com/catalog.asp?ProductID=1230 



Smiley

I would definitely go for a new case to build a new engine. Alloy for a preference.
I would only use magnesiim if it was for a racing application and weight was an issue.

So, if you want a big bore kit ($400), you also need some machining ($300), but while you're there you may as well get a stroker crank ($300), then a new case ($800) and a set of rods to go with it! Soon enough you will need new heads, carbs and exhaust to flow all the extra air for that big motor and you have spent $6-10 grand! And don't forget the gearbox and clutch either!

This snowball effect is the reason that I don't want to open up my nice stock 1600TP. As soon as you think about doing one little modification, you end up with a whole new engine!

The larger sizes have thinner wall thickness. The thicker cylinder walls are better at keeping the cylinder perfectly round as the temperature changes. 90.5 mm is considered the best compromise between large diameter and cylinder stability.

The biggest hassle with increasing displacement, whether done by stroke or bore, is that as the size increases so does the compression ratio. A high compression ratio creates a hotter running engine, so whenever an engine is rebuilt and especially when it's been modified, the compression needs to be checked and setup correctly for long engine life.
It's not unusual for a 'thrown together' large displacement VW engine to be 'worn out' in as few as 10 000km, build it right and 100 000+km is easily achievable.

Thanks Matt, thats cleared up some things for me. Playing with V8s and Datto engines you need to up the compression considerably to start making the numbers. After reading a few Volksy mags I was wondering why (for street driven bugs) a compression ratio of nearly 9.0:1 was specially mentioned. Thats really helped a lot in my decision making, havent quite nailed the final combo yet but am getting closer. When funds permit am going to build an engine myself (using this forum as much as possible) and see how it goes, if I can get 120hp I will be stoked, if it holds together I will be even happier

120hp is quite a lot out of a streetable bug engine. You're definitely getting into expensive territory there! From what I hear, you're looking at a cost of $5-10 grand for that kind of power, and you'll never see that money again if you sell the car. Enough to buy you a Subaru conversion, a Chev LS3 crate motor, or build a 400hp V8 of your choice. Certainly a lot more than I can afford to put into the engine bay of my bug at the moment. Good luck to you and enjoy!

I didn't say it's not worth it Matt, just that I can't afford it!

Is there a formula to get you in the ballpark for what size carbs to use depending on displacement, revs etc?

1585 cc 7.5-1 comp twin 45 dels 112hp ATW,2332cc 9.6 twin 48 ida's 140plus ATW 13.41@97(stay tuned for more)CLA hot street vw's driven daily raced often rarely beaten by a daily driven anything.Although my stroker is heaps of fun I'd probally build a basic 1600 hot rod bottom end cw crank Vw rods with arp bolts full flow and the like but put a real nice set of modified Vw heads and a nice set of carbs.I'd be surprised if done corectly you wouldn't get your 120 hp. And a lot nicer on your wallet.

Has anyone heard of those crazy 1680cc 88mm slip in piston kits?

The barrels slip into the normal bore at the case, but the barrel walls widen to (i could be wrong here) nearly 5mm thick!! as they use 92/90.5mm head bore at top.

To have that capacity, that means crazy thin at bore, but super thick at head. Dunno what the thoughts are.
Machining the case or purchasing one pre-bored etc. would be the way to go still, as its tried and tested, but thought i would throw a spanner in the works of thought and discussion.