Hi fellow car fiddlers, I'll be removing my cylinder head in the next couple or three months (to up the valve sizes) and was toying with the idea rebuilding the bottom end in 2.1 form. I guess that you use the 95.5mm diesel throw crank and some new pistons. I have a couple of question about this - I guess the extra throw will reduce the revability even with big valves so is it worth it? Piston wise I don't have a clue what to use - Do I have to purchase new pistons or can I source appropriate pistons from another engine. Anyone any idea what the diff (pwr and tq wisae) would be between a BVH 2.0 and BVH 2.1?
Ive been advised to steer clear of 95.5mm cranks. The engine just won't rev out at all.. Stay 2L. The Big Valve head makes a world of difference especially with a lightened flywheel & 276-280 deg cam!!. My car makes it maximum power at 5700-5800, with a 92.8mm crank, so I would guess a 2.1 would be lower than this [:^(]
Cheers Chris; I thought as much as I'd heard people say that it wasnt worth the hastle or expense. I just don't want to go thru the hastle of discovering there was something else that I could have done when the bottom end is done. I felt such a twit when I discovered that I should have fitted big exhaust valves and I can still remember being at the engine builders and thinking nah surely it wont make that much difference (capital TW*T! ). Big valves and a lighten and balance it is then. That's a beautiful MKII BTW!
Got to disagree here. My mate is running a 2.1 16v (diesel crank 95.5mm stroke) with 296 cams and 48 dellortos, and belive me it revs VERY well indeed!! All I can suggest is that if your gonna go down that route, get the crank and flywheel lightened and balanced. The crank is alot heavier than a standard one, so removing some weight will help it rev up. Couple this with some nice cams and it'll go well enough. As an example Morreuce Reeves(spelling) regularly used to use these a few moons back, built by John Jones. So if its good enough for him to use around Combe then who am I to argue.
I agree with Southy. The 8 Valve, be it with Big Valves or not does not have anything like the valve area of a 16v engine. This is why a 16v will rev to 7200 as standard and an 8v 6500. Those 2.1 16v engines are running very lumpy cams & breathing thru 48s to allow them to rev.. An 8v just wont do it. Maybe with a crossflow head, silly cam & throttle bodies, but thats a different story! Edited by: chrismc
My fault there lads, didn't read it all....doh! Yeah the 8v ain't gonna breathe enough for it really so won't rev as well. Think I'll get me coat
Any ideas on part nos. for the diesel crank? Or model/year. I'm running a hi-spec 2L16V and am always after the next upgrade. Thanks.
8v not rev......mine revs extremely fast but then again iv'e done everything i can to mine. (16v's are SO slow ).
Wished you'd have asked about the crank number a few months ago. I'd just built one using a diesel crank. Have to watch out for clearence inside the casing, I found the crak was just touching the bolts for the oil squiters in mine.
If its a genuine VAG part, then I'd be ok taking it higher than 6500. Prob 7500. Are the mains and b/end journals the same diameter? Is the crank nose and tail the same as an 18/2L?