Is it worth to build high rev M20B22?

[TobyB]

The KM rockers for the M10 seem to hold up pretty well up towards 9000.

But the ONLY times I've ever broken even Febi rockers with voids has been when
the spring pressures went soft. I think that as long as the valve isn't allowed to float,
the rocker isn't the weak point. Up to the point where the valve spring breaks the
rocker on its own, or wipes the lobe from the cam, anyways.

But I'm just some guy with an internet connection...

heh

t

[mr2peak]

I'd love to see a honda K20 hybrid in an E30. High revving, proven, relatively cheap, and tons of potential. Basically a modern S14

[digger]

other sources

http://www.racehead.com.au/?wpsc-product=bmw-m20-complete-roller-cam-kit

http://www.tommisbillet.com/fi/tuotteet/tuotteet-automerkeittaein/bmw/muut-osat/keinuvivut

[digger]

I think he meant
http://savarturbo.se/stuff/images/ro...s/dsc_0968.jpg

are those VAC's parts? or PPM?

edit those arent VAC those are the junk from PPM

http://www.bimmerforums.com/forum/showthread.php?1710628-FS-Miller-W-A-R-Chip-VAC-billet-rocker-arms-292-Camshaft-19-injectors-etc

the feet on the PPM rockers are poorly done, they aren't square and hence you will get eccentric load which does all sorts of nasties

[raudonis]

dont know what you mean by a hard piece falls out

I think he meant

http://savarturbo.se/stuff/images/robban_e21_turbo/ppm_rockers/dsc_0968.jpg

[digger]

dont know what you mean by a hard piece falls out

if you cant afford the RHD roller rocker setup then with conventional cam VAC billet will be the go. find a good cam grinder and make sure the pads are upto spec finish wise and squareness to the lobe as the PPM ones are junk in this regard and certainly need refinishing if you want them to last.

[Jasu]

There are also steel rockers from KM cams in Norway.

Same that Enem ones.
I have not heard any good of them. Are indeed cheaper than originals, so can not expect miracles.

[Jasu]

standard rockers are not ok at 9000rpm for an extended period. gotta do it right if youre gonna do it. the billet rockers from VAC are cheaper than the roller rockers, then there is the heavy duty rockers (cast) that have been around for a few years now.

I know that they may not last long, the same applies to any other.
Usually a hard piece falls out, that's a problem of billet ones. HD rockers again are not very equal quality. And I've seen a lot of them broken, unlike BMW's original.

Of course, that roller kit might be the best option. But the information about those just does not exist.

edit. typo

[nomansland92]

standard rockers are not ok at 9000rpm for an extended period. gotta do it right if youre gonna do it. the billet rockers from VAC are cheaper than the roller rockers, then there is the heavy duty rockers (cast) that have been around for a few years now.

I always wondered what are the heavy duty cast rockers good till with stock springs?

[raudonis]

There are also steel rockers from KM cams in Norway.

[digger]

standard rockers are not ok at 9000rpm for an extended period. gotta do it right if youre gonna do it. the billet rockers from VAC are cheaper than the roller rockers, then there is the heavy duty rockers (cast) that have been around for a few years now.

[Jasu]

Believe it.
Course I would like to use roller kit, but the price is too high for me.

[raudonis]

Std rockers are ok ~9000rpm, if cam and springs are "correctly selected".

[Jasu]

id start with a 731 or 200 head and heavily work it, as you wont need/want the same port volume that the 885 has in a small cubic inch engine and with a small cubic inch you want the small chamber volume to make it easier to achive a high CR.

on e85 i wouldnt go below 13:1 especially with a huge cam like that

also 40mm ITB will be plenty

I have in stock -731 and -885 ported heads (both with 42/36 valves and 40cc)
I know that with so short stroke it is difficult to get so high compression ratio, but the idea is interesting, and have had it more than 10 years in my mind.

OP is from Finland. They do NUTS shit there.

I say go for it.

But you WILL want a DOHC head to do it. That shouldn't be a problem, right?

Frm M10 experience, the rockers really do limit you at a certain point, and that's
probably going to be lower than the bottom end can take.

Swap in an M88?

Hee.

t

Doch head is not a problem, but money is. :D
Std rockers are ok ~9000rpm, if cam and springs are "correctly selected".

OP for that cost, just get an s14. they can be wound higher and are in the same Liter-age as you are looking to get. they are lighter and pair with a much better transmission. i had a lot of fun winding the crap outa my m3.

Basically, it would be wise. And my big dream.
But I have those M20 parts damn much. And one new Cosworth YB race spec engine. I should get rid of those first.
And now is not the seller's market.

[Cabriolet]

OP for that cost, just get an s14. they can be wound higher and are in the same Liter-age as you are looking to get. they are lighter and pair with a much better transmission. i had a lot of fun winding the crap outa my m3.