rocker ratio recommendation for phase 2 cam
Turbo Mini Forums

Hi there!

After a 2nd dead 274i cam I will go for a phase 2 cam. Any good/bad experiences with 1,3 or 1,5 rockers?
What rocker ratios are you using with this cam?

Thanks!

Harry

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Mine is timed in at 109 degrees - last year it was 108 degrees. Last year I ran 1.25 and was reasonably happy with the drivability, this year it's definately lost low down drivability and smoothness after fitting the 1.5 rockers...

I plotted some graphs (because I was bored) and looked at comparing going up an exhaust valve size 29>32 and that gave +10% more area, the 1.5 rockers give a 15% increase. But, it does have a greater area under both curves. (more area to blow across).

From the best of my judgement, I am going to forego the 1.5's at the moment and have big exhaust valves. The lift is loads anyway.

Having said, I want all my power down well before 6000 revs (Bini Blower)

Bugger off, I'm getting there.

I am using a 36/31 head at the moment. Dave, did you gain some power at the top end with the 1,5 rockers? Or was it a "lose bottom end and gain nothing at the top end" game?...

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Well the car is definately quicker, but I'd also change exhaust size aswell - I'd been using a 1 3/4" downpipe, but switched to a 2" downpipe at the same time... Basically, I feel i didn't see enough of a change to warrant the need for the 1.5 rockers. I'll be switching back to 1.25 cooper S rockers next time the head is lifted.

I haven't got any S-Rockers yet. I had some forged A30 ones but I think they were weak as cheese :) I was debating running my sintered ones just to see what I thought, but I think I will go for a set of S ones and forget the 1.5's.

Anyway I wonder with a turbo whether if you ran bigger exhaust clearances than you should, if the puffing action would cause the turbo to spin up earlier. Get some really good valve accelleration.

I mucked about with my clearances on a very open system to see if I could get a better shockwave effect and came to a conclusion the engine was too shagged to tell.

Bugger off, I'm getting there.

i wouls stick to 1.25 or 1.3 roller tips as 1.5 roller tips do put a ;lot of stress onto the cam lobes and shag them up after a year.

always looking for them bigger bunches of bannanas

Do many 1,5 rockers user on this board destroy camshafts? Never had cam problems with longer duration cams and 1,5 rockers. The problems started with my 274i cam and 1,5 rockers on the inlet lobes. (only 248? inlet duration)

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Personally - I'd be speaking to Kent about the cam... What do the followers look like?

I will speak with them! The followers on the inlet lobes are pitted, the exhaust followers look like new!

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

my 276 which i took out of 1275 was the same inlets shagged but exhausts were ok.

the 276 which i took out of my 1380 was the same but just one inlet was shagged.

i recon it would be a good idea if the came makers made a oil way through the cam and had a small oil hole on the back of the lobes to add lubrication this would sort it out what do you all recon.

always looking for them bigger bunches of bannanas

1.3s with phase 2 cam is the way i have gone with my re-build,

Edited by sauber 200 on 31st Dec, 2004.

I thought pitting was a result of shit in the oil. Funny, 2 of my inlets were pitted and the rest fine. Apparently, the cam follower problem is only with the transverse type engines. They last for ever on the inline stuff. Even with silly ramp rates.

That's what I heard anyway.

I suppose the inlet valve being heavier, may exceed some sort of threshold of the metals surface hardening. That can really be the only explanation.

Bugger off, I'm getting there.

Do you think the gears throw particles up, which will find their way between follower and cam and destroy it? What speaks against this theory is, that only the inlet lobes are affected. If debris is the cause all lobes should have this problem?! Will contact Kent and see what they are telling!

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm