cam choice for low CR eta

[Gruelius]

Hey all

Car is as follows
3.73 lsd
5spd
gay suspension
Megahurt with wasted spark

9:1 ETA bottom end (not getting a rebuild)
855 AMC head with 40k miles

basically the main thing i wanted this to do is have a more reliable motor (i.e. lower blowby, more torque (b23 + 3.46 is killing me) and for it not to cost too much (overcapitalising). Ive spent alot of money on my e30 repairing and replacing stuff but like i dont want to go ahead an spend $10k on a m20 for it to be beaten by a daewoo lanos or something.



Anyway seeing as the 323i cam while hotter is unsuitable with lower lift (unless someone can debunk this for me) i can either buy a new 325i cam, or buy a 272 cam. This car is dailied to work and while i do drive like a nutcase lower down torque and fuel economy does sould like a nice thing.

If the 272 will still really shine with such a low CR (~8.3-46:1) id go ahead and buy it.. if i allready had a 325i cam id just reuse the 325i cam.

feel free to give opinions

[wakdog]

Probably wont make much of a difference, pretty much no matter what you do, that motor wont be making any power past 5200rpm, so you dont want to be running a cam that makes power anywhere past that...

Should try source yourself some 10.2:1 or 11:1 pistons from europe (i got a set of 10.2:1 525e pistons for $185AUD Delivered)

[Gruelius]

yeah but new pistons means a set of rings + rod bolts + rod bearings + machining e.t.c.

pretty much i need to do brake master + clutch in the next year. and i figure itd be easy if i swapped the motor too when doing all that.

[nando]

Probably wont make much of a difference, pretty much no matter what you do, that motor wont be making any power past 5200rpm, so you dont want to be running a cam that makes power anywhere past that...

Should try source yourself some 10.2:1 or 11:1 pistons from europe (i got a set of 10.2:1 525e pistons for $185AUD Delivered)

not really true, the low CR coupled with a cam will mostly hurt low end torque, as the dynamic compression will drop, but at high RPM it will still be an improvement.

I'd say a B25 cam is best, but if it costs as much as a 272, I say go for it. Worst thing that can happen is you aren't happy with it, you can always build a different head (maybe use a 731 instead?) or sell it.

[matt0300]

With hotter cam wont u also need valve springs? Idk anything about 855 heads.

[nando]

New stock springs are plenty for a 272

And its an 885..

[matt0300]

Ok yea stock 885 springs are. Makes sense now, I thought he was talking about some eta head that I've never heard of lol with a hotter cam.

[Gruelius]

272 is double the cost of a 325i cam.