Cam install advice

[JordanBbradley]

Hey dudes, 

 I've been absent from the boards for a while, but I completed a full 5 speed and interior resto thanks to guides from the pros here. The car is running great, engine feels strong and I can squeal the tires when I stomp the pedal. Anyways, the engine is setup with a 32/36 that I want to swap to dual 40s and i would like to install 292 cam. Maybe new pistons later on. Anyways questions to address:

 

- are the 40s with the 292 a good marriage? Should I just go for a 300( I drive the car around town and enjoy being on the highway too, no crazy hills or excessive stop and go)? I guess I don't completely understand what the degree on the cam is defining. If anyone has litterateur on the subject I'd love to read it. 

 

- can I change the cam myself( I'm great at stuff with the help of guides but can't find anything)? Do I need to remove the head to do so? Additionally is it worth just changing the cam and nothing else to start? 

 

JB 

[Preyupy]

One of the problems with running higher duration/overlap camshafts with stock low compression pistons is you will loose low and midrange torque to gain a bit at the top end. My recommendation is to save up your $$$ and do the entire engine all at once.  If you are going to change cams you might as well do a valve job at the same time.  You will probably need new valve springs (if you are still running the 40+ year old single springs they are past their sell-by-date)  No you cant change the cam without taking the head off. 

 

If you have never done a BMW head you might consider having the machine shop do the whole thing.  There is a special tool for compressing all of the valve springs so you can slide the cam out before you remove the rocker shafts and arms.  Without it you can disassemble the head by turning the cam and removing one rocker arm at a time but it can be a bit tricky. 

[Oldtimerfahrer]

As noted by Preyupy, compression is the main ingredient you need to effectively use the 292 or 300 degree cams. You don't even need that "much" carburation to achieve a good result (i.e. going to side drafts is not necessary unless you want to use the full power over the full RPM range the valve train can handle). The 300 can be driven around town, but generally speaking the power curve should cut in late and continue to rise until well past 6000RPM which is not appropriate for city use. I have seen very tractable engines with 300 degree cams, but the restrictors (chokes) in the carbs have been swapped to smaller diameters to ensure good velocity at low RPMs, which kills the top end. You can conversely put 40's/45's on an otherwise stock engine and just blow the gas out the tailpipe without any performance benefit, but its expensive and a waste of time. Since there are so many options you need to consider how you will use it, what are your priorities in terms of responsiveness and economy as well as the $$$ question. There is a lot out there on the various cams available for the M10 engines and this is a link to a hotrod page where they explain the operating principles and how the degrees are measured (http://www.hotrod.com/articles/ccrp-9812-secrets-of-camshaft-power/). More degrees is generally more peaky and will bring a number of unpleasant side effects at least for street use once you go over 300.

Forged pistons, hotter cam, appropriate distributor, appropriate carbs and appropriate exhaust all assume you have a healthy engine and suspension/steering/braking system as pre-requisites. My father has always had a strong bias against 2002's because he test drove one 40 years ago that had a heavily modified engine, but standard brakes, which made the thing dangerous at the speeds it was capable of going.

Think it over!

Andrew

[chargin]

Also keep in mind the "Bigger" cam should also be accompanied by heavy duty rockers, springs and retainers. Each item is inexpensive on its own but you need 8 of each one.

 

[AceAndrew]

A very recent thread that may help you....

 

 

[JordanBbradley]

Guys thanks for the input. I guess I'll just setup all my other pieces I can easy do myself before the rebuild( headers, exhaust, etc.). Additionally how cost effective is MM or Korman vs using a local machine shop, I'm in Houston so they should be plentiful.  I like the idea of a korman rebuild, but it's only a pride and reputation thing. Thanks again dudes, amazing community!