Cam Questions

[lateracer]

Not to threadjack, but I have a question about the 272 cam as well. I noticed that the IE site recommends you use oversize rocker eccentrics with that cam.

Is that a "would be good to do" or "seriously, you should do that" kind of thing?

[briansjacobs]

I believe IE cam ships with the proper eccentrics now. But yes, I used larger eccentrics with my 272. I now have a schrick 288 and the VAC billet rockers with the swivel foot adjuster, very slick!

[nando]

ah, shitty IE regrinds.

they can call them new billet grinds all they want, but they're still regrinds if they need oversized eccentrics.

[digger]

you need oversized eccentrics because they reduce the basecircle diamater which can mean the stock eccentrics may not have enough adjustment to properly adjust the valves.
Don't buy a cam from anyone who doesn't give you a cam card with the specs of the cam on it. Saying a cam is a 272 actually means next to nothing.....

[briansjacobs]

you need oversized eccentrics because they reduce the basecircle diamater which can mean the stock eccentrics may not have enough adjustment to properly adjust the valves.
Don't buy a cam from anyone who doesn't give you a cam card with the specs of the cam on it. Saying a cam is a 272 actually means next to nothing.....

oh yeah, i totally forgot that they would not give us a profile to properly degree the cam.

[RangerGress]

M20's are under-cammed from the factory. The BEST way to improve the head is with a cam. actually as far as "bolt ons" go, the only other thing close to a cam for an B25 motor is exhaust.

Can you elaborate all of this a bit?

[nando]

I dunno, there's not really a lot I can say without writing a book, and to be honest the more I learn the more I realize I don't know anything yet. :p

it's fairly straight forward - the size of the ports and valves on the 885 are fairly big (maybe even too big for the stock cam). among 2v heads, it's in the top (there are flow charts to support this). If you want to stuff more air into the cylinders, you need more lift and duration. There are some turbulence issues that arrive above 11mm of lift, but that's taken care of with a specific valve seat cut. But hogging out the ports is the wrong way to go. The main issues are lack of velicocity (big ports) and the short side radius is realy tight. It needs material added to the roof the intake port to fix these problems, but nobody does that because it's too much work. Still it can be improved substantially.

the other stuff is everything you need to match the cam for your chosen powerband - CR, exhaust design, intake, etc. Typically it tends to be random stuff from ebay, or whatever is cheapest (ebay again), and whatever random cam. There's a reason people are often dissapointed.

The turbo arguments are funny. An M20 with a built head will make more power on less boost than one with a totally stock head. It's totally not true that you don't need headwork or a cam if you have a turbo.