Are Cams the same? M20B20 vs. M20B25

[frankiej]

Is the cam in the M20B20 the same as the cam in the M20B25?

[james_obryan]

I am 99% sure that they are not, with the B25 being more agressive

[frankiej]

Or, I could also ask: What, if any, cam from another BMW engine could I throw into my M20B20 to produce any amount more power and have the engine still be streetable?

[StuBeeDoo]

Or, I could also ask: What, if any, cam from another BMW engine could I throw into my M20B20 to produce any amount more power and have the engine still be streetable?

I'm not completely 100% on this, but I don't think it's that simple. All the different engine sizes of M20 have different stroke lengths. The position of the piston in the bore dictates the cam opening and closing positions, therefore a different stroke length will require a different cam profile.
If I'm wrong, someone like Ant or Andyboy will correct me.

[dannyboy759]

Curious one this,
A 320 has a cam shaft that is the same for both the Kat version and the non kat version....plus there is a hardened one!!!
The 325 on the other hand has two different cam shafts, one for the kat version and one for the non kat version but no hardened one.
And the 325e has another two cams different from the 325i and the 320 but with pre and post 87 versions.
So no there not the same as was said before the stroke of the 325 is.
Different...opps

[Simon13]

no they aren't the same, if you use a 325i cam it will barely run, not a good idea. Your only option is an aftermarket cam if youre going down this route

[reggid]

no they aren't the same, if you use a 325i cam it will barely run, not a good idea. Your only option is an aftermarket cam if youre going down this route

why would it barely run?

[reggid]

Or, I could also ask: What, if any, cam from another BMW engine could I throw into my M20B20 to produce any amount more power and have the engine still be streetable?

I'm not completely 100% on this, but I don't think it's that simple. All the different engine sizes of M20 have different stroke lengths. The position of the piston in the bore dictates the cam opening and closing positions, therefore a different stroke length will require a different cam profile.
If I'm wrong, someone like Ant or Andyboy will correct me.

thats not 100% correct you can use a shrick 272 or other streetable cam on a 2.5, 2.7, 2.8, 2.9 etc etc whatever capacity you want and it will run fine. They will produce slightly different results though....... but very few people get a custom cam and your correct a custom ones would be a bit better as you can match the stroke and rod length combo to the opening and closing timing points aswell as the overlap etc etc.

[daimlerman]

Folklore says that the 323 cam is the best profile of the standard cams.A week or two back someone posted in(I think) tech help detailing the opening and closing angles of the standard cams.Be aware that the eta cams run in less bearings than the others,so they are a little suspect above 5000rpm.The same minor difference in the head casting means that other cams will not run in eta heads without work on the head casting.

[reggid]

Folklore says that the 323 cam is the best profile of the standard cams.A week or two back someone posted in(I think) tech help detailing the opening and closing angles of the standard cams.Be aware that the eta cams run in less bearings than the others,so they are a little suspect above 5000rpm.The same minor difference in the head casting means that other cams will not run in eta heads without work on the head casting.

depends what you mean by best profile.

I have heard of people simply drilling a few holes to allow oil into the extra journals.

[frankiej]

Thanks for all of the input everyone... so where can I find a hotter cam for my M20B20?

[daimlerman]

zone shop or ant!!....reggid,I entirely agree with you.....lots of people would suggest that the most effective way of tuning a 320 is a bigger engine....

[Simon13]

no they aren't the same, if you use a 325i cam it will barely run, not a good idea. Your only option is an aftermarket cam if youre going down this route

why would it barely run?

you tell me how it's going to work then

[reggid]

no they aren't the same, if you use a 325i cam it will barely run, not a good idea. Your only option is an aftermarket cam if youre going down this route

why would it barely run?

you tell me how it's going to work then

same as any m20 cam apart from slight profile and hence powerband changes....still not sure what your getting at when you say barely run unless its the number of bearings thing in which case any head shop should be able to ensure proper lubrication to the extra bearings if installing a m20b25 cam.

[Simon13]

the bore and stroke is different on each engine so valve lift is going to be at different times, bearings number is the same

go ahead try it prove me wrong!

[StuBeeDoo]

the bore and stroke is different on each engine so valve lift is going to be at different times

Seconded.

[murran]

in theory if it phisically fits and has the same firing order it will work fine, i dont see bore or stroke making any difference...... i know with 8v vw engines you can put 1600 carb engine cam in a late 1800 gti and it will run and visa versa. in fact a gti cam in a carb engine gives it bout 6-8 bhp!!!
i say try it, see what its like. id be interested to know wether it works, rather than these guesstimators telling you it wont.
just turn it over by hand before you try starting it up!!

[murran]

the bore and stroke is different on each engine so valve lift is going to be at different times

Seconded.

so what?? the times will be the same if it has the same firing order. id hope it has more lift or there would be no performace advan. so no point fitting it.

[reggid]

the bore and stroke is different on each engine so valve lift is going to be at different times, bearings number is the same

go ahead try it prove me wrong!

so what size bore and stroke will a shrick 284/272 only run with? I have seen them used successfully on 75, 81 and 84mm stroke engines and bore has nothing to do with it.

As Murran said if the crank configuration and firing order are the same as i belive they are with the m20's then there are no issues because the intake valve will still open before 20 degrees BTDC and close 60 ABDC and the exhaust valve will still open 56 degrees BBDC and close 20 ATDC for a late m20b25 cam and 18/62/62/18 for a early cam. This might not be the best profile for the spec of m20B20 engine but it should work just fine.

Also provided the lift is not to great to cause interference then that should be fine

[Simon13]

so alot of theory M20 engine champ go ahead and do it. lots of talk and no action a bit like the M20 thread about fitting a cam to a 2.5 on it's it's own and using it everyday but a btb makes 18bhp on a stock engine.

oh my 32 litre M20 makes 14bhp at the fly it has a metre stroke now and 12mmm on the stroke and runs on a 323 cam just fine.

[oguz327]

so alot of theory M20 engine champ go ahead and do it. lots of talk and no action a bit like the M20 thread about fitting a cam to a 2.5 on it's it's own and using it everyday but a btb makes 18bhp on a stock engine.

oh my 32 litre M20 makes 14bhp at the fly it has a metre stroke now and 12mmm on the stroke and runs on a 323 cam just fine.

chill out and go to sleep bert

[frankiej]

What the hell is going on?

[daimlerman]

The kids are out to play,frankie!!

[frankiej]

Yeah, I can tell. I was just wondering if I could pull a cam from another M20 and drop it in my B20 to make a little more torque or hp?

[daimlerman]

TBH,the most effective way is a longer stroke motor...did you get the 525e in Italy?I used the bottom end of one with a 320 head,made 189BHP...and the underbonnet looks stock....

[frankiej]

I don't know if there are any 525 Eta's running around...? What I will ultimatly end up doing is droping a B25 head on the Eta 2.7L block. But for now, I have the head on my B20 all taken down to the tiny parts and I wanted to drop in a hot cam before I put it back together.

I've seen ONE 325e running around the area and I'm trying to chase the guy down so that I can buy it off of him. The body is shit, so I can't imagine paying too much for it.

[daimlerman]

Sounds like the making of a plan!!Have you got a 325 throttle body lying around?Just open up the 320 inlet to match it(take care at the bottom)and that will give you a bit more....

[frankiej]

No, not yet. I'm looking for one, but engine bits are hard to come by in Italy because they usually take the engine out of the car at the junk yard and don't sell parts off of it. It's frustrating, but on occasion you can find a car in the yard that doesn't have the engine out of it... and that's when you know that it has something wrong with it.

The yards here have an abundance of 318 and 316 E30's, but I have yet to see a 320 or 325 in a yard.