323 vs 325 cam e30

[Gruelius]

Hey all

Which cam is better suited to the 855 head? i got a AMC head for cheap but comes with no cam. i have spare barely worn 323i' cams but no 325i cam. its a low comp so no real point going as high as 272.

Does the 323i cam have less lift?

[HairyScreech]

the 323 cam is alleged to have 10 degrees more duration, but as they have not been accurately measured as far as im aware, no one really knows if this is true or if the 323 cam has the same lift profile as the 325.

[Gruelius]

yeah im hoping someone knows..

[daimlerman]

323 cam is more aggressive than the 325 item.

I swapped in a 323 cam into my 2.7 last year,comes 'on cam' a little later(at about 2500rpm) but is still pulling strongly at the red line.

With the 325 cam,it came 'on cam' at 2000rpm and was all done by 5000rpm.

Down side is fuel consumption,325 cam would give 35/36mpg with gentle touring use,323 cam i struggle to better 31mpg.

I used to be able to overtake quickly in 5th,now I need to drop at least one gear for the same effect.

[eta]

I have also found that the E30 320i/323i/E28 520i exhaust manifold + down pipes and stock exhaust on an 2.7i with 885 head with a 325i cam was doing nothing above 5000 rpm and gave 27-33 mpg and 160hp. Now with a E30 325i exhaust manifold, 325i down pipes and a Fritz system I get an engine the peaks at 5900 rpm @ ~175hp and gives better fuel economy (29-35) mpg. But I get less torque below 5000 rpm compared to the old setup.

So I get more power but due to a little less torque the car is actually a bit slower in the rpm range I actually use. Howover the car sounds so wonderful the the wife now is going to be using to get to work as I no longer need it on adaily basis (I am probbly buying a van) and you can hold a gear for longer which is fun.

So you don't neccessarily have to cam the engine to get more out of it.

[retroboyo]

I thought the 320 and 325 exhaust manifolds were the same

http://bmwfans.info/parts/catalog/11621716443/

[HairyScreech]

in my experience they are also the same, i have had several taken off breakers and all have a 34mm (? have to check my notes but its written on the development cylinder head) exhaust port, which is interesting as neither the 885 or 371 head have ports that big.

[jonny323i]

i know its the complete engine im talking about but ive owned a 323i obviously and a 325i and i found the 323i faster off the mark but the 325i had more top end but that is also to do with the shorter crank

[Gruelius]

the rhd log manifolds we have, the 325i one is like 1-2mm larger diamaeter. no idea RE port size.

dont think we got those 2 piece manifolds like you guys got

[HairyScreech]

we have single piece log style exhaust manifolds like all rhd markets.

[Jhonno]

Iirc the 323i cam has longer duration, less lift than the 325i cam..

It also won't work with the the 885 head iirc..

[HairyScreech]

what stops them working with the 885 head? (genuine question as i havent got my hands on one to measure yet.)

if i can get one to test then i can take a lift profile and compare it to the airflow measured on the flowbench for the head, this gives the ability to say for sure which one will get more air into the engine.
as theres no point lifting a valve more if its not giving anymore flow, sometimes a lesser lift for a longer duration is preferred.

[Jhonno]

I can't remember.. It's a 731 cam and iirc you can't use them in an 885 head that's as far as I remember. Quick search would probably reveal all..

[eta]

Well daimler man has used a 731 cam in a 885 head.

[daimlerman]

Well daimler man has used a 731 cam in a 885 head.

Err no!

I have a 731 head!

In effect,just like a 323,with a stock eta short motor....

[duracel79]

Differences in the cam which may prevent fitment are all in the cam nose. the earlier 323i cam doesn't have a counterbore to suit the distributor parts as they ran a nomal dizzy in the block. the cams can be machine to fit though. Had to machine an earlier E21 323i schrick cam to fit into a motronic E30.

[reggid]

i got a 320i cam from a 731 head, i wonder what specs this has. Don't these run the same motoronic system as a B25? Might get around to measuring and plotting it out one day. I have a B25 cam i could do the same with for a direct comparison.

[Jhonno]

There is somewhere on the forum a graph with the lift/duration plotted from the 3 M20 cams.. I'll be buggered if I can find it though..

[daimlerman]

Differences in the cam which may prevent fitment are all in the cam nose. the earlier 323i cam doesn't have a counterbore to suit the distributor parts as they ran a nomal dizzy in the block. the cams can be machine to fit though. Had to machine an earlier E21 323i schrick cam to fit into a motronic E30.

Interesting....

The one I bunged in had the same nose as the cam I took out,the rotor arm thingy bolts up to the cam belt wheel,which in turn bolts up to the cam.

[duracel79]

Differences in the cam which may prevent fitment are all in the cam nose. the earlier 323i cam doesn't have a counterbore to suit the distributor parts as they ran a nomal dizzy in the block. the cams can be machine to fit though. Had to machine an earlier E21 323i schrick cam to fit into a motronic E30.

Interesting....

The one I bunged in had the same nose as the cam I took out,the rotor arm thingy bolts up to the cam belt wheel,which in turn bolts up to the cam.

Realoem shows the parts for the cam nose are different:
323i E30


325i E30


Part 7 on the 325i diagram goes through the cam sprocket into the cam. not all cams have the counterbore to accept this.

Not specific to the head type (ie 731 which was used throughout the 320i manufacture) but more a change by date

Duracel79

[HairyScreech]

thats no problem then, just a case of sinking a counter bore into it, pretty simple alteration really.


jhonno i havent seen a graph of the cams, if there was a nice accurate one then that would be helpful, save me doing a tedious task repeatedly but it would need to be done every degree at the eccentric with a dti.
i know there is a graph of the 325 cam plotted against the airflow readings of the 731, alpina and 885 head as i did it, could it be that you were thinking of?

on a slightly side note does anyone know the centreline of the cam in degrees relative to the crank angle?

[whodwho]

There is somewhere on the forum a graph with the lift/duration plotted from the 3 M20 cams.. I'll be buggered if I can find it though..

This the one?

[HairyScreech]

well thats odd, k must be for katalyzer then as that m20 2.5 cam is showing 0.4mm too little lift.

not bad as a guide but im still going to measure a set myself at some point.

the stock e30 325 cam is shown here:
measured with zero valve lash and done with a dti at the valve head.
(blue trace, ignore the pink one its a prototype roller rocker)



edit - oh and the eta engine cam, thats a lot of lift with such a small amount of duration for such a large valve to be doing, talk about holy valve acceleration batman, no wonder a lot of them have cam and guide wear and break rockers at high rpm.

[Jhonno]

I am sure there was one with the b23 cam and b20 cam also. However it.does deffo look like that!

[HairyScreech]

I am sure there was one with the b23 cam and b20 cam also. However it.does deffo look like that!

would be interesting to see.

and i would hope it looks like that, if it dosent then they have seriously screwed up the measurements.

[daimlerman]

Realoem shows the parts for the cam nose are different:
323i E30


325i E30


Part 7 on the 325i diagram goes through the cam sprocket into the cam. not all cams have the counterbore to accept this.

Not specific to the head type (ie 731 which was used throughout the 320i manufacture) but more a change by date

Duracel79

Just had a rumage through the box in my garage that is labeled 'M20 head spares' and found these two bits;



As you can see,the offset peg engages the nose of the cam,then is held there by the bolt that passes through both components,no 'centre bore' of the cam nose is required.
Piccies of the bits seperated;




So as I wrote further up the page,a swap to the earlier 323 type cam is a simple 'one out,other in' operation.

[Gruelius]

no need for cam dizzy

[Gruelius]

yeah the 855 head does flow well right up to ETA cam lift levels. but all i want is for the 323icam to have the same lift as the 325icam. not really fussed about the duration.

[HairyScreech]

if you want the lift to remain the same, and your not worried about the duration, why not use a 325 cam?

whats the goal of putting the 323 cam in? what are you aiming for?

[Gruelius]

well i have 2 v good cond 323i cams, if i want to use a 325i cam i have to buy one. thats the only reason why. if it was a full on N/a engine rebuild id buy a schrick but im just putting in a fresher 2.7 with new pumps/seals when i do the clutch pretty much lol.

[HairyScreech]

iv got 325 cams floating about around here that you can have simply for the price of a loan of a 323 cam that i can take accurate measurements from.