m50 non-vanos hot cam timing

[dave.a.cote]

Hey guys,

I am building a non-vanos m50 for my e30 and plan on doing the "hot cam" swap I have been hearing about where I get a second intake cam and put it on the exhaust side of the engine. I want to run the geometry by you guys to see if I still have my marbles.

I have attached a picture showing two configurations. I have drawn the stock m50 cams in the top picture. As far as I know the stock cams are timed as follows:

Intake opens: 19 BTDC (9.5 degrees on the cam)
Intake closes: 41 ABDC (20.5 degrees on the cam)
Exhaust opens: 35 BBDC (17.5 degrees on the cam)
Exhaust closes:13 ATDC (6.5 degrees on the cam)

How am I doing so far?

For the hot cam configuration, to keep the same cam centerline, then the exhaust cam changes to:

Exhaust opens: 41 BBDC (20.5 degrees on the cam)
Exhaust closes: 19 ATDC (9.5 degrees on the cam)

To achieve this, the end plates which align the cams must be rotated. According to my drawings, the intake cam which is on the exhaust side must be rotated by 101 degrees.

Can anyone confirm?

[Cracker Red]

Sub-scribed. The m50 I have waiting for my e30 needs the cam swap job as well. Any info is appreciated!

[CorvallisBMW]

There is a good thread all about M50NV performance over at the e34 section of bimmerfourms, check it out.

[dave.a.cote]

Ive looked but all I can find is people saying "put the intake cam on the exhaust side" and they neglect to include any details. I will look again tonight.

[SamE30e]

There is a good thread all about M50NV performance over at the e34 section of bimmerfourms, check it out.

Where is it, I can't find it?!?!?

[LouieD]

Dave your fancy drawins' confuse me. I'm a crayon kinda guy... here's what my "hot cam" set up looks like. Notice the two front lobes pointed at each other just like when you had the exhaust cam in. Just make sure that after you have set it up that you spin the motor by hand and have no contact.



and the rear of the cams...

[dave.a.cote]

Alright, thanks for the pics, that helps a lot. I think I may have been all backwards when I was drawing that image the first time. I was trying to do it from memory and apparently my memory sucks.

That picture is with cylinder #1 at TDC, right? How did you time them? I was going to machine a jig once I got everything sorted out.

[SamE30e]

I would be interested in knowing how this is done. I'm scared to touch my cams lol.

[LouieD]

Yeah, at TDC. I set the exhaust cam like Bentley says with the slotted holes to the left, but I timed the intake at full advance... 4°.

[dave.a.cote]

I did some geometry numbers again and I am missing the angle between the bank of intake valves and exhaust valves. Does anyone know where I could find that?

[dave.a.cote]

So this is what I have so far - the image I drew at the start is still correct but I drew it at TDC of the exhaust stroke. LouieD's images are at TDC of the compression stroke.

101 degrees is kinda correct - it should be 101 degrees minus the angle between the bank of intake valves and the bank of the exhaust valves. I will try and get a measurement of that this weekend.

[Scyber]

Hey!
I´m interested about timing jig for a hot cam swap. Has anyone made one?

Would be nice to have measurements for cutting the metal sheet.

[th3blue]

interesting thread... I want to know more also... is there new software needed? or is this simply a matter of adjusting the cams and done?

[Scyber]

So is the exhaust cam timing same that if i take intake cam and turn it anticlockwise 101 degrees?

i could draw the pic about regular timing tool with dimensions

[Scyber]

Heres pic about timing tool dimensions for cams (original)