DIY: Setting Cam Timing on M96

[JFP in PA]

Nice write up..............

[dirkdiggler]

Thanks for the nice write-up Kenvin ......... this should be the standard for DIY threads!


I do have one more question regarding the intake cam notch location.

1.) My pulley is set to top dead center
2.) my exhaust cam notches for bank 1 are lined up parallel to the seam between the head & the valve cover

My question:

My intake cam notch(one next to air oil separator thing) is pointed too the right but its not perfectly horizontal like to ones in the pics you provided. Mine is sorta at a angle pointed upwards a little. Pic attached of how mine is situated with all other things lined up. Red arrow shows the angle.

Is this normal??

[Bladecutter]

Originally Posted by dirkdiggler

My question:

My intake cam notch(one next to air oil separator thing) is pointed too the right but its not perfectly horizontal like to ones in the pics you provided. Mine is sorta at a angle pointed upwards a little. Pic attached of how mine is situated with all other things lined up. Red arrow shows the angle.

Is this normal??

To answer the question as simply as possible, the answer is:

NO!!

If you re-read the write up, you will notice that the most important thing to tell that the timing is correct is to line up that one single notch so that it is perfectly pointing to the right, and then see if the cam-notches are parallel to the engine cases.

That notch is the important one, and you will adjust the other notches to line up with regards to it. When it is pointing perfectly to the right, if everything is fine, then the notches on the cams are lines up. If everything isn't set right, then the two cam notches are not lined up.

Your description means that your cams are out of time.
You need to align them, and honestly, it sounds really, really easy.

BC.

[Cloudsurfer]

Originally Posted by Bladecutter

To answer the question as simply as possible, the answer is:

NO!!

If you re-read the write up, you will notice that the most important thing to tell that the timing is correct is to line up that one single notch so that it is perfectly pointing to the right, and then see if the cam-notches are parallel to the engine cases.

That notch is the important one, and you will adjust the other notches to line up with regards to it. When it is pointing perfectly to the right, if everything is fine, then the notches on the cams are lines up. If everything isn't set right, then the two cam notches are not lined up.

Your description means that your cams are out of time.
You need to align them, and honestly, it sounds really, really easy.

BC.

Actually, no it's not. The "timing marks" that the factory tools hold are on the NON-driven side of the cam. I'm still not exactly sure how Insite managed to hold the cams EXACTLY parallel to the valve cover/ head seam without the tool.

These engines are actually very tolerant of small timing errors, and I'm sure that Insite is within the allowable limits, but it's not how I'd do it.

[dirkdiggler]

Now I am confused...ugghh

sooooo with:

1.) My pulley is set to top dead center
2.) my exhaust cam notches for bank 1 are lined up parallel to the seam between the head & the valve cover

3.) My other notch is at the angle shown in the pic below


Is my Timing considered off or on?

I have heard yes and no so far......?

I can turn the motor over by hand with-out it binding up so I dont think I can blow it by starting it....right?

[insite]

cloudsurfer is 100% correct. the cams with the single notches are the intake cams. their timing is set relative to the exhaust cams, and is done so at the factory. it is not possible to alter the baseline timing between intake & exhaust cams without physically removing the camshafts from the head.

variocam, of course, DOES alter the timing between the two ('overlap'). we are only using the single notch to determine whether we are on the compression stroke or the exhaust stroke when we set TDC. we are checking that it's pointing ROUGLY outward (compression) or ROUGHLY inward (exhaust).

in fact, even the factory shop manual shows it pointing a bit upward as you describe:

[insite]

Originally Posted by Cloudsurfer

These engines are actually very tolerant of small timing errors, and I'm sure that Insite is within the allowable limits, but it's not how I'd do it.

cloudsurfer: i initially planned only to CHECK if i could set timing without the tools. i actually used metrology shots to index the cams to the heads. after rotating the crank, i shot them again to make sure the cam hadn't turned. they didn't move even a sliver. setting TDC compression on bank 1 & TDC exhaust for bank 2 ensures that the cams are 'off lobe' and no valve springs are creating a polar moment. in this position, the cams actually 'WANT' to center on the timing marks. in fact, if you rotate the cams like 20deg one direction or the other, they will rotate back!

that having been said, it's pretty easy to eyeball the groove in the cams & the seam between the head & valve cover. the only concern for me at that point was whether the cams would move at all when i rotated the crank. they don't.

this is the only car i've worked on where the factory tries to get you to use all these holding fixtures. every other car involves us simply eyeballing the crank to a matchmark & doing the same thing w/ the camshaft. i find it hard to believe that only the porsche would be affected by thousandths of a degree here.

in fact, before i timed my motor, both banks were visibly off. jake says he sees them this way ALL THE TIME and that many are set improperly from the factory. IMO, the chains stretch over the engine life cycle, too.

it's not important to be PERFECT here, merely very good.

[Cloudsurfer]

Originally Posted by insite

cloudsurfer: i initially planned only to CHECK if i could set timing without the tools. i actually used metrology shots to index the cams to the heads. after rotating the crank, i shot them again to make sure the cam hadn't turned. they didn't move even a sliver. setting TDC compression on bank 1 & TDC exhaust for bank 2 ensures that the cams are 'off lobe' and no valve springs are creating a polar moment. in this position, the cams actually 'WANT' to center on the timing marks. in fact, if you rotate the cams like 20deg one direction or the other, they will rotate back!

that having been said, it's pretty easy to eyeball the groove in the cams & the seam between the head & valve cover. the only concern for me at that point was whether the cams would move at all when i rotated the crank. they don't.

this is the only car i've worked on where the factory tries to get you to use all these holding fixtures. every other car involves us simply eyeballing the crank to a matchmark & doing the same thing w/ the camshaft. i find it hard to believe that only the porsche would be affected by thousandths of a degree here.

in fact, before i timed my motor, both banks were visibly off. jake says he sees them this way ALL THE TIME and that many are set improperly from the factory. IMO, the chains stretch over the engine life cycle, too.

it's not important to be PERFECT here, merely very good.

All very good points. As I mentioned in another thread, I think the way the procedure works is less than ideal when you really think about it anyway. How much variation is there from pulley to pulley, as far as where that mark is machined and/or where the hole is to insert the locking pin? How much variations is there from cam to cam in terms of those slots being machined? There are several places where these potential errors can add up.

While it's absolutely true that the bulk of production car engines simply have visual marks to line up, and that's just what it is. However, on air cooled engines, you actually (or rather, the guys who really know what they're doing do so) time them by true TDC (dial indicator on cylinder 1 or 4) and split overlap method, which is DEAD on if you do it right.

No matter how careful you are timing an engine the M96 way, or visually (for most other engines), the best you're going to get is within a degree or two, which on a street car, admittedly, just doesn't matter. However, watch the race team guys and the cool looking tools they use....ya....their engines are DEAD on.

I'm still interested in solid lifters and "race" cams (no VarioCam BS) for my 3.8 and if/ when I find them or get them made, will time those via split overlap method with a dial indicator to determine TDC.

[BYprodriver]

+ cam timing off 1 way increases low rpm torque & the other way increases high rpm power.