New guy with engine question
 

Hi everyone. Found this site online and thought I'd ask my question here since it seems like this is a good group of smart Porsche owners. A friend of mine has been rebuilding my SC motor here over the past couple weeks off and on in between all his other engines and he's supposed to stop by tomorrow to finish it up. Figured I would go ahead and try some of the stuff myself and maybe save him a little time if possible.

He left off at the cam installation, which was pretty easy and straightforward for me to do tonight. I read up on and did the cam timing and while I think I did it right I'm still confused and wanted to check with you guys to see if I did it correctly. I have and read Waynes book on the steps.

Went ahead and did all the jazz with the little pins and cam nut stuff and with with the motor at TDC on cylinder #1(Z1 mark on the case parting line) the indicator is reading .039- .040" of valve lift right off the top of the valve retainer. I used his indicator tool and little z block part that he had brought here to my garage. Then if I rotate the crankshaft over 360 degrees clockwise and again line up the Z1 mark, I get the same reading of valve lift on cylinder #4, about 1mm or .040". That was the setting I read in Waynes book to use.

Did I do that right? Does the number sound right, Or should I have something else(or be setting it to something else)?? I'm going to have him check it over regardless but I figured I'd at least try and help him out since he's not charging for the labor to assemble this for me.


Rick

Seems to me that you are not quite right... It is pretty well explained in Waynes book. Looks like you got it misunderstood. You should have 1 mm overlap at the #4 cylinder when you have TDC for #1. TDC is the compression cycle and this means that the valve is supposed to be firmly shut on that cylinder. But the opposite cylinder is just finished exhaling th exhaust and beginning to open the intake valve at this point.
But don't freak out yet. Your distributor will determine which of the cylinders are at TDC. If you point the distributor "hand" towards cylinder #4 when you have a 1mm overlap on cylinder #1, you have set it correctly. This position is now TDC for #4. Turn it 360 degrees, and the distributor hand will point to #1. Meaning TDC for #1. Then you should have 1mm overlap on #4.

Hope that explains it...

thanks for the response. Just got an email from him and he's not coming over tomorrow, so more incentive for me to tinker and try to get this right. Not sure where I went wrong though but definitely would like to learn. I've put a few V8's together before but they were far more simplistic than this one here

Following Waynes book:

Set Z1 for TDC #1, cams rotated so "930" is up(up as in pointing to the top of the engine I presume), installed and clamped the tensioner arms as pictured, installed pins and tightened gear nuts as stated, intake rocker installed and adjusted to .004" clearance.

Appendix A in book says range for "intake valve overlapping TDC for .1mm clearance" for the SC camshafts is .9mm to 1.1mm. I picked the middle just like the book recommended(.040"). Started rotating the crank clockwise until the indicator needle started moving and continued to turn the crank until the needle registered 1mm of valve lift.

the book then says that I'm supposed to remove the nut and pull the pin out, then rotate the crank clockwise the remaining little bit until the Z1 mark lines up again and then re-insert the pin back into the gear in whatever hole it lines up with. But that's where I get confused because when I get the dial indicator to read exactly what I want for the valve lift, the crankshaft pulley is lined up just a hair away from the Z1 mark being right on the case parting line already. It's not past a full 360 degree revolution, but not before it either. Just near right on it. There's no measurable amount of rotation I could make to make any difference it seems. I mean I probably could put a degree wheel on it but I'd guess less than 1 degree at best.

I know the valve clearance is properly set on that rocker, and even tried swapping in a different rocker to see if maybe the rocker was bad or something.

Just not sure what I'm doing wrong, or if I'm doing anything wrong at all I apologize if my question here is redundant on this forum. You guys probably get a ton of dummies like me asking about this :(.

Any other insight for me?

What you need to to is this:

1:
After you have made a measurement of the valve overlap, at EXACTLY TDC for the oposite cylinder, make a note to how much off you are on your reading.

2:
Rotate the crank 360 degrees to TDC for the cylinder you are adjusting the overlap.
Unfasten the sprocket/adjusting assembly, and change the position of the pin. (Note the direction of adjusting the sprocket/cam for later referance)

3: Turn the crank 360 degrees to the oposite cylinder TDC (EXACTLY), and measure again. Make a note of the new measurement. Was it improved? -if so go back to point 2 and make further adjustment in the same direction. Was the lift worse? -if so go back to point 2, and adjust the other way. Sometimes, if you can't get exactly the overlap lift you want, you may have to take off the chain, and rotate the sprocket a bit (Skip over a few teeth) before wrapping the chain over it again. Then start from point 1 again.

Rick,

I think you have done it just about perfectly. You have set both cams very close to the value you are shooting for and they are 360 degrees apart (like they should be). The act of setting them determines which TDC for #1 and #4. The check of the setting is to turn the crank to TDC and see what the overlap measurement shows. That's why there is a window from .9-1.2mm.

-Andy

Engine type.......
 

Rick,

Depending on your SC's engine type/model, the cam timing value differs. What year or type of engine do you have? Do you have '78-'79 or late SC motor? Thanks.

Tony

Thanks guys! The car is an 82.

the whole procedure described in Waynes book is pretty straightforward it seems. The only thing that was/is throwing my head off is the part where he describes that after getting the dial indicator to the specified valve lift, you're supposed to remove the pin and then rotate the crank the remaining little bit back to TDC then install the pin in the camgear hole it fits into now. On my motor, it seems that I have to rotate darn near a full 360 degrees just to get that 1mm reading on the indicator, which made me nervous that I'm doing something wrong. Definitely doesn't go past 360 degrees, but if I put on a degree wheel and it cam to 358.5 degrees I wouldn't be surprised in the least.

I've been typing all sorts of search querries into the search feature on the site here and reading other peoples posts lately but haven't found much of use to my issue. Other than some saying that sometimes you have to remove the cam gear(s) from the cam and chain completely and rotate them a little bit, then reinstall to orient them differently on the cam.

But if I'm technically supposed to see that specified amount of lift at TDC then I guess it's good to go. Basically it's TDC right before the intake stroke, so the exhaust valve should just be closing(or damn near completely closed) and the intake valve should just be opening, which it is.

Such a cool setup, but so damn confusing to newguys like myself SmileWavy

Thanks again!!

Here is a picture I made to help understand the cycles of the engine.

http://forums.pelicanparts.com/uploa...1242665497.jpg

As you can see, when #1 is at the timing point (overlap TDC), #4 is at TDC on the compression stroke. So the cam settings will always be 180 degrees out of phase. If you set up with TWO dial indicators you should get the same reading on each bank-- nail it on #1, then turn the crank 360 degrees and nail it on #4.

Engine type.......
 

NY82SC,

The 1-mm valve overlap tolerance is not for '82 SC engine (930/16 type). Check the stamped number on top of your engine. It should have 930/16 on it. If that's the case, you are using the wrong value. Keep us posted.

Tony

Tony is right. The 80-83 SC uses a more advanced cam setting. It provides more torque and is more compatable with the smaller intake ports (35mm). I believe the setting is 1.4 to 1.6mm. There is a possiblility that the Euro SC for those years had bigger ports (39mm). In that case the 1mm setting would be better.

-Andy

Ah crap ok I now see that written just below where I was looking on the appendix in the book. Can't believe I overlooked that part where it states the year.

Ok with the actual spec aside, is my reasoning behind this whole process correct? I mean in the end with the cam timing all set correctly(say 1.5mm for this instance) it should read 1.5mm AT Z1 on cylinder #1, then if I rotate the crank 360 degrees it should read the same 1.5mm on cylinder #4 AT Z1. The emphasis on having the lift spec arrive at Z1 on each bank during the appropriate phase....

You need to specify which cylinder Z1 (TDC) is for. When the TDC (Z1) is at cylinder 1, the distributor "hand" is pointing towards the ignition wire for cylinder 1. (And the other way around)
Z1 can be TDC for any one of the two cylinders. (1 or 4)

SO:
With the distributor pointing at cylinder 1 ignition wire connection: It should read 1.5mm AT Z1 on cylinder #4, then if I rotate the crank 360 degrees it should read the same 1.5mm on cylinder #1 AT Z1.

Rick, you've got it.

Otto, we are timing the cams, there is no distributor involved yet. After you time the cams, you can install the distributor in the correct orientation. Your information is correct about how the ignition timing works.

-Andy

you can put the distributor in before you time the cams.. In fact, I would say you should (unless you are running a crank fire ignition), as it gives an easy reference for what cylinder you have at TDC, and ensures that you have it in right. I've seen many cases where the distributor was put in reversed (with the 1 indicator being actually #4 at TDC). Causes heck when trying to do it.

In fact, even though I use a crank fire.. I put the old distributor in just for this purpose. Keeps me from doing something stupid

The easiest way to know which cylinder is on the intake stroke for TDC mark is to observe the intake valves of 1 & 4. The intake valve that is starting to open is the one you want to measure. Once it's set, rotate 360 degrees and measure the other. I always start with #1 and then go to #4.

When you install the pins on the cam chain gears with the dots straight up and with the crank @ TDC, you have established rough cam timing and the engine will probably run. Past that setting you are fine tuning the cam timing.

You got the wrong concept.........
 

NY82SC,

At TDC (Z1), it could be either compression or exhaust stroke. You want to be at the compression stroke. For cylinder #1 @ TDC (Z1) compression (zero @ dial indicator)........... turn pulley 360°.......gives you the valve over lap for #1. At this point, it is cylinder #4 @TDC (Z1) compression (zero @ dial indicator)............another 360° rotation of the crankshaft pulley gives you the valve overlap for #4. Are you using two (2) dial indicators or just one? Please take note of the positions of the two (2) cams when you do #1. Both '930 markers' should be pointing upward. The value you get for cylinder #1 (say 1.5 mm) is independent to the number you would get on #4. Both cams have to be set correctly to obtain your target values. Keep us posted.

Tony