here we go again... rebuild questions

[Leland Pate]

Yes, you all know the drill...

Tomorrow I start on the top end. When my rings get here I will get everything together and proceed to the heads.
Here are some questions I have as well as my vauge plan of attack.

In my manuals, some things make perfect sense and other things do not...and somethings contradict themselves.
I haven't been able to figure out whether or not it is best to install each cylinder head onto the cylinders, evenly torque them down, then place the cam housings on top of the torqued heads and tighten the cam housings to the heads. Or, if you are supposed to torque the heads to the cam towers and then tighten the whole bank of three to the cylinders. It makes more sense to me to tighten each head to a cylinder then place the cam tower on top. Am I right?

Next, I understand that I have to "rough" time the motor.
I do that by placing the engine to "Z1" TDC for the #1 cyl. then slide both cams into place and make the punch marks face up.
This is rough timed.
Now to ensure that my valve overlap is properly set, I install the intake rocker for #1 and #4 only...all others can wait until I have the overlap in spec right? After the two rockers are installed, I adjust my valve clearance on the left bank (.004") then place my dial indicator and mount (with 10mm. of pre load) on the valve spring cap. I want to clarify, at this point, I have both cams installed, chains, gears and tensioners installed...right?
So now I spin the motor 360 deg. (hoping not to hear a clunk) and observe the dial indicator. According to my book, the cams I have put it into the 1.55mm. overlap adjustment. That must be ideal? And the tolerance of 1.4-1.7mm. is my "ok" range?
I'm basically Shooting for 1.55mm but anywhere between 1.4 and 1.7mm is ok right?

So if at this point my adjustment is ok (in spec.) I just move on to the other bank and do the same thing for #4.
If it is not in spec. then I must remove the cam nut and gear and try to realign the pin hole in the cam flange and gear into another hole. That part I get...what confuses me is that to do with the tensioner at this point.
It makes no sence to me to have to remove and install the tensioner every time an adjustment has to be made to the cam gear. Is this where I use my handy dandy little idler arm holding tool that I spent $20 for?

I hope I have made myself clear enought to understand. Atleast let me know that I am on the right path.
Lee

[john walker's workshop]

you have it down pretty much. i would recommend assembling all the heads to the cam towers, and installing cams and all the rockers in them. then position the cam keyways at 12 o,clock. with the engine positioned with #1 and #4 pistons at TDC, install the head assemblies and torque them up. don't forget the tin around the cylinders or the oil return tubes. then install the chain housings, and all the stuff inside, except the left tensioner, which is in the way of the cam nut. that's where the tool fits in. adjust it to remove any slack in the chain. .004 clearance on #1 intake, dial gauge installed, rotate 360° clockwise until you reach the timing spec you're shooting for, regardless of crank position. if you got lucky and the TDC mark on the pulley lines up with the case split, tighten the cam nut and recheck. if not, remove the cam nut and washer, pull the pin, turn the crank forward or backward slightly to line up the TDC mark, reinstall pin in whatever hole will take it, tighten cam nut and recheck. no need to remove the tensioner to do this. the threaded tip of a sparkplug fits the pins to pull them out, as well as taillight screws. if the cams have to be moved a lot from where they started, it's a good idea to recheck the initial .004 clearance. if it has changed, so will your cam timing. repeat on #4.

[This message has been edited by john walker's workshop (edited 09-06-2001).]

[This message has been edited by john walker's workshop (edited 09-06-2001).]

[Thomas Owen]

Leland,
The majority I found said assemble the tower onto a bank of three heads on the bench. Then torque that assembly onto the cylinders using a cris-cross pattern. That is what I did and it worked perfect.
Cam timing:
You are correct about the installation of the cams, chains, and device to hold tension on the chain. I installed only #1 and #4 intake rockers, then started on #1 with a close adjustment of .004".
Yes, you 'shoot' for the middle of the range, however, when you find you are off, you don't have to disassemble the entire arrangement, you just remove the nut on the end of the cam, rotate the crank to the proper position, then re-insert the pin and tighten the bolt/nut. In other words, rotate the crank until the dial indicator shows you the reading you want. Then loosen the sprocket nut, remove pin, and continue rotating crank until your pulley notch lines up on the seam. THEN put the pin in the 'best' hole and tighten the nut . Rotate crank 360 degrees and re-check. You are aiming to have your ideal # come up when the notch aligns with the seam. NOW adjust # 4 to .004" and repeat!
Tom

[Early_S_Man]

Lee,

Yes, the heads go on individually. Or, together.

Don't forget to prep all of the cylinder base and chain case paper gaskets with Loctite 518 or 574!

When you have the camshaft housings installed and torqued properly, and sealed with Loctite 518, lube the cam bearing journals liberally with Moly-based assembly lube and test-fit the cams and make sure that both turn over by hand easily and without any binding! If you do encounter any binding ... don't proceed any further until the reason for the binding is found and rectified! Even if it means pulling off the cam housing, cleaning up, and reasealing and retorquing a half-dozen times!!!

Preload the dial indicator 20 mm ... your intake valve max. lift value is 11.6 mm.

At the factory, the max lift of a 'range' is set, and timing chain wear or break-in is expected to shift the lift value to mid-range. The cam timing is normally checked at the 1000 mile service by dealers, just to make sure everything is going as expected with the engine break-in.
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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[This message has been edited by Early_S_Man (edited 09-06-2001).]

[stormcrow]

Leland,

I would adjust your cams to be on the low number side of the tolerance - 1.4. When I did my adjustment, I adjusted it mid way between both high and low. As a result of this, the engine doesn't really torque up until about 4000 rpm. If I adjusted it towards the low end, it would torque up sooner. There are some previous posts on the board addressing this issue.

Steve

[BRAINIAC]

Stormcrow, you have it backwards. A lower number equals retarded cam timing. You want to advance the cam timing for more bottom end, so you'd want a higher number.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[BRAINIAC]

No wait, I think i have it backward, since it is measured at overlap. Then it's on the backside of the lobe. Disregard the above post

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[Early_S_Man]

Tyson, you had it right the first time ... at TDC overlap the Exhaust valve is on the back side of its' lobe. Stormcrow just had the benefits of advanced and retarded cam timing mixed up, as has just about everyone at one time or another!

Bruce Anderson explains this specific case of the SC cams on page 125 of his 2nd edition!

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[ChrisBennet]

I don't have the years experience of some of the other listers but my mistakes are a lot fresher I bet! Here are some cam timing tips in no particular order.
1.Install the fan housing first. The mark on the fan housing is much easier to use than the case seam IMO.
2. Get the tool that takes the place of the tensioner. This is the only way that I could get repeatable results. (If it isn't repeatable it isn't a good measurement in my book.)
3. Install and torque the heads (before the cam towers) and then check across all 3 heads for straightness with a machinist type straightedge. If they aren't the same height the cams may bind. You can remove the heads and do the heads and cams together or continue and install the cam towers (the factory manual's method).
4. Put the cam in the cam tower before you torque the cam tower or heads (depending on your method) and twist the cam to check for binding.
5. When I set the "rough" timing, I mark the first hole the pin goes in with some yellow crayon. It helps keep track of which holes I've tried as I move around the sprocket one hole at a time. I usually end up 3-5 holes away from the initial hole.
6. When you are done the cams will probably be tilted a little one way or the other. If they are, they should be tilted in the _same_ direction. I.e. if the left cam's "up" side is at 1:00 o'clock, the right side cam should be at 1:00 o'clock also.
7. I found that the thick moly lube on the cam lobes effected my measurements. Smear it thin or turn the engine over a few times so the rocker isn't "floating" on a layer of lube.
8. The low side of the range makes power at the top end (valves open later). Nice to have on that long back straight at the Glen. Larger values make more low end torque (open the valves earlier). Good on the street and just the thing for getting back up to speed if you use my "Slow in, slower out" technique at the track.
9. Getting the same values left and right is more important than getting a particular value.
good luck, Chris

[Leland Pate]

Guys, thank you all very much for the replies. I have a much better picture of what the hell I am supposed to be doing now.
I was thinking that you spun the motor 360 deg. and if you didn't get the value you were looking for than you had to undo the cam gear and try another hole all together. Now I understand that you spin the motor until the dial indicator gives me the value I want, and if it hasn't reached or has past the TDC mark then you undo the cam gear and rotate the crank (alone) until it reaches TDC and repeat to see if it reaches the desired value this time.
Did I just make sense?????

Warren, you do have me confused as to why I need to put loctite on gaskets though. I have never heard of this before.
Chris, what could I do to make the cams "pointed" in different directions?


And am I correct in thinking that it dosen't matter which way the distributor is facing in relationship to TDC on #1 intake because TDC is TDC on #1 and #4 period...it's just that #1 and #4 are on either compression or exhaust stroke at the same time.
Am I thinking right here?
Tonight I got the heads torqued to the cam towers. I had an assistant constantly turn the cams to make sure there was no binding. 18 ft. lbs all the way around. Looks great! Tomorrow, I should get my new rings in the mail and by Saturday, I should have the top end "on" the motor. I can't do the cam timing until Towen's dial indicator shows up, but I don't see any reason why I can't get a start at installing the CIS system and heat exchangers.
What do you guys think?

[ChrisBennet]

Hi Leland,
If you bolt the heads to the cam towers first you won't be able to detect binding until you torque the heads. You want the heads to be at the same height so the cam tower will sit on them evenly. Since you attached the heads to the towers first you won't detect binding until you torque the heads.
When I change the timing I:
1. Leave the crank at TDC.
2. Note the pin position relative to the initial position ("2 holes CW") and pull
the pin out.
3. Rotate the cam to the approximate desired value and reinsert the pin. The dial indicator will only give you a rough indication until you tighten and rotate the crank 2 revolutions. (2 revolutions of crank = 1 rev of cam) If you don't know the hole you took the pin out of you will probably try the same hole more than once. If you look at 11 o'clock on the cam gear in the picture you can see the yellow crayon mark I used to mark the initial pin hole.
I usually try several holes and note their lift so I can determine my options in the allowable range.
Suppose for example: 2(holes)CW=.97, 3=1.17, 4=1.26 5=1.34. If the allowed range was 1.25+/-.1 I'd have 3 choices with this cam.

The cams will "tilt" once you change the cam timing away from the "rough" setting you started with. Checking to see that they tilt in the same direction when you're done is a sanity check.

I'm probably not understanding you correctly but it _does_ matter where the distributor is pointing. When it points at #1, #1 valve will be closed. When it points at #4, #4 valve will be closed. In other words, though #1 and #4 pistons are doing the same thing (both going up at same time, etc), the valves for those cylinders are not (one is open, the other is closed).
-Chris

[Leland Pate]

Ok, now I am straight on some things and a bit confused on others.

If I spin the motor one revolution, well actually from what I understand, I spin the motor until i get the desired value from my dial indicator. If the motor is a bit past or not quite to TDC then the cam gear needs adjustment. Am I right so far? So if it needs adjustment, The cam shouldn't move...I don't move the cam, right? I just loosen the nut and move the crank to TDC so another hole lines up with the cam gear flange. That is the way I understand it. Then I re insert the dowel pin and spin it another 360 to check it again.

If it takes two revs of the crank to make one complete rotation of the cam then how can you measure the overlap of the valves with just one revolution of the crank?

I really like the marking the holes with greese pencil idea. It will definately help.

As for the distributor pointing to any particular cylinder....why does it say nothing about that in any manual I have?
What I guess I was thinking is this. With the crank pulley @TDC, both #1 and #4 are both at the top of their rotation, right? It is just that when lets say, #1 is @TDC and the cam is installed pointed up, #1 is on the compression stroke (intake valve closed), and if you were to install the #4 cam and rocker, @ TDC it would be on the exhaust stroke. So I guess my question is this: DO I need the distributor set to fire #1 at TDC for reference or what?
God, I hope I'm not confusing anyone anymore than I already have.
Thanks guys, Lee

[This message has been edited by Leland Pate (edited 09-07-2001).]

[Natchamp]

Leland, as you know this can be a confusing topic and I don't mean to add to the confusion. The following is part of what I have on my website regarding cam timing. It's not meant to be a step by step instruction. It's meant to convey the concept. For me, once I "got it" it was a piece of cake and realized its not at all as complicated as first thought.

The basic concept of course is to align the camshaft timing with the rotation and indexing of the crank, no big surprise here. The thing to keep in mind is that the Porsche motor takes 2 revolutions to complete a full cycle of firing all six cylinders (3 ignitions per revolution). OK, so if that's the case then all of the cam timing has to be done somewhere in that 2 revolutions. Period. No argument can be made otherwise. This is where I was initially confused because a lot of the readings tell you to go to Z1, turn 1 revolution, set #1, turn 2 rev, etc. etc. To me this blurred the basic principle and made me think that you have to do all of these revolutions to get everything right. The only reason to go numerous revolutions is to double and triple check your work, which you absolutely should do. The bottom line is.....because the complete engine cycle is accomplished in 2 rev, you adjust 1 cam at TDC on one revolution and the other cam at TDC on the other revolution. When your engine is at Z1 TDC the #4 cam is on overlap and can be adjusted, the #1 at this point is on firing stroke. When you turn the crank 1 revolution from this point #4 is now on firing stroke and #1 is on overlap. Thats it! No matter what.......when you are on TDC one cam is on overlap and one is on firing stroke. You simply recheck your work by turning the crank 2 times to get back to the overlap stroke no matter which cam you are timing. Z1 just tells you that #1 is on firing. NOT accounting for re-checking your work, which you always do!, you can theoretically set both cams by turning the crank once. I'm not saying this is how you should do it, it just helped me understand it a lot better......if you had the motor at Z1 TDC you could adjust #4. Turn the motor 1 rev and adjust #1.

Also, on the head,cam tower,cylinder question, make sure you fully attach/torque the cam towers to the heads first and then torque the heads. The cylinders are the last thing you torque. There are a lot of pictures on my website that might help. Cheers.

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Mark
The Beast
mark@hargett.com

[This message has been edited by Natchamp (edited 09-07-2001).]

[john walker's workshop]

as you can see, there are multiple ways to skin the cat. but in the end, he be skinned.

[Early_S_Man]

Lee,

You can't just put the distributor anywhere, because of limitations on rotation of the body by the vacuum diaphragm, and because there is only one spot that the body is marked for Z1 -- firing of #1 cylinder. So, the distributor goes back to approximately where it was before!

You don't HAVE to use the distributor during cam timing ... it can be left out if you wish! But, if you put it in place with the rotor pointing to the #1 mark on the body and the #1 intake valve is closed with a gap you can feel and the crank pulley is at Z1 ... then you will only have to worry about fine-tuning adjustment of the ignition timing with a timing light, later! You will also be able to tell by indentations on the slotted part of the distributor body where the 13 mm locknut and washer were tightened before!

About the paper gaskets ... it has been a common practice for decades to use something brushed on, rolled on , or sprayed on both sides of paper gaskets before assembly. I have used Permatex 'Hi-Tack' in both brush-on liquid form, and spray on versions, and it works well, but it is messy to clean up! The instructions for the Loctite 518 specifically mentions prepping paper gaskets, so I thought I would mention it. The Loctite 574 has been discontinued, and the 518 product is supposed to have superior adhesion to aluminum, so that is why I mentioned it! Dry gaskets have a tendency to seep oil, and once you have seepage of oil from the chain cases or cylinder bases ... it is to late to fix the problem without a teardown!

Good luck!
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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[This message has been edited by Early_S_Man (edited 09-07-2001).]

[Superman]

Yes, it is my understanding that Loctite is necessary to properly seal the cam tower/head connection. Only if you want your engine to not leak. I believe Bruce Anderson recommends it. It appears to be fairly routine. And I'd agree that, while most folks hesitate about using goop on gaskets, my experience has been that gaskets sometimes leak after installation if you don't.

You can put the distributor in any time you want. I believe there is a kind of worm-gear drive, so installation can happen any time prior to starting, basically. I don't think it matters.

Boy, I'm gonna be printing this thread and it's going into my binder FOR SURE.

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'83 SC

[Leland Pate]

LOL @ Jim,

Thanks for the clarification guys, I think I'll be ok. I already put the distributor back in and yes, I know I got it fairly close to where it was before the teardown, I am just unsure of where the rotor itself is pointing. I just stuffed it in there to plug up the dirt enticing hole.

Mark, I did have your entire rebuild page printed out, but I've lost it somewhere. I too will print this out after I'm sure everyone is done giving suggestions.

I definately did put loctite 574 between the heads and cam towers...I just remember reading that Bruce Anderson suggests not putting anything between paper gaskets because they could slide around. So I should put a small dose of Loctite between my metal cylinder base gaskets and cylinders and case?
Seems to make sense...and I think I have a bit left. 574 is NLA, but I managed to get some.

Sometimes after I re-read what I wrote...I find that I answer my own questions.


[This message has been edited by Leland Pate (edited 09-07-2001).]

[RoninLB]

When I read I can have timeless notoriety in Supermans library I thought " I want IN ".....After I think I got it right ,I rotate crankshaft 9 revolutions to move all the parts back to original position. The drive gears on the crank don't come back to original position until then. You then have the same sprocket tooth back to same link on the chain. Thus, you have evened out wear factor when adjusting. This eliminates possible insanity of trying to figure out how timing keeps changing with less revolutions. Mechanics aren't pompous, they're too tired.

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RoninLB

[ChrisBennet]

Originally posted by Leland Pate:
...If the motor is a bit past or not quite to TDC then the cam gear needs adjustment. Am I right so far? So if it needs adjustment, The cam shouldn't move...I don't move the cam, right? [This message has been edited by Leland Pate (edited 09-07-2001).]

Ah no, you're not right, well maybe you are but um I don't think so.
Just leave the crank at TDC and rotate the the CAM. Just turn the cam and when the dial indicator gives you the correct reading you put the pin in. What could be simpler? Of course when you rotate things and torque the nut the reading will change some. If you don't like it, just move the pin to the next hole and try again.

Even if this wasn't a little confusing all of us telling you different ways to do it would make it that way.

Sealant: I use 518 on the cam towers and I leave the gaskets dry. I don't have leaks from the dry gaskets and they are easy to remove when I take the motor apart. I'm pretty anal about getting the mating surfaces clean and burr free. I would think that rubbing some 518 into the paper gaskets would be good insurance. I do that on the thin paper transmission gaskets and it stops the weeping. Rub it into the gaskets before you install. You just don't want any leftover sealant getting into your oil supply. 574 is nice because it won't harden into oil passage blocking "boogers". It only hardens in the absence of air.
Did they really discontinue Loctite 574? That's the orange cheeze wiz I use for case sealing I think. Tell me it isn't so!
Chris
email me: chris@a3ds.com and I'll give you my phone number

[Leland Pate]

HA! I was just getting to the point to where I was going to say: "Ok...one of you noodleheads give me your phone number so I can just call someone and get this straightened out."
The BBS is a great resource...but sometimes, typing isn't the easiest way to comunicate...especially when the topic is kinda complicated.
Ronin, there shouldn't be any difference in in wear on my gears...every single one is brand new!
Chris, I'm going to call you.