3.2 Engine Timing (aftermarket web camshafts)

[Fahrvergnuugen]

I am assembling the top end of a 3.2 carrera motor.
The cam card (from Web Cams) references TDC.
It all needs to be setup using a degree wheel, no problem.

The Bentley manual however has the procedure done @ TDC on the overlap stroke.
I fear if I time this engine based off the web cam card @ TDC as I know it, the distributor may be 180 out.

Should this all be done on the overlap cycle or based off of TDC on the compression cycle?

[2.7RACER]

Does the cam card just give valve opening and closing in crankshaft degrees?
Does it give any dial indicator readings at TDC on the overlap stroke?
Ultimately either method will agree when the cam is set properly.
The dial indicator method at TDC on the overlap stroke eliminates the need for a degree wheel.
When you have the first cam timed, generally the left cam for cyls 1-3, just check the distributor and reset as necessary.
Just be sure TDC for cyl. 1 and cyl. 4 are 360 crankshaft degrees apart. That is TDC for cyl. 1 compression stroke is TDC overlap for cyl. 4.
No big mystery when you think it through. Keep us advised.
Good luck,

[aigel]

Doug is right. Typically the cam timing should read in a range of mm. Like 2.0-2.2 mm. Then you just set it up per Bentley instructions at overlap and you are done. Nobody uses a degree wheel on the flat six.

I'd be curious to see the cam card from web cam. I guess it gives you cam specs like angles and lift, but you should also get the mm range for setting it up.

If you can not find it on the cam card, give web cam a call and ask them for the "cam timing" in mm.

FYI: Cams from DRC (John Dougherty) "camgrinder" always have the overlap dial indicator spec right on the box! His cams, including the billets, are less than web cams and he can be easily found for advice on this forum.

George

[Technik MS]

Its actully quite simple, its much easier than initially thought.
I appreciate your input.
looks like 2.3mm lift on the intake @ TDC overlap.

cam card below:

Engine:
Set Porsche 911 GT2 "EVO" (Mech Rocker)

Grind #
563/564

Set @ 2.3mm with .10mm Lash

. Intake Exhaust
Valve Lash
.004 .004
Valve Lift
.480 .460
Duration
264º 250º
Duration @ .050
248º 236º
Lobe Center
111º 111º


Intake
Opens
13° Before
TDC
Exhaust
Opens
49° Before
BDC
Intake
Closes
55° After
BDC
Exhaust
Closes
7° After
TDC

Valve timing is checked with zero valve lash
@.050 inches of valve lift.

[aigel]

Did you change identity? Yes, that 2.3mm is your number. You are all set. I recommend Wayne's book. I feel it has the clearest instructions for cam timing.

George

[Technik MS]

Originally posted by aigel
Did you change identity?
George

Not at all, The car belongs to Fahrvergnuugen.
Its in our shop at the moment.
We are two different people

It was the 2 different procedures on mirroring pages in the Bentley that made me want to be 100% certain before sealing it all up.

A clear head after a nights sleep make all the difference in the world.

Thank you for your assistance.
Matt McClosky

[aigel]

I think you are one person - split personality! Take another nights' sleep and thing swill clear up.

Seriously now, I got it. Good luck with the engine!

George

[Fahrvergnuugen]

Thanks for the help guys.

[Fahrvergnuugen]

Still having problems.

The timing card for these cams say to set @ 2.3mm with 0.1mm lash. I put the motor at TDC compression. "930" marks on the camshafts are pointing upward (so its rough timed). I put the dowel pins in to lock them and installed cylinder 1 rocker arms and set the lash on the intake rocker.

I mounted my dial gauge, set to 0mm and rotate the motor clockwise 1 full turn. At TDC overlap, I took the dowel pin out and rotated the camshaft by hand until the dial gauge reads 2.3mm (with the crank still at TDC). Put the dowel pin back in.

I then set the lash on the exhaust valve. The piston hits the exhaust valve on the exhaust stroke. The valve opens all the way and then begins to close, but the piston tries to come up all the way before the valve shuts completely. The crank is about 10 - 15 degrees before TDC when this happens.

I've checked it several times and verified my steps with the bentley.

What the heck did I do wrong?

[ChrisBennet]

Originally posted by Fahrvergnuugen
Still having problems.

The timing card for these cams say to set @ 2.3mm with 0.1mm lash. I put the motor at TDC compression. "930" marks on the camshafts are pointing upward (so its rough timed). I put the dowel pins in to lock them and installed cylinder 1 rocker arms and set the lash on the intake rocker.

I mounted my dial gauge, set to 0mm and rotate the motor clockwise 1 full turn. At TDC overlap, I took the dowel pin out and rotated the camshaft by hand until the dial gauge reads 2.3mm (with the crank still at TDC). Put the dowel pin back in.

I then set the lash on the exhaust valve. The piston hits the exhaust valve on the exhaust stroke. The valve opens all the way and then begins to close, but the piston tries to come up all the way before the valve shuts completely. The crank is about 10 - 15 degrees before TDC when this happens.

I've checked it several times and verified my steps with the bentley.

What the heck did I do wrong?

Fahrvergnuugen ,
Any chance you put the cams in backwards? (Doesn't sound like that but easy to check.)
The left cam will have an odd number for the 3rd digit from the right. The right cam will have an even number. (This works for all Porsche parts AFIK.)
In the case of an SC:
Left: 14710 odd number
Right: 14810 even number
-Chris

[Fahrvergnuugen]

Nope, the cams aren't backward. I have 14810 on the right and 14710 on the left. (actually, I don't think you can put them in backward... IIRC, the journals are in different places)

[ChrisBennet]

Originally posted by Fahrvergnuugen
Nope, the cams aren't backward. I have 14810 on the right and 14710 on the left. (actually, I don't think you can put them in backward... IIRC, the journals are in different places)

You can put them in backwards. Trust me.
-Chris

[Fahrvergnuugen]

Maybe I should have phrased it "I didn't think you could put them in backwards". I wasn't questioning you, I just didn't think it was possible.

[TimT]

Nobody uses a degree wheel on the flat six.

thats not entirely true

here we are setting the cam timing on a 4 cam Supercup engine

[/hijack off]

[ChrisBennet]

Originally posted by Fahrvergnuugen
Maybe I should have phrased it "I didn't think you could put them in backwards". I wasn't questioning you, I just didn't think it was possible.

No offense taken. I was just poking fun at myself.
-Chris

[Wayne 962]

I spelled out this procedure in extreme detail in my Engine Rebuild Book:

http://www.101projects.com

-Wayne

[Bill in OKC]

I've been meaning to get one of those books, I've already done just about all of the 101 projects

[2.7RACER]

Once you have double checked the cam timing, if the exhaust valve still contacts the piston at 10/15 degrees before TDC, something has to happen.
Keeping in mind the new cam exhaust is closing 7 degrees later, (7 ATDC vs. 0TDC stock). This puts the exhaust valve around 0.050" (or more) closer to the piston at cross over, compared to stock.
Either the pistons are in upside down, not likely. Or you may have to machine the pistons.
The nice folks at Web Cam may have some advice on this as well.
Assuming all is right, looks like you may need to shave each piston at least 0.050" off the exhaust side.
The Web cam exhaust lift of .460" compared to .402" stock can't be helping your case either.
Another possibilty is if you have had the cylinders off recently the deck height may be too close, S/B 0.040"
I would assemble the right side cam and check to see if it has the same issues.
I also would double check the clearance of the intake valves to the piston top, they may be closer than you think.
Sorry to hear about your problems, but we'll all learn when you get this solved.

[Fahrvergnuugen]

Wayne, I picked up two of your books (101 projects & restoring and modifying) and am reading through them tonight.

Originally posted by 2.7RACER
Once you have double checked the cam timing, if the exhaust valve still contacts the piston at 10/15 degrees before TDC, something has to happen.
Keeping in mind the new cam exhaust is closing 7 degrees later, (7 ATDC vs. 0TDC stock). This puts the exhaust valve around 0.050" (or more) closer to the piston at cross over, compared to stock.
Either the pistons are in upside down, not likely. Or you may have to machine the pistons.
The nice folks at Web Cam may have some advice on this as well.
Assuming all is right, looks like you may need to shave each piston at least 0.050" off the exhaust side.
The Web cam exhaust lift of .460" compared to .402" stock can't be helping your case either.
Another possibilty is if you have had the cylinders off recently the deck height may be too close, S/B 0.040"
I would assemble the right side cam and check to see if it has the same issues.
I also would double check the clearance of the intake valves to the piston top, they may be closer than you think.
Sorry to hear about your problems, but we'll all learn when you get this solved.

Now you've got me thinking. Maybe a little backstory will help:

First of all, I am a novice mechanic. The car is at my friend's shop (Technic MS). He was gracious enough to let me work on my car in his shop and to offer a hand when I get in jam.

This motor has 10,000 miles on a complete ground up rebuild (before I bought the car). The motor was rebuilt with this cam and ran like an absolute animal...until the shift linkage coupler between the seats came lose on me when I was about tho upshift into fourth. Instead I got second and zinged the valves.

I took the heads off and sent them to a local machine shop that has a great reputation. The pistons & jugs were not removed from the motor. The machine shop installed 12 new OEM valves. He also informed me that the motor has aftermarket springs (higher tension).

I got the heads back and put them and the cam towers back on the motor, installed the cams and the cylinder 1 & 4 rocker arms. I got the timing card from web and was a little surprised to learn that the cam is called "GT2 Twin Turbo "EVO"" since this is not a GT2 nor a turbo motor - but anyway....

One problem I have is that my dial gauge only has about 12mm of travel - my cam lobes have 12mm of travel - which means when turning the motor over, the dial gauge loses contact with the valve spring retainer. I got around this by zeroing out the dial indicator between compression TDC and overlap TDC. In my mind this should work just the same unless I'm misunderstanding something...

After I made the last post (trying and failing to time using the dial gauge), I printed out a degree wheel thats the same exact size as the crank pulley. I taped it on and set the crank to 13 degrees before TDC. I then used the dial indicator and found the exact spot where the intake valve begins to open - then I locked it down with the dowel pin.

Same deal, exhaust valve doesn't close soon enough.

Could something be monkeyed up with my timing chain or tensioner?
I am so frustrated with this project right now.... I need a beer. Sorry about the novel... time to get back to wayne's books

[aigel]

I do not understand what you are doing with you indicator. Come on, can't you find an indicator with more travel? Go to your next tool store and buy a nice mitutoyo digital indicator - 1" travel. It will be worth your sanity.

Were the head surfaces machined at all and by how much? I agree with 2.7racer, do the other side and see if it has the same problem.

Also, apart from the ID number, have you ever sanity checked the cams? The left cam has the intake and exhaust lobes spaced apart in a big angle like an "L". The right cam should have them together like "R"abbit ears. Report back with your finding.

If I remember right, the 964 cams are timed around 2 mm. If your cams are more agressive than that grind, may you have a problem there? What I mean is:

How do you know your cam specs match the actual cams? Could these cams have been reground without changing part number? I would get out a degree wheel (and an idicator with plenty of travel) and MEASURE the cam specs. A cam analyzer, if your friend has one, could do this even quicker. Maybe the cams were reground at some point in time ...

Otherwise you describe timing cams like it's usually done, so there should be nothing wrong with your procedure.

George