Cam timing question

[cmcfaul]

1973 911 E
9.5 / 1 CR
DC30 Cams
MFI

I rebuilt my engine back in December and have not gotten to drive it much with the weather.

My car idles a bit rough when warm (smooth when cold). I checked the cam timing and the right side is off a bit.
Should be 3.8
is 4.48 (cold)

It's advanced by .68. Would the group consider this out of spec?

Is it easy to adjust while the engine is in the car?

Many Thanks,

Chris
73 911 E

[Flat6pac]

Chris, That is above the window, I wouldnt even consider it in the neighborhood.
Bruce

[cmcfaul]

Bumnmer, I ordred the Crows foot and Cam socket already (borrowed them last time). Thats the bad news. The good news is that I should find a few ponys when corrected and solve my idle issue.

During the rebuild I did not have the Z holder and the right sIde gage holder I used was being a PITA. I have the Z holder now.

I assume I can remove the muffler, the timing chain covers and make the adjustment without too much drama?

Thanks,

Chris
73 911 E

[JFairman]

With the back of the car up on jack stands take the bumper and rear engine tin off, remove the rear motor mount carrier and cross bar and lower the motor down around 10 or 12 inches on to a jack stand placed under the case seam at the back of the car. A piece of carpet or folded rags on the jack stand protects the aluminum case.
Watch for hoses and wires that may be twisted or tweaked while lowering the motor down.
Then you can sit on the ground behind the car, remove the chain case covers, and have at it.

[Walt Fricke]

If you do lower the motor, I'd disconnect the transmission shift coupler.

Lowering is going to let rather a lot of oil come out when you remove the cover plate. When I did something like this (I had neglected to tighten the three 10mm head/M6 bolts holding the aluminum seal plate and its gasket in place, so it leaked a whole lot), I jacked the car way up at the rear, and didn't have oil spills.

On the other hand, this was a race car with no muffler, easily removed substitute engine tin, etc - as in lots more working room. But I think I'd take that approach anyway - hold chassis up with jack stands on the torsion tube ends, pull muffler, put jack under engine so the engine cross mount can be removed, pull relevant engine tin, and have at it.

Or you could drain your oil from the tank and the engine sump first, and use the lower the motor approach.

Pulling the spark plugs will make moving the crank easier.

[cmcfaul]

I have replaced the timing chain gaskets in the past by only removing the tin, muffler and covers so I know I can get them off without a partial engine drop. From what I am hearing, there will not be enought room to get at the cam and cam nut without lowering the engine.

Chris
73 911 E

[camgrinder]

plus .68 is about 3 degrees advanced. not sure it will cure the idle issue when cold, but moving them back will help top end power.

[cmcfaul]

Hey John, One the things that led me to check the timing was top end performance is not what it used to be. 7000+ rpms used to be full on power band...I miss that

Will post an update when procedure is done...waiting on parts / tools and warmer garage temps.

Chris
73 911 E

[Walt Fricke]

If you remove the rear motor mount - the long cross piece with the two 19mm head bolts (either with or without the formed piece which attaches to the motor with 4 M10 studs), I'm pretty sure you have room for your tools. You can tell that by looking. With the mount and the tin and the muffler gone, the only thing in the way is the rear cross member, and you can see right away how much room there is between that and the chain housing cover plate. If I had my SC in the garage I'd go look.

[cmcfaul]

Thanks Walt. I am hoping to have this done by this weekend. I bet I will have to remove the motor mount which is not a big deal once the muffler is off. I am hoping the cam timing will be made a little easier by having the engine installed in that if I put it in gear it will help keep the crank positioned as I tighten the cam nut while applying counter pressure to the cam which everyone knows who has done this is easier said than done.

Parts and tools should arrive by Wed or Thursday. Hopefully it will stay warm here in the Mid Atlantic

Chris
73 911 E

[cmcfaul]

success! So for anyone who has to make a cam timing adjustment while motor is installed in the car I can definitively say it can be done with little drama.

Remove upper valve covers
Remove Muffler
Remove rear tray (sheet metal)
Remove timing chain covers
Adjust timing
Reassemble

Did not need to remove the engine mount or lower the engine. There was plenty of room to get it done. Still a knuckle buster working with the crows foot when it slips off at max torque. In the end, both sides are exactly to spec.
Raining now and have to buy more oil before test drive but confident it's right.

Chris
73 911 E

[Walt Fricke]

Good going.

Did you use the "put it in gear" method you mentioned to tighten things?

I was doubtful that that would help or be needed. You can hold the holder easily enough to get the big nut pretty tight with the crowfoot. At that point, things are locked down, so you can use the crowfoot to rotate the cam (and the engine, as long as not in gear) until the holder bumps up against some suitable part of the chassis or engine. Then you can let that hold the holder while you crank on 105 lbs/ft with the crowfoot

[fred cook]

When I rebuilt the engine in my SC, I used a set of 964 cams. Partially to get a bit more power and partially to have cams that use the bolt and washer rather than the large nut. Much easier to deal with!

[Walt Fricke]

Fred - I am just the opposite. I got comfortable with the large nut and washer, because it was so easy to rotate the cam to where you wanted things, snug the nut down to where things weren't going to change, and then do the final torque.

I had problems with the bolt system because you can't do this. If you are willing to let the locating pin dictate your timing, no problem. But if you are trying to tweak things to your idea of perfection, I found that much harder. I found I could stick something in through one of the holes (other than the one with the pin) and nudge the cam into about the right position within the range a pin will allow. But then had to rely on things staying put pretty much by themselves in order to get the bolt and washer to do their clamping.

[cmcfaul]

I did do the in gear thing to help keep the crank at TDC. It helped a little. I also got the cam wrench tight against an inmobil object but in the end used my leg to apply pressure to the cam wrench and both hands on the crowfoot... SOP.

Having driven the car since the adjustment, it makes a significant difference. At 6k+ RPMS the engine is in full power band. Prior, at 6K+ RPM's it was unimpressive. (redline is 7300)

Chris
73 911 E