Camshaft Timing

[vouvray]

Over the years, my appreciation for engines has evolved from Volkswagon, to Corvairs, and now to Porsches. I am now rebuilding my 1st 911 engine ("73 Targa).

My question is concerning the camshaft timing. Is there any way to achieve this without buying a dial gauge. Its not the cost of the gauge, I just don't have one and would like to complete the assembly this weekend.

Any suggestions?

[cowtown]

If I understand your question correctly:

You can "rough time" the engine by setting it to TDC and then setting the cams up so that the markings point up also.

However, this is the starting point for timing with the dial gauge, and you can NEVER start up the engine this way

Looks like a dial gauge purchase is in your immediate future

[vouvray]

Thanks. I'll find one before I go any further.

[boyt911sc]

Vouvray,
You definitely need a dial gauge to correctly set the cam timing. One place you can get decent dial gauge set is from Harbor Freight. You would never be able to set it correctly without this instrument. Good luck.......

[Groesbeck Hurricane]

Vouvray,

I received some very good additional advice on cam timing some time ago. Here is the link: Help--Cam Timing

[Wayne 962]

You cannot perform the cam timing without the dial gauge (the Z-block is necessary too, unless you have a universal mount that will work).

-Wayne

[vouvray]

Thnks for help, Wayne.

BTW, does Pelican have a printed catalog available?

[DavidPorter]

OK, I really do believe after reading the relevant authorities that you can't do this without the full rigamarole of dial gauge, etc. I look forward to learning the procedure when I rebuild my engine.

What no one has yet told me is WHY this is necessary. If you have a TDC reference mark on the crank and similar marks on the cam sprockets, how is the uncertainty introduced into the system, thus needing a more precise final adjustment? Any other cars that use this procedure?

[911pcars]

You could probably time the cams w/o a dial indicator, but Porsche's setup allows precise settings. Why chance the timing to a mark on the end of the camshafts?

In addition, you're timing two banks of an opposed engine. The chances of getting the two out of synch are greater than a Vee or inline engine with a single cam sprocket and mark.

For that matter, does everyone assume the mark on the crank pulley indicates exact TDC?

Sherwood Lee
http://members.rennlist.org/911pcars

[snowman]

Note. YOu must also find the TRUE tdc mark on the pully. The factory mark was off by over 3 degrees in my case. TO find the true tdc use a positive piston stop and a degree wheel along with a dial indicator. The piston stop is inserted in the spark plug hole or if the head is off on the top of a the number one cylinder. The engine is rotated to stop on the insert, the degree noted. The engine rotated ccw to the stop and the degree noted. True tdc is halfway between the two degree noted. THIS is the ONLY way to really get the correct tdc. Other ways will be slightly less accurate.

[911pcars]

Superman,
Just the answer I was alluding to. This is good info. Most DIY rebuilders (I think) skip over this important check.

I've done this w/o the cylinder head. With the head installed however, the piston stop might interfere with the intake and exhaust valves at the TDC, overlap position. What do you think?

Sherwood

[snowman]

I modified a spark plug by cutting off the tip and glueing on a short piece of aluminum rod about 3/4 of an inch long. Nothing seemed to interfere with it contacting the piston. making a stop that can be used without the head on works just as well. Warning be carefull, very carfull not to crank the engine to hard or use the starter to turn it over when the piston stop is screwed in or you will have a hole in the piston. Remove all spark plugs first, use the smallest wrench that you have to turn the engine and be as gentle as possible when contacting the piston stop. If you have any doubts about your ability to do this proceedure, don't.