difference between compression stroke TDC and expansion stroke TDC

[AlfaNeely@domain.elided]

In a message dated 02/03/2002 8:31:27 AM Central Standard Time, 
owner-alfa-digest@domain.elided writes:


> 
> Date: Sat, 2 Feb 2002 20:27:29 -0500
> From: "Douglas Kunzman" <doug.kunzman@domain.elided>
> Subject: difference between compression stroke TDC and expansion stroke TDC
> 
> Hi
> 
> What is the easiest method to tell the difference between TDC compression
> and expansion on a 84 Spider ?
> 
> Doug K
> 2 84 Alfa ( one not running)
> 1 Truck to move alfa parts...
> 
> 

       I do not understand your question.  TDC at the end of the compression 
stroke is the same as TDC at the beginning of the expansion stroke.  Thus 
there is no difference.
       I assume you want to know if you are at TDC on the compression stroke 
or at TDC on the EXHAUST stoke.  The easiest way is to put the timing pointer 
at the P = TDC mark and remove number one spark plug.  If you can see that 
the valves are open, then that is the exhaust stoke.  If you are not sure 
what you are looking for, pull number 4 spark plug also.  By aiming a 
flashlight toward the intake and exhaust sides of the engine, you should be 
able to see the valves in one and only one of the two cylinders.
       For timing purposes, the distributor rotor should be pointing toward 
the spark plug wire terminal of which ever cylinder (either #1 or #4) does 
NOT show open valves.

       You can put your finger over the end of the spark plug hole as you 
bring the engine up to the P mark.  If it blows your finger off, it is the 
compression stroke.  Just make sure you do not let your finger get sucked 
down the hole!
       The BEST way to tell what stroke you are on is to pull the valve 
cover.  With the timing on the P mark, the cylinder with both intake and 
exhaust camshaft lobes pointing away from each other is on the compression 
stroke.  The advantage to removing the valve cover is you can check cam 
timing and tension on the timing chain.  You might even run the valve 
clearances and change the half quart of dirty oil while you have the valve 
cover off.

Ciao,
Russ Neely
Oklahoma City

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