Pelican Parts Forums - More tdc questions

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More tdc questions

TDC is on the compression stroke isn't it???? If this is the case, will a 911 run if it is 180 degrees out? My number one cylinder makes compression with the Z 1 mark in the right position but the rotor is pointing exactly opposite the mark on the distributor. Perhaps I am doing something wrong. I will try to verify this in the am (with my stomski tool) but if any one could help shed some light on the topic that would be great. trying to get things back to factory and get the valves adjusted. Has any one used the back of the rocker method to adjust the valves?
Thanks

If you have valve covers off, rotate crank until TDC mark. Both rockers on #1 cylinder should have freeplay indicating that it is in compression stroke (i.e. both intake and exhaust valves are closed). If not rotate crank 360 degrees (which is actually only 180 camshaft degrees). The TDC mark comes up on both compression stroke and exhaust/intake stroke.

It will not run 180 degrees out.

Quote:

Originally Posted by trojwl (Post 5770859)

Sorry I know this is a remedial question but,,,,,
The compression stroke is just before the piston comes down building pressure or is it at the top after the valve has let the compressed air release? In other words, If I put a compression tester on the #1 cylinder, when it makes pressure on the test gauge that is it's compression stroke and the marks on the pulley should line up with the distributor mark also? Is this correct?
Thanks

Quote:

Originally Posted by trojwl (Post 5770859)

Better question,
The only time the number 1 cylinder valves will have free play is on the compression stroke??

Not to be a jerk, but if it is 180 degrees out, then WE ALL DIE.

Yes! By being 180 degrees off, the rotor would be pointed in the wrong direction for setting your valves. As mentioned above, when at TDC and on the compression stroke both valves for cylinder number 1 are closed. Should be able to move the rocker arm some.

The compression stroke is when, after the piston travels downward to "suck in" air through the intake valve, intake valve closes, piston travels upward compressing mixture. Ignition occurs near very top of stroke (before pison reaches top of bore - usually a few degrees before top of stroke). It takes a few milliseconds to ignite. The explosion actually occurs when piston is actually moving downwards again. If timing is too advanced, the ignition will occur too early and bad things happen.
And yes, the only time both valves are closed is when mixture is being compressed. The length time valves are open is referred to as "duration". The amount of distance valve actually travels is referred to as "lift".
Duration and lift characteristics of camshaft will determine power delivery of engine. The bigger the numbers, the more you approach having a race motor that is unsuitable for everyday driving (i.e. poor idle, no vacuum at idle, etc.).
Hope this helps.
I could talk about this stuff all day long.

Warren

http://forums.pelicanparts.com/uploa...1294491353.jpg

Quote:

Originally Posted by trojwl (Post 5771134)

thank you so much for the clarification Warren. I am pretty sure the distributor is off by a tooth. I will be checking things out today. I am glad you love talking about this stuff.

Good point!

The explosion of gases within the chamber is what creates the inertia (opposition forces) causing the piston to move in the opposite direction; thus horsepower.

I really like your engine bay. Red is a nice fan color to have, I think. SmileWavy