Topic: Why a camshaft can't be 180 out

[scottly]

In order to save Dave from pulling his hair out anymore, (he's down to using tweezers ) I'll try to explain this to the math challenged among us.

A four stroke, single cylinder engine requires 720 degrees of crankshaft rotation for each complete cycle: intake, compression, power, and exhaust. Each stroke of the piston requires 180 degrees of crankshaft rotation.
The cam shaft turns at 1/2 the speed of the crankshaft, so it only rotates 360 degrees, or one full turn, for every 720 degrees, or two full turns of the crankshaft.
Following so far?

Our motors have four cylinders arranged to fire one cylinder every 180 degrees of crankshaft rotation, or 90 degrees of camshaft rotation. Cylinders 1 and 4 are 360 crankshaft degrees apart, and 180 camshaft degrees apart, and the same is true of 2 and 3.

[kghost]

I am sorry to say that you are incorrect.

[kghost]

Davies hair is fine.

He does not use tweezers.
 
Yeah yeah......troll!

[dave500]

i use bowling ball polish now thanks to this #$%*ing thread!umm better study the firing order next?

[kghost]

On a Pratt and Whitney R-1830 it's +9 then -5 lol

[Bodi]

Fail. Any explanation for "math challenged" mustn't have any numbers higher than 3.
Believing the cam can be 180 out doesn't hurt anyone. The faithful can take extraordinary measures to ensure the cam is back in exactly the same relation to the crank, it just doesn't make any difference. Let them enjoy their superstitions.

[dave500]

im with bodi,,let them bend valves,,#$%*,,you can only offer help so much?

[Dream750]

umm better study the firing order next?

Firing order? 

The SOHC firing order is: 1-2-4-3 and here’s a good animated example:

http://www.salocal.com/sohc/tech/fire4-lcnt.gif

[Bodi]

"let them bend valves"

Another true believer.

[dave500]

anytime you assemble an engine,,rotate it over slowly/gently a few times by hand,bring it back to tdc and recheck your marks,,then do that again,,and recheck your marks,,its all too late if you hit that button and youve #$%*ed it up!

[trueblue]

anytime you assemble an engine,,rotate it over slowly/gently a few times by hand,bring it back to tdc and recheck your marks,,then do that again,,and recheck your marks,,its all too late if you hit that button and youve #$%*ed it up!

Is that what I've been doing wrong all these years? I thought you were meant to just slap it together and crank it up, then wonder why it just went crunch and now backfires.

[Rigid]

Scottly nailed it.  What is all of this other babbling?