This is open to all engine experts here about these parts.
On a Cleveland engine of the cobra jet spec, IOW, 8 something to one compression ratio, can both valves be open AND not hit the piston at TDC?? Open = about a half inch.
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It is called overlap DT. It is measured in degrees of rotation. They are both open at the same time. I believe at some point at maximum lift briefly.
Look at your cam specs.
Look for the part of the specs that say, "Bad things".
If they hit the piston, that is a bad thing. You know like the "Cream" song, "Born under a Bad Sign".
Look at your cam specs.
Look for the part of the specs that say, "Bad things".
If they hit the piston, that is a bad thing. You know like the "Cream" song, "Born under a Bad Sign".
Congrats Doug. You are the first one who had guts enough to answer the question. With the stock cam, the CJ spec, is indeed a non-interferance engine. You have won ten Pantera points. 
There is no such thing as an interference engine.
An interference engine is an engine that is broken because the valves are imbeded into the pistons.
...ok, what do I win now?
An interference engine is an engine that is broken because the valves are imbeded into the pistons.
...ok, what do I win now?
DeTom, just what are you asking?
If the intake valve is open 0.500" at TDC (never happens normally) then the piston would most certainly hit it when it reached TDC. The edge of the intake valve nearest the cylinder wall is pretty close to the deck level, even when closed. The Cleveland piston has a big ol' intake valve notch in it, not found in other motors.
The exhaust valve on the other hand is up inside a pocket, its really not a worry in normal use. There are no reliefs for exhaust valves with Cleveland pistons, except for those with pop up domes.
Under normal use, as the piston strokes upward on the exhaust cycle, it chases the exhaust valve closed as it nears TDC. Then, as it begins to stroke downward on the intake cycle, the intake valve chases the piston away from TDC.
The best engine builders, the big name guys, the race teams, understand how much cam lobe profile they can get away with during this "tango", they have the valve to piston clearance relationship all mapped out, down to the 0.001" of an inch.
Its amazing to read just what is really going on with race engine technology in the area of combustion chamber design, valve & port geometry, and how camshaft events simply support those design parameters. You'll find the Cleveland cylinder head, designed in the mid 1960's, is not that far away from what is considered the ideal, here in 2006.
So what was the question?
If the intake valve is open 0.500" at TDC (never happens normally) then the piston would most certainly hit it when it reached TDC. The edge of the intake valve nearest the cylinder wall is pretty close to the deck level, even when closed. The Cleveland piston has a big ol' intake valve notch in it, not found in other motors.
The exhaust valve on the other hand is up inside a pocket, its really not a worry in normal use. There are no reliefs for exhaust valves with Cleveland pistons, except for those with pop up domes.
Under normal use, as the piston strokes upward on the exhaust cycle, it chases the exhaust valve closed as it nears TDC. Then, as it begins to stroke downward on the intake cycle, the intake valve chases the piston away from TDC.
The best engine builders, the big name guys, the race teams, understand how much cam lobe profile they can get away with during this "tango", they have the valve to piston clearance relationship all mapped out, down to the 0.001" of an inch.
Its amazing to read just what is really going on with race engine technology in the area of combustion chamber design, valve & port geometry, and how camshaft events simply support those design parameters. You'll find the Cleveland cylinder head, designed in the mid 1960's, is not that far away from what is considered the ideal, here in 2006.
So what was the question?
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quote:Originally posted by PanteraDoug:
There is no such thing as an interference engine.
An interference engine is an engine that is broken because the valves are imbeded into the pistons.
...ok, what do I win now?
They say that hondas are interferance engines, And bimmers too.
Oh shucks. That will make it hard. I was going to experminet with variable valve opening and i figured that no matter what I did I wouldn't hit the piston so I wouldn't break it. That means I am gonna have to be vrey carefull about when and how much I do open the valves. Rats.