4.6 zero tolerance?
Site Mod
Joined: Jan 2004
Posts: 8,667
From: Oh, Hi.... Oh?
RE: 4.6 zero tolerance?
It means that when the piston is at the peak of its stroke, it's in space that the valve operates in. So in a working motor the valves are closed upon final compression, and the gas is ignited, when the piston retreats, the valves open in the space the piston was just in. Therefore, if you lose a timing chain/belt, the piston can slap the valves, damaging them.
4th Gear Member
Joined: Aug 2003
Posts: 1,974
From: United States
RE: 4.6 zero tolerance?
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
4th Gear Member
Joined: Nov 2005
Posts: 1,271
From: Central FL
RE: 4.6 zero tolerance?
That is good info, I actually read about this on howstuffworks.com but I didn't know it applied to our motor. It describes the process when you ask how CAM's work. It also explains how diesels work, very interesting in my opinion.
4th Gear Member
Joined: Sep 2005
Posts: 1,925
From: AR
RE: 4.6 zero tolerance?
ORIGINAL: Acer2428
It means that when the piston is at the peak of its stroke, it's in space that the valve operates in. So in a working motor the valves are closed upon final compression, and the gas is ignited, when the piston retreats, the valves open in the space the piston was just in. Therefore, if you lose a timing chain/belt, the piston can slap the valves, damaging them.
It means that when the piston is at the peak of its stroke, it's in space that the valve operates in. So in a working motor the valves are closed upon final compression, and the gas is ignited, when the piston retreats, the valves open in the space the piston was just in. Therefore, if you lose a timing chain/belt, the piston can slap the valves, damaging them.
a interfernece means that if the valves are open when the piston hits tdc then they will hit causing damage to the valve and or piston. a noninterfernece means that the manufacuter left enough room for the vavles to be fully open at tdc, os if there was a failure in the timing chain/belt then it would not result in damage to the vavles.
