Interference vs non interference motors (differences)

SuffolkD at SuffolkD at
Wed Jan 14 11:57:36 EST 2004

Dan et al:
Not positive of the exact engine code, but my old 87 4000Q (JT?) engine was:
N/A = Normally aspirated
non interference = when the timing belt jumps or breaks the valves can be 
anywhere without hitting (damasge) because there is enough clearance to the 
piston in the engine head. 
Most newer engines are,
Interference = most (if not all) Audi 5,4 & 6 cyl turbos
If the valves (intake and exhaust) are not positioned properly by the timing 
chain (due to a break or jumping a few teeth), the pistons can hit the valves. 
 That interfer(ing) costs a lot of money tearing down the engine to replace 
those now broken or bent valves.

HTH - Scott by BOSTON

In a message dated 1/14/2004 7:39:16 AM Eastern Standard Time, 
d_dibiase at writes:

> Dumb question: what is the difference between an 'interference' engine and

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