Which are the interference engines?
#1
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Which are the interference engines?
I have a 1981 4.5L...is it an interference engine? Which are the interference engines? Could not find this info from any other source.
#6
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the 10.4 /1 compression 310 hp Euro S 16 valve LH injection engines would seem to be the most likely to bend valves.
Also if the heads have been resurfaced shaved at some point in time or there is significant carbon build up it can be possible for some other 16 valve engines to bend valves.
Your 81 4.5 should have no problem......
Also if the heads have been resurfaced shaved at some point in time or there is significant carbon build up it can be possible for some other 16 valve engines to bend valves.
Your 81 4.5 should have no problem......
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#9
Nordschleife Master
I put each cylinder to TDC then rotated the camshaft. There was no intereference. The factory manual backs this up.
#10
Three Wheelin'
By hand they probably aren't but with a fast spinning engine you have inertia come into play. I had my 32V S4 (stock) engine at points where it should have bent valves (by accident) and i don't think it did. Timed cams to 45 BTDC, forgot to move engine to #1 TDC compression stroke... You guys think fully drained/collapsed lifters would have something to do with this though? I cranked it through a full rotation with it timed to 45 instead of TDC and it spun just like normal, no resistance points. Perhaps the lifters offer enough cushion for no valve damage when hand cranking? This was just with a regular 1/2" drive ratchet. I think you'd deffinitely feel alot of resistance if you were bending a valve by cranking it over by hand.
#11
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Gates has a lookup function...
http://www.gates.com/part_locator/in...o=Interference
http://www.gates.com/part_locator/in...o=Interference
#12
Drifting
Doing it by hand with no oil pressure will let the lifters collapse some.
#13
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Dave
Last edited by davek9; 01-10-2014 at 04:49 PM.
#14
Nordschleife Master
The manual states this too.
However the tolerances are much smaller, and valve pockets can be the first place for carbon to build up. So even if you have a small amount of carbon build up it is possible to make the 310bhp euro 16V motors interference.
123Quattro,
The engine was run only a couple hours before. The loss would not have been enough to change the fact. When the car was restarted there was no lifter tick present. The amount of change which might have been lost would be negated by the thermal expansion of the aluminium block.
17 prospective,
The engine RPM has little to do with this. Either things touch or they dont. If the valve is lifting off the cam lobe then you will have other more noticeable problems. The only thing that the speed the engine is spinning will do is increase (with RPMs) the possible amount of damage that can happen if things DO touch. If they do not touch when stopped, they wont touch when spinning.
So to all, if you have a 16V engine which is stock, has never had the heads off, and you have no carbon build up, the engine is non interference. But if you have almost any carbon build up in the valve pockets on the pistons, then you likely have an interference motor. This can be viewed with a borescope pretty easily.
#15
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Gates has a lookup function...
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."