who's been a lucky boy
23 February 2009, 01:33 PM
#1
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who's been a lucky boy
me lol....after the timing belt tensioner bolt sheard 
resulting in my exhaust cams being 180 degree out
i thought i would just fit a new timing belt kit & turn it over by hand,all seemed ok so thought i'd start it up & it did
& runs spot on...
resulting in my exhaust cams being 180 degree out i thought i would just fit a new timing belt kit & turn it over by hand,all seemed ok so thought i'd start it up & it did
& runs spot on...
24 February 2009, 11:12 AM
#5
Watch out for what appears to be noisy tappets.
Common thing on imprezas is for the valves to bend "very" slightly. The valve spring is strong enough to pull it back into the guide and make a good seal. Problem is this straightens the valve as it goes into the guide, causing guide wear and fatigue of the valves stem as its constantly flexed every time it opens and closes.
Long term effects? Well, say 20,000 miles later you might expect something, or nothing:
Any tapping noise from the cam-cover areas is an indicator that some valves aren't seating properly. Which causes the valve and seat to wear and burn out prematurely, also increased valve guide wear. Finally, the worst is a risk of the valve stem breaking from fatigue...with very catastrophic consequences.
My friend davidsfarm (nutcase Canadian
) demonstrates the the action of a bent valve pulling into the head perfectly on this vid at 2mins onwards: YouTube - how to set cam timing and fix bent valves ...SKIP FORWARD to 2mins and he shows exactly how a valve pulls straight into the guide even when its still very slightly bent.
Straighten with a screwdriver at your own risk
Of course he's bending a solid valve, if you have hollow stem valves (of which are fitted to some Sti Impreza engines), then they are alot weaker so don't take kindly to being bent in any form.
I'm not trying to be alarmist, but these are interference engines, also being pent roof head, the inlet and exhaust valves can foul each other too. If in doubt, have a word with someone who build these engines for a living: Dave@api.
Common thing on imprezas is for the valves to bend "very" slightly. The valve spring is strong enough to pull it back into the guide and make a good seal. Problem is this straightens the valve as it goes into the guide, causing guide wear and fatigue of the valves stem as its constantly flexed every time it opens and closes.
Long term effects? Well, say 20,000 miles later you might expect something, or nothing:
Any tapping noise from the cam-cover areas is an indicator that some valves aren't seating properly. Which causes the valve and seat to wear and burn out prematurely, also increased valve guide wear. Finally, the worst is a risk of the valve stem breaking from fatigue...with very catastrophic consequences.
My friend davidsfarm (nutcase Canadian
) demonstrates the the action of a bent valve pulling into the head perfectly on this vid at 2mins onwards: YouTube - how to set cam timing and fix bent valves ...SKIP FORWARD to 2mins and he shows exactly how a valve pulls straight into the guide even when its still very slightly bent. Straighten with a screwdriver at your own risk
Of course he's bending a solid valve, if you have hollow stem valves (of which are fitted to some Sti Impreza engines), then they are alot weaker so don't take kindly to being bent in any form.I'm not trying to be alarmist, but these are interference engines, also being pent roof head, the inlet and exhaust valves can foul each other too. If in doubt, have a word with someone who build these engines for a living: Dave@api.
Last edited by ALi-B; 24 February 2009 at 11:15 AM.
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