Ok, my buddy just told me the timing belt in his Subie RS (DOHC) broke. He said he's goin to "rebuilt the heads". I told him the pistons are going to be damaged. I don't know how fast the engine was spinning yet. But, if there are valve dents in the pistons can they just me smoothed and left alone? He thinks so. I think it's asking for trouble. What say you?
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July 5, 2011 10:08 a.m. DrBoost SuperDork
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July 5, 2011 10:12 a.m. Ranger50 Dork
Depends on if the piston has a sharp edge and how deep from the valve hitting it. If it does just have a nick, just use a quick pass with a cookie and reuse it all.
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July 5, 2011 10:42 a.m. mad_machine SuperDork
you don't have to be spinning fast. I got a fiat from a friend who's belt broke pulling into his driveway (tensioner came off) and it had two holed pistons from basically near idle speeds.
That said, I had a belt slip on one of my Fiat's due to the cold -5F and while I managed to bend a single valve, I did not hurt anything else.. AND the car got me home from Trenton to below Atlantic City with only a loss of power
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July 5, 2011 11:39 a.m. N Sperlo HalfDork
Not too familiar with the timing systems in... Anything, but the tensioner crumbled in my escort throwing the belt and we just put a new timing kit on it. No problems.
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July 5, 2011 11:52 a.m. yamaha Reader
Thats the difference of an interference vs. non-interference engine If it is non, you can just put a new timing set on it. Bent valves are an indication of interference tho
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July 5, 2011 12:15 p.m. bravenrace SuperDork
In reply to DrBoost:
I once had a timing belt break on a honda at ldle and it didn't do any damage at all. Then I had the belt break on another honda on the freeway and all I had to do was replace couple valves and put the head back on. I'm still driving it. BTW, neither belt was due to be replaced for many more thousands of miles.
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July 5, 2011 12:25 p.m. DrBoost SuperDork
He said it was about 3,000 rpm. I guess we'll see when we get in there. I've replaced many timing belts, but the only first-hand experience I've had with belts that broke were on DSMs. Ranger50, do you think I could have done a quick pass with a cookie and a little bondo to save the customer some money with these
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July 5, 2011 12:49 p.m. foxtrapper SuperDork
This wouldn't be Jerome's would it? He's already replaced it and was saying he was going to get rid of it.
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July 5, 2011 12:53 p.m. mad_machine SuperDork
ouch.. yes, looks like the pistons in the fiat I got
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July 5, 2011 1:19 p.m. Taiden HalfDork
So glad my impreza will soon have a non-interference engine in it
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July 5, 2011 4:16 p.m. 44Dwarf Dork
Also depends on how close the ring lands are to the top of the piston. Some makes the rings are so close the ring land pinch the rings when the valve hits. Car will run fine for about an hour or so then start smoking up a storm that just gets worce.
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July 6, 2011 4:40 a.m. DWNSHFT Reader
yamaha wrote:
Bent valves are an indication of interference tho
Quoted for troof. This one is worthy of the magazine.
David
