motor question

[kosslo]

i have a question about a 1990 plymouth laser rs N/T

the other day was comming home from work car was acting funny
while pulling up to a red light car died tryed to start it relised by the sound it lost the timming belt well got new belt got everything takin off to fix it now the question i have is while the belt is off and the car is in nuetral shouldnt i be able to turn the crank gear around as many times as i want it should be free turning right well it doesnt it only turns about two compleat rotations and then it stops like it is hitting something i thought maybe i droped a valve so i pulled off the valve cover and what i found wasent good a couple of the rockers had came off and were lying in the top of the head what i want to know is is the bottom of the motor supposed to turn more then twice and if not what should i be looking for as far as damage to the pistons p.S this is a 2.0 dohc non turbo

 

[DSMGSX95]

Whenever the timing belt breaks or jumps, there is almost alwys damage to the valves. Depending how fast it was running at the time will also determine how much if any damage to the pistons. You also need to check rod and rod bearings on any cylinder that was damaged by broken or stuck openvavles. The force of the piston hitting a broken or stuck open valve can bend the rod at the time of the incedent.

 

[Old Mitsu Tech]

The reason the rockers fall off is that the piston jams the valve sideways and it can't return to its fully relaxed position which holds the rocker next to the cam. I am currently going through this as I bought a 90 gsx and that's the reason I got it so cheap.

Good Luck

 

[wolf20043]

And keep in mind, if you have a valve stuck or broke, that would mean the valve is in the same place as the piston needs to be on its compression stroke, causing the piston to be stopped before TDC. You should never try to turn the crank with the belt off due to the valves not opening and closing as they should when the crank is turning.
Mike

 

[Doug99RS]

You should never try to turn the crank with the belt off due to the valves not opening and closing as they should when the crank is turning.
Mike

This is not entirely true. There should be caution taken as you're trying to promote here but it's a common practice to rotate the crankshaft to a neutral position (all cylinders half-way down) when rotating the camshafts independently. This may be required when the cams are removed and reinstalled and attention to orientation is not taken. A better recomendation would be always line up timing marks prior to removing timing belt. Also, remove spark plugs to reduce cylinder pressure build up to help detect an interference issue. Finally, always rotate an engine very slowly in order to verify valve to pistion clearance.
Doug

 

[kosslo]

well that kindof confirms my worst night mare but that is what i had thought would be the issue at the time dang all this from a timebelt break think i will spend the extra money and get the kevlar belt grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

P.S. appriciate all yalls help