Checking Timing?
11-11-2008, 12:25 PM
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Checking Timing? So I had a massive over rev on an accidental 3 to 2 shift (shifted from 3rd at 5,500rpm) and I'm worried that among other things I may have jumped timing. How can I check timing and verify that everything is right? Fixing this problem (however extensive it may be) will be by far my biggest DIY attempt ever so excuse my dumb question. Thanks in advance...
11-11-2008, 12:52 PM
#2
You can't "check timing" or "jump time" in an LS engine. It doesn't have a distributor 
Depending on how high the engine mechanically over reved, the worst that could happen is smacking some valves to the pistons. Less severe damage can be bent pushrods or even nothing at all.
If the motor is noticeably down on power or making any noises, pull the valve covers and pull all your pushrods. If none of the pushrods are bent, your motor should be fine.
Depending on how high the engine mechanically over reved, the worst that could happen is smacking some valves to the pistons. Less severe damage can be bent pushrods or even nothing at all.
If the motor is noticeably down on power or making any noises, pull the valve covers and pull all your pushrods. If none of the pushrods are bent, your motor should be fine.
11-11-2008, 01:04 PM
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Car is misfiring bad, I pulled my pushrods and they are all straight. I'm convinced that I bent a few valves (it definately isn't running right). I thought with all the sudden force that the motor incurred from the over-rev that the timing chain may have jumped a gear or something. Maybe I'm just really underinformed here...
11-11-2008, 01:26 PM
#4
The chain won't jump a gear but it definitely can break. You'd know if it was broke though, the engine wouldn't run at all.
Did you pull the plugs?
Best way to check for bent valves (aside from yanking heads) is do a leak down check. If you've got more than 20% leak down on any given cylinder, more than likely you've bent the valves. A lot of times you can actually hear the air blowing past the valve if it's bent bad enough.
Did you pull the plugs?
Best way to check for bent valves (aside from yanking heads) is do a leak down check. If you've got more than 20% leak down on any given cylinder, more than likely you've bent the valves. A lot of times you can actually hear the air blowing past the valve if it's bent bad enough.
11-11-2008, 02:35 PM
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I pulled the plugs, nothing about them stands out to me at all, they all look good. I see myself just pulling the heads and checking the valves. I'm hoping its just valves since that would be the cheapest fix. Here are the simptoms the car had after the misshift, it struggled to start but did start up, it was misfiring bad (sounded like it had a big cam) but would hold idle, and it made some power (enough to get me from 40mph to 50mph in 4th gear so I could get off the highway).
So if I pull the heads and it turns out I bent a few valves do you all think I would be ok to just get new heads (241's) and say problem solved or is there anything else I should check before putting it back together and starting it up? One of my friends who will be helping me work on the car thinks I should drop the oil pan to see if there is any damage to the bottom end and to check the oil for metal flakes. I would like to avoid doing this since it looks like it would be a huge PITA.
So if I pull the heads and it turns out I bent a few valves do you all think I would be ok to just get new heads (241's) and say problem solved or is there anything else I should check before putting it back together and starting it up? One of my friends who will be helping me work on the car thinks I should drop the oil pan to see if there is any damage to the bottom end and to check the oil for metal flakes. I would like to avoid doing this since it looks like it would be a huge PITA.
11-11-2008, 02:52 PM
#7
have you run it since the problem happened-in some rare cases the lifters can lose their preload and pump up, but will settle down later and be all right-
the valves will "float" and not seat untill the lifters settle down
i would at least run a comp test, in the event their is a valve problem, it might help identify the bad valve
i have found top dead center, mark it on the balancer, fab a pointer, and ck timing-i did this on a carb LS motor, wanted to know that the timing i was seeing was really correct-just hook up a timing light to #1, view it on the balancer(i used a dial back to ck total advance)
good luck with it
the valves will "float" and not seat untill the lifters settle down
i would at least run a comp test, in the event their is a valve problem, it might help identify the bad valve
i have found top dead center, mark it on the balancer, fab a pointer, and ck timing-i did this on a carb LS motor, wanted to know that the timing i was seeing was really correct-just hook up a timing light to #1, view it on the balancer(i used a dial back to ck total advance)
good luck with it