car surging at high rpms
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From: Chattanooga,TN
car surging at high rpms Can anyone help me with this problem? My SS (M6) only has 45K miles on it and when I wind it out in the upper rpms, I feel a surging effect, or more like a dead spot around 5K rpm. I don't have a lot of mods, but the only thing I have done different lately is change to NGK TR6 plugs when I installed my NOS kit. This surging effect happens when I am on motor and on the juice. Sometimes my NOS comes in harder than others, and sometimes I can barely even tell if it is firing or not. I thought it might be a fuel issue and the fuel pressure safety switch was preventing the solenoids from opening. I thought maybe the fuel filter was getting dirty, so I replaced it. That was not the problem. I also have heard of a poly tranny mount possibly causing a false knock situation, so I went to a 1LE mount.. Guess what, that was not the problem either. Can anyone give me any ideas? I don't have access to autotap right know, so I am kind of in the dark. Any suggestions apreciated.
Thanks in advance,
Kevin
Thanks in advance,
Kevin
Re: car surging at high rpms (sorry, long) Honest opinion? I think it could be your valvesprings. At 45K miles, and run on nitrous, those suckers are probably weak. This will allow your valves to float at high rpm (stay open too long) and the computer will pull some serious timing out when this happens. On a dynojet graph, this occurence typically appears as a huge dip at around 5K on stock LS1s. You can definitely feel it too, and it does feel like a fuel issue.
If you are going to continue spraying, I would HIGHLY recommend you invest in some replacement valvesprings. Especially for an M6 car, and this will help you keep pushrods straight too.
CompCam 26918 springs would work great. They fit with the stock retainers.
Tony
If you are going to continue spraying, I would HIGHLY recommend you invest in some replacement valvesprings. Especially for an M6 car, and this will help you keep pushrods straight too.
CompCam 26918 springs would work great. They fit with the stock retainers.
Tony
Thread Starter
TECH Enthusiast
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From: Chattanooga,TN
Re: car surging at high rpms (sorry, long) Thanks for the tip. How hard is it to replace the valvesprings in an LS1? Is there any way to tell for sure before replacing them? Autotap right? I was afraid of that. Is there a significant way to tell if I have already bent a pushrod or would I already know? Would there be a lot of vibration felt if a poly tranny mount was installed? I did notice a bad vibration after I installed the mount (more than I did on my LT1.) Do you know anything about clutches?
Thanks,
Kevin
Thanks,
Kevin
Teching In
Joined: Nov 2001
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From: South Florida
Re: car surging at high rpms (sorry, long) Hey Kevin, I have the exact same problem you have and I have an '01 SS with only 4500 miles
did the same thing you did, Went with the TR6 NGK plugs and I get the surging too. Also at times I can't even feel the NOS hit....?
The car is stock.....
did the same thing you did, Went with the TR6 NGK plugs and I get the surging too. Also at times I can't even feel the NOS hit....?
The car is stock.....
Re: car surging at high rpms (sorry, long) Poly mounts will definitely make more vibrations inside the car and transmit more road noise, but they rarely induce enough to cause false knock. I've been running a poly mount for years now with no false knock from it. Check out my website below for causes of false knock.
No way to test the valvesprings. But, trust me on this one. Even when they are brand new, they are WEAK for these cars. That is why you hear about bent pushrods with M6 cars, its caused by valvefloat at high rpm. Valvefloat is caused by the springs being too weak to shut the valve quick enough, and the piston comes up and hits the valves. This causes the rocker arms to hammer down on the pushrods, causing them to bend.
You can usually hear alot of ticking when you have bent pushrods, and your track times will fall about 2 tenths and 2 mph from normal. Been there, done that MANY times haha.
Changing the springs isn't so bad. You can get a small spring compressor from Sears that will work, and I think they are only like $15 or something.
Clutches? I know a lot about those. Take a look at my "Busted parts" section on my car modification website LOL.
Tony
No way to test the valvesprings. But, trust me on this one. Even when they are brand new, they are WEAK for these cars. That is why you hear about bent pushrods with M6 cars, its caused by valvefloat at high rpm. Valvefloat is caused by the springs being too weak to shut the valve quick enough, and the piston comes up and hits the valves. This causes the rocker arms to hammer down on the pushrods, causing them to bend.
You can usually hear alot of ticking when you have bent pushrods, and your track times will fall about 2 tenths and 2 mph from normal. Been there, done that MANY times haha.
Changing the springs isn't so bad. You can get a small spring compressor from Sears that will work, and I think they are only like $15 or something.
Clutches? I know a lot about those. Take a look at my "Busted parts" section on my car modification website LOL.
Tony
