Stock 5.3, Valve float at 4800RPM???
05-13-2016, 06:20 AM
#1
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Stock 5.3, Valve float at 4800RPM??? I have a 100% stock 2002 5.3 with unknown mileage that I put in my car with my turbo kit while I finish building my other engine.
Im running 10psi, the car launches and feels good until 4800rpm, its like its bouncing off a rev limiter. Same exact RPM every time. My rev limiter is set at 6000 and plug gap is .026, so those 2 things are ruled out.
Can the stock springs be causing valve float at that low of a RPM? Im not sure what else would cause it to act this way.
Im just looking for real world examples. Thanks in advance
Im running 10psi, the car launches and feels good until 4800rpm, its like its bouncing off a rev limiter. Same exact RPM every time. My rev limiter is set at 6000 and plug gap is .026, so those 2 things are ruled out.
Can the stock springs be causing valve float at that low of a RPM? Im not sure what else would cause it to act this way.
Im just looking for real world examples. Thanks in advance
05-13-2016, 07:09 AM
#2
I have a 100% stock 2002 5.3 with unknown mileage that I put in my car with my turbo kit while I finish building my other engine.
Im running 10psi, the car launches and feels good until 4800rpm, its like its bouncing off a rev limiter. Same exact RPM every time. My rev limiter is set at 6000 and plug gap is .026, so those 2 things are ruled out.
Can the stock springs be causing valve float at that low of a RPM? Im not sure what else would cause it to act this way.
Im just looking for real world examples. Thanks in advance
Im running 10psi, the car launches and feels good until 4800rpm, its like its bouncing off a rev limiter. Same exact RPM every time. My rev limiter is set at 6000 and plug gap is .026, so those 2 things are ruled out.
Can the stock springs be causing valve float at that low of a RPM? Im not sure what else would cause it to act this way.
Im just looking for real world examples. Thanks in advance
05-13-2016, 07:18 AM
#3
Could very well be springs, but could also be spark blow-out. Anything more than .022 for me and the dam thing breaks-up like a rev limiter is engaged.
I'd tighten-up the plugs first. But, I'd throw some springs in there anyway for safety. A new set of LS6 springs could be had for like 60.00 and are drop-in.
I'd tighten-up the plugs first. But, I'd throw some springs in there anyway for safety. A new set of LS6 springs could be had for like 60.00 and are drop-in.
05-13-2016, 07:18 AM
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05-13-2016, 07:22 AM
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Could very well be springs, but could also be spark blow-out. Anything more than .022 for me and the dam thing breaks-up like a rev limiter is engaged.
I'd tighten-up the plugs first. But, I'd throw some springs in there anyway for safety. A new set of LS6 springs could be had for like 60.00 and are drop-in.
I'd tighten-up the plugs first. But, I'd throw some springs in there anyway for safety. A new set of LS6 springs could be had for like 60.00 and are drop-in.
05-13-2016, 07:32 AM
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3 days ago I installed BR7's at .026 gap and it made no difference.
So these plugs have about 2 miles on them
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05-13-2016, 07:40 AM
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05-13-2016, 09:38 AM
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With the miles these can handle, its not surprising to find one with 250k+ miles that still runs good. At that point, its not surprising that the valve springs have softened and need replaced.
Which coils are you running? Heat-sink coils have a very strong spark even at larger plug gaps.
Which coils are you running? Heat-sink coils have a very strong spark even at larger plug gaps.
05-13-2016, 09:49 AM
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Non-heat sink coils. Same ones I ran on my 150k mile LQ4 that took 15psi with stock everything and revved to 6000rpm without a hiccup.
Hopefully new springs and tighter plug gap fix this. Its just weird it is exactly like a rev limiter. It wont go above 4800.
Hopefully new springs and tighter plug gap fix this. Its just weird it is exactly like a rev limiter. It wont go above 4800.
05-13-2016, 08:32 PM
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Just a quick update. Reving in park or neutral went up past 5000rpm no problem. I disconnected the turbo cold side and drove it and the "valve float" was now happening around 3800-4000rpm. I went home, installed ls6 springs amd left my plug gap alone. Took it out and was issue free. Trned boost up to 15psi and still issue free.
05-14-2016, 07:29 AM
#16
Just a quick update. Reving in park or neutral went up past 5000rpm no problem. I disconnected the turbo cold side and drove it and the "valve float" was now happening around 3800-4000rpm. I went home, installed ls6 springs amd left my plug gap alone. Took it out and was issue free. Trned boost up to 15psi and still issue free.
05-16-2016, 10:35 AM
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Well last year I had a setup similar to yours.....LQ4 with LS6 cam/S475/ TH350/ 3.55 gears and I went 10.52@130 on 8 PSI.
Honestly this setup with the stock cam feels like it will destroy my old setup. I will be sure to post the results when I get to the track.
Honestly this setup with the stock cam feels like it will destroy my old setup. I will be sure to post the results when I get to the track.
05-16-2016, 01:26 PM
#19
Well last year I had a setup similar to yours.....LQ4 with LS6 cam/S475/ TH350/ 3.55 gears and I went 10.52@130 on 8 PSI.
Honestly this setup with the stock cam feels like it will destroy my old setup. I will be sure to post the results when I get to the track.
Honestly this setup with the stock cam feels like it will destroy my old setup. I will be sure to post the results when I get to the track.
I did run ~130mph on like 10.5psi though. Just doesn't seem to do any better with anymore psi so I need to find the bottleneck if there is one.
05-16-2016, 01:48 PM
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Unfortunately I did. The engine ran fine for 2 years with a gt45 and stock cam at 15psi. I put the s475 on and installed the ls6 cam. When I installed the cam, the bearings looked horrible but everyone said run them......well, first time out it spun the cam bearings, that metal went everywhere, wiped out 3 mains and 4 rod bearings. All that happened in my 1 and only pass with that setup. So yea, my 130mph pass was with all those engine issues too. I had to have my turbo cleaned and inspected with only 4 miles on it because so much metal was sent through everything. I should've known better to not run those cam bearing....but live and learn.
