Am I getting valve float? Dyno sheets inside
Thread Starter
TECH Apprentice
iTrader: (20)
Joined: Jul 2009
Posts: 390
Likes: 0
From: Liberal land
Am I getting valve float? Dyno sheets inside Just got the car on a dyno today and was very disappointed. After talking with a few turbo buddies it looks like I may have valve float going on. Figured I'd get some opinions on here.
My setup:
-5.3
-317's
-LS6 cam
-LS6 yellow valve springs (bought used)
-T76 @ 15 psi
-alky control meth injection
The car basically made power up to 5200 rpm and then flatlined and the chart from that point on looks like a seismograph during an earthquake. That was even with the smoothing set to 5. Def thinking valve float. I logged the pulls and there was no issue there. Held a steady 14* timing through the pull with no knock, and everything else looked pretty good.
I also included my dyno chart when I was still on 11 psi for comparison purposes. If you note, I made 485 rwhp on 11 lbs at 5200 rpm, and almost 560 rwhp on 15 lbs at the same rpm, but then the power flatlines. Picked up considerable torque over the last dyno as well. 580 lbs ft as opposed to 522 lbs ft. The car should have been well over 600 rwhp. Just trying to get it straightened out, so any ideas are appreciated!
My setup:
-5.3
-317's
-LS6 cam
-LS6 yellow valve springs (bought used)
-T76 @ 15 psi
-alky control meth injection
The car basically made power up to 5200 rpm and then flatlined and the chart from that point on looks like a seismograph during an earthquake. That was even with the smoothing set to 5. Def thinking valve float. I logged the pulls and there was no issue there. Held a steady 14* timing through the pull with no knock, and everything else looked pretty good.
I also included my dyno chart when I was still on 11 psi for comparison purposes. If you note, I made 485 rwhp on 11 lbs at 5200 rpm, and almost 560 rwhp on 15 lbs at the same rpm, but then the power flatlines. Picked up considerable torque over the last dyno as well. 580 lbs ft as opposed to 522 lbs ft. The car should have been well over 600 rwhp. Just trying to get it straightened out, so any ideas are appreciated!
Why are you using stock shitty valve springs? Brian Tooley dual springs with tool steel retainers are cheap and work well. Hell, I've got a set of brand new Comp 918's sitting on my shelf you can have for the price of shipping. Most people don't trust them anymore and if money is a concern for you, you can have them. What pushrods are you using? Get some BTR or Comp 5/16 .080" at a minumum. I've got some used Comp .080" wall 7.4's and 7.375's if you want to buy a set from me for $40.
Thread Starter
TECH Apprentice
iTrader: (20)
Joined: Jul 2009
Posts: 390
Likes: 0
From: Liberal land
Why are you using stock shitty valve springs? Brian Tooley dual springs with tool steel retainers are cheap and work well. Hell, I've got a set of brand new Comp 918's sitting on my shelf you can have for the price of shipping. Most people don't trust them anymore and if money is a concern for you, you can have them. What pushrods are you using? Get some BTR or Comp 5/16 .080" at a minumum. I've got some used Comp .080" wall 7.4's and 7.375's if you want to buy a set from me for $40.
Just get you some BTR's with the tool steel retainers and good pushrods. You could just try the pushrods first. They might be deflecting enough to cause that. Since pushrods are easy to do, that's what I would do first. Cheaper also. 
If you do need 7.375 or 7.400 pushrods then the $40 offer still stands for my Comp .080" wall pushrods. Or just buy new BTR's. They are only $100 if I remember right.
What lifters do your have? You could try setting them with less preload as well when you measure for new pushrods.
If you do need 7.375 or 7.400 pushrods then the $40 offer still stands for my Comp .080" wall pushrods. Or just buy new BTR's. They are only $100 if I remember right.
What lifters do your have? You could try setting them with less preload as well when you measure for new pushrods.
Thread Starter
TECH Apprentice
iTrader: (20)
Joined: Jul 2009
Posts: 390
Likes: 0
From: Liberal land
Just get you some BTR's with the tool steel retainers and good pushrods. You could just try the pushrods first. They might be deflecting enough to cause that. Since pushrods are easy to do, that's what I would do first. Cheaper also.
If you do need 7.375 or 7.400 pushrods then the $40 offer still stands for my Comp .080" wall pushrods. Or just buy new BTR's. They are only $100 if I remember right.
What lifters do your have? You could try setting them with less preload as well when you measure for new pushrods.
If you do need 7.375 or 7.400 pushrods then the $40 offer still stands for my Comp .080" wall pushrods. Or just buy new BTR's. They are only $100 if I remember right.
What lifters do your have? You could try setting them with less preload as well when you measure for new pushrods.
As for lifters, I'm on stock ones but I really don't think thats my issue. The motors only a 40K mile 5.3 so they should be very healthy still. Lots of guys push the stock lifters to 18-20 psi without issue.
Trending Topics
Thread Starter
TECH Apprentice
iTrader: (20)
Joined: Jul 2009
Posts: 390
Likes: 0
From: Liberal land
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
