VERY strange mid range power loss
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
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VERY strange mid range power loss 05 Automatic trans GTO with a 230/236 cam, stage 3 heads..
Got the AFR dailed in 13.0 across and a strange thing is happening...
the car pulls up to 5200 and falls on its face and stumbles...and strugles to get past 5200-5400. If we stay in the throttle, eventually around 5800 the power picks back up and starts pulling again.
Could this be valve float or what? The power curve is like so...
3800-5200 the power climbs as it should.
5200-5700 the power falls off nasty
5800+ it picks back up and the power can be seen climbing again up to 6800.
AFR is steady entire time and never goes lean...there is plenty of fuel.
Any ideas?
Got the AFR dailed in 13.0 across and a strange thing is happening...
the car pulls up to 5200 and falls on its face and stumbles...and strugles to get past 5200-5400. If we stay in the throttle, eventually around 5800 the power picks back up and starts pulling again.
Could this be valve float or what? The power curve is like so...
3800-5200 the power climbs as it should.
5200-5700 the power falls off nasty
5800+ it picks back up and the power can be seen climbing again up to 6800.
AFR is steady entire time and never goes lean...there is plenty of fuel.
Any ideas?
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
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Originally Posted by Pwebbz28
Any KR being picked up at those RPMs?
I thought valve float too, but it is strange that it starts to come back to life after 5700...I guess it could still be valve float, because its not making near the power it should be.
Could be the torque converter coupling up if you ran it unlocked. What is your stall and did you dyno it locked or unlocked? A graph would help in this case.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
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Originally Posted by V6 Bird
Its the tune...try fattening the car up in that area and see if it comes around.
Originally Posted by Patrick G
Could be the torque converter coupling up if you ran it unlocked. What is your stall and did you dyno it locked or unlocked? A graph would help in this case.
Im still leaning toward valve float but not sure...
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Originally Posted by SSkeet
This could be, I didnt think of it. No I didnt tuen out the converter, I imagine this can be done in real time with the scanner? Still though, this happens on the street as well so I dont think this is the answer, even though it still could be trans/converter related.
Im still leaning toward valve float but not sure...
Im still leaning toward valve float but not sure...
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Yep...
Originally Posted by Outlaw1
BS.
Originally Posted by georgevette
they are on shaft mount rockers that are adjustable. but when you over adjust them they will fill in the gap of .400 but it will throw the valvetrain geometry off thus the problem with it making decent power until you get everything back in line.
Thread Starter
Launching!
Joined: Sep 2004
Posts: 246
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Originally Posted by 1997bird
"George" you are so full of **** your eyes are brown! There is NO way that you can get a shaft mount rocker to adjust that far.
Teching In
Joined: Feb 2007
Posts: 11
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Originally Posted by 1997bird
"George" you are so full of **** your eyes are brown! There is NO way that you can get a shaft mount rocker to adjust that far.
no need to insult if your the one that does'nt know ****. i had to shim the bottom of the pedestal almost and 1/8 of an inch to get the whole valve train to sit higher and it stills needs a little more to make it perfect. I dont want to turn this into a pissing contest but get all your facts staight before you give your all mighty advice. Yea you know alot alright shiming is the oldest trick in the book to change your geometry.
Last edited by georgevette; Mar 29, 2007 at 05:45 PM.
Shimming your heads 0.125" is not going to make up .400" (that was your origonal posting before you deleted it), I guess now it is .300", you can't adjust the rockers that far without oiling problems. Good luck with your long lasting engine combo.
Originally Posted by SSkeet
It actually responded best when it was between 13.5-14.0 but that is too lean and I could not let him leave with the car tuned like that. But that did not fix the problem by any means, Im just saying the car seemed to run best there. In the 12's it was really bad and richer than that forget it.
This could be, I didnt think of it. No I didnt tuen out the converter, I imagine this can be done in real time with the scanner? Still though, this happens on the street as well so I dont think this is the answer, even though it still could be trans/converter related.
Im still leaning toward valve float but not sure...
This could be, I didnt think of it. No I didnt tuen out the converter, I imagine this can be done in real time with the scanner? Still though, this happens on the street as well so I dont think this is the answer, even though it still could be trans/converter related.
Im still leaning toward valve float but not sure...
Put a cold plug in there. Sounds like the heads are pretty efficient and if its responding to being lean, a cold plug and going leaner will make it happy. Dont fight the feeling man. Its after peak torque and VE's are dramatically down from 100%, it cant hurt itself with a NGK8 or 9 in the plug hole. Efficient cylinder head port work wants to run leaner to make power. Put precautions in place to remove heat from the chamber and let her rip.
Originally Posted by SSkeet
PROBLEM SOLVED> He called me today, told me his pushrods were the wrong length He replaced them and readjusted his rockers and now it pulls like a beast all the way through. 
He replaced them and readjusted his rockers and now it pulls like a beast all the way through. Its the part the puts you in the middle of the pack with your combination or sets you out 2 or 3 cars and everyone else chases.
Teching In
Joined: Feb 2007
Posts: 11
Likes: 0
Originally Posted by 1997bird
Shimming your heads 0.125" is not going to make up .400" (that was your origonal posting before you deleted it), I guess now it is .300", you can't adjust the rockers that far without oiling problems. Good luck with your long lasting engine combo.
and it feels alot smother now. crisper throttle response and smoother all the way across the rpm range. thanks for contributing your wealth of knowledge to this thread and helping a fellow member solve his problem and not just being an *** and saying negative things that dont help anyone on this board.
