Generation III Internal Engine 1997-2006 LS1 | LS6
Sponsored by:
Sponsored by:

Mis-shifted 3rd to 2nd, engine underpowered now?

Thread Tools
 
Search this Thread
 
Old Oct 3, 2008 | 11:34 AM
  #41  
Tony Mamo @ AFR's Avatar
Flow Wizard
20 Year Member
iTrader: (13)
 
Joined: Feb 2004
Posts: 2,197
Likes: 7
Default

You NEED to do a leakdown test at this point.

The time spent doing that will tell you whether you need to pull the heads and swap out some valves or not.

If your pushrods aren't bent (which appears to be the case) and the engine was down on power it is highly likely that you did in fact bend/tweak a few valves.

If you get a decent leakdown on all eight holes consider yourself lucky and move on although if the car still doesn't feel right that would require further digging to find the problem.

I hate to be the bearer of bad news but if the car doesn't feel quite right and your pushrods aren't the culprit, its very likely you have a few bent valves.

Get a leakdown tester (or borrow one) and have at it....

Regards,
Tony

BTW....I consider myself a good driver when it comes to piloting high horsepower manually shifted hotrods (20+ years experience). About a year ago I nailed the infamous 3-2 shift for the first time at WOT (with my 383) and was data logging at the time....can you say 8507 RPM's

Three things saved my ***....one, Im **** about my engine assembly and thankfully was running good aftermarket parts....two, I run a solid roller which has better high RPM valve control, and three, I have a buttload of piston to valve clearance (.180 / .210). Car ran perfect after that but it shook me up for awhile....I do admit loving another "octave" in the exhaust note I had never heard before....LOL


Oh yeah....all of you who think you can run a mid 230's hydraulic cam without flycutting (or running aftermarket pistons) would have been crying if something similar happened to you (and it can happen to the best of us especially if your trying to pull off really fast shifts). Guaranteed you would have bent practically every valve and a good chance you might have bent one bad enough to break a head off and trash your engine.
Reply
Old Oct 3, 2008 | 02:37 PM
  #42  
Haans249's Avatar
TECH Addict
iTrader: (24)
 
Joined: May 2005
Posts: 2,045
Likes: 4
From: Fort Worth, TX
Default

Originally Posted by Tony Mamo @ AFR
You NEED to do a leakdown test at this point.

The time spent doing that will tell you whether you need to pull the heads and swap out some valves or not.

If your pushrods aren't bent (which appears to be the case) and the engine was down on power it is highly likely that you did in fact bend/tweak a few valves.

If you get a decent leakdown on all eight holes consider yourself lucky and move on although if the car still doesn't feel right that would require further digging to find the problem.

I hate to be the bearer of bad news but if the car doesn't feel quite right and your pushrods aren't the culprit, its very likely you have a few bent valves.

Get a leakdown tester (or borrow one) and have at it....

Regards,
Tony

BTW....I consider myself a good driver when it comes to piloting high horsepower manually shifted hotrods (20+ years experience). About a year ago I nailed the infamous 3-2 shift for the first time at WOT (with my 383) and was data logging at the time....can you say 8507 RPM's

Three things saved my ***....one, Im **** about my engine assembly and thankfully was running good aftermarket parts....two, I run a solid roller which has better high RPM valve control, and three, I have a buttload of piston to valve clearance (.180 / .210). Car ran perfect after that but it shook me up for awhile....I do admit loving another "octave" in the exhaust note I had never heard before....LOL


Oh yeah....all of you who think you can run a mid 230's hydraulic cam without flycutting (or running aftermarket pistons) would have been crying if something similar happened to you (and it can happen to the best of us especially if your trying to pull off really fast shifts). Guaranteed you would have bent practically every valve and a good chance you might have bent one bad enough to break a head off and trash your engine.
Been there; DONE that! Listen to this very well informed, experienced mastermind. And learn from all of our mistakes so you don't make the same! That is, unless you want a 427 LS7 monster under your hood Fix it better when it breaks!
Reply
Old Oct 3, 2008 | 02:45 PM
  #43  
derek91RS's Avatar
Teching In
 
Joined: Sep 2008
Posts: 17
Likes: 0
From: Tullahoma, TN
Default

check spark plugs to and rods and valves and springs
Reply
Old Oct 3, 2008 | 03:14 PM
  #44  
texsls1's Avatar
Teching In
 
Joined: Jun 2008
Posts: 7
Likes: 0
From: Knoxville, TN
Default

been there 2, I bent 7 pushrods and 1 valve and 1 rod bolt
Reply
Old Oct 3, 2008 | 04:55 PM
  #45  
bballr4567's Avatar
TECH Fanatic
15 Year Member
iTrader: (5)
 
Joined: Mar 2007
Posts: 1,199
Likes: 0
From: Evansville, IN
Default

At the Z pushrod! That is BAD.

First time I got on my car hard I misshifted from 3rd to 2nd. It has the factory Hurst so I wasnt used to it. The only good thing is that I was shifting around 4500 and as soon as I let out the clutch I got a huge wake up call. Immediately pushed it back in and went on my way. Pulled over on the side of the road to check it out and no abnormal sounds or anything.

Getting a MGW soon to solve the tricky stock shifter problem.


Great info Tony! 8500 RPMs is a LOT to turn over on accident.
Reply
Old Oct 4, 2008 | 01:36 PM
  #46  
Tony Mamo @ AFR's Avatar
Flow Wizard
20 Year Member
iTrader: (13)
 
Joined: Feb 2004
Posts: 2,197
Likes: 7
Default

Originally Posted by bballr4567
Great info Tony! 8500 RPMs is a LOT to turn over on accident.
Sure is....LOL

But when your shifting WOT in the 7200-7300 range grabbing the next lower gear will tend to do that!

Honestly I stabbed the clutch quickly as the engine was exploding into the higher RPM's....if I hadnt it would have probably been slightly higher. I thought to myself as it happened that was easily 8K.....nope....it was a bit higher than that!

-Tony
Reply
Old Oct 4, 2008 | 07:26 PM
  #47  
tigerls1's Avatar
11 Second Club
iTrader: (2)
 
Joined: Sep 2005
Posts: 29
Likes: 0
From: Virginia
Default

I'm with Tony..it can happen to anybody...happened to me when I was drag racing a mustang trying to eke out a win...I wasn't as lucky as Tony I bent at least half my valves. It was over 8 years ago so thankfully it's a little fuzzy. Along with Tony I was an experienced racer with well over 200 passes on that car along with many other manual cars.
Reply
Old Oct 5, 2008 | 08:16 AM
  #48  
Chhh Chhh's Avatar
Banned
iTrader: (2)
 
Joined: Sep 2008
Posts: 113
Likes: 0
From: DFW
Default

Originally Posted by back in black
DO NOT DRIVE IT AGAIN. REPEAT. DO NOT DRIVE IT AGAIN.

first of all, i dont know why you would be flogging it like that after missing a shift and noticing something wrong.

pull the valve covers and check for bent pushrods, and any other problem.............naw. forget that, go ahead and pull the intake, accessories and heads. cause your gonna need some work.

one more thing.......learn to drive.
****** dick
Reply
Old Oct 6, 2008 | 10:17 PM
  #49  
scottHMT's Avatar
Thread Starter
Launching!
iTrader: (5)
 
Joined: Apr 2007
Posts: 237
Likes: 0
Default

Well, i ripped off the head, and everything looks kosher, no piston to valve contact marks, valves look OK, I think I am going crazy. Anyway, its H/C time since i've already gotten this far.
Reply
Old Oct 7, 2008 | 07:42 AM
  #50  
Pushead's Avatar
Staging Lane
 
Joined: Dec 2007
Posts: 99
Likes: 0
From: Cleveland, OH
Default

Originally Posted by scottHMT
Anyway, its H/C time since i've already gotten this far.
Exactly how I felt.

I didn't miss shift, I just floated the valves and ended up bending one:



Here's what happened to the head:




And here is the piston:



Consider yourself lucky!
Reply
Old Oct 7, 2008 | 07:57 AM
  #51  
lifeisgood's Avatar
11 Second Club
iTrader: (4)
 
Joined: Oct 2006
Posts: 1,029
Likes: 0
From: ky
Default

that sucks my buddy did the same thing a couple of years ago. its sounds like an exhaust leak. sry man
Reply
Old Oct 7, 2008 | 10:28 AM
  #52  
scottHMT's Avatar
Thread Starter
Launching!
iTrader: (5)
 
Joined: Apr 2007
Posts: 237
Likes: 0
Default

im willing to bet it was an exhaust leak or a fouled plug. one of my plugs was a bit dark. And wehn i pulled off the passenger side head, the header kinda just slid right out of the y pipe
Reply
Old Oct 7, 2008 | 12:02 PM
  #53  
HSESWS6's Avatar
9 Second Club
iTrader: (3)
 
Joined: Nov 2001
Posts: 282
Likes: 0
From: Central, IL
Default

I'm just putting my motor back in the car after doing the same thing as well in the first round of an event a couple of weeks ago shifted 3-2 at 6800 RPM and it over reved to 8050 on the data logger.

Noticeably bent 5 valves and left marks on all but one piston.









Reply
Old Jul 26, 2010 | 10:35 AM
  #54  
2000chargedss's Avatar
Teching In
 
Joined: Jul 2010
Posts: 6
Likes: 0
Default

Glad to hear I'm not the only one to do this because I did it yesterday! Scared the hell out of me but luckily everything seems to be ok...
Reply
Old Jul 26, 2010 | 12:04 PM
  #55  
SladeX's Avatar
TECH Addict
15 Year Member
 
Joined: Nov 2005
Posts: 2,379
Likes: 2
Default

been there with the 3-2 shift... not liking seeing the tach pegged at 7k...

it happens to the best of us, just count your blessings if nothing goes wrong.
Reply




All times are GMT -5. The time now is 07:09 PM.