A little LT1 help please....
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
A little LT1 help please....
Aloha all, I need to ask for some help for my dad's 92 LT1. He recently pulled the heads to do some repair work on a bad plug socket. In the process he removed the corresponding bracketry and hardware to access the job.
Upon reassembly he lashed the valves according to the GM service manual and all seemed OK until it was time to start her up.
Infact, the car was unable to start and run on it's own. There is backfiring coming up through the intake and it's evident from the popping in the rubber intake tract to the TB. It would seem to be that there is a mechanical problem as there are no service codes. Before he goes ahead and relashes the valves or disassembles the electronics again, I wanted to ask you all for your expertise.
Please post up if you know what the problem may be.
Mahalo, Dave :thumbs:
Upon reassembly he lashed the valves according to the GM service manual and all seemed OK until it was time to start her up.
Infact, the car was unable to start and run on it's own. There is backfiring coming up through the intake and it's evident from the popping in the rubber intake tract to the TB. It would seem to be that there is a mechanical problem as there are no service codes. Before he goes ahead and relashes the valves or disassembles the electronics again, I wanted to ask you all for your expertise.
Please post up if you know what the problem may be.
Mahalo, Dave :thumbs:
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Re: A little LT1 help please.... (EFI-1)
Sounds like the valve lash is wrong.Way to tight.If you overtightend a lifter, the valve won't fully close and you'll hear it popping back though the intake. :chevy
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Re: A little LT1 help please.... (EFI-1)
How far past zero lash did your manual say?
If it said 1 full turn then you are to tight.
GM states 1 full turn past zero lash but that is way to tight.
Only go 1/2 turn past zero lash.
I didn't go into how to set the valves to much because there are a lot of post on valve adjustment if you need more info do a search and you should find what you need.
If it said 1 full turn then you are to tight.
GM states 1 full turn past zero lash but that is way to tight.
Only go 1/2 turn past zero lash.
I didn't go into how to set the valves to much because there are a lot of post on valve adjustment if you need more info do a search and you should find what you need.
Drifting
Joined: Jul 2002
Posts: 1,273
Likes: 0
From: Olathe, KS USA
Re: A little LT1 help please.... (SPEED750)
Sounds like the valve lash is wrong.Way to tight.If you overtightend a lifter, the valve won't fully close and you'll hear it popping back though the intake. :chevy
Hope this helps, Good luck. :seeya
PS. My LT1 does run with the lash set at 1 full turn, double check all your plug wires.
[Modified by C4Crazy787, 1:09 AM 11/28/2003]
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Re: A little LT1 help please.... (C4Crazy787)
Thanks for all the help gang. I have relayed the info to my dad and he will be rechecking the lash this weekend. I read the shop manual and it does state 1 full turn once lash has been set to zero. I have always used only a 1/4 turn, but I figured maybe the LT1 runs a little tighter....
Again, thanks for all of the help in the matter, and I'll keep you all posted on the outcome!
Aloha & Happy Turkey Day, Dave
Again, thanks for all of the help in the matter, and I'll keep you all posted on the outcome!
Aloha & Happy Turkey Day, Dave
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Re: A little LT1 help please.... (93 ragtop)
This probably is not the problem, but id check the firing order of the wires before tearing back into the motor.
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Re: A little LT1 help please.... (EFI-1)
Dear C4 Friends: Many thanks for all your help and encouragement. I backed off 3/4 turn on all the rockers last night and the car started right up. In the recent past, I replaced all the plugs, installed new Delco wires, and rebuilt the Optispark. The new wires are not labeled like the stock ones, so I have been very paranoid about their order. Also, when I set the valves initially, I was careful to set 0 lash without preloading each lifter(the lifters all compress as soon as you load them and the pushrod will turn after a couple of seconds), so my settings should be as close as you can get with an engine-off setting. In the "Old Days", I always set the lifters on my small blocks with the engine running and always 1/4 turn in from 0 lash. On this '92, the AIR, fuel rail, A/C-Alternator mounting bracket and harnesses have to be pulled to access the valve covers. This makes engine-on setting a bit difficult and I'm not so sure that engine-on setting is any more accurate. Right now the car is running strong, thanks to your help. EFI-1's Dad
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Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Re: A little LT1 help please.... (EFI-1)
Good job on getting the car up and running. At least you have the option of how you want your valves adjusted. A lot of people set the valves at 1/4 (Including my machinist), I usaly set them at 1/2, but I installed non-adjustable LT4 1.6 RR and they hit torque spec. at 3/4 of a turn past zero lash. My car runs fine so I guess its ok but I may go to shorter push rods to get it back between 1/4 and 1/2 turn.
Drifting
Joined: Jul 2002
Posts: 1,273
Likes: 0
From: Olathe, KS USA
Re: A little LT1 help please.... (84LT1)
On my 92 LT1 I have never had to remove my fuel rail to get the valve covers off, if I did that every time I pulled the vc's the O'rings would be worn out. I use the fuel rail cover bolts to hold the fuel injector harness up and out of the way, vc's slip on and off no problem. :seeya
Le Mans Master
Joined: Nov 2002
Posts: 7,080
Likes: 0
From: Corvette valley Georgia
St. Jude Donor '06
Re: A little LT1 help please.... (84LT1)
How far past zero lash did your manual say?
If it said 1 full turn then you are to tight.
GM states 1 full turn past zero lash but that is way to tight.
Only go 1/2 turn past zero lash.
I didn't go into how to set the valves to much because there are a lot of post on valve adjustment if you need more info do a search and you should find what you need.
If it said 1 full turn then you are to tight.
GM states 1 full turn past zero lash but that is way to tight.
Only go 1/2 turn past zero lash.
I didn't go into how to set the valves to much because there are a lot of post on valve adjustment if you need more info do a search and you should find what you need.
:iagree: