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Knocking on Cylinder 6?

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Old Mar 10, 2016 | 10:25 AM
  #1  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Knocking on Cylinder 6?

Sorry if it's the wrong place to post, but I need help.

Last night while driving, I noticed I'm having a massive loss in power. 0-60 felt like it went up to 10.
I swear it felt like the acceleration of my friend's v6 mustang.
Then on stops, my oil pressure hits red. I believe there was a time I even reached the far red point of the gauge.

Once I got home, popped the hood, it sounds normal. I pulled the throttle a little bit and as the rpm slightly rose, there's a knocking noise. It sounded like theres a rock in my engine.
It's either barely noticeable or non existing when it's on idle.

Okay now when I pulled the spark plug wires on a few cylinders, there's no knocking sound. But once I take off the wire on cylinder 6, the knocking is apparent even on idle. So I guess with this diagnosis, the problem is on cylinder 6?

What's the fix on this and what is wrong?
Please help.
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Old Mar 10, 2016 | 11:01 AM
  #2  
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From: Temecula, CA
Car: 1989 Pontiac Formula 350
Engine: L98
Transmission: 700R4
Axle/Gears: BorgWarner 3.27 Posi
Re: Knocking on Cylinder 6?

Oil pressure dropping? Engine knock.

Unless you are really lucky, it's rebuild time.
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Old Mar 10, 2016 | 11:06 AM
  #3  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Originally Posted by thtanner
Oil pressure dropping? Engine knock.

Unless you are really lucky, it's rebuild time.
I wanna be really lucky right about now.
Lol
How much is a rebuild without really improving anything?
I only have a few days left at work since I'm leaving for basic training.

Without me being lucky, selling it is an option.
But I really hate just thinking about it.
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Old Mar 10, 2016 | 12:02 PM
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From: Temecula, CA
Car: 1989 Pontiac Formula 350
Engine: L98
Transmission: 700R4
Axle/Gears: BorgWarner 3.27 Posi
Re: Knocking on Cylinder 6?

It cost me 3200 for my rebuild. That included removal, the rebuild, and re-installation. Replaced most hoses, the radiator, water pump, bunch of stuff (all ACDelco parts). 2y24k mi warranty. The labor cost a lot, like 900 for removal, 900 for reinstall. That was my choice as I wanted them to do all the work and warranty it (very reputable engine rebuilding shop).
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Old Mar 10, 2016 | 04:32 PM
  #5  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Originally Posted by thtanner
It cost me 3200 for my rebuild. That included removal, the rebuild, and re-installation. Replaced most hoses, the radiator, water pump, bunch of stuff (all ACDelco parts). 2y24k mi warranty. The labor cost a lot, like 900 for removal, 900 for reinstall. That was my choice as I wanted them to do all the work and warranty it (very reputable engine rebuilding shop).
You know how much it would run me in parts if me and my friend do the rebuild ourselves?

He's got the tools and has done a rebuild on his car.
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Old Mar 10, 2016 | 08:33 PM
  #6  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Will this rebuild kit work just fine for a stock rebuild?

Summit Racing Parts #: FEM-CSMHP761-000

Last edited by rubblerubble; Mar 10, 2016 at 09:35 PM.
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Old Mar 11, 2016 | 09:37 AM
  #7  
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
Re: Knocking on Cylinder 6?

Post #2 sums it up. As for the loss of power the ECM is retarding the spark timing thinking that the rod knock is real knock.

RBob.
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Old Mar 11, 2016 | 11:42 AM
  #8  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Drove the car today. First run for the day and oil pressure was pretty normal, didn't hit the red part of the gauge, still loss of power. Knocking isn't really noticeable when the hood isn't open.
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Old Mar 11, 2016 | 11:44 AM
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From: Temecula, CA
Car: 1989 Pontiac Formula 350
Engine: L98
Transmission: 700R4
Axle/Gears: BorgWarner 3.27 Posi
Re: Knocking on Cylinder 6?

More you drive it, more internal damage you cause.
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Old Mar 11, 2016 | 11:49 AM
  #10  
rubblerubble's Avatar
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Originally Posted by thtanner
More you drive it, more internal damage you cause.
Sorry for being insistent but will this kit work for a stock rebuild?
Summit Racing Parts #: FEM-CSMHP761-000

My friend agreed to help me do the rebuild.
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Old Mar 11, 2016 | 11:54 AM
  #11  
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From: Temecula, CA
Car: 1989 Pontiac Formula 350
Engine: L98
Transmission: 700R4
Axle/Gears: BorgWarner 3.27 Posi
Re: Knocking on Cylinder 6?

Appears so, but you can contact the mfg to be sure.

Just make sure you'll have access to proper machine tools. A rebuild is not just taking it a part and putting it back together. Some skilled machine work will need to be done, and you may find one or both of your heads will need replacement depending on what went wrong. Coolant passageways in a head can crack when the engine overheats, ruining the head.
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Old Mar 17, 2016 | 07:09 PM
  #12  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

Will this cam, Summit Racing Part Number:SLP-CS-1573 work for my stock rebuild?
I'm gonna get the engine pulled tomorrow, don't wanna buy something that's not gonna be okay.

Will I also need new springs or retainers etc?
I see that flat tappet camshafts are cheaper but has higher lift than a roller like this, but would those work with this stock rebuild?

Would I also need new connecting rods? I have a strong feeling the cause of knocking is a rod bearing.

Last edited by rubblerubble; Mar 17, 2016 at 07:14 PM.
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Old Mar 17, 2016 | 08:41 PM
  #13  
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From: TX
Car: 1992 Firebird Formula 350
Engine: 5.7L V8 L98
Transmission: 700r4
Re: Knocking on Cylinder 6?

bump
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