After rebuilding engine when attempting to start it there is banging and will not start

Tiny
FIVEMOBBS
  • MEMBER
  • 1997 CHEVROLET SUBURBAN
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
I rebuilt the motor and now when trying to start it there is a banging when turning it over and it won't start. It sounds like it coming from the driver's side. It doesn't even sound like it is trying to start. What could be the problem?
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Sunday, June 28th, 2020 AT 6:09 PM

12 Replies

Tiny
FIVEMOBBS
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Sunday, June 28th, 2020 AT 6:11 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The engine isn't timed correctly. I can tell simply by how fast it is turning. There is no compression.

Don't continue cranking it until we confirm something. First, this shouldn't be an interference engine, but I don't like the sound of the banging. Take a look at the attached picture. Is that how you had the timing marks on the crank and cam shafts when you installed the timing chain?

Let me know.
Joe
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Sunday, June 28th, 2020 AT 9:35 PM
Tiny
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I did line up the 2 dots if remember correctly.
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Sunday, June 28th, 2020 AT 9:44 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Then something else is wrong. The engine has no compression. That is why it sounds the way it does. It sounds like the spark plugs are removed. If the timing was correct, the only other thing I can think of is if you over tightened the rocker arms in the heads and the valves are not closing. Did you adjust the valve lash? See pic 1.

Let me know.
Joe
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Sunday, June 28th, 2020 AT 10:15 PM
Tiny
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I did not! Is it something I can do with it in the truck or do I need to pull the motor again?
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Sunday, June 28th, 2020 AT 10:25 PM
Tiny
FIVEMOBBS
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Would that also cause that slapping noise while cranking?
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Sunday, June 28th, 2020 AT 10:29 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
No need to remove the engine. If you didn't remove the rocker arms, that shouldn't be the issue. I honestly feel the timing marks were off. When you installed the chain and gears, are you certain that the marks were as indicated in the picture I sent? That's the only thing I can think of that would cause it. If you perform a compression test, I think you will find very little compression.

Also, let me know what all was replaced in the engine when you had it apart.

Joe
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Sunday, June 28th, 2020 AT 10:32 PM
Tiny
FIVEMOBBS
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All valves and push rods. Timing set. Everything else was cleaned and checked by a mechanic friend that told me that the rest was good. I checked the timing again today and it was good. I did have the rocker arms off and when I re-installed them I tightened them to a torque spec I found online. I didn't know about valve lash. I just watched a video from Summit Racing on how to do it. Is this the proper way?

https://www.youtube.com/watch?v=8ROU7D-6meY
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Sunday, June 28th, 2020 AT 10:44 PM
Tiny
FIVEMOBBS
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I originally had a blown head gasket and wanted to do as much as I could afford to do. So I pulled the motor and had at it since it was a spare vehicle. I rebuilt the transmission in it so I figured why not try the motor.
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Sunday, June 28th, 2020 AT 10:47 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Here are the directions for adjustment. There really isn't a torque spec. Basically, you loosen the rocker and then tighten it until lash is taken away. Then, you turn the nut one more full turn.

The noise you hear may be a rocker arm that is off or too tight.

Here are the directions:

__________________________________________

1997 Chevy Truck C 1500 Suburban 2WD V8-5.7L VIN R
Valve Adjustment Procedures
Vehicle Engine, Cooling and Exhaust Engine Camshaft, Lifters and Push Rods Lifter / Lash Adjuster Service and Repair Removal and Replacement Valve Adjustment Procedures
VALVE ADJUSTMENT PROCEDURES
VALVE LASH ADJUSTMENT

pic 1

1. Remove the valve rocker arm cover.
2. Crank the engine until the mark on the crankshaft balancer lines up with the timing mark on the front cover and the engine- is in the number one firing position. This may be determined by placing fingers on the number one valve as the mark on the balancer comes near the timing mark on the front cover. The valve rocker arms are not moving, the engine is in the number one firing position. If the valve rocker arms move as the mark comes up to the timing mark, the engine is in the number six firing position. Rotate the crankshaft 360 or one complete revolution in order to reach the number one position.
3. With the engine in the number one firing position as determined above, adjust the following valves (Even numbered cylinders are in the right bank. Odd numbered cylinders are in the left bank):
- Exhaust: 1, 3, 4, 8
- Intake: 1, 2, 5, 7
4. Back out the adjusting nut until lash is felt at the pushrod then turn in-the adjusting nut until all lash is removed. This can be determined by rotating the pushrod while turning the adjusting nut. When the play has been removed, turn the adjusting nut 360 or one full additional turn in order to center the valve lifter plunger.
5. Crank the engine one revolution until the timing mark on the front cover and the crankshaft balancer mark are again in alignment. This is the number six firing position. The following valves may be adjusted:
- Exhaust: 2, 5, 6, 7
- Intake: 3, 4, 6, 8
6. Install the valve rocker arm cover.

_________________________________

Let me know if this helps.

Joe
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Sunday, June 28th, 2020 AT 11:07 PM
Tiny
FIVEMOBBS
  • MEMBER
Sorry for not replying sooner. You are amazing! Set the valve lash and boom fires right up. The banging sound was a torque converter bolt hitting. Put a shorter on in and no more banging. Thank you again for all your help.
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Wednesday, July 1st, 2020 AT 10:07 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
You are very welcome. I could hear that there was little to no compression, so other than timing, that was my next guess.

Regardless, I'm happy to hear it's running for you. Feel free to come back anytime in the future that you need something.

Take care of yourself,
Joe
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Wednesday, July 1st, 2020 AT 9:43 PM

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