Transmissions and Drivetrain Need help with your trans? Problems with your axle?

Flexplate knock or spark knock due to timing way off

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Old Jun 10, 2020 | 08:33 PM
  #1  
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From: Utica NY
Car: 88 Trans Am
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3:42 open diff
Flexplate knock or spark knock due to timing way off

Well, talk about having butterflies in my stomach. I know this kind of might be somewhat unrelated. I got my car somewhat all done. When I removed my transmission to rebuild it I had to remove my distributor so it wouldn’t hit the firewall and I didn’t mark anything. I have done this many times before and have gotten lucky finding top dead center compression stroke on number one with my thumb on the spark plug hole.

I was so excited and I think I’m not really thinking clearly. I think I have my timing waay off and at this point I’m starting to panic because I am hearing a little bit of knocking that wasn’t there before. I guess flexplate knock should be a lot louder. The somewhat good news is that I was able to add coolant and try out reverse and drive which worked so I’m kind of out of the woods?? Also when I give it a little gas it stumbles.

I would greatly appreciate some help in this desperate time!!

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Old Jun 10, 2020 | 09:33 PM
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From: Utica NY
Car: 88 Trans Am
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3:42 open diff
Re: Flexplate knock or spark knock due to timing way off

Also I forgot to mention that the engine is shaking
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Old Jun 11, 2020 | 09:10 AM
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From: Utica NY
Car: 88 Trans Am
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3:42 open diff
Re: Flexplate knock or spark knock due to timing way off

Ok let me explain some additional details that just occurred to me. When I was trying multiple attempts inserting and removing the distributor I did come very close in which the car started within a touch of the key. By the time I could run over to the other side and put the hold down clamp in place, the neck lifted slightly. I do slightly remember the engine was not ticking.

In the subsequent attempts I was aiming the rotor at #8 thinking in my mind that it was close enough. I know I should be over in the engine forum. Is there a really good way of checking for tdc #1. I was using the vacuum gauge with a compression tester gauge hose with the Schrader valve removed
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Old Jun 11, 2020 | 10:09 AM
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Re: Flexplate knock or spark knock due to timing way off

Pull off the valve cover on the passenger side. Watch #6 rocker arms. While rotating the engine observe when the exhaust is almost closed and the intake is starting to open. That would represent TDC and cylinder one will be at the top of its compression stroke. Your timing pointer (if it's accurate) should reflect this.

Last edited by skinny z; Jun 11, 2020 at 05:52 PM.
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Old Jun 11, 2020 | 12:57 PM
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Car: '83 Firebird (T/A Clone)
Engine: 350 with L-69 components
Transmission: 700R-4, 2000 RPM stall converter
Axle/Gears: 10-bolt/3.73 ..
Re: Flexplate knock or spark knock due to timing way off

Adjust your timing with a timing light. It's either right or it isn't. I doubt you installed your distributor that far off...
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Old Jun 11, 2020 | 02:06 PM
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Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Re: Flexplate knock or spark knock due to timing way off

This is easy to get right, just don't rush it. If you need to, go back and get TDC on compression stroke of 1 with your finger and then check the distributor. Reset it if needed. Install the clamp and bolt. Loosen a little but do not remove the clamp. Just enough clamping so that you can turn the distributor by hand with some effort. That way it won't move on you. When I rebuilt my 350 and fired it up I was off two strokes! It ran like crap. No harm in it though.
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Old Jun 11, 2020 | 02:59 PM
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Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: Flexplate knock or spark knock due to timing way off

It's in! Finally!

Just to pile on:

1. Remove #1 spark plug.
2. Rotate engine until timing mark is at TDC.
3. Stick a screw driver or other probe into #1 spark plug hole.

4. Feel for the piston.

5. If the engine is at TDC, #1 on compression, you'll feel the piston up near the top.
6. If you don't feel the piston near the top, the engine is at TDC #6 compression.

7. Install the distributor with the rotor is pointing at either the #1 or #6 plug wire (determined in Step 5 or 6).

This should be close enough to get the engine to run.

8. Connect timing light, adjust to spec (or where ever).
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Old Jun 11, 2020 | 05:49 PM
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Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Flexplate knock or spark knock due to timing way off

Originally Posted by paulo57509
It's in! Finally!

Just to pile on:

1. Remove #1 spark plug.
2. Rotate engine until timing mark is at TDC.
3. Stick a screw driver or other probe into #1 spark plug hole.

4. Feel for the piston.

5. If the engine is at TDC, #1 on compression, you'll feel the piston up near the top.
6. If you don't feel the piston near the top, the engine is at TDC #6 compression.

7. Install the distributor with the rotor is pointing at either the #1 or #6 plug wire (determined in Step 5 or 6).

This should be close enough to get the engine to run.

8. Connect timing light, adjust to spec (or where ever).
A little flaw in your logic - steps 5 and 6.
The pistons for #1 and #6 are both at TDC at the same time - it's just that one is on the compression stroke and the other is starting on it's intake stroke.
They are 180 degrees apart. The same goes for numbers 8 and 5, 4 and 7, and 3 and 2.
You could actually connect your timing light to #6 plug wire and set your timing. The mark on the balancer and timing tab will not know the difference.
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Old Jun 11, 2020 | 05:52 PM
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Re: Flexplate knock or spark knock due to timing way off

Originally Posted by skinny z
Pull off the valve cover on the passenger side. Watch #6 rocker arms. While rotating the engine observe when the exhaust is almost closed and the intake is starting to open. That would represent TDC and cylinder one will be at the top of its compression stroke. Your timing pointer (if it's accurate) should reflect this.
I still think this is easier.
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Old Jun 11, 2020 | 07:14 PM
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From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: Flexplate knock or spark knock due to timing way off

Originally Posted by NoEmissions84TA
A little flaw in your logic - steps 5 and 6.
The pistons for #1 and #6 are both at TDC at the same time - it's just that one is on the compression stroke and the other is starting on it's intake stroke.
They are 180 degrees apart. The same goes for numbers 8 and 5, 4 and 7, and 3 and 2.
You could actually connect your timing light to #6 plug wire and set your timing. The mark on the balancer and timing tab will not know the difference.
Sorry. The dementia is setting in these days.
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Old Jun 11, 2020 | 07:43 PM
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Re: Flexplate knock or spark knock due to timing way off

Originally Posted by paulo57509
Sorry. The dementia is setting in these days.
I know the feeling well...!
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Old Jun 11, 2020 | 07:54 PM
  #12  
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From: Brainerd, MN
Car: '84 Trans Am
Engine: 357 SBC
Transmission: 700R4
Axle/Gears: 10 Bolt 3.73, Torsen Diff
Re: Flexplate knock or spark knock due to timing way off

Is there any change you're not getting oil pump shaft into the distributor?
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Old Jun 11, 2020 | 08:13 PM
  #13  
zupta82's Avatar
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From: Utica NY
Car: 88 Trans Am
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3:42 open diff
Re: Flexplate knock or spark knock due to timing way off

Thanks everyone I figured it out, I ended up using a vacuum gauge.
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Old Jun 11, 2020 | 08:39 PM
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Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Flexplate knock or spark knock due to timing way off

Originally Posted by skinny z
I know the feeling well...!
I keep telling myself that it's because I have too much on my mind. But sometimes I'm not so sure.
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Old Jun 11, 2020 | 08:50 PM
  #15  
zupta82's Avatar
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From: Utica NY
Car: 88 Trans Am
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 3:42 open diff
Re: Flexplate knock or spark knock due to timing way off

I just posted in another related post about the new problem I discovered during the test drive. The car feels very sluggish
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