403 timing question

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Old Jul 3, 2021 | 01:27 PM
  #1  
liquify33's Avatar
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403 timing question

Bone stock’77 Vista Cruiser, EGR/ smog deleted (broken) and distributor vacuum line tee’d from transmission (manifold).
With distributor line disconnected and plugged it’s at 10* advance.

The timing chain came loose on a lemons rally, we installed a new set and I think the timing is off. We initially installed the timing 180 out so I reinstalled the distributor with the rotor pointing at #1 at TDC (0 mark on timing tab).

10* is all I can get without the vacuum hitting the firewall. Car runs smooth at idle, bogs at part throttle.

Main question: what should my timing be at with the distributor vacuum plugged?

Thanks in advance (no pun intended).




Old Jul 3, 2021 | 02:21 PM
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You need to get the engine at #1 TDC, pull the distributor and reorient the body so you'll have clearance. Then reinstall with the rotor pointing to #1.
Old Jul 3, 2021 | 04:40 PM
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Originally Posted by oldcutlass
You need to get the engine at #1 TDC, pull the distributor and reorient the body so you'll have clearance. Then reinstall with the rotor pointing to #1.
I was thinking I need to advance it a tooth. What ballpark degree should I be aiming for with the emissions stuff bypassed? Stock system was a weird hybrid ported w/EGR and a spark advance modulator that was found broken in the glovebox. I can’t tell if 10* is too much or not enough, great in P or N but a bog dog in D. It was not this boggy before the timing chain came loose, but when that happened any “how was it before” info went out the window.
Old Jul 3, 2021 | 05:35 PM
  #4  
olds 307 and 403's Avatar
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You want the 20 degree at 1100 rpm, that is usually the spec. I have seen 13 to 22 degrees at 1100 on Olds V8'S, so it does vary some. You can put the spark plug wires one post back to get enough advance without removing the distributor.
Old Jul 3, 2021 | 06:25 PM
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Originally Posted by olds 307 and 403
You want the 20 degree at 1100 rpm, that is usually the spec. I have seen 13 to 22 degrees at 1100 on Olds V8'S, so it does vary some. You can put the spark plug wires one post back to get enough advance without removing the distributor.
I may do that and test, I did not remember that trick until your reply. If it’s good I can fix it right later.

Thanks!
Old Jul 3, 2021 | 06:43 PM
  #6  
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Rather than pull the distributor you can accomplish the same thing by moving all the plug wires one tower on the cap.
Old Jul 3, 2021 | 06:47 PM
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If an engine is at TDC on the compression stroke, then rotated in the shortest direction to the base timing spec e.g.' 20° before stabbing the distributor with the rotor pointing at #1 it will start much more easily. When the engine is left at TDC 0° on the compression stroke and the spec is 20° the engine is struggling to start due to the timing being off by 20°.​​​​​​
Old Jul 13, 2021 | 09:30 AM
  #8  
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She's back!

@oldcutlass @olds 307 and 403 @joe_padavano @Sugar Bear
Thanks for the help fellas. I reinstalled distributor around 16*, did some ear tweaking and she's back! No bog at part or full throttle -- there may be further tweaking required but I'm gonna go cruise some Vistas and enjoy that marshmellow ride!

In case anyone else runs into timing problems after losing a chain: The fuel pump fits in perfectly at #1 TDC, but will not seat at #6 TDC. Lesson learned.

Thanks again for all of your help, I'll put up some pics of the old girl in the general thread soon. A basket case but FUN!
Old Jul 13, 2021 | 09:32 AM
  #9  
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Glad you got it.
Old Jul 13, 2021 | 11:53 AM
  #10  
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Originally Posted by oldcutlass
Glad you got it.
Thanks to the advice here! I did have to lube up the mechanical advance and the vacuum advance was slightly bent (maybe binding?).

Corrected those issues and all is well. I’ve been after this and a leaking gas tank for 2 weeks and she’s so happy now.
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