I have a 455 oldsmobile that lost power while I was driving once I stopped it would not start again. I have replaced spark plugs have spark fuel and air when I turn it over it'll fire but very rough and will not run I have the firing order right 18436572 going ccw. When I have looked up diagrams online it has shown the #1 on the distributor on the right side front I have tried this and had no luck but when I put #1 as back side left this is when it'll fire really rough but will not start running out of ideas any help is much appreciated.

 

Has the motor ever been rebuilt? Possibly your timing chain jumped teeth on a worn out cam gear. Or easier... possibly bad points, condenser, or coil. Cracked distributor cap.

 

As stated above, your going to have to do some trouble shooting. You can check dwell and timing just by cranking the engine.

 

No clue if the motors been rebuilt or really any history on it it is put in a pontiac firebird so not sure if anything was adjusted or changed while they put the motor in.

 

Never really had these engine issues before so how am I able to check timing and dwell just by cranking it over? And what are you referring to when you say dwell

 

Does it have points?

 

Yes it has points

 

Do you have a tach/dwell meter and a timing light?

 

Lets start with verifying that your distributor is pointing to #1 when the engine is at #1 TDC. Then double check that your wired according to your firing order from there. Then hook up your dwell and timing light, have someone crank the engine a bit and ensure you have a steady dwell of 30. Then have them crank the engine again and verify that your timing is at the proper setting, probably around 7-10 degrees before TDC.

 

Had it been running good prior to this problem? Any work done on it lately?

 

Was the #1 plug wire on the right front when you first started working on it, and now you have to put the firing order 180° out to make it even run? If so the timing has some how jumped, chain or distributer gear, sheared pin? If so that is probably where I would start. If the # 1 plug wire was always at the rear I would take all the wires off, dist out and start all over. Put the #1 plug wire terminal on the cap pointing towards the left front plug on the motor. Consistentsy make its easier on me.

 

If you have no idea of history of the motor, if you have never tuned it up, you might just try new points, condenser, rotor, cap, coil, plugs, and plug wires. I also use Berrymans B12 carburator cleaner, works great better than Sea Foam IMO. If that dosent help, you can pull the fuel pump and feel the timing chain through the hole see if it has alot of slack, or if you have an inspection cam put it in the hole and look at the chain and gears. Alot of GM motors had a nylon tooth cam gear, which will eventually disintegrate. If yours does and did, the timing chain probably jumped one or more teeth. If so, its time to replace chain and gears.
Steve

 

From his first post, sounds to me like it was a running driving car, and it took a big dump on the road. Could be a number of issues.

Steve

 

we are all using "left" and "right" as _the car's_ L&R, not the observer's... yes ?


I have a 455 oldsmobile that lost power while I was driving
once I stopped it would not start again.
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stumbling to a halt tends to indicate a fuel issue
sudden halt tends to indicate ignition fault


I have replaced spark plugs
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gapped correctly?


have spark, fuel, and air
================
Strong spark at the right time and place
Fuel by means of a good carb?
Air is getting compressed well according to your compression gage?


when I turn it over it'll fire but very rough and will not run I have the firing order right 18436572 going ccw.
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Back to basics. Set point gap to 0.018"
feel for actual compression at #1 plug
then slowly bring timing mark to 10 BTDC
Then set dist'r so that spark is just happening [pts are just opening]
Then see where rotor is pointing
Put #1 wire there, and others in order ccw about the cap.
Verify spark at coil output, then at the plugs.

 

The OP said it lost power while driving. I bet it jumped a tooth.

 

This sounds logical to me but never gonna hurt to check other stuff anyway.

You say when you stopped it did this. You mean stop at a light or when you parked it and shut it off? The chances of it being certain things is slim if it was an abrupt difference. Jump a tooth, yes. Points/condenser going bad, yes. Check those little wires back by the dist. They're known to get funny..

But sounds like timing issue to me

 

lol I say it jumped time, probably wore all the nylon off the cam gear and skipped a tooth or two. I have picked up a couple good engines because of that. get a good chain and gear set and swap that crap out , might want to drop the oil pan if I am right and get as much of that nylon gear out of your oil pump pick up and pan before it causes a starvation issue.