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Wits end.


MarkB2PW

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I could use some help with my recently purchased stock 1950 Olds 88.
It ran a little rough when I first got it so I rebuilt the carburetor, new points, plugs, rotor, cap and adjusted the timing. When I step on the gas it still coughs and wants to die.

303 Rocket motor with 73,000 miles. It does idle ok. Setting the timing I went right by the book. I put the distributor clamp arm at "O" position, then rotated the distributor to get the crank pulley pointer in the middle of the machined slot. It ran worse after that. So, I put the distributor back to where it was when I started. I rotated the distributor clockwise almost as far as it would go and it ran much better. About 12 degrees.  BUT, it still coughs when I step on the gas.
The spring on the points seemed to have the same force as the ones I took out.

 

So, summing it up:

I replaced the coil,condenser, rotor, cap, points, plugs.
Rebuilt the carb.
Checked the compression. 75-80 psi.
Purged the fuel line and got fresh fuel.
Added a clear fuel filter so I could see if the carb was getting fuel (It is).
Checked the timing chain when I had the fuel pump off. It has about 1/4" play as checked from the fuel pump hole.
So, still same issue. It will fire up & run at low speed,but, when it warms up and I put load on it (drive up hill) it stumbles.


Ok, I accepted my automotive knowledge limitations and took it to a local shop in Placerville, Ca.
$154 later they told me that the 80 psi compression is enough for them to say the 303 Rocket needs to be rebuilt.


What do you think? I honestly don't know. How much compression is enough for smooth operation?
Thanks again for the help.

 

1950 Olds 88.jpg

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You might ask here:  https://forums.aaca.org/

 

Lot of folks there with  lots of information about various cars and make specific forums as well

 

Found this page with a search:

 

http://rocket100.com/olds-engine-specs/oldsmobile-303-rocket-v8-spec/

 

Home for the above page:  http://rocket100.com/

Edited by plymouthcranbrook
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10 hours ago, MarkB2PW said:

 

Checked the compression. 75-80 psi. 

 

That is the answer to your problem.  It will run but not well.  

 

If you want confirmation squirt a little engine oil in each cylinder and measure compression again.  

Edited by lonejacklarry
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3 hours ago, lonejacklarry said:

 

That is the answer to your problem.  It will run but not well.  

 

If you want confirmation squirt a little engine oil in each cylinder and measure compression again.  

The wet compression test with a little oil brought it up to 90psi. 

What are my budget conscious

options going forward? 

 

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5 hours ago, MarkB2PW said:

The wet compression test with a little oil brought it up to 90psi. 

What are my budget conscious

 

options going forward? 

 

There are no "budget conscious" options.  If you re-ring it and the valves need grinding you have not accomplished anything but depleting your checkbook.  If you re-ring it and do a valve job then you will still have oil pressure problems due to wear.  Maybe you could find another engine that might be better. 

 

Rings, pistons, main bearings, cam bearings, rod bearings, valves, etc.  Add in machine work and labor to pull the engine, rebuild the engine and reinstall the engine.  Buy yourself an engine manual for that engine and shop it around.  I'd be amazed if it came under $5,000.  

 

There is absolutely no sense in partially rebuilding the engine, in my opinion.  

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   The few things that I can think of are fuel quality, oil diluted with gas, because a bad fuel pump will work but still leak and go into the crankcase, vacuum advance, distributor is worn and points should be set to dwell not gap. The gap is .016, Set it at .011, it will change the dwell. It should be about 30. Check the dwell reading before and after you adjust the points and see if there is a difference in response. Re-check cap wiring. 

Edited by 9 foot box
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IMHO, the low compression is not the problem with the stumble/hesitation etc.

 

Low compression will definitely cause low power and/or oil burning.  But, the engine should still run smoothly,  IF the loss is fairly even across the cylinders and the valves are in generally fair to good condition. A leaky valve or two will always cause a rough idle and you stated that it runs good at low speed. Stumbles on acceleration are more often than not due to fuel issues.  Accelerator pump not providing a large enough shot, air leak in manifold or vacuum lines etc.  You can verify the pump operation easily, just watch the pump shot when opening the butterfly rapidly while looking down the carb throat.  I think that year of Olds used a carb with an adjustment for pump throw. 

 

 

Not to say the engine couldn't benefit from a rebuild, but be sure the carb and ignition are perfect.  'Cause if they're not, they won't be if on a rebuilt engine either.

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  • 4 weeks later...

UPDATE:

I was considering changing to 12 volts anyway so I put on a 12v coil, and alternator, lights...

Wow, what a difference.  It ran much better, not perfect, but better.

Then on the second test run, the fuel pump died!  So, I put on a new one and now it runs right. No more stumbling.

Maybe it was a combination of not enough spark or fuel?

I'm just happy to have a running classic again.

Thanks again for your help.

 

 

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