Projects Could use some help with my recently purchased 1950 Olds 88

I'm new to the forum and 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.

Yep 303 Rocket with 73,000 miles. It does idle ok. Setting the timing I went right by the book. I put the dist. 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. BUT, it still coughs when I step on the gas.
It did not always stumble, only since I put the new points, rotor and cap.( I did not change the condenser).
The spring on the points seemed to have the same force as the ones I took out.

Any ideas are welcome.

 

The usual answer here is to check for your timing mark being on TGC. The damper may have moved

 

Late timing will cause an acceleration stumble, see which way the rotor turns, turning the distributor the other direction advances the timing. Keep advancing the timing until you get a little " spark rattle" or " pinging" and back it up a little. The carburetor being too lean will cause a stumble as well. Look in the carb and crank the throttle, you should see the accelerator pump " squirt" a stream into each throat. Also backing out the idle mixture screws can help a little..NOW if you have to buy this ethanol blended shit we get in New Jersey you will probably have to get a set of " number drill bits" and drill one or two numbers bigger and try it ....repeat as necessary....

 

A 50 Olds has a solid crank pulley. The coil out put could be low. The timing chain could have a lot slack.

 

If the engine has never been apart in 73,000 miles it needs a timing chain. It may have already jumped one tooth. This was very common back in the day.

 

You may want to check your points adjustment again, preferably with a dwell meter, also are you sure the accelerator pump is working?

 

Accelerator pump … Rochester or Carter ? Hope you kept any serviceable parts from the distributor.

 

Oh Mark, forgot to tell you on your intro that the forum boys (like me) really like to see pics

 

Well that's a lot of things for me to look at this coming week. I'll let you know what worked. Here's a couple of pics of my "new" car. I look forward to cruising to my local cars&coffee this spring.

 

sweet Mordor Mark! That looks to be in great shape.

 

This is it

 

Mark I would suggest that you fill out your profile. If you are close to me I would help you as will others here. I run a 49 olds v8 in my roadster and I am familiar with them. Welcome to the forum, Gary

 

Gary, Thanks for the welcome. I would have taken you up on the help, but, I left Wisconsin back in 1978 to work for Uncle Sam.

 

Cool ride!
Before throwing any more parts at it run a compression check. Also if you've put a few miles on those new plugs when you pull them they may tell you something too.

 

I would think it has the Rochester AA 2barrel back-draft carb. These have a flat diaphragm accel pump which is "gear driven". You need to have made sure the gear teeth "timing" on the accel pump is correct to insure that there is the proper volume at the nozzles.

If I remember correctly, being a back draft, it is not possible to "see" if the squirters are working properly.

The best & complete rebuild info I have seen for Rochester AA is in the later 50s Chilton manuals, (and I have found that MoTors Manuals have almost no in-depth info on the AA).
.

 

How do the wires look? I think you should save yourself a world of grief by selling the car to me.

 

The Old Car Manual Project has a Rochester manual posted also. It is for AA carbs from '49- '50.

 

Everything above is correct, and necessary.
I'd add fuel line. From experience, don't ask.

 

Nice 88. About 22-23 years ago we had a couple young guys who drove a black 50 four door just like yours. They got all liquored up one afternoon and decided to rob a bank. They were drunk enough to forget an old black olds would stick out like a sore thumb and were dumb enough to drive the olds back to their house to count up the $$$...parked it in their alley and before they could finish counting their loot, the cops had arrived. I never saw that olds again.
Good luck with finding your tuning problem.
BTW, in my small Oregon town, we had a lot of those 50s olds. The best improvement the young guys did to them was change the electric system over to 12 volts.

 

Check Compression - easy enough
Check Points with a dwell meter- easy enough
Timing chain- I'll have to investigate that effort
Accelerator pump - Do you mean the one in the picture that I replaced when I rebuilt the Rochester AA Carb? Or is it something else?
Wires- easy enough
Fuel Line- easy enough

I can check most of these this weekend.

 

To do a quick check of the timing chain, first remove the distributor cap. Then turn the engine over by hand until the rotor moves. Mark the crank pulley for reference with the timing mark. Now turn the engine over in THE OTHER DIRECTION until the rotor just starts to move. Note how far the crank pulley has moved from your mark. If more then 1/4" your timing chain is stretched and loose. Another way is to remove the fuel pump and turn the crank pulley CCW to put the slack in the chain on the pump side. Now stick your finger in the fuel pump hole and you should be able to feel the timing chain to check for slack. I have done this on a few V8's, I think it will work on an Olds Rocket motor also.

 

Yes, the accelerator pump in the carb. As Frank mentioned earlier it is kinda hiding, and I don't know how you could check it's function without removing the carb.

 

At 73,000 miles the timing has pretty much had the meat. Grab the distributor and give it a bunch of advance for the time being. A 50 timing chain is the same as a 75 455. A new chain at NAPA is cheap. The sprockets are not the same.

 

Well I got sidetracked by another project but I'm back to the Olds 88.
So 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 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.

 

My Motor's Manual from 1957 lists your compression ratio at 7.25 to 1, and lists minimum pressure at cranking speed at 120 psi. You may want to do a leakdown test, you might get lucky and get by with a valve job, instead of a complete rebuild. Hopefully some others will chime in.

 

What happens when you just rev the engine when not moving ? Does it rev up or stumble then ? Does the car want to coast ok ?

 

not familiar with that year but did they have a vacuum advance?just asking as that is something I would check.

 

Do this: Join the Olds Club. Best way to get parts and good advice on these engines. If you need a valve job and you don't have too much wear in the cylinder bores, find a set of #10 heads. That's where the Olds Club comes in. A set of #10 heads and a 550cfm Edelbrock carb will wake that car right up.

 

Unlike the cars of today that are still going strong with 200K on the clock, cars of that era were looking for a ring & valve special at 75K.

 

Maybe this line from your initial post is a clue:

"It did not always stumble, only since I put the new points, rotor and cap.( I did not change the condenser)."

Check under the cap for moisture.

Was the carburetor rebuilt before or after you experienced the stumble?

Low compression shouldn't cause a stumble.