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The long Maine winter helped me tackle some big projects. Many of you were a big help with the 1949 Olds 88 restoration! Today was the maiden test drive after every major mechanical system (and lots of body work) was done. The original 303 with 30,000 miles fired right up and ran great for the first 15 min or so. Then it began to stumble a bit. I’ve replaced the plugs, ignition system, set idle, dwell and timing all to spec. New exhaust system. After an hours drive it began to run so poorly I had to pull off the road. Backfiring through the air filter. It ran better at wide open throttle, but still wasn’t “right”. I’m suspecting vacuum leak. Maybe at the intake manifold? Ideas?
It could be a condenser. I don't care if it is brand new. Most of the chinese stuff is junk. I had one in my 54 that didn't last 300 miles. The car would barely run. Now I buy the NOS Delco Remy stuff that is made in the USA off ebay. The current Delco stuff is either made in Mexico or China. One other thing could be dirty gas tank and/or fuel line. A bad coil can do strange things also.
Good thoughts but I don’t think it’s any of those. I got the Elgin (USA made) condenser and even tried the original. No change. Can’t be fuel, it’s all new, as are the filters. Mechanical pump is working and aux electric pump is as well. The aux pump is on a switch. I see no difference with it on or off. I added it for hot starts. Keep those ideas coming and I’ll try em! I’m enjoying an unexpected afternoon in a random parking lot at the moment! Waiting for the car to cool down. Hoping it runs better again when cold. I’ve got another 20 miles to home.
Could be vacuum leak, but I’d definitely check what vacuum you are capable of maintaining at idle. You sure carburetor A/F mixture is correctly established to specs? Could certainly be A/F mixture (vacuum) is poorly adjusted.
Since you’re looking for ideas, when it does this again, immediately pull a plug and check to see if it’s saturated with fuel.
EDIT: Actually I said that backwards. Check the plug for being white hot instead of saturated w/ fuel since you’re backfiring through the carburetor which would be an indication you’re far too lean and that’s most likely causing the engine to heat up as well.
Last edited by Vintage Chief; April 3rd, 2021 at 12:59 PM.
Made it home! Barely!!! Easter miracle for sure. Pulled all the plugs. None are fouled. All look very clean after the two hour drive. However, two plugs on the passenger side looked BONE DRY. Odd. I wonder if I have an issue with valves? I then checked for vacuum leaks at the carb and intake manifold using both propane and carb cleaner. I cant seem to see or hear any leaks. I swapped out the coil for a new one from Napa on the way home. I had an Echlin IC-9 (a 6v coil) on it before that tested good. I was told at my Napa that the correct part number is IC7SB. Thats a 6v coil too. I am using the stock 6v. So coil is out. I am curious about the difference between the IC-9 and the IC-7 coil... Either way, it didn't change a thing.
I have no reason to believe any of my carb settings changed. It was a total carb rebuild that I did myself. It had this stumbling problem before all the work was done. My carb rebuild and adjustments using a vacuum gauge, timing light and dwell meeter helped it run much smoother at idle, but this recurring issue happens once its been driven a bit.
Does it have a vented gas cap? It has that goofy carb that 49's and 50's had so you can't take the air cleaner off and look down the carb and see if it is getting gas. We are all just guessing at things it might be and going through a process of elimination.
Were all on the same page anyway! haha. I replaced the fuel cap as part of the restoration. Remember, it was dong this before all the work I did. The work I did certainly helped acceleration. It's MUCH smoother when its running right. I just hooked up the timing light to see if the distributor timing changed. It didn't change, but I did discover something new. My spark is super weak and erratic. I swapped out known to be good points and condenser for a new Pertronix unit I'd been saving. No change. I wonder why ignition is so weak? What am I missing?
* new Optima battery
* new American made coil
* new Pertronix ignitor electronic ignition/new points and condenser also tested
* new cap
* new Standard rotor
Prior to suspecting the distributor (at this point), I would double-check your spark plug wires - i.e. two plugs on the passenger side looked BONE DRY. Of course, the question is why?
(1) Double-check your spark plug wire(s) routing to ensure (double-check) the wires are routed correctly to the distributor cap; and,
(2) Test the resistance of each spark plug wire to ensure all spark plug wires fall within the same range of resistance to one another.
Regarding spark plugs:
(1) They should all be of the same color - a light chalky brown - not black, and not white.
(2) White = too lean
(3) Black/Dark/Sooty = too rich
For the two passenger side spark plugs which appear to look BONE DRY, what color are they? Do they match the same color as the remaining spark plugs?
The next thing I would be certain of is your tune-up method. I mention this because some folks are under the impression it does not matter the order in which you tune-up the engine when in fact, it makes a large difference and sometimes this difference, when not understood, causes the engine to struggle very poorly.
Do not attempt to make adjustments to engine operations without FIRST establishing the correct dwell. The order in which the tune-up proceeds is important:
(1) Establish Dwell;
(2) Establish timing;
(3) Adjust A/F mixture (via highest achievable vacuum).
Dwell effects timing. Timing DOES NOT effect dwell. If you attempt to make adjustments to timing thinking/considering this will overcome any maladjustment to dwell, optimal engine firing will diminish - sometimes rapidly. Therefore, ensure dwell is always established first before adjusting timing.
Attempting to examine the basics here first before even thinking of deep-diving into valves & distributor.
all had proper coloration. two were not wet at all. 6 were slightly wet at the base, but nothing alarming. What's, most interesting is that cyl 2 and 6 (the dry plugs) feed off separate sides of the carb on the intake manifold. See pic.
I've tested the ignition wires. most show .3 for resistance. Two show slightly higher, at .5. those two wires WERE NOT the wires that lead to cyl 2 and 6. No smoking gun there. I'm still thinking ignition coil. I cant explain why I was given a different part number today than what was in the car. Sadly I can't call to explore the difference between the 9 and the 7 coil till Monday. First rule of thumb when chasing a problem, change one thing at a time! Replacing a suspect coil with another coil of a different part number may lead me on a wild goose chase. I'm going to replace the ignition wires just for age sake.
From personal experience I would throw the Pertronix in the garbage. Been left on the side of the road too many times or came limping home. Never ever again. One thought is to make sure the wire going to the coil is in good condition. If it is cracked or intermittent it could cause your problem. This thing is going to be something like that.
Glenn - You just went to the exact next place I was going. That distributor coil wire and both contact points need to be sharp, crisp & clean.
I still have to ask the same question I asked previously - did you DOUBLE CHECK to make CERTAIN each spark plug wire is connected into the CORRECT plug-in receptacle on the top of the distributor? I fail to see where you answered that question unless I missed it.
FOUND THE ISSUE! While examining the distributor cap and rotor again I noticed that the rotor had advanced its self clockwise some how. When I tried to take the rotor off to examine it, it popped back an index mark counter clock wise. I put the cap back on and fired it up. smooth as butter! now, what the heck caused it to skip clocking rotation? I bet it does this on it's own after a bit. who knows why.
I was assisting a young man (neighbor) with an older Chevrolet pick-up truck - he was smitten with love for this old truck he just bought and couldn't wait to get it running great - spent enormous amounts of time doing very good work and would occasionally ask for my help. During his second tune-up (which he learned how to do) with a timing light, he got stranded on the side of the road.
He tightened one side of the distributor cap spring-held lock down correctly, but the spring-held lock down on the opposite side was not completely engaged and popped off its seat. The distributor cap shifted upwards on one side and killed the truck but a super easy fix.
I got my 54 out this week after sitting in the garage most of 2020. I kept it started throughout the year and even changed the distributor to a 56 model with external adjustment points. When I took it out it crank and idle fine and run good at low speeds. When I tried to accelerate it would cough and sputter. Most of the gas in it was fresh but even though I had put Sta-Bil in it I thought maybe it has some water in the gas. I had a bottle of Heet I poured in the tank to no avail. I had been over at a friends house and when I pulled into the garage I heard this little tic tic tic on the right side of the engine. I popped the hood and I could see the #6 plug wire was not all the way on the plug. Simple fix. I probably pulled it off when I was changing the distributor. I hate those old distributors with the clips on each side. I am glad I don't have them on my 54 anymore.
I got my 54 out this week after sitting in the garage most of 2020. I kept it started throughout the year and even changed the distributor to a 56 model with external adjustment points. When I took it out it crank and idle fine and run good at low speeds. When I tried to accelerate it would cough and sputter. Most of the gas in it was fresh but even though I had put Sta-Bil in it I thought maybe it has some water in the gas. I had a bottle of Heet I poured in the tank to no avail. I had been over at a friends house and when I pulled into the garage I heard this little tic tic tic on the right side of the engine. I popped the hood and I could see the #6 plug wire was not all the way on the plug. Simple fix. I probably pulled it off when I was changing the distributor. I hate those old distributors with the clips on each side. I am glad I don't have them on my 54 anymore.
glad it worked out! These olds are so great. Not knowing, please tell me the advantages to the 54 distributor. Any others besides what I assume is an adjustment window for the points? Just curious.
The 54 distributor is for all purposes identical to what you have in your 49. They are a pain to set the points with since the points are on the backside of the distributor and are usually set with a feeler gauge although they can be set with a dwell meter. You still have to adjust them with the cam screw on the distributor plate. And then you have those stupid clips to hold the cap on. On the 56 distributor the cap is held on with two screws that you just twist 180°. The points are on the front side of the distributor by two screws and will usually be close enough our of the box to get the car started. Then you can hookup a dwell meter and open the window on the cap and set them very accurately to 30°. Then if you prefer you can use a uniset that has the points and condenser all made into one unit. I believe I could change a set on the side of the road in about 10 minutes and be on my way. The only way I could get anywhere close to accurate on the 54 distributor was to pull it out of the car.
April 3rd, 2021, 11:49 AM
