Vintage Oldsmobiles Curved Dash, Limited Touring, Models 40, 53, 66; Series 60, 70, 90

Awakening a 1941 Straight 8

Old September 10th, 2018, 12:51 PM
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Awakening a 1941 Straight 8

Hi, my buddy and I picked up a pretty rough 1941 Olds 98 earlier this year, and now we're trying to get it running. A previous owner "reportedly" got it running a few years ago, and it has a few components that are obviously pretty new like the cap, rotor, points, and condenser. Plugs were in fair shape but one of them broke when pulling it out, so I replaced all 8. Plug wires were in pretty rough shape, especially the coil wire which actually looked original. The radiator had pretty clean green coolant in it. Transmission is pretty full, although the fluid is dark and I can't verify the actual level without the engine running. (I would bitch about the dipstick location, but I can't really complain about access since the car has no interior.)

We started out by topping off the engine oil (it was about a quart low but looked decent), pulled all the plugs, and poured a little MMO in every cylinder. We let that sit for a while and then turned the engine over by hand; it spun freely. After doing a little research and determining that 12V wouldn't hurt the starter, we removed the secondary wiring and connected 12V battery positive to the starter solenoid. Pressed the starter pedal and the engine spun beautifully. Hooked up a compression tester and got relatively good results. All but 1 cylinder made at least 100 psi, with one (I think #4, but I'd have to check my notes) making 80-85 psi. Hoping it's either a stuck compression ring or some trash on a valve seat that'll clean up with time.

Now to make the engine fire. We want to convert the car to 12V for several reasons: reliability, ease of parts replacement, better lights, new gauges, etc. (I know some people are going to complain and say these cars worked perfectly fine on 6 volts, but I have no interest in maintaining an antique electrical system that's different from every other car I own.) So I installed a 12V coil with matching ballast resistor, swapped in a 12V ignition condenser, cleaned up the existing points (since my research leads me to believe 6V points will work fine with 12V) and temporarily wired everything under the hood. I put together and installed a new coil wire from the remains of a V8 wire kit I had used on a 6-cylinder.

Opened the throttle plates, gave it a healthy spray of starting fluid, and hit the starter... spin but no bang. Hooked up a test light to #1 plug wire; no spark. Checked all my connections. Tested the coil resistance and ballast resistor; both good. Checked my new coil wire resistance; it was higher than I expected at about 15 kOhms, but considering how long it is, that's actually not bad. Tested a few spark plug wires... they were worse. Looks like I'm making all new plug wires. While I wait for those, I figure I'll make sure everything else is adjusted properly.

What are the general tune-up specs for this engine, and how do they change (if at all) when you convert to 12V ignition? The old plugs were all around 0.030" and that's what the new plugs were out of the box, so I didn't change them. The points gap was around 0.020" after I cleaned them up, which seems a little high, but I left it there for lack of any better ideas. I pulled the distributor to inspect it; all the things that should move do and the things that shouldn't don't. Some of the wires inside are very old, but it looks fine and has good conductivity everywhere I could check.

It could just be crappy plug wires, but is there something else I'm missing?
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Old September 10th, 2018, 01:07 PM
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Make sure the wire to the points is not grounding somewhere inside the distributor.You can put a test light on the coil neg., open the points with a non conductive stick and it should light with the ignition hot. If the wire, points or condenser is grounded or the points are closed, the light will not be lit.
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Old September 10th, 2018, 05:19 PM
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The distributor is off the car at the moment. With the points held open (either by the cam or a non-conductive block), I get about 200 kOhm between the hot terminal (from coil negative) and the distributor body. I'm guessing that's effectively "insulated." With the points closed, the hot terminal is grounded to the distributor body. Is this correct?

I also need to verify I have good contact between the rotor and the cap. The contacts on the underside of this cap look pristine.
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Old September 10th, 2018, 06:33 PM
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Your best bet would be to get a 1941 Oldsmobile Shop Manual ;
That has all the specifications you could want .
"Cleaning up " points might be OK in an emergency . But you really need to replace them with new . Yes , those points will work with either 6 or 12 volts .
12 volt systems use a ballast resistor because the coil only takes about 9 volts while running . A by-pass wire brings full battery voltage to the coil while cranking through the solenoid . This gives you additional spark when starting . 6 volt systems didn't have this and there is no provision on the solenoid for the additional terminal .
As much as you think converting to 12 volts is an "upgrade " it is not .
Also check the plate inside the distributor that the points mount on . This plate rotates inside the distributor by the vacuum advance .
There is a small ground wire attached to this plate and the body of the distributor . If this wire is broken , or has any appreciable resistance , the ignition won't fire .
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Old September 16th, 2018, 02:37 PM
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Thanks for the tip on shop manuals; glad to see they're not too expensive. I'll pick one up.

Well, turns out the problem was a bad ground. Cleaned up the terminal that goes to the distributor body, threw it back together, and the engine fired right up with a little starting fluid. With a temporary fuel supply rigged up it'll start up and idle, but it seems like it's not getting enough fuel when you give it gas. It'll only stay running then if I hold the choke partially closed. Maybe a vacuum leak, but more likely a clogged fuel passage somewhere. Time to start researching this Carter carb and see if it needs to be rebuilt or not.
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Old September 16th, 2018, 02:57 PM
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Chances are the fuel pump is done. They used a lousy rubber compound or leather in those for diaphragms and modern gas makes very short work of them. Vacuum leaks are very likely, considering the design of the intake/exhaust manifolds. The spacer underneath the carb may also be an issue as can the heat riser. If the heat riser is blocked, the carb will quickly overheat and boil off any fuel in the bowl.
It's probably a Carter YF or something like that, and the bowl is actually cast iron. Rust can get into the smaller passages. A rebuild should be undertaken pretty much regardless due to the car's age and the volatility of modern fuels. E-fuels will eat and destroy old leather and rubber parts, meaning an increased risk of fire.
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Old November 19th, 2018, 02:15 PM
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Been a while since I posted, but to make a long story short she's running and driving now.

The carb is a Carter WDO; I pulled it apart to find it full of white powdery gunk. Mostly aluminum oxide with a dash of fuel varnish, I guess. It took a lot of scrubbing, repeated soaks in carb cleaner, and compressed air to clean up the major subassemblies and clear out all the passages. I ended up rebuilding it with a kit from Mike's Carb, which was a little disappointing for what it cost, but I made it work. Had to clean up and reuse the metal filter screens, do minor surgery on a couple gaskets, and find a diagram online that was more accurate to my application than the one that came with the kit. Anyway, bolted it back on and the engine ran great (again from a temporary fuel supply). Probably still needs a little adjustment, especially on the choke. We also added a standard 1-wire GM alternator on a conversion bracket from Vintage Auto Garage. (I feel a little guilty paying $60 for two bent pieces of flat stock welded together, but I was feeling lazy that week and really wanted to finish up the electrical.) We had to swap on the pulley from the original generator and modify the existing upper bracket. Getting the right size belt took several trips to the parts store.

We pulled the gas tank to clean it up and found it in worse shape than we originally assumed. Had to weld a number of holes... thin wire, low voltage, and a lot of patience. Once it would actually hold liquid, my friend cleaned it up with a vinegar soak and coated the inside with POR-15. One of the tank support straps was also missing, but we were able to adapt one left over from a '60s Dodge. I didn't even bother testing the mechanical fuel pump, so for now I built a bracket to hold a cheap electric pump down near the tank outlet. Would've preferred it under the hood, but there's no way an electric would "pull" that far. The stock metal fuel line was rusty enough to kink where I (gently) removed it from the tank, so I cut it back to a healthier section, put a hose barb on the tank fitting, and plumbed in the electric pump with soft lines. The rest of the fuel line was solid all the way up the frame rail, but it was rotten to hell where it crossed in front of the K-member. I cut it back on the driver's side of the engine bay and ran rubber line to the carb (with an inline fuel filter for the sake of modern convenience). We ran a 12V wire back to the pump, and now the car runs from its own tank.

Of course if you're gonna drive a car, you should probably have brakes. My youthful sensibilities will probably lead me to install a front disc conversion at some point, but Scarebird doesn't seem to be shipping any product for the time being due to "vendor constraints." So for now we bought a full stock rebuild kit from Kanter for about $400. Some online research says this stuff is probably made in China, but it's better than nothing. New hoses, wheel cylinders, shoes, hardware kits, and master cylinder (which we bench bled first, having learned that lesson on previous cars). Cleaned up the drums and replaced a broken wheel stud. The original brake pressure switch still works, to my surprise. Although I was alright with using most of the original steel fuel line (operating at 4 psi or so), I decided not to take any chances with the rusty brake line running back to the rear. So I bought a length of cunifer (copper/nickel) tube and bent up a new one. Seriously, if y'all have never used this stuff, I can't recommend it enough. It doesn't rust, you can bend it all by hand, and it flares so much easier than steel. I'm never using steel to run new hard lines ever again, and I swear no one paid me to say that. Anyway, the hard line on the rear axle and the ones under the hood were coated in enough grease that I figured they were fine, so I left them alone for now. Bled the system with a power bleeder and now the car can stop. The E-brake still works as well.

Which brings me to the test drive. Before I pulled the carb to rebuild it (and we had the engine idling from a big funnel zip-tied to the A-pillar), we did test to see if the car would at least go into gear. So we knew the transmission wasn't completely screwed. Well, with the engine fully running, this old Powerglide didn't disappoint. All 4 forward gears and reverse work, although depending on throttle position the 2-3 upshift can be a real kick in the ***. The straight 8 pulls way harder than I expected for its age. The brakes are barely adequate, even though we took care to dial the adjusters as far out as they'd go. The system may need to be bled a little better.

The big remaining issue is of course the suspension. These lever shocks probably haven't seen any real damping since the Eisenhower administration, and the car wallows like a boat just driving in a straight line. What's even more exciting is what happens when you hit the brake pedal too hard. As bad as the brakes are, they're still strong enough to get the undamped rear axle to unload and climb up the trailing arms, then start bouncing one of the rear tires like a basketball. (The first time it did that, I thought we'd lost the driveshaft.) It also doesn't help that every rubber bushing in the car is slowly returning to dust. It looks like you can get a lot of suspension parts from Kanter or Fusick, but even from Kanter the replacement price of lever shocks is pretty high. Does anyone have experience rebuilding these things? Maybe I should start a new topic about this.

One other thing. We stripped out what was left of the interior and have some potentially usable parts I'm never going to need. (This car was never in a condition to be restored; its future lies somewhere on the spectrum between hot rod and art car.) If you or someone you know is interested in any of the following parts from a 1941 Oldsmobile 98 sedan, let me know and I can send you pictures. If this stuff is useless, please tell me so I can throw it away in good conscience.
-Front bench seat. Mechanically okay, but pretty rusty on the mounting hardware. Upholstery is probably a biohazard. Beware of hantavirus.
-Headliner bows. Rusty but solid
-Inner doorskins from all but the front driver's door. Fabric is trash, trim is serviceable.
-Inner window surrounds, again from all but the front driver's door (you can thank the previous owner who took that one door apart to fix the exterior handle and threw these parts away) Made from wood. Surprisingly good condition! Somebody out there probably wants these.

Last edited by SpaceFrank; November 19th, 2018 at 02:23 PM.
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Old November 19th, 2018, 09:42 PM
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Congrats on getting your 98 running and driving. Nothing like a little success to provide incentive to keep on going.
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