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Rescuing Oswald, the Old Blue Amazon (1965 Volvo 122S)

September 10, 2024

Been a frustrating week.

I'm still waiting on my other IPD box. So, I’ve been working on my SU’s in the meantime.

When I was installing my (front? right? forward? Whatever you wanna call it) SU, I noticed that the piston was binding on the carb dome. It had always been a little finicky, but never that bad. So I pulled the carb apart, but couldn’t see an issue. I dropped it off at a local carburetor shop, who observed:

1. The carburetor was a hodgepodge of parts that probably weren’t together originally; he said SU’s can be picky about having its original parts for clearances.
2. I hadn’t noticed it, but there was a knick in the carb piston, which was binding on the dome. He said he could work on filing it down for $200/hour, but no guarantees on it helping.
https://imgur.com/a/TRcyaym

I certainly didn’t want to pay that, so I tried doing it myself, and I proceeded to accidentally drop the piston down my engine bay and onto the pavement below, causing a worse dent and bending the needle. Sigh.

I had a couple thoughts go through my mind: Was this a good opportunity to say adios to my tired SU’s and roll with a Weber? Maybe Mikunis? Maybe even DCOE’s?

The local friend who helped me save some other Volvos from the crusher said he had SU and Weber parts in storage. I dug through his stash yesterday and worked out a deal. I scored two SU’s, a mirror, wiper arms, a coil, and a new fuse block for $90 - great deal! My wife was certainly relieved I went that route instead of buying brand-new carburetors, haha.
https://imgur.com/a/Hn9ATWy

After buying them, I’m glad I stuck with SU’s. I’m familiar with SU’s now, and they’re so simple, it’s hard not to like them… even if they can be emotionally needy.
 
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September 16, 2024

Welcome to the second week of my SU shenanigans.

While the “new” carbs were SU HS4 models like my old ones, they came from an MG or a Triumph, so the shafts for the throttle plates didn’t match what I needed for my Amazon’s throttle linkage. I know it’s possible to drill the shafts to allow for the Amazon’s needed attachments, so I may do that in the future.
https://imgur.com/UhQ3siq
https://imgur.com/iQjApZ5

To my surprise, only one of the “new” SU bowls had their float and needle. Oh well, the ones from my old carbs are the same part number and will work fine.

Before I install the carbs, I decided now’s a great time to clean my engine bay, so I’ll be doing that in the next couple days.

https://imgur.com/MFxedKU
https://imgur.com/B4QKc3m
https://imgur.com/gTm0Tms
 
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September 21, 2024

Alright experts, chime in please.

Got the carbs on. Even with the air/fuel mixture nut maxed out for running lean, the car is still running rich…. REALLY rich. Black smoke and popping from the exhaust. The jets are nice and snug; maybe my float in my fuel bowl isn’t adjusted proper? Insight appreciated!

https://imgur.com/a/ZfysbIS
 
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In the earlier pictures, the choke cable housings aren't secured to the carbs. And they look to be stretched tight. Based on that, I'd first guess that the cold start mechanisms aren't working/disengaging correctly.

If the cold start mechanisms are confirmed correct and fully disengaged: first, confirm that the valves are properly adjusted. This won't make the mixture weird, but we want things as consistent across all 4 as we can get them. Second: confirm that the ignition timing is correct - if you're not sure, set it to 32 degrees with the engine revved up just enough that the distributor is fully advanced. Depending on the distributor, this should put you somewhere between 12 and 18 degrees BTDC at idle - anywhere in that range is fine for now.

Finally, adjust the carbs. First make sure that the center rod is correctly adjusted such that there's a little bit of slack before the throttle plates engage - make this slack match as precisely as you can. Only after all that can you begin to adjust the jets for proper mixture. The Haynes presents the process well. Loosely: start with the jets 12 flats down from flush, and turn them upward until the idle degrades, then back down just far enough that the idle smooths out - this will get you close *for the idle mix* but if the needles aren't matched to the engine you may end up too lean or too rich under load.

It's close. You'll get there.
 
volvorelix said:
In the earlier pictures, the choke cable housings aren't secured to the carbs. And they look to be stretched tight. Based on that, I'd first guess that the cold start mechanisms aren't working/disengaging correctly.

If the cold start mechanisms are confirmed correct and fully disengaged: first, confirm that the valves are properly adjusted. This won't make the mixture weird, but we want things as consistent across all 4 as we can get them. Second: confirm that the ignition timing is correct - if you're not sure, set it to 32 degrees with the engine revved up just enough that the distributor is fully advanced. Depending on the distributor, this should put you somewhere between 12 and 18 degrees BTDC at idle - anywhere in that range is fine for now.

Finally, adjust the carbs. First make sure that the center rod is correctly adjusted such that there's a little bit of slack before the throttle plates engage - make this slack match as precisely as you can. Only after all that can you begin to adjust the jets for proper mixture. The Haynes presents the process well. Loosely: start with the jets 12 flats down from flush, and turn them upward until the idle degrades, then back down just far enough that the idle smooths out - this will get you close *for the idle mix* but if the needles aren't matched to the engine you may end up too lean or too rich under load.

It's close. You'll get there.
Click to expand...
adding some color. When he says to make that center rod adjustment, get it close until you can get the engine to op temp, then revisit setting the air balance by loosening all these links and set the idle screws on each carb then reset linkage, and revisit the fuel adjustment.

For fuel, follow the above process. There should also be a pin under the side of each dashpot. When pressed upward this will lift the piston 1/8”(you can use a screw driver or 1/8” drill bit to lift the piston if needed) You can use that to help get fuel dialed at idle. It will either stumble, rev and hold, or rev and return. Your aim is rev and return.
 
volvorelix said:
In the earlier pictures, the choke cable housings aren't secured to the carbs. And they look to be stretched tight. Based on that, I'd first guess that the cold start mechanisms aren't working/disengaging correctly.

If the cold start mechanisms are confirmed correct and fully disengaged: first, confirm that the valves are properly adjusted. This won't make the mixture weird, but we want things as consistent across all 4 as we can get them. Second: confirm that the ignition timing is correct - if you're not sure, set it to 32 degrees with the engine revved up just enough that the distributor is fully advanced. Depending on the distributor, this should put you somewhere between 12 and 18 degrees BTDC at idle - anywhere in that range is fine for now.

Finally, adjust the carbs. First make sure that the center rod is correctly adjusted such that there's a little bit of slack before the throttle plates engage - make this slack match as precisely as you can. Only after all that can you begin to adjust the jets for proper mixture. The Haynes presents the process well. Loosely: start with the jets 12 flats down from flush, and turn them upward until the idle degrades, then back down just far enough that the idle smooths out - this will get you close *for the idle mix* but if the needles aren't matched to the engine you may end up too lean or too rich under load.

It's close. You'll get there.
Click to expand...
Thanks for the helpful reply! As for the choke cables, they aren't finished yet. They're disconnected from the knob in the cabin, I just didn't want them flopping around in the engine bay. New choke cables are on-order. Before redoing the carbs, the car handled cold starts well in the warm weather without the choke (I was daily driving it in 100+ degree temperatures).

I did adjust the valves, so those should be good to roll.

Thanks for the reminder about checking my timing; I'm dropping in my Pertronix today, so I'll want to double-check the timing anyway. :-)

I did confirm that my center rods were adjusted, per my SU manual, which matched what you said. I also originally had the jets 12 flats from flush, but the car would not start. I raised them to seven flats from flush, where the car would start and stumble until it died or the exhaust popped. Raising the jets completely up to flush (zero flats) would let the car idle, but still incredibly rich.

I perhaps thought that my piston needles weren't centering properly in my jet, so I re-centered them and am getting the solid metallic "clunk" of the piston falling.

cwdodson88 said:
adding some color. When he says to make that center rod adjustment, get it close until you can get the engine to op temp, then revisit setting the air balance by loosening all these links and set the idle screws on each carb then reset linkage, and revisit the fuel adjustment.

For fuel, follow the above process. There should also be a pin under the side of each dashpot. When pressed upward this will lift the piston 1/8”(you can use a screw driver or 1/8” drill bit to lift the piston if needed) You can use that to help get fuel dialed at idle. It will either stumble, rev and hold, or rev and return. Your aim is rev and return.
Click to expand...
Thanks for adding on to the response from Volvorelix - I appreciate the help! I know these carbs like to be adjusted when the car's warm, I'll go through the steps you mentioned in the first section to see if that helps.

For the fuel mixture process, my idle races when the side pin is depressed, implying the car is still running rich, despite the jet being raised to zero flats (versus the twelve flats recommended).


Today's game plan:
1. If my box of choke cables aren't here from the mail, I'll swing by a local bicycle shop and buy some to get the choke properly hooked up.
2. Plop in my Pertronix and adjust timing.
3. Double-check my throttle plate engagement.
4. Double-check my float measurements in the fuel bowls to make sure the needle in the seat is properly sealing off excess fuel flow.
5. Reset my air/fuel settings with the car warm.

While I'm at it, I'm going to verify that the carbs are wearing all their proper parts. After all, these were used and sitting in the trunk of a parts car for 20+ years with an unknown history.

Thank you, volvorelix and cwdodson88!
 
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If the engine started cold without using the choke, it's way too rich. This happens fairly often and needs only a simple adjustment to rectify.
If it's running with the jets all the way up and is still rich, my first thought would be that you have the wrong needles.
I'd think that you had a stuck piston, but it sounds like you've confirmed that this isn't the case.

In looking at your photos, it's clear that at least two of the carbs aren't for a Volvo application [note the difference in float bowl lids]. You can sometimes get away with mixing and matching carb parts to build up a decent pair -- if you do so, and you manage to get a pair that acts proper (pistons falling, jets centered, etc) the single most important thing to confirm next is that the needles are 1) matched, 2) correctly installed, 3) appropriate for your engine. Related to this and equally important: other applications use different sized jets -- so if you install (for example) a pair of SUs that came off a 3.5 liter Rover V8, it's going to run pig rich all the time, if it runs at all.

I'd start by IDing the current needles. Whatcha got?
 
volvorelix said:
If the engine started cold without using the choke, it's way too rich. This happens fairly often and needs only a simple adjustment to rectify.
If it's running with the jets all the way up and is still rich, my first thought would be that you have the wrong needles.
I'd think that you had a stuck piston, but it sounds like you've confirmed that this isn't the case.

In looking at your photos, it's clear that at least two of the carbs aren't for a Volvo application [note the difference in float bowl lids]. You can sometimes get away with mixing and matching carb parts to build up a decent pair -- if you do so, and you manage to get a pair that acts proper (pistons falling, jets centered, etc) the single most important thing to confirm next is that the needles are 1) matched, 2) correctly installed, 3) appropriate for your engine. Related to this and equally important: other applications use different sized jets -- so if you install (for example) a pair of SUs that came off a 3.5 liter Rover V8, it's going to run pig rich all the time, if it runs at all.

I'd start by IDing the current needles. Whatcha got?
Click to expand...
Sounds like you're pretty familiar with SU's, I appreciate the knowledge sharing.
I have no idea what the carbs were from, I bet I could look up the part number for the float bowl lids to see what they're applicable to.
I'll do some investigating when I'm home. :-)

The carbs on my `68 145S were cake to rebuild, but this car has been fighting tooth and nail.
 
Good point, though excessive pressure will lead to the float bowls overflowing rather than a significant change in mix ratio. Float level matters, but unlike the Weber family, with SUs it's not a mixture tuning element.
 
I appreciate you guys helping me figure this out. I'll be able to head out to the car this evening to start tinkering.

I did slap a new pump on the car back in June? July? Somewhere around there. Haven't ever checked the PSI.
 
You can measure the jet orifice as well. Remove the jets and using gauge pins, a drill index, or calipers. You should have something right around a .1” orifice that the needle sits in. Inspect the hole is round, check that the needle’s aren’t worn.
 
volvorelix said:
Good point, though excessive pressure will lead to the float bowls overflowing rather than a significant change in mix ratio. Float level matters, but unlike the Weber family, with SUs it's not a mixture tuning element.
Click to expand...
True, the float bowls overflowing is what happened to me. I figured if it's too high a pressure it could affect the tuning.
 
dl242gt said:
True, the float bowls overflowing is what happened to me. I figured if it's too high a pressure it could affect the tuning.
Click to expand...
It can but rarely (in my experience) without over flowing, or at the very least pittling a few drops when idling.

Check the float level, and I’m assuming a mechanical pump, so I wouldn’t expect fuel pressure to be as much of an issue.

My best guess is needles, either incorrect, badly worn, or not centered, jets either incorrect or badly worn from being not centered.

Check those few things and consult the needle charts. There’s a few that work, although DX are pretty much the go to.
 
September 22, 2024

SOLVED!

You guys get a cookie, gold star, or something like that - thanks for helping me figure this out!

The culprit: the needles.

The "new" carbs I put on the car had needles that were significantly shorter/narrower than my old needles. I can't believe I missed it the first time, but oh well. I threw on my old needles and the car is no longer sputtering or blowing smoke.

I've fiddled with these carbs so much that doing it under a street lamp with minimal lighting was no problem.

Still need to fine-tune the idle and maybe re-seat the throttle plates, but we're back in business!

Side note: The Pertronix upgrade was totally worth it. No more occasional misfires or stumbles.

https://imgur.com/a/Ek0WpK9
 
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