Volvo RWD 120-130 Forum

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Some success with B20. 120-130 67.5

posted by  someone claiming to be mario on  Tue Dec 4 19:51 CST 2001 [RELATED]

Thanks to all of your help my engine is now running much better.

It wasn't idleing evenly, I couldn't properly adjust my dwell angle, when I adjusted the timing I would sometimes get a good zap from the coil, and it would start to stall out when the engine got cool after cruising and coming to a stop.

What I did:

1. I checked my thermostat in hot water with a thermomater and it checked out fine, but I switched it out with another good one just in case.

2. I put the mechanical advance distributor in from my B18 (real easy swap, only took me about 20 minutes to get it switched and dialed in)

3. Adjusted my timing with a Tachometer and found that a base setting of around 30 degrees BTDC was perfect (just like George said).

4. Readjusted carbs and all.

Results:

The engine now runs more smoothly and has a surprising increase in pep. I highly recommend ignoring the timing in the manual and just do it with a tac or by ear I think going to 30 from 20 BTDC gave me a big performance boost. Unfortunately it still wants to die after cruising at speed and coming to a stop. I don't know what I am doing wrong. I get the engine to idle smooth at about 900 - 1000 rpm. After a good stretch of driving the engine cools to a temp lower than the standing idle temp that I tune it at, and the engine won't idle and I have to pull out the choke a bit. Do they make thermostats higher than 81C?? Would a higher thermostat even help (it doesn't seem like it would)?? I don't want to just turn up the idle becuase it don't like the engine running fast when I am stuck in traffic (irrational pet peeve). I just want my standing idle temp to be the same as my cruising temp, or is that too much to ask from this old car???







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Re: Some success with B20. 120-130 67.5

posted by  someone claiming to be Dan Carey on  Thu Dec 6 08:04 CST 2001 [RELATED]

Mario,
sounds like your carburation is a hair lean to me. Are the throttle shafts tight, or do they wobble? HS-6 carburators are famous for that and it causes a lean condition that makes getting a reliable idle a challenge. Try backint the jets out a 1/4 turn or so and see if it helps or hurts the stalling.
Just how are you using a tach to set your timing? I'm not busting your chops, I just want to know. I'd be the first to agree that the timing marks on a thirty year old car are mostly cosmetic. You can't rely on them to actually set the timing to "factory" specs. This is because of at least two things: First, the factory timing was determined using gasoline that doesn't exist today. The 87 octane swill you get at the pump nowadays has significantly different burn characteristics than the stuff you got for $0.25/gallon back in '67. Second, wear and tear on the engine means that it the timing marks lie to you. I've torn down engines that had so much slop in the timing gears that the timing marks were off by many degrees. But you can use the marks to reset the timing once you know the "correct" timing for your car.
I learned the finer points of tune ups from a Swede named, and I'm not making this up, Walter Larsson at European Auto in Long Beach, CA. As to timing, I've found that a B18/B20 runs pretty well when the timing is advanced to just before the engine starts to ping. I advance the timing until the engine starts to idle rough and back it off a few degrees. Then, I hop in and drive it. Tooling down the road at about 25mph in second gear, I switch to fourth and floor the gas pedal, lugging the engine. If I get a little pinging, that's probably Ok. If I get a lot of pinging, I back the timing off a few degrees and try it again. The idea is to get the engine just to the point where the timing has a healthy advance, but only pings if I use bad gas or really lug the engine.
As to carburation, I like to keep my car running a little rich, like 1-2 "flats" on the jet adjuster hex. Yeah, it costs me an mpg or two and the car smogs up the place a little bit more, but it runs well and burns cooler. With unleaded gas, your valve seats will last a lot longer if you run it a little rich. I'll lean it out a little if I'm going cross country to pick up that extra 10-20 miles per tank. The SUs are really easy carbs to keep in tune once you get a feel for them.
Well, good luck. If you want any free advice, which is guaranteed to be worth what you paid for it. e-mail me at danimal_57@yahoo.com and I'll get back to you.

Dan








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Re: Some success with B20. 120-130 67.5

posted by  someone claiming to be GRMPer@aol.com on  Thu Dec 6 08:22 CST 2001 [RELATED]

I was replacing my crank pulley last night...I noticed that there was several degrees of leeway when I was bolting it on....surprising. I rotated so that it was the most "optimistic"

Per

> means that it the timing marks lie to you. I've torn down engines

> that had so much slop in the timing gears that the timing marks were

> off by many degrees.







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Re: Some success with B20. 120-130 67.5

posted by  someone claiming to be George Downs on  Wed Dec 5 02:22 CST 2001 [RELATED]

Everybody is amazed when I recommend 21-24° BTDC, but if 30° works

for you and you don't get a lot of knocking (pinking) under hard

acceleration at low speeds, that's great. Might be that your timing

marks are a little off. But it is how it runs that really counts.

If I were you I would do a thorough check for vacuum leaks. This

sounds like a manifold gasket or some such to me. If anything I would

expect it to idle slower when cool.






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