My Alfa Romeo 33 rebuild - FIRST TIMER

[Brit01]

with a jubilee-clip possibly with a piece of sheet metal under it.

That's exactly what popped into my mind but thought it was a silly idea. There you go. Great minds think alike.
Maybe some fold of aluminium foil under the jubilee as it may seal better around the hole.

We have a builder here who does crossover stainless steel manifolds for a good price. A friend just had one done for his Alfa 33 and was very pleased.

But the wife?? That is the main issue.

[TomLouwrier]

Dunno if your wife does crossover stainless steel manifolds for a good price. You tell us when she's done.

regards
T

[Brit01]

Won't be able to tell you when she's done because I'll be a pile of ashes after the cremation!

[Brit01]

Hole is right on the weld where the 2-1 is so no chance of getting a clip on that.

I stuck a piece of duck tape on the pinhole (cold) and started her up. no change in AFR.

At one point it did jump to 10 then settle on 13 for a second then back to 20 (without the tape on). Very strange indeed. Clueless at the moment.

Also checked the gaskets while engine was running. Couldn't see any smoke coming out or hear any puffing. But could be such a small leak.
The end of the gaskets did look more compressed than the middle where it joins the cylinder head.

Or maybe the lambda has failed but I doubt it as it's a Bosch and has had very little usage.
The control unit is supposed to show a #3 is the lambda fails anyway. I guess it checks the voltage from the sensor.
Maybe I need to check it with a DMM. Have to check up on that how to do it.

[Brit01]

One thing about the manifold gaskets - there was a flat side and one raised side
Is there a specific side I should attach these between the head and manifold?

I think the flatter metal side to manifold. And more fibrous to head.

Think I messed up and put one the wrong way.

I have some spare so will change them to see if that makes a difference.

I will also check the flange for levelness. If it's slightly off maybe 2 gaskets will help seal it better.

[Brit01]

Changed the gasket.

No change - sensor still reading incorrectly (well first it stayed at 13.5 for about 3 seconds then flickered off the scale again to 20+). Even held a fine piece of paper around the flange to see if it moved - nothing. I think they are sealed just fine.

Tech support said it could be a dirty Bosch sensor - remove and clean was their advice.

(or could be a hairline crack in the 2-1 welded part of the manifold where I can't see after all the head removing and replacing!)

Bit fustrating.

[Nobby]

Its probably the sensor. You could remove it and give it a clean - I've heard people use lemons to clean lambda sensors but I don't know if its going to make any real difference. When mine went (a bosch 4.9 5-pin sensor) there was no change.

How close is your lambda to the exhaust ports? You don't want it too close as your EGTs will kill it fairly quickly. Mine is about 2 foot along my downpipe.

[Brit01]

How close is your lambda to the exhaust ports?

Probably about 3 feet.


I'm planning to do an oil change in a few days so I'll take advantage of the garage pit and remove the sensor to inspect it.
It's also a 4.9 5 pin.
Only had it for a year and done about 3000 kms on it.
Tech support told me the control unit would show a #3 error if the sensor is not working.

Can I use carb cleaner to clean it?

As it's been sitting unused for 4 months during the damp winter months most likely clogged up or something.

[Guy Croft]

The attached plot is from a 1600 8v engine in rally trim but nothwithstanding the differences cf your engine the Lambda trend is worth examining.

I'm not sure you've indicated the engine speeds at which your A/F goes high but if it's off load when you open the throttle it should go rich because you're pulling in fuel the progression jets. All carbs do that. Moreover snap-opening will bring the pump jets in which makes them go rich too. If yours is going so lean (A/F parts air-gasoline by mass 20/1) it would not run at all, a gasoline engine will struggle to run at much over 15/1 and certainly lower - 12.5/13 (rich) is better for power.

You are wasting your time tuning the idle settings with an A/F gauge. Frankly all you need is an accuarate tacho - best mixture will always correspond with highest idle speed, in saying that you have to keep resetting the idle speed screw to hold idle at 850rpm. Lean out the speed will drop, as you enrich and approach optimum setting it will climb and when you go past optimum it will not climb higher and then start to misfire as the plug fouls up. A Gunson Colortune device is the IDEAL way to set this, see links. See also my YouTube channel (gc1438).

If you're talking about under-load settings then that's another matter but the graph f Lambda below is safe and will give you a comfort factor. To get air-fuel ratio multiply Lambda by 14.5.

(Hope I got my facts right here. Not myself these days with this wretched eurozone crisis going on.)

G

[Brit01]

Many thanks Guy for the graph and explanation.

best mixture will always correspond with highest idle speed,

Yes this is the method described in the Dellorto and Alfa carb set up procedures.
I set the idle mixture screws using this method at 850 rpm. The sensor tends to show 13.1, as I know the boxer prefers a slightly richer mix.
It's a back and forth tuning process. Adjust the idle mixture jets to peak rpm then back off idle adjusting screws to 850rpm, then adjust again until it's balanced. At the final point the gauge normally shows around 13.1. (not now as it's malfunctioning).

When cruising the gauge shows around 14.5 on the main jets which is good.

And you are right and from my experience of tuning with different settings/jets it stumbles/hesitates a lot if the AFR goes above 15/16.

The sensor is flashing at 20 which indicates a sensor problem. See what happens after I clean it.

But the engine runs great with a smooth transition.

p.s yes I've seen the colourtune - good little tuning device. Also the 4 bar carbtune for the twin carbs on the boxer.

Best regards.

Hope the crisis settles down soon.

Here in Uruguay we had a serious crisis in 2002 (spin off from Argentina)
Total bankruptcy and all bank employees laid off (including my wife). ATM's blocked and the people lost all their money from their accounts.
Property values fell about 600%! Pensions frozen.

[Guy Croft]

Thanks for your reply & kind remarks Chris

the acid test, honestly - is if the engine runs well it is probably absolutely fine!

G

[timinator]

Hi Chris,

When my wide band does the flash 20 thing I drive to the top of a long grade and coast down in hi gear with my foot off the throttle. Once the gauge reads full lean hit the calibrate button. After it resets get back on the throttle and it should work properly. The leak upstream should not cause the flashing 20. It will only make your readings inaccurate.

Tim

[Brit01]

When my wide band does the flash 20 thing I drive to the top of a long grade and coast down in hi gear with my foot off the throttle.

Lol might be a little difficult as Uruguay is like Holland! FLAT. But thanks for the tip Tim.

There is a slight hill on the way to work which takes about 3 secs to go down, I will try that (but the calibration takes 8 seconds!).

If not tomorrow I have a oil change scheduled outside my workplace.

They will give me time to take out the lambda and give it a good clean.
As it's been sitting unused in damp exhaust for months maybe this will help.

[Brit01]

Had to do some town driving this evening (which means hot engine - starting/stopping every 10 seconds), the AFR gauge came to life a few times! Maybe it's cleaning out a little with more use?? Maybe some oxidation on it from the months sitting in the damp garage during winter.

Well tomorrow I will remove it anyway and rinse it out with carb cleaner while they drain the oil.


Radiator worked nicely also. smile

[Brit01]

Best place to measure oil pressure on this engine?

The low oil pressure sensor is located at the filter. Most people place a T adaptor her and put the extra oil sensor for the gauge here.

Now I have mine on the main oil channel which I believe leads to the cams and cranks.

Would it be better to measure the oil pressure at the filter? How much difference it pressure would I expect to see between the 2 locations?

Just curious.

Update: Just done the last oil change (3rd) for the rebuild. Now I have Motul 6100 15W/50. This will be in for the next 3000-4000 kms or so.
Fitted a Coopers Fiaam filter this time - never used one before but the web site and technology illustrations were well written. French oil with a French filter.

I see the Motul has a slightly higher viscosity value at 100 degrees than the Valvoline even though they are both 50 index viscosity oils.

Motul: Viscosity at 100°C (212°F) 19.6 mm²/s
Valvoline: Viscosity at 100°C (212°F) 18.5 mm²/s