My Alfa Romeo 33 rebuild - FIRST TIMER

[timinator]

Hi Chris,

Sounds like your tune could be too lean causing a misfire on no.4 resulting in the popping you hear at idle. The indicator for fuel mixture is found on the bottom third of the porcelain and only seen after full throttle acceleration with immediate shutoff of the engine. It is not visible without magnification and artificial light. It can take several attempts with unleaded fuel to see anything.

Your exhaust tubes should not be colored black or white. With a possible misfire you could have both. I believe GC pointed out in your thread that wide band sensors are not dependable at idle.

Tim

[Brit01]

Yes that makes sense now Tim. Thanks.
I thought when you said the porcelain part you you referring to the exterior part as once I had a brown Bosch plug.
Now I see you mean the porcelain part inside.

Once rebuilt I will be finely tuning them by ear using the Dellorto manual instructions. I don't have a carbtune yet. Christmas is here and a lot of bills to pay.

On the piston with the orange specs there is also a little white flaky substance inside the exhaust manifold which makes sense all leading to a lean mixture.

Never had this before the starting issues a few weeks ago indicating possibly the fuel filter I found behind the tank is too blocked and not feeding the carbs with enough fuel.

It always used to start well and prime with the starter motor up until about a month ago.

Also was getting a flat spot under hard acceleration around the time the start up issues began.

Well some weeks to go before the engine goes back in to get it running with the correct mixture levels.

[Brit01]

I have 2 sets of standard size Glyco big end bearings and not 100% sure of the differences.

Slight differences from the data below (bearing clearance and shaft diameter vary by 0.01mm):
By shaft do they mean crank journal??
The bearing clearance of the 6625RA is 0.01 mm smaller than the 66635RA. So I assume this would be slightly tighter.


Part Number: 66625RA

Chemical Properties: Unleaded
Component Number: 66625RA
For bearing clearance from: 0,02 mm
For housing diameter from: 53,7 mm
For shaft diamater from: 49,99 mm
Quantity Unit: Pair
Supplementary Article/Supplementary Info 2: Aluminium alloy on steel base
Thickness: 1,84 mm
To bearing clearance: 0,07 mm
To housing diameter: 53,71 mm
To shaft diameter: 50 mm
Width: 17,8 mm

Part Number: 66325RA

Chemical Properties: Unleaded
Component Number: 66325RA
For bearing clearance from: 0,02 mm
For housing diameter from: 53,7 mm
For shaft diamater from: 49,98 mm
Quantity Unit: Pair
Supplementary Article/Supplementary Info 2: Aluminium alloy on steel base
Thickness: 1,84 mm
To bearing clearance: 0,08 mm
To housing diameter: 53,71 mm
To shaft diameter: 50 mm
Width: 17,8 mm

[Guy Croft]

They are effectively the same - provided the slots & oilways (such as they are) are correct.

I don't know why bearing mfr do that - 0.01mm difference. I have to cope with it all the time. That's 0.0004" which one could see easily in crank journal deviation. In other words nothing.

GC

[Brit01]

Yep they are identical in regards to grooves and width etc. Both standard size also.

I will post photos of the plastigauge results once I manage the get the clutch/flywheel etc removed.

Holidays start on Saturday. Looking forward to it.

Chris

[Brit01]

Great job done on my small ends.

New pins and honed small ends to fit. Perfect. Very pleased with the result and delivered to my house by the mechanic.
Totally different feel to the old ones.

We had a small chat and he was impressed with my knowledge of the Alfa flat four. He thought I had worked in the UK. Lol.
All self taught and of course a lot of assistance from experts on these forums.

Regards

Chris

[Guy Croft]

yes watch out you don't end up doing it for a living!

G

[Brit01]

yes watch out you don't end up doing it for a living!

Maybe it's my destiny Guy! Instead of being stuck in an office cube for 9 hours a day in front of a monitor with square eyes evolving.


Chris

[TomLouwrier]

hi guys,

The 0,01mm variance in 'standard sized' shells is probably to compensate for different classes of bores that have the same nominal diameter. They are usually marked something like A, C and E class just like cylinders and pistons are. The parts themselves often are marked with yellow, red and blue paint if OEM.
For some engines you have a large list in the manual that gives all combinations of crank pin and rod bore classes, and the corresponding shells. You may fit a combination (if available!) of an A and a C class shell to match a A class bore to a B class crank pin, etc.
This, of course, has everything to do with producing and assembling these four mating parts (rod, crank pin, 2 shell halves) by the thousands. You want reasonable tolerances (price) with good overall fit (bearing play). So you mix 'n' match.

This class system can be pretty confusing at times, especially when buying spare parts. You think you're getting something with the right nominal size only to find it's off by about the same amount as the fit (play) you need in there. I'm still looking for a set of 80mm pistons to fit a 1608, but they have to be C class which is about 79,99-80,00 (from memory).


Chris, I want to see pics of your new small ends and pins!

regards
Tom

[Guy Croft]

journal class - sorry - nice try Tom but it's not that!

G

[Brit01]

Chris, I want to see pics of your new small ends and pins!

Sure will do. I will be leaving the city tonight to start my summer holidays and returning to where the car and camera reside in our holiday home.

But may I ask what you are looking for in the photos (specific macros of the honing of the small ends or something)? Or just general interest?

Eager to start work on it again, removing the clutch/flywheel and crank over the next few days.
Then the cleaning process will begin.

Regards

Chris

[Brit01]

Photo of one of the new small ends and pins. Haven't had the chance to clean them thoroughly yet. Looking a bit grimey.

[Urbancamo]

X marks the spot!

Not the most common type for pin lubrication, but might be very effective.

[Brit01]

The original Alfa shells have the same X grooves.

These are Glyco.

[Brit01]

Some pictures of the crank and old shells. Thrust washers have taken a battering. Journals look good but still need to measure them with the new shells.