Mrfiat's fiat 131

[festy]

You want a sharp transition, so the square teeth would be a better choice than the triangular one.
A round slot in a thick cast iron pulley will give a better signal than a square tooth on a thin steel plate, ideally the plate should be at least as thick as the sensor's pickup.

[mrfiat]

Just reviewing my options for my trigger wheel and ive got two options. One is to use the standard front pulley, make a trigger wheel out of steel and weld it to the back of the pulley, Due to space restrictions the widest i could make the wheel would be 3-4 mm.
The second option would be to use another front pulley that i pulled from a fiat which had a crank sensor. This pulley has a nice thick rear section that could easily be machined for slots. The only issue is that while it bolts up the the crank fine, the offset is different so both the alternator and water pump pulleys need to be moved forward on the engine so the belt will line up. Would it be better to have the thicker (almost 15mm) slotted trigger wheel but have to adjust position of alternator and water pump pulleys. Or make a 3-4mm thick toothed trigger wheel and weld it to the back of the standard pulley?

About 10mm difference in pulley position. Alternator and water pump pulley would need to be moved forward 10mm

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rear of thick pulley

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Side of thick pulley

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Side of standard pulley

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Wheel can only be 3-4mm thick on the standard pulley

20130506_143424 (Medium).jpg (194.36 KiB) Viewed 5280 times

Using the thicker pulley saves me from making a trigger wheel and its nice and thick, but i need to move the alternator and water pump forward.
Using the standard pulley i need to make a trigger wheel which can only be 3-4mm thick but i dont need to touch the water pump of alternator.

What do you guys think?

[festy]

Are you sure those pulleys are steel, and not cast iron? Do you have a way of welding CI?
Is there any way the thicker pulley could be machined down to remove the offset?
One of the pics looks a bit like the center might be a pressed in splined hub - if it is, could it be pressed out and reversed so the thick edge was on the outside?
Spacing the alternator forward should be simple, but the water pump may be a bit tricky...

[Holden202T]

well im not sure how the water pump works but if its anything like a holden 6 I just used a fan spacer, machined to the size I needed and put between the pulley and the pump!

[festy]

Well that would be easy in that case - my Alfa's water pump pulley isn't removable, which makes things a little more complicated.
Fiats are often a bit more sensible than Alfas, so spacing the water pump pulley could be quite a practical solution...

[mrfiat]

The pulleys are both cast iron and one piece...so yeah ill be better off bolting a wheel to the pulley rather than welding. Moving the altenator wont be hard and the waterpump pulley is also removable so making a spacer wont be too hard.
Any tips on machining the slots into the pulley? How did you do it festy? your front pulley looks very professional.

[festy]

I printed out the template that's been posted in one of the DIS threads, reversed it (because it's backwards), scaled to the size I needed, printed/cut it out and glued it to the pulley.
Then I used my turret mill to cut the notches to match the template.
I don't have a rotary table or indexing head (yet), I did start making one for this job but ended up using the template instead.

To work out where the template lined up, I first made up my CAS bracket and mounted on a spare engine, brought it to TDC and lined up the template with the sensor.
What I *should* have done was line it up so there was 10* static advance, it turned out that my engine really didn't want to start with 0* timing, and I had to modify my CAS bracket to add some advance by moving the sensor a tad

[mrfiat]

Can anyone recommend a place where i can get some alloy welding done in the Sydney area? I want to get my manifold done.

[0081(2)]

Where in Sydney are you located??

[mrfiat]

Where in Sydney are you located??

Inner west