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The crank on the 2.5 12v motor protrudes +- 7mm while the crank on the 24v motor protrudes 3mm hence the need for a 4mm spacer if you are using the 2.5 flywheel(re balanced ofcourse) and you want the starter to engage in the exact same place(also using same 2.5 bell housing). Took pics today to avoid any confusion.

kevin wrote:The crank on the 2.5 12v motor protrudes +- 7mm while the crank on the 24v motor protrudes 3mm hence the need for a 4mm spacer if you are using the 2.5 flywheel(re balanced ofcourse) and you want the starter to engage in the exact same place(also using same 2.5 bell housing). Took pics today to avoid any confusion.

Ok, that seems to make sense. Can you post a couple of the pics?

does anyone know if the 12v rings are the same as 24v?

Side view of back of 2.5 12v motor showing crank protrusion.

Side view of GTA crank in 164 block. Bit blurry but you can still see the crank protrusion.

Spacer

Thanks for the pics Kevin!
However I was in the garage yesterday and found an interesting thing.

The 2.5 flywheel differs from the 3.0 12V flywheel.
Actually the crank differs also. i.e. the 3.0 12V crank looks like the 3.0 24V in terms of protrusion.
That means that the 3.0 12V flywheel is thicker than the 2.5 flywheel where the bolted connection is and therefore I don't need a spacer.

I took a couple of pictures with the mobile to show you, unfortunately its poor quality but you may be able to see the difference if you look at the boltheads compared with the flywheel edge.

And here are the 3.0 12V flywheel that I'm going to use

Daniel wrote:

The only thing I had to do was to get new bolts to the flywheel since its a different thread in the Q4 crank than in the 12V engines

Now you have me worried - I know that the 12v engines have M12x1.5 thread, what does the 24v have?

I am going with the 2.5 bell housing and retaining the standard 24v flywheel (somewhat modified) and starter motor. My flywheel mod requires me to use bolts 15mm longer than the standard 24v ones. I hope I can get the thread in a grade 10.9 or better.

Took a pic on the flywheel bolts.

Edit: Realized that it was M12 x 1.25 so I changed the info in the pic.

Mats (fo) .You must just assemble it as it works for you as long as you have the correct lenght and grade of bolt and your fly wheel is in the same postion relative to the origional one with the origional starter set up. I have never seen a 75 3.0 motor as we never got them so i actually cant advise you whats the correct set up that will work.

I measured my 24v flywheel bolts - they are too short for what I want but they are definitely M12x1.25, not M12x1.5 (I measured the 2.5 12v engine that I have pulled out)

kevin wrote:Mats (fo) .You must just assemble it as it works for you as long as you have the correct lenght and grade of bolt and your fly wheel is in the same postion relative to the origional one with the origional starter set up. I have never seen a 75 3.0 motor as we never got them so i actually cant advise you whats the correct set up that will work.

Ok, I didn't realize that you haven't gotten 75 3.0
However it's good to share the plans and see if you guys think it will work and get some input.
I had heard about the spacer earlier but couldn't sort out why I didn't seem to need one.
Thanks to you I now know where the difference are and can go on as planned.

Daniel wrote:I measured my 24v flywheel bolts - they are too short for what I want but they are definitely M12x1.25, not M12x1.5 (I measured the 2.5 12v engine that I have pulled out)

Strange, I'm pretty sure my 24V bolts are M12x1.0 (see my previous posted pic).
However I will double check that at the garage tomorrow.

As far as I know alfa bounced back and forth with thread pitch
you have to just check which you need.

I am not sure if this info is useful to anyone, but I was able to buy a stock set of pistons and liners with rings and pins for the 164 3l 24v for 450GBP ($1007 shipped to NYC). That is cheaper than tyunder.nl (i think i spelled that right) merely because of the exchange rate.
Paul Spruell (www.paulspruell.com) is willing to make a custom set of forged pistons in any comp ratio that i want for the 3l 24v for $1035 (but i know that does not include all the trimmings) and there is a 4-6 week turnaround time. I believe tha JE would produce them, however i cannot wait that long.
Cheers,
Victor