Technical 500 Nuova Engine Rebuild

[500nuova]

Question: That plugged hole seems to go straight to the pressurized oil gallery?

If the answer is "yes" it's probably a show stopper for my electric scenario for the following reasons: - I would still have to plug oil pump, drill 2.5 mm hole etc. - The electric pump would have to provide the main oiling pressure, i.e. it would have to be something like an (expensive) engine driven dry sump pump instead, and not just a (cheap) electric scavenge pump. - High pressure oil would be routed through long, potentially leaky lines increasing risk for oil loss. - And if the pump is electric and providing the oiling pressure a blown fuse equates blown engine.


So basically I'm looking for a "hole" that's not part of the pressurized oil path to just dump oil back into the crankcase en route back to the sump.


Am I wrong about that?

 

[500nuova]

Update after a long silence: While waiting for the (perpetually tardy) US Postal Service to deliver from the UK I decided to open up the engine for inspection and cleaning.

Apart from being absolutely incredibly dirty it looked mostly OK except the main bearing on the "bell housing side", that looked like this. Possibbly spun at some point and subsequently ignored? No big deal, I thought at first, since new bearings are going in anyway.


But unfortunately, it seems the crank journal wasn't happy about that, and will have to be ground under-size. My question is, how much under is it prudent to go? Or is it better/safer to use another crank and let the existing one be a conversation piece?

As always, any insights will be greatly appreciated.

 

[the hobbler]

The Fiat "book of words" allow you to go 0.6mm undersize, but these days how much you can go very much depends on what bearings you can obtain. I will search and see what can be obtained--I have a good source in Germany

 

[the hobbler]

Axel Gerstl in Germany have a SET (pair) of crankshaft bearings for a 0.4mm undersize crank---199 euros--in stock

 

[Toshi 975]

MotoBambino ltd, the 500 specialists in Lancashire are listing main bearings in all sizes up to +0.8mm and price of a little over £80 for the pair.
As for the regrinding the machinist will normally remove the minimum from the crankshaft journal that will give a good surface.

 

[500nuova]

Tom, David, Thanks for the information. Very helpful.

 

[500nuova]

Unobtainium: Two sets of NOS Borgo pistons arrived from Bella Italia today. Will upload a picture or two as soon as I figure out how to do it...

 

[500nuova]

This is what they look like! Very excited.

 

[500nuova]

:d

 

[the hobbler]

What piston oversize did you go for in the end Thor?

 

[500nuova]

I went +0.6 over.

 

[500nuova]

Here is my newly arrived Dellorto FZD. Fresh jets and nice patina.

 

[TeleSpeed]

Beautiful carb. What is the proper jetting and Venturi for a Nuova engine?

 

[the hobbler]

If it is a 30/24,a good starting place is as follows:--
Main:-------------------128
Idle:--------------------38
Air correction----------190
Accelerator pump:----40 (absolute max)
Emulsion tube:--------6747-6

The 6747-6 Emulsion tube is the one to use on ALL variants of the FZD when used on ALL sizes of the 500/126 engine. They are difficult to find these days, but there is a company in Italy who can supply them. Not 'pukka' Dellorto parts, but new and seem to be made to a high standard. My engine is running with one of their Emulsion tubes with no problems. Alternatively, a 6747-1 can be easily modified to match the '6'
The pump jet might need a smaller size--it is easy to fit too large a pump-jet, and all it does is 'bog' the engine down when accelerating.
On my engine I have done away with the choke as on most of the FZDs, the choke mechanism is on the side facing the rear of the car. To start the car,I use the accelerator pump to give me the neccesary enrichment. Yes, it does take a bit longer to warm up, but is easier than trying to modify cables etc to make the choke work.