Holt 75 from Italy

[Foketry]

Hello guys
This is my first post, but I've been following this forum for years, to learn the techniques of engine construction .I live in northern Italy just a few miles from the Ferrari factory cars, Lamborghini cars, Maserati cars and Ducati motorcycles.This area in the north Italy is called Motors valley.
I also have mechanical passion and this is one of the first engines i am building.
Some of my friends here in Italy have already built the complete Holt tractor, fully working with the engine ,
and through them i had some suggestions to build an engine.
I had to build the foundry moulds to make alluminium and cast iron castings

 

[Foketry]

 

[Foketry]

 

[Foketry]

 

[k2steve]

Welcome to the Forum Foketry, I recently have been lucky enough to have picked up a older casting kit of a Holt 75 kit.
I will be looking forward to your post on the one your making for tips about the build. I don't know much about making castings but yours look great to me.

 

[e.picler]

Be well come to the world of model engines!
Congratulations for your castings looks good. Did you cast at home or used outsource foundry?

About four years ego I spent couple days at your area. I visited Ferrary Museum and had a tour at the Ferrary manufacturing building (not inside the building)

Expect to see lot of pictures. Good luck.

Edi

 

[Foketry]

Hi Steve
The original aluminum casting is a single piece, my castings are made in 2 pieces ,top and bottom, in my opinion it is easier to make the seats for the bushings.
It is possible to cut the original alluminium casting into 2 pieces

 

[Foketry]

Hi Edi
I'm glad you've been to visit the Ferrari museum, i live about 20Km from this museum
I hope you could also appreciate the food of this area, here is produced the typical and original Parmesan cheese, Lambrusco wine, and original Balsamic vinegar.
Both castings, cast iron and aluminum, were made by 2 small factories specialized in small batches , i only made wooden moulds.

 

[Foketry]

 

[Foketry]

my castings were full of aluminum inside because i did not build the internal model , but only the external one
I preferred to empty the inner part with the end mill

 

[Foketry]

the seats or support for crankshaft bushings

 

[Foketry]

The seat for crankshaft bushings

 

[Foketry]

 

[johnmcc69]

Nice work!

John

 

[gbritnell]

I built my Holt the same way with a two-piece crankcase except mine was from bar stock. It made it so much easier to machine the main bearings. Very nice work on your engine. Should you have any questions please don't hesitate to ask.
gbritnell

 

[Foketry]

Hi G Britnel, before building my Holt i read your posts several times and i downloaded your photos, practically you were my teacher.
I also followed the advice of an Italian friend of mine who had aluminum castings some years ago from USA , after several problems, he divided the aluminum castings into 2 parts.
A small difference: you have fixed the bushings supports on the upper part, i have them fixed on the lower part to facilitate the entry of oil.
I suppose you made this choice to get more precision between the crankshaft and cylinders.

 

[Foketry]

I need some advice, in the original project of the heads the spark plug is very hidden, I'd rather hollow the head to bring the spark plug more towards the chamber.
In addition to this i would like to put a Viton OR to seal the head on the cylinder and increase the compression rate up to 8: 1.
Below you can see 2 drawings: original and modified

 

[Foketry]

the spark plug is very hidden

 

[Foketry]

the spark plug is closer to the combustion chamber and there is a ORing groove

 

[gbritnell]

When I first built my engine I machined the heads from the drawings. Like you I thought there would be an issue with the depth of the spark plug hole and initially made my own plugs with a much longer reach. When it was time to replace the plugs I tried a set of Rimfire plugs, the longest version and the engine runs just fine with those so I wouldn't work about trying to make a counterbore for the spark plugs. If you make it like you show on the model it would probably help.
gbritnell