All Small Six DOHC 250ci

[Cox Custom Mechanical]

Hey Guys.

I started this project about 12months ago, I haven't made a lot of progress due to customer engines and other jobs, but I hope to get back to it in the next few months. It is a modified Barra head on a 250 Pre X Flow block.

The head now bolts to the block after plugging re positioning the head bolt holes, the oil and water galleries are sorted. Next step will be setting up the auxiliary shaft (former camshaft) machining a new front timing cover for a timing belt drive, followed by water pump modification in conjunction with timing belt assembly.

These photos were taken right at the beginning to see if it would even be possible, so please excuse the grubby block and head.


Watch this space.

I'm also putting Barra heads on a Windsor but that's a story for another day.

Cheers

Andrew Cox
Cox Custom Mechanical

 

[gb500]

Very good. Be watching with interest

 

[wme013]

DIY kit comming soon??

 

[aussie7mains]

Barra, wouldnt that be tonnes easier? A NA barra is around $400 down here.

 

[Cox Custom Mechanical]

DIY kit comming soon??

Thats the plan.

 

[Cox Custom Mechanical]

Barra, wouldnt that be tonnes easier? A NA barra is around $400 down here.

Absolutely aussie7mains, but the reasoning behind it is to do something different.

Some Speedway guys here have to run earlier crossflow blocks but are allowed to do any engine modifications they like so this would be perfect. The potential for the US market enabling people with pre crossflows and crossflows to maintain their current driveline and bottom end.

If all goes well version 2.0 may be able to be done in car to a stock block without the need to rebuild it at the same time.

Using my a Barra as a test mule the head will be a 250hp bolt on kit with flat top pistons, dish pistons will reduce that number if the end user decided to keep their bottom end due to a drop in compression.

 

[CNC-Dude]

Thats the plan.

So, the Barra and 250 have the same bore spacing. What is it exactly just for reference...?

 

[Cox Custom Mechanical]

So, the Barra and 250 have the same bore spacing. What is it exactly just for reference..

Hi CNC-Dude.

They sure do, its 4.08". The Barra engine also shares the similar stroke as the 250 but a slightly smaller bore.

 

[CNC-Dude]

Ok thanks!

 

[Cox Custom Mechanical]

Ok thanks!

Any time Mate.

If you have got some CNC skills I may have some work for you, can you design as well?

 

[CNC-Dude]

Yes, I'm very fluent with Solidworks 3D modeling software as well....

 

[gb500]

So, the Barra and 250 have the same bore spacing. What is it exactly just for reference...?

Actually the last ford Australia six - the barra has the same bore spacing as the first 144log /precrossflow- and all the sixes in between.

 

[Cox Custom Mechanical]

Actually the last ford Australia six - the barra has the same bore spacing as the first 144log /precrossflow- and all the sixes in between.

Which is why I am putting a 144 crank in a 250 block for a vintage speedway midget, the mains need to be modified but that's a piece of cake.

 

[gb500]

Very good
So making a 4 mains crank fit a 7 mains 250 block?

How? blocking and grinding clearance on the redundant 250 mains

 

[Cox Custom Mechanical]

Very good
So making a 4 mains crank fit a 7 mains 250 block?

How? blocking and grinding clearance on the redundant 250 mains

Morning gb500.

Yes, block goes in the mill and is clearanced for the counterweights. The biggest challenge is the bearing size and width of the 4 main crank as only the main spacing is the same, the diameter is not.

The finer details are a secret....

 

[gb500]

Yeah thought the mains are diff diameter.

 

[Cox Custom Mechanical]

Head is now bolted up, I've changed to a crossflow block because I have several of them gathering dust and the Pre Crossflow blocks have been assigned to other customer engines. It wont change much other than create a bit more work due to the larger pushrod holes with the wider deck.

I took some photos while attempting to clean up part of the shop yesterday




If you look closely at the cylinder head and deck you can see the areas that need to be plated to close the wider deck



The plan for the first engine is to run a full length cam shaft for the distributor, fuel pump eccentric and oil pump. One other aspect id like to maintain is the factory water pump, which presents some complicated belt pathways but is still achievable. As time permits ill keep chipping away with this one.

Cheers,

Andrew Cox
Cox Custom Mechanical

 

[wme013]

Are the crossflow and the pre crossflow blocks the same width?
Not so much for what your doing, but future kits and customers here. Crossflow blocks are sorta scarce around here

 

[Cox Custom Mechanical]

Are the crossflow and the pre crossflow blocks the same width?
Not so much for what your doing, but future kits and customers here. Crossflow blocks are sorta scarce around here

Different width and larger push rod holes in the deck, but the bolt holes are the same.

This will just be a test mule, its actually easier for me to adapt it to the pre crossflow blocks. Its just because I have crossflows lying around at the moment.

 

[aussie7mains]

Different width and larger push rod holes in the deck, but the bolt holes are the same.

This will just be a test mule, its actually easier for me to adapt it to the pre crossflow blocks. Its just because I have crossflows lying around at the moment.

I see the block is the late 86DA, but do you know what all the Ss are?