12 replies to this topic

[Professor Simon Peach]

Can the holes that allow the coolant flow from the block to the head be modified to allow better cooling? I heard if you enlarge the ones at cylinders 3 and 4 end it helps even out the heat along the engine. Is this true? I'm unable to find any info on if this is true.

[nicklouse]

Why do you think you need more cooling? What is your current cooling setup?

[Shooter63]

Can the holes that allow the coolant flow from the block to the head be modified to allow better cooling? I heard if you enlarge the ones at cylinders 3 and 4 end it helps even out the heat along the engine. Is this true? I'm unable to find any info on if this is true.

I think what you are talking about is semi dry decking, which is/was used in appendix K cars where dry decks aren't allowed. The restriction of some water holes to push the water along the head. Hopefully someone like OZ of O.A.P fame can give you more details.

 

Shooter

[DeadSquare]

Can the holes that allow the coolant flow from the block to the head be modified to allow better cooling? I heard if you enlarge the ones at cylinders 3 and 4 end it helps even out the heat along the engine. Is this true? I'm unable to find any info on if this is true.

On an unmodified engine, the holes around 3&4 are larger than 1&2.

 

You could easily make the 3&4 larger, but it might result in less flow around 1&2.

[imack]

KAD semi dry decked my block when they carried out the rest of the block machining.

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Edited by imack, 31 December 2025 - 06:15 PM.

[Spider]

For just about any street car and many competition engines, these kind of modifications aren't necessary. While your engine maybe capable of making light speed horse power, the reality is, when driving around the streets, you can only ever use a small percentage of that perhaps with short bursts of tyre smoke in between. If the engine is set up correctly, then around 35% of the power actually being used is what ends up in the cooling system.

 

[Cooperman]

[quote name="Professor Simon Peach" post="3797032" timestamp="1767186097"]
Can the holes that allow the coolant flow from the block to the head be modified to allow better cooling? I heard if you enlarge the ones at cylinders 3 and 4 end it helps even out the heat along the engine. Is this true? I'm unable to find any info on if this is true.[/quot.


Unless you are using your car for ultimate competition, typically medium to long distance racing, if you have an overheating issue, then look for the cause, as the block to head hole sizes will not be the cause.
Even with competition engines of up to around 110 bhp and running up to 7000 rpm, with a fairly standard cooling system overheating should not be a problem. If it runs generally a bit too warm, fit a 6-blade export fan and the latest type of radiator. An auxiliaries electric fan can be fitted to help in traffic on very hot days. On rally cars it is usual to remove the thermostat and fit a blanking sleeve. Don’t ever run with the thermostat removed completely.

Edited by Cooperman, 31 December 2025 - 07:42 PM.

[Earwax]

Hi Professor

 

I am with the leave it alone crowd on this one. ( for normal driving situations)

 

The only thing I am an advocate for is removing the bypass hose - and so choose the correct water pump type

[Lplus]

Hi Professor

 

I am with the leave it alone crowd on this one. ( for normal driving situations)

 

The only thing I am an advocate for is removing the bypass hose - and so choose the correct water pump type

Or put a restrictor in the bypass hose.

[Spider]

 

Hi Professor

 

I am with the leave it alone crowd on this one. ( for normal driving situations)

 

The only thing I am an advocate for is removing the bypass hose - and so choose the correct water pump type

Or put a restrictor in the bypass hose.

 

 

I have been doing as Earwax has suggested and plugging them (for a very long time). They take some hot coolant from the head, and put that straight back in the block, bypassing both the radiator and the thermostat. They were in fact designed for a very different thermostat that shortly after the introduction of the 850 Mini became unavailable. The factory did eventually cotton on to it many years later and did away with it. There's more here;-

https://www.theminif...e-by-pass-hose/

 

[Lplus]

 

 

Hi Professor

 

I am with the leave it alone crowd on this one. ( for normal driving situations)

 

The only thing I am an advocate for is removing the bypass hose - and so choose the correct water pump type

Or put a restrictor in the bypass hose.

 

 

I have been doing as Earwax has suggested and plugging them (for a very long time). They take some hot coolant from the head, and put that straight back in the block, bypassing both the radiator and the thermostat. They were in fact designed for a very different thermostat that shortly after the introduction of the 850 Mini became unavailable. The factory did eventually cotton on to it many years later and did away with it. There's more here;-

https://www.theminif...e-by-pass-hose/

 

yes, I contributed to that thread too.
 

[Professor Simon Peach]

KAD semi dry decked my block when they carried out the rest of the block machining.

 

Yeah, This is what I was talking about. But if everyone thinks I don't need it I'll

leave it so. 

Thanks All.

[Cooperman]

The question is whether your Mini is a full-on racer with over 120 bhp. If it is, then you might want to dry-deck it.