8 replies to this topic

[mini670]

Hi,
Just wondered if anyone has advice and or experience in semi dry decking please.
I had never heard of it until MED mentioned it in one of thier videos.
I have already tapped out the three smaller coolant holes around number 1 cylinder, but still have the larger one to do.
Began to wonder why these were not blocked when the castings were cast if it makes a difference to cooling at number 4...
Just wondered what others thought about this approach.

[nicklouse]

It all depends on what you mean by semi dry decking. My block is sealed of but the head is not,

[mini13]

ive seen metro turbo cup engines with the waterways restricted on cyls 1,2&3 i an effort to promote cooling of no 4,

 

on my turbo 7 port, I tapped the block and plugged the waterway,s but leaving a small bleed hole of a 3mm, and ran a drydeck hose from the block to head, I left the head holes un blocked.

[mini670]

It all depends on what you mean by semi dry decking. My block is sealed of but the head is not,

From what I can gather its sealing off cylinder 1 waterways to promote a bit more flow to number 4

[mini670]

ive seen metro turbo cup engines with the waterways restricted on cyls 1,2&3 i an effort to promote cooling of no 4,

on my turbo 7 port, I tapped the block and plugged the waterway,s but leaving a small bleed hole of a 3mm, and ran a drydeck hose from the block to head, I left the head holes un blocked.

Had wondered about restriction over blocking for the larger cooling hole at top left of cylinder 1.. Perhaps grub screwed with hole through it?

[Maccmike8]

MED would block holes on 2 and 3 too but the racing regulations says you cant hence they only block #1.

[Spider]

I can understand the thinking that No. 1 Cylinder runs cooler than No. 4 due to coolant flow and just where the Water Pump is located, but for the most part, I disagree with that thinking.

 

If you stand the block on the Flywheel and and look down the cooling jacket through the opening for the Water Pump, you'll see that the passageway is tapered like a funnel, starting off large at the front of the Block and getting smaller as it gets down towards No, 4 Cylinder. That, and the restriction the holes in the Deck of the Block have to the Flow Rate of the coolant gives a fairly even Flow across all Cylinders. If you grab a block without the head on it, bolt up a Water Pump and attach a garden hose to it, you'll see at moderate to high flow from the hose, that similar water quantity will flow from all holes in the Deck. The Pump Rate of the Pump above around 2000 rpm, exceeds the flow rate through these holes. 

 

Looking at the Head it is a bit of a different story though. Certainly the Flow Rate through the Deck Holes is very similar to that of the Block however as the Coolant from No 4 needs to pass by all the other Chambers to get to the Radiator, it actually heats more the closer it gets as that part of the Coolant has heat from no. 4 and picks up more as it passes the other Chambers. And so it also goes for Chambers 3 and 2 as well, though it tends to 'pool' under the Thermostat. What also helps with the heat distribution across the Head is it's fairly small size.

 

From my experience though, what does make No. 4 hotter down that end than no. 1 is rust and junk that's built up in the cooling jacket and it tends to settle at that end of the Block.

[mini670]

MED would block holes on 2 and 3 too but the racing regulations says you cant hence they only block #1.

Cheers,

That obviously is getting more an more like a dry deck, but I would guess the cross sectional area for flow is a fair bit lower than using a true dry deck

[mini670]

I can understand the thinking that No. 1 Cylinder runs cooler than No. 4 due to coolant flow and just where the Water Pump is located, but for the most part, I disagree with that thinking.

 

If you stand the block on the Flywheel and and look down the cooling jacket through the opening for the Water Pump, you'll see that the passageway is tapered like a funnel, starting off large at the front of the Block and getting smaller as it gets down towards No, 4 Cylinder. That, and the restriction the holes in the Deck of the Block have to the Flow Rate of the coolant gives a fairly even Flow across all Cylinders. If you grab a block without the head on it, bolt up a Water Pump and attach a garden hose to it, you'll see at moderate to high flow from the hose, that similar water quantity will flow from all holes in the Deck. The Pump Rate of the Pump above around 2000 rpm, exceeds the flow rate through these holes. 

 

Looking at the Head it is a bit of a different story though. Certainly the Flow Rate through the Deck Holes is very similar to that of the Block however as the Coolant from No 4 needs to pass by all the other Chambers to get to the Radiator, it actually heats more the closer it gets as that part of the Coolant has heat from no. 4 and picks up more as it passes the other Chambers. And so it also goes for Chambers 3 and 2 as well, though it tends to 'pool' under the Thermostat. What also helps with the heat distribution across the Head is it's fairly small size.

 

From my experience though, what does make No. 4 hotter down that end than no. 1 is rust and junk that's built up in the cooling jacket and it tends to settle at that end of the Block.

thanks,

a bit to think about here. Wonder if it simply just does even out. Beginning to think that Leyland would have blocked cylinder 1 cooling if it provided even cooling