Coolant connections for 3.9 block to 3.5 SU Carb manifold

Eurostang · Post by **Eurostang** » Thu Mar 16, 2017 10:41 am

I'm really stuck trying to make my 3.9 Disco 1 V8 engine with interim timing cover and pump hook up to a 3.5 'twin SU' carb manifold.

Does anyone know if this is possible and if so, how do I achieve it?

I've made an album of photos below to give some more context;

https://goo.gl/photos/i4qs9zUZ4C1HBVyw6

Thanks!

unstable load · Post by **unstable load** » Thu Mar 16, 2017 11:18 am

It should just bolt on. There is a guy running carbs on a 4.6, so it's certainly doable.
What part are you struggling with?

By the way, the manifold in your picture isn't the twin SU one, it looks like a Holley/Weber type manifold.

Eurostang · Post by **Eurostang** » Thu Mar 16, 2017 4:33 pm

unstable load wrote:It should just bolt on. There is a guy running carbs on a 4.6, so it's certainly doable.
What part are you struggling with?

By the way, the manifold in your picture isn't the twin SU one, it looks like a Holley/Weber type manifold.

It's the twin SU one modified to take a 4bbl carb.

Darkspeed · Post by **Darkspeed** » Thu Mar 16, 2017 8:54 pm

Eurostang wrote:
unstable load wrote:It should just bolt on. There is a guy running carbs on a 4.6, so it's certainly doable.
What part are you struggling with?

By the way, the manifold in your picture isn't the twin SU one, it looks like a Holley/Weber type manifold.
It's the twin SU one modified to take a 4bbl carb.

The 4.6 pump does not have the 2/3 return connections on the pump that the 3.5/3.9 has

The two at the back are the heater flow ( manifold connection) and the return, steel pipe that runs under.

The other small pipe at the front of the manifold is the engine circulation line when the stat is closed - also needs to go into the pump return. The 4.6 does not use a stat in the manifold it uses a separate plastic stat assy that the returns connect into. What are you planning to use?

You also need to establish where the header tank will connect into at this also needs to go into the return / pump inlet.

ChrisJC · Post by **ChrisJC** » Thu Mar 16, 2017 9:07 pm

What vehicle is it going in?, and what is the rest of the cooling system?

Chris.

garrycol · Post by **garrycol** » Thu Mar 16, 2017 11:25 pm

The manifold just bolts up to the 3.9 the same as the 3.5 - just as hard or just as easy. I have a 3.5 manifold on my 4.6 at the moment and it just bolted up - do not tightened any bolts until you have them all in with only a few threads in contact then tighten them up.

Garry

Eurostang · Post by **Eurostang** » Fri Mar 17, 2017 8:32 am

garrycol wrote:The manifold just bolts up to the 3.9 the same as the 3.5 - just as hard or just as easy. I have a 3.5 manifold on my 4.6 at the moment and it just bolted up - do not tightened any bolts until you have them all in with only a few threads in contact then tighten them up.

Garry

Sorry yes I've got no issues at all bolting the manifold to the block.

My issue lies with how to hook up all the coolant connections

Eurostang · Post by **Eurostang** » Fri Mar 17, 2017 9:13 am

Darkspeed wrote:
Eurostang wrote:
unstable load wrote:It should just bolt on. There is a guy running carbs on a 4.6, so it's certainly doable.
What part are you struggling with?

By the way, the manifold in your picture isn't the twin SU one, it looks like a Holley/Weber type manifold.
It's the twin SU one modified to take a 4bbl carb.

The 4.6 pump does not have the 2/3 return connections on the pump that the 3.5/3.9 has

The two at the back are the heater flow ( manifold connection) and the return, steel pipe that runs under.

The other small pipe at the front of the manifold is the engine circulation line when the stat is closed - also needs to go into the pump return. The 4.6 does not use a stat in the manifold it uses a separate plastic stat assy that the returns connect into. What are you planning to use?

You also need to establish where the header tank will connect into at this also needs to go into the return / pump inlet.

Yeah I've noticed my timing cover and pump does not have the one or two return lines that the earlier engines had.

I'd like to use the stat in the thermostat housing you can see in the pics if possible?

Not sure where I plumb in the header tank

The engine is going in a ford capri.

I've drawn a crude picture and numbered the connections:
(Ignore my labelling that was my best guess!)

4 & 1 are joined as they're the pipe that runs under the manifold.

5 & 2 come straight out of the manifold and both flow water outwards

3 contains the thermostat

ChrisJC · Post by **ChrisJC** » Fri Mar 17, 2017 8:06 pm

If your header tank is higher than the top of your radiator, and it's pressurised, then it's pretty easy.
4&5 go to 6&7 for the heater
8 goes to 9
3 goes to 10
assuming 12 is small, 12 goes to 13 to let the radiator bleed
11 goes into the bottom hose
1 & 2 go to 8

1 & 2 are returns (one is the heater return, the other is the thermostat bypass). So they just go into the bottom hose near the pump. The older manifolds had this return path cast into the timing cover. On the front cover you have, that return path was via the remote thermostat in the bottom hose.
11 going to the bottom hose just keeps the system full, and 12 to 13 keeps it bled.

HTH,

Chris.

Eurostang · Post by **Eurostang** » Sat Mar 18, 2017 10:52 am

Cheers Chris this is a great help!

I'm going to use a header tank that is pressurised and higher up than the rad. Not sure which header tank yet.

It looks like I'll need 3 things going to my bottom hose? 1 & 2 and the bottom of the header (11)?

If I bought a different header tank with 2 large inlets at the top; could I run 1 and 2 to those and the bottom header connection teed into the bottom hose?

A bottom hose like this?

The rad can bleed to atmosphere then.

Eurostang · Post by **Eurostang** » Sat Mar 18, 2017 11:09 am

And a tank like this

http://www.ebay.co.uk/itm/Coolant-Expan ... SwsN9XBPH-

unstable load · Post by **unstable load** » Sun Mar 19, 2017 4:34 am

Do you absolutely have to have the thermostat in the manifold?
The Range Rover P38 units are made to connect all those pipes without the need for a bunch of fittings. It even has a flange to allow you to attach it to the vehicle.
https://encrypted-tbn3.gstatic.com/imag ... uh_FGiruhk

You could then use the Rangie tank that has all the connections you need, too.