Water cooled manifolds - '72 240z

[uk66fastback]

For those with US cars of this year that had the later design with the water-cooled manifolds, have you kept that system when working on the cars over here - or blocked off the pipework - probably all bunged up with sludge anyway - and bypassed it?

I have also junked the smog unit and am wondering if anyone has done this, how they resolved the six pipes that go into the exhaust manifold? Some of the bungs on the balance tube will fit into the manifold and block off where these pipes went. So I'm torn between buying some of these bungs or cutting off them off the pipes and welding up the holes and reusing them ... that is if I don't end up buying one of Sean's headers (sorely tempted) which would remove the problem ...

 

[SacCyclone]

Pipe plugs for the exhaust manifold Mike.
I have plugged the water lines or changed out the intake manifold to the older style w/o water passage.
Mike

 

[AliK]

I have a 260 but the principle is the same.

When I removed mine, it wasn't blocked at all.

The benefits: carbs no longer hot - in fact they are fridge cold to the touch and often have condensation on the domes after a spirited blast! Less pipework to go wrong (mine sprang a leak) and a cleaner engine bay.

The downsides: the manifold after carb insulators is much hotter than before. No arctic condition driving for me any more (as if my Z would see a winter!!!!) as the carbs may ice up and finally, manifold temps not constant - again, not sure that matters in the real world use of our Zs.

 

[toopy]

There's no real point of all that shenanigans on a UK car, it just simply doesn't get cold enough for long enough to be effective, and who would be out in the snow and ice anyway, unless you were fortunate enough to have a rally Z!

I removed mine many years ago, the manifold pipe wasn't completely gunked up, but as near as dammit, the rubber hose from the thermostat housing to the front of the manifold however was solid with crud, as was one of the bends in the metal pipe that goes round the back of the block.

 

[Alphabettispaghetti]

is it to cool or to circulate heat to prevent carb icing in colder climates?

 

[Rob Gaskin]

Most things have been discussed before:

https://zclub.net/community/index.php?threads/water-cooled-manifold.21307/

 

[uk66fastback]

Thanks Rob, I did actually do a search and couldn't find anything. I did have the final reply on that thread as well, so even more embarrassing. Technically, it is water-heated, franky, you are right ...

Thanks for the advice, everyone.

 

[Alphabettispaghetti]

Thanks Rob, I did actually do a search and couldn't find anything. I did have the final reply on that thread as well, so even more embarrassing. Technically, it is water-heated, franky, you are right ...

Thanks for the advice, everyone.

Sometimes things don't seem to quite turn up in the search. FWIW you can get issues with carb icing in the UK, however i'm not sure if the SU's are prone to it. I wonder how the thicker oil inside when cold effects things?

 

[AliK]

Sometimes things don't seem to quite turn up in the search. FWIW you can get issues with carb icing in the UK, however i'm not sure if the SU's are prone to it. I wonder how the thicker oil inside when cold effects things?

Well, I drive mine hard and when I stop in a car park to adjust something under the bonnet, they are cold but never freezing cold.

Damper oil viscosity change is not noticeable - to me at least. If anything the thicker the oil the more smoothly they operate when you go back on the power (goes briefly rich). Those dodgy triples of yours on the other hand ....

 

[Rob Gaskin]

Guys, as most of us don't use the water heated manifold, what do you do about blocking off the piping?

I think most people use a threaded plug in the thermostat housing and modify their 'y pipe' on the block. I think the 'y pipe' is unnecessary clutter and want to run my heater hose direct to the water pump inlet but of course it's the wrong size to push on so I would need a 'reducer' which again is clutter.

What have you done?

 

[jonbills]

Guys, as most of us don't use the water heated manifold, what do you do about blocking off the piping?

I think most people use a threaded plug in the thermostat housing and modify their 'y pipe' on the block. I think the 'y pipe' is unnecessary clutter and want to run my heater hose direct to the water pump inlet but of course it's the wrong size to push on so I would need a 'reducer' which again is clutter.

What have you done?

As far as I remember, the outlet from the heater is the same size as the inlet to the water pump - I just have a straight hose between the two (16mm maybe?). If they're not the same size, they were close enough for the hose to be stretched over the bigger end.

 

[Rob Gaskin]

As far as I remember, the outlet from the heater is the same size as the inlet to the water pump - I just have a straight hose between the two (16mm maybe?). If they're not the same size, they were close enough for the hose to be stretched over the bigger end.
View attachment 39294

They aren't the same size Jon. The pipe from the inlet to the y piece is bigger by 4mm. Your plumbing is not standard.

 

[jonbills]

My heater outlet and water pump inlet are standard though, and they're the only relevant bits aren't they, if you're trying to delete the Y piece?

 

[Rob Gaskin]

My heater outlet and water pump inlet are standard though, and they're the only relevant bits aren't they, if you're trying to delete the Y piece?

Yes agreed but your heater pipes look big to me. Are you sure they fit straight on to the heater?

 

[jonbills]

Hmm, I haven't examined other cars for comparison, but the pipes and the firewall all look unmolested and I haven't noticed any strange adapters by the heater.
a decade ago, the hose from the heater failed on me. it looked old enough to be original.
so in summary, I don't know, but I believe my fittings to be original

 

[Rob Gaskin]

Hmm, I haven't examined other cars for comparison, but the pipes and the firewall all look unmolested and I haven't noticed any strange adapters by the heater.
a decade ago, the hose from the heater failed on me. it looked old enough to be original.
so in summary, I don't know, but I believe my fittings to be original

Well they aren't the standard 'preformed' hoses so you will have joints.

Anyway what have other people done with their Y piece?

 

[toopy]

I kept mine and just used a silicone end cap to seal the unused bit.

 

[jonbills]

Well they aren't the standard 'preformed' hoses so you will have joints.

Where will I have joints Rob? I'm wondering if we're talking about different things!

 

[Rob Gaskin]

Jon, I'm now realising that the 260 must be different than the 240.