I've ran a straight hose from the bottom coolant inlet to the rear bypass tube for the intake manifold and plugged the cylinder head water outlet. This is temporary until I can get the heater hoses and heater valve replaced, this winter.

Thanks for any opinions.

Cliff

It will be fine. The pressure isn't going to blow hoses off or any thing the car

It would be better to cap all the ports. The way you have it connected creates a path for the hot water to bypass the radiator which reduces cooling efficiency.

If you have the hot=closed thermostat attached to the rear of the intake manifold then it will work as designed, warming the intake at start-up and supposedly reducing W.P. cavitation before the main thermostat opens. For some reason a lot of cars including mine have a corroded hose barb screwed into the manifold instead of the hot-closed thermostat, so it's like beerman said.

I think those thermostats are available, seems like it would help on cold days. Otherwise, plug and cap.

1/4" BSPT thread for the outlet at the thermostat.

Slightly off-topic, wonder if there's a problem with Z's popping heater cores from the water pressure? From what I've read it seems to happen to a lot of Mustangs; easily solved by clamping a restrictor like a washer or socket in the heater hose.

Are those Dorman rubber caps? If so, they're no good, mine started falling apart after less than six months. I put some tapered rubber plugs from Ace hardware with silicon caps from M-C clamped over them instead.

It would be better to cap all the ports. The way you have it connected creates a path for the hot water to bypass the radiator which reduces cooling efficiency.

Coolant is also bypassing the head, just looping back around to the pump inlet. The effect is like having a smaller water pump. You might just clamp something on to the long hose to reduce it's internal size. Create a flow restriction or block it completely to force the coolant to travel through the head where it can do some good.

I can't plug the hardline running behind the head then into the manifold, then going into the thermostat housing can I? I thought the manifold had to have the heat? It circulates from the bottom radiator inlet on the front cover around the back of the head then through the manifold back to the themostat housing up top then I suppose through the radiator but it is under the thermostat so I guess it does bypass the radiator until the thermostat opens. I'm confused. If I plug all that up I won't have any heat circulating through the intake manifold for the carburetors.

It will be ok like that. I though you had the line connecting the port on the back of the block to the water pump input.

Stanley is correct about the Dorman caps. I tried them and they failed in a few months. Use a NPT pipe plug for the port in the block.

This picture might help you visualize how the big hose connected directly to the back of the head and back the water pump inlet can short-circuit flow that would otherwise pass through the head.

A single overheat can warp a head. It's not just a steamy inconvenience. Just saying, why take a chance. I would leave the small hose to the carbs, and block the big hose back the pump inlet. Win-win.

I would leave the small hose to the carbs, and block the big hose back the pump inlet. Win-win.

Where would I get coolant for the carbs before the thermostat opens?

Edited July 4, 201410 yr by siteunseen

Stanley is correct about the Dorman caps. I tried them and they failed in a few months. Use a NPT pipe plug for the port in the block.

That's off a fuel injection intake, the AAR plumbing. I will get something more suitable for the heat and pressure of the cooling system but it's a temporary fix until this winter when I re-do the heater valve and hoses and reconnect things back to spec.

Sorry site, I think I looked at your first picture wrong, I'm confusing things. I thought that was a T at the head with one port blocked and one straight back to the pump inlet. Apparently it's a line looping around the block and up to the carbs?beerman knows what he's talking about.

On plugging the hole in the head - if you have a spare block, the coolant drain plug in the block is the same thread size as the fitting in the head. I know it is on the L28. There's two parts listed but looks like the dealer might have them. They're cheap, buy two. Looks like maybe they just changed the head of the plug, not the thread.

Datsun 240Z/260Z Cylinder Block & Fitting L24, L26 (To Nov.-'74)

PLUG-DRAIN :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

PLUG :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

I just so happen to have a junk L28 block. :stupid: