Carb preheater inlet fitting

[jlm_1951]

Hi,

I'm looking for the heater hose fitting that threads into the rear carb manifold. It's the inlet for the carb preheater line, near the back of the head/block on a '72 Z.

thanx!

joel

[Bambikiller240]

Good Luck. My experience has been that after 30 years, they will not come out of a manifold without getting destroyed. I've been trying to get one for a spare manifold for 2 years now and I've broken 4 in attempts to remove them from JY cars.

IF Nissan still sells them, they are way too pricey for me.

[jlm_1951]

That's the problem I've had, and of course the part is NLA from Nissan. I was able to get the broken part out using Kroil and a screw extractor.

Has anyone tried to find a suitable tubing fitting? As far as I can tell it's a 3/8" JPT fitting (which should be the same as a 3/8" BPT fitting), but I can't find a U.S. supplier for them. Haven't had time to see if there is similar fitting from a British manifold setup, since they also used a preheater.

joel

[Bambikiller240]

Keep in mind that the Datsun OEM part is a valve that shuts off water flow at a pre-determined water tempurature so that the carbs and manifold are only heated until the engine warms up. Allowing water flow at all times will likely result in issues with the carburetors not operating well. Many of us (even those with a valve) disconnect or otherwise disable the manifold/carb preheat feature if we don't have really cold weather to deal with.

[jlm_1951]

Understood, but here in Colorado I've noticed that ever since disconnecting the circuit, cold performance is not very good. Possibly due to true carb icing. Alsp, the various British makes that had preheaters didn't have a thermovalve (that I can find reference to). I'll keep trying to find an original -- there has to be one somewhere!

thanx,

joel

[Daniel]

It seem that based on Carl's history with removal. I would suggest a machine shop. Perhaps they can drill it out and rethread to an available part or make one to fit the datsun thread.. I cant see that being very expensive.

[Bambikiller240]

If the valve has snapped off like in this picture, you can drill out or EZ-Out the threads that are stuck in the manifold. I'm going to try dressing up what is left of the threads on the valve and re install it. It won't matter much to me if it isn't water tight since I block off the other end of the valve with a bolt and silicone so there won't be any flow.

From what 2ManyZs told us, the valve shuts off water flow at 80 degrees F, so just using a nipple and allowing flow at all times would seem to be a sure fire recipe for carb problems (once the water is up to 180 to 190 degrees F)

Here are a few threads:

http://www.classiczcars.com/forums/showthread.php?t=14245

http://www.classiczcars.com/forums/showthread.php?t=13973&highlight=80+degrees

[jlm_1951]

well, push comes to shove, I can drill/tap for NPT and add a valve, not unlike my '64 Land Rover's heater shutoff valve...God Save the Queen.

joel