Drilling and tapping water pump housing .

[Bucket]

My 1961 361 BB has only got one port for the temp sender unit on the water pump housing .
This port currently has a mechanical temp gauge adapter in it .
I would like to hook up the original temp gauge as well just so i can see it working but rely on the mechanical gauge .
From what i can gather there is about 5mm of metal i can drill and tap on the passage next to the original temp sender port location .
That or about 9mm of metal in the block just behind where the water pump mounts .
Water pump is off the engine at the moment so drilling the pump or block won't be a problem.
So has anyone drilled and tapped in these locations before ? .
Rock Auto lists the thread size for the original sender unit as 1/4-18".
I can't seem to find a thermostat housing spacer with this thread size port .
Cheers,
Greg

 

[sprice]

Not familiar with a 61' pump, however if its cast iron it won't be easy.

 

[Welder guy]

Don’t do it . Get later made water pump housing with the extra holes you need or install a threaded nipple and a tee in your heater hose hole then your hose nipple into the top of the tee. Mount the sending unit into the side of the tee . Drilling through thin cast and tapping it is a recipe for disaster down the road even if it works. it’s a weak spot and it will crack .

 

[Bucket]

Don’t do it . Get later made water pump housing with the extra holes you need or install a threaded nipple and a tee in your heater hose hole then your hose nipple into the top of the tee. Mount the sending unit into the side of the tee . Drilling through thin cast and tapping it is a recipe for disaster down the road even if it works. it’s a weak spot and it will crack .

Thanks for that , i did think about the later model housing but they seem a bit light on in Australia .
I think i understand what you mean about the tee , would you have any photos of this set up ?

 

[Welder guy]

I don’t have any pictures of the set up but it’s a low cost alternative to what you want to do.

 

[Big_John]

Rock Auto lists the thread size for the original sender unit as 1/4-18".

BTW, that's a tapered pipe thread, and will have NPT designation after it. Need the correct tapered pipe thread tap and you need to understand that it only gets threaded down about 2/3 of the length of the tap.

I'm not sure what you guys have there, but I believe you use a British Standard pipe thread, and IIRC, that's 1/4-19, but it also has a different thread form (Witworth) and will basically mess everything up if you try to match it all. It may actually start to screw together, but it won't go well from there.

Much easier to use a tee as described above, but again, correct NPT fittings will have to be sourced and I have no idea what you guys have available at the corner hardware store. We take this stuff for granted here, so no one but somebody like me that's had to summon the devil a few times to work with different types of threads would ever think of it.

For those that want to know the difference: National pipe thread - Wikipedia British Standard Pipe - Wikipedia

 

[Trace 300 Hurst]

We take this stuff for granted here, so no one but somebody like me that's had to summon the devil a few times to work with different types of threads would ever think of it.

Except those of us who have worked on the mechanicals of a 1953 MG TD. Sheeeeeeeeesh!

 

[Big_John]

Except those of us who have worked on the mechanicals of a 1953 MG TD. Sheeeeeeeeesh!

My late buddy Bill had the pleasure of owning and working on a Royal Enfield motorcycle. He learned the joy of Whitworth threads. It was especially fun when a few odd pieces here and there had been screwed up/replaced/screwed up worse/replaced with SAE threaded fasteners. I think every accessible bolt and nut was changed on it the last time I saw it. He had a love/hate relationship with that bike.

BTW, the correct term is actually Unified, but when I say "SAE", everyone seems to kinda know what I'm talking about.

Another BTW, and it's a memory that made me smile... I would always refer to his bike by some other hyphenated English name, like "Webley Vickers" or something like that. Often just making something English sounding up on the spot. Not much got under his skin, but that would make him shake his head.

 

[Bucket]

BTW, that's a tapered pipe thread, and will have NPT designation after it. Need the correct tapered pipe thread tap and you need to understand that it only gets threaded down about 2/3 of the length of the tap.

I'm not sure what you guys have there, but I believe you use a British Standard pipe thread, and IIRC, that's 1/4-19, but it also has a different thread form (Witworth) and will basically mess everything up if you try to match it all. It may actually start to screw together, but it won't go well from there.

Much easier to use a tee as described above, but again, correct NPT fittings will have to be sourced and I have no idea what you guys have available at the corner hardware store. We take this stuff for granted here, so no one but somebody like me that's had to summon the devil a few times to work with different types of threads would ever think of it.

For those that want to know the difference: National pipe thread - Wikipedia British Standard Pipe - Wikipedia

We have a couple of good hydraulic fitting stores in town which have a lot of brass NPT fittings , i will try my luck there .

 

[live4theking]

This is the type of tee I had installed at one point in time.

 

[Trace 300 Hurst]

I'll point out that we also have threaded drain plugs in each side of the block, but I forgot the size. The hole is about 1/2 inch in diameter, but it's NPT so I think that makes it 1/4 NPT. Someone here will know.

Anyway, that location won't give you the same temps as the water at the pump's sensor fittings (they'll be cooler because the water hasn't been through the heads) but once you've benchmarked the block's water temps under normal and proper water pump temps, you would have a fallback number. As OP Bucket said "I would like to hook up the original temp gauge as well just so i can see it working but rely on the mechanical gauge.", and this would allow for that. Just a thought.