J.C. Denton

iTrader: (1)

I have a strange problem at a buddys car. It's a 92 base TBI firebird with a 5 speed. Some unknown PO found it a good idea to remove the coolant fan switch in the pass head and plug the hole with a brass plug from sanitary equipment store and to ground the relay permanently so the fan would always run when ignition is on.
I found the original wire cut and zip tied to the starter harness. I soldered on a new connector and removed the sanitary plug from the head. But the new coolant fan switch from rockauto is too small for the threads in the head. Never had that happen. The size seems to be 1/2"... hard to tell, I only had metric thread tools on hand, inch threads are uncommon over here. I looked up the sensor for the gauge in the drivers side head and there is some kind of adapter installed for the sensor.
Anyone ever had this happen? Maybe the heads are from another car or aftermarket parts? I am at a loss now, I don't know where I can get such adapters and I also wasn't able to find out what thread size the original coolant fan switch is. The car is parked 50 miles away from me at my buddys garage and he has no tools or abilities to find out the thread sizes.
I can provide a few pics next week when I can get there if needed.

Thanks!

84 1LE

iTrader: (9)

Could the PO have enlarged the hole in the pass head? I dont remember the size, but i dont think its metric. Later engines (like LS) are metric/smaller (dia) threads. Sounds like someone used a metric sender on the driver head, maybe. The original threads on both heads are the same size/pitch, 1/2" sounds about right though. So fan switch/sender will fit on either side/head. Even aftermarket/SBC heads.

sofakingdom

iTrader: (1)

Sounds like it has heads from before about 74 on it.

They changed the holes from ½" pipe to 3/8" pipe somewhere in that time frame. The actual hole diameters are about 7/8" and 5/8", give or take.

You can buy a bushing at the hardware store. Such as https://www.homedepot.com/p/LTWFITTI...8605/313734408 Incidentally, that part # is a pack of 5, but the car only needs the one. For the temp gauge sending unit he can just use the one for something like a 69 Chevelle 350, which will fit and work just fine.

Drew

iTrader: (58)

J.C. Denton

iTrader: (1)

This is the temp sender from the other side, you can see the adapter on it. It has the original center bolt valve covers, so I doubt that these are heads from the 70's.

sofakingdom

iTrader: (1)

Then someone must have drilled them out and tapped them to the larger size from days gone by.

You can be sure that they didn't leave the factory the way they are now.

Even so, it's an easy fix, no matter how strange or how they got like that.

84 1LE

iTrader: (9)

Thats the proper sender for the gauge. So maybe the original threads were stripped and then "repaired" with that adapter

sofakingdom

iTrader: (1)

Zackly.

J.C. Denton

iTrader: (1)

Thank you guys, very weird. I'll watch out for an adapter to make it fit.

8t2 z-chev

Dart heads and probably other aftermarket heads have the larger sender size.

91banditt2

iTrader: (1)

My World Products S/R heads circa 2005 have the 1/2 NPT threads