67ls1CamaroProject

Does anyone know what the thread dimensions are for the temp sending unit in the block (M12, M14 X 1 or 1.5). I wanted to keep my mechanical autometer sending unit. It has a 5/8 - 18 UNF fitting that can adapt to an M16-1.5. This will be to big to tap as it will interfere with the exhaust flange. I need some options from all of you resourceful types. My options so far:

-Where could I buy a 5/8 - 18 UNF tap? (easiest)
-Adapt from M16 to M14 or M12. (Probably will not work because of probe length)
-Change to an Electrical Gauge with 1/8 NPT to Metric adapter.

What about tapping the block? How do you keep metal from getting into the water pump seals?

Speartech

iTrader: (14)

The water temp hole is M12x1.50.
I don't know how to tell you to get up to the size you need, that's pretty big!

We pretty much use all electric gauges here and I usually start with a 1/4 NPT sending unit, turn it down, and thread it with the M12x1.50 die. That works about as good as anything I've seen. There is an adapter available to get over to 1/8 NPT, but I've heard of a few people having it break off in the hole over time. Don't know anything about and I haven't used it.

67ls1CamaroProject

John,

Do you know what the stock GM sending unit specs are? Is it compatible with any Autometer Electric gauges?

pmg

I assume that these signals, like water temp and oil pressure, go to the PCM as well. Do the guages tap off of the same signal wire, is there 2 sensors for each (for PCM and guage), or how does that all work?

Thanks,

Perry

Speartech

iTrader: (14)

The oil pressure is gauge only.
The water temp is indeed 2 separate sensors in one housing (98 only).

99 and newer don't have ANY sending unit for a water temp gauge; the gauge is fed a serial data signal from the PCM, and that's why the water temp gauge in the 99 and up F-bodies is so crummy.

I go back to the 98 combination sender on any of the conversions here that are using factory type gauges.

Never tap into the coolant temp wire going to the PCM; it's only for feeding info to the PCM for fueling, spark advance, etc.

John

pmg

So for oil pressure, we're pretty free to put whatever sending unit we need for our guage into the hole where the stock LS1 came out of.

For temp, we need to find a guage that will handle the same sensor output that the 98 sending unit provides. We can hope that that resistance/temp output is somewhat standard <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

Do you know if there is another water port anywhere in the block that we can stick another sending unit for the guage into if that doesn't work?

Speartech

iTrader: (14)

Yes, your free to do whatever on the oil pressure. For aftermarket gauges I usually break-off the sending unit from the base and then TIG weld an 1/8 or 1/4 NPT bushing onto it. It's an easy way to get the correct metric thread for the engine!

For the coolant, the same port exists on the back of the passenger side head (since the heads are interchangeable). If you have room there, you can use it, or you can tap into the water pump and do about anything you need there.

I kinda think the GM sending units are not too compatible with aftermarket gauges, but I don't know for sure. I've always used the sending unit that came with the gauge.

John

68LSS1

Passenger side head, outboard side, right aft of the last exhaust port, there is a plug (allen head). Remove it and your all set.

Lesrace82

iTrader: (8)

Im running a mechanical water temp guage on my LS1. Im not going to have heat in my car, so I pulled out the nipples going to the heater core lines and tapped the holes. I am using one of these holes for my guage and the other one is plugged off. Just an idea if you weren't going to have heat in the car.

Speartech

iTrader: (14)

The LS1 sending unit is 55 ohms @ 260 degrees, and 1365 ohms @ 100 degrees.

I don't know if that's compatible with the aftermarket gauges or not.

John

MrDude_1

iTrader: (4)

is the 98 LS1 sending unit 100% linear? are thoes teh specs for the LS1 unit?