What to do with steam line?

[dayj1]

Originally Posted by bigmoe

This looks interesting. So that sender is compatible with Gen III and IV engines?

It has the correct thread to screw into the cylinder head. However, the sender is calibrated for GM gauges from about '88 and up. Factory gauges that are older than that won't indicate the proper temp with the newer sender.

[kipps]

Originally Posted by dayj1

It has the correct thread to screw into the cylinder head. However, the sender is calibrated for GM gauges from about '88 and up. Factory gauges that are older than that won't indicate the proper temp with the newer sender.

Can you clarify? How far off will a squarebody gauge read? What about a '91 Suburban(squarebody) gauge? Is that pre-88 style, or post-88?

[prodjay10]

It depends but my guess is use a scan tool to see what the temp is and check the gauge. Then use resistors to calibrate.

If you search the part number and ls swap you should find the instructions.

[dayj1]

Originally Posted by kipps

Can you clarify? How far off will a squarebody gauge read? What about a '91 Suburban(squarebody) gauge? Is that pre-88 style, or post-88?

Here's a good reference on troubleshooting Chevy truck gauges:

http://forum.73-87chevytrucks.com/sm...1241#msg211241

According to the document at the link above the following information pertains to the temp gauge in 79-87 trucks (or up to 91 Suburbans/Blazers/2500s/etc)

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω (100 degrees)
Middle Line when sender resistance = 96 Ω (210 degrees)
Right Line (Hot) when sender resistance = 55 Ω (260 degrees)

Here is a link to a resistance chart for an "LS" sender. There are actually 2 of these senders inside the 3 wire Camaro sender that was referenced earlier in this thread. There are senders available with 1/2" NPT, 3/8" NPT thread, or 12mm straight threads depending on the original application. Almost all GM temp senders that were intended to be used with an engine computer are electrically the same, but they were all over the board prior to that.

https://ls1tech.com/forums/pcm-diagn...l#post15884132

Here are the LS sender resistances/ temperatures closest to the gauge marks/temp that we used above:

1459 Ω = 104*
177 Ω = 212*
77 Ω = 266*

As you can see, the 100* resistance is about the same for both senders. But, when the engine is at operating temp (about 210*), the LS sender has a resistance of 177 Ω vs the factory truck sender's 96 Ω. For the gauge to point at 210* with the LS sensor, you'd have to subtract about 80 Ω of resistance from the sensor. It's kind of hard to remove resistance by adding resistors. The best bet would be to swap out the resistor on that back of the gauge that biases the two coils in the air core movement (gauge) but that's still never going to be perfect.

The simplest fix is just to tap the unused temp sender hole in the passenger side head to the size of your factory sender and use the sender that goes with the gauge.

[bigmoe]

My plan is for aftermarket gauges along with keeping the ECM info.

[prodjay10]

Well thanks dayj1 for raining on my parade. Jk! Thanks for the info. I think I’m gonna go with an obd2/tablet solution for speed and temps until I figure out a speedo.