jbates346

I'm curious to know what you guys are doing with your LS1/2 and using the stock 3rd gen gauges. What confuses me about it, is the the instrument cluster has that one plug and makes all the gauges work (except speedo). I know the LS gauges are ran by the ECM electrically. So how are you making the gauges work from the ECM? Are you just sodering the wiring to the back of the cluster plug? How do you know which is which?

Apeiron

Forget the ECM, just put your stock senders on the new engine.

jbates346

so basically have the stock sender to the new engine? Will all the old senders work with the LS motor? Can i just leave the gauge's connector alone and just switch the sender/sensor to the new block. I would assume i can't put it to the new engine. Also if the water temp sensor doesn't go to the ECM how would the ECM know when to go into closed loop and when to turn on the coolant fans?

Apeiron

The coolant temperature sender for the gauge is different than the coolant temperature sensor for the ECM.

jbates346

So can i just soder the wiring from the stock gauges to the new coolant sensor on the LS2. That should work. Then the coolant sensor for the ECM i'll just leave on the motor and route to the ECM. Sounds right doesn't it?

Apeiron

No, from the gauge to the old coolant temperature sender which you've installed on the LSx.

jbates346

Ok i didn't know that the old coolant temp sender will work on the LS2. Does it have to get modified? How much? Thanks for all your help. I'd like to at least have an idea before i dig into this thing.

88 350 tpi formula

iTrader: (9)

use the 1998 3 wire ls1 coolant sensor or you need to turn down the thirdgen sensor and thread it to go into the ls1 head. there are some pictures around here

jbates346

I think I understand what you guys are saying. What you happen to know if the '88's gauge's ECT is on the same scale as the LS1's. What I mean is the resistance and the voltage on the same scale. Cause if they are, I don't see why i can't use the LS1's sensor and just soder it to the 3rd gen's connector. Is that what you guys are saying cuz i'm a lil confused, lol.

88 350 tpi formula

iTrader: (9)

the 1998 ls1 used a 3 wire sensor. the third terminal can be used for your temp guage and is as accurate as your stocker is.


your only other option is to take your thirdgen sender and turn it down and thread it to fit the cyl. head. (or drill the cyl. head and tap it)

jbates346

Ok gotcha. Thats the way were gonna do it then. I'm assuming the rest of the gauges (oil pres, volts) are the same. The fuel level if i remember right comes from the ECM so i think i'll have to soder the wire from the ECM to the stock connector. Hopefully their on the same scale.

Apeiron

Or use a bushing.

mw66nova

iTrader: (13)

do you have a link to said bushing? i've never seen a bushing that converts tapered pipe thread (stock thirdgen sender) to straight pipe thread (ls1 cylinder head) but i'd sure love to use one rather than screw with this modifiying bullshit.

SheldonZ28

iTrader: (1)

Autometer makes an adapter thats fits a 1/8 npt sensor into a 12x1.5mm hole (IIRC that was the thread pitch)

Water temp - 98 sensor, or adapt stock.
Oil press - Drill out a LS1 sensor and tap for a thirdgen, or run off peice on the side of the motor.
Fuel level - If your using a stock tank, no worries here. If an LS1 tank, mod your fuel level sender, or use an autometer programmable gauge.
Volts - No change
RPM - LS1 has a tach output wire
Speedo - 4k PPM signal, should run any electronic thirdgen gauge.

mw66nova

iTrader: (13)

after spending the last two hours on here and ls1tech, i may go with another set of aftermarket gauges...

i was under the impression that the stock oil pressure sender will work as long as you have the correct pigtail for your harness....what exactly do you mean by drilling out and tapping an ls1 sensor?

V8Rumble

iTrader: (2)

On the F-body oil pan there is a little "bypass fitting cap" (for lack of a better term) immediately above where the oil filter attaches. In the picture below, you can see it protruding up slightly at the rear of the pan in the top image:


(Image is from the 'LSX oil pans' FAQ on LS1Tech.com)

As I understand it, what people do is to unbolt that little "cap" or fitting from the pan itself, & then tap it with a 1/8" NPT thread which matches the thread for the most-commonly used electrical sending unit.

Hope this helps.

five7kid

iTrader: (14)

Like this:



Drilled & tapped for 1/8" NPT mechanical gauge fitting.

mw66nova

iTrader: (13)

ah, i got ya. i did some more reading on ls1tech.com and the stock ls1 oil pressure sender will send the correct reading to the factory thirdgen gauge so i'm set there. now all i gotta do is get a factory thirdgen coolant temp sender turned down to an m12x1.5 and i'm set on the water temp stuff too. i'll deal with a tach/speedo output later. i just need to be sure i have the vitals reading well so i can get this thing fired up soon.

macdadyZ28

iTrader: (1)

I can vouch for that. I'm using an ls1 oil sender with my stock oil pressure gauge and everythign works fine.

five7kid

iTrader: (14)

There are two "stock" 3rd gen oil pressure gauges, one 0-60, the other 0-80.

macdadyZ28

iTrader: (1)

thats one i didnt know,

i can vouch for the 0-80 then lol.

screeminchicken

iTrader: (2)

So if I have the 0-60 kind.I would have to do the drill tap mod on the LS1 oil pan right ?

Klortho

Just buy a '98 sender it was the only year LS1 that still had a temp gauge that read the actual water temp instead of being a "guide" to what the temp was.