LT1 conversion temp.gauge help!
Thread Starter
Instructor
Joined: Apr 2004
Posts: 110
Likes: 0
From: FRANKLIN SQUARE NEW YORK
LT1 conversion temp.gauge help!
Ok, here's the problem . I'm doing a '94 Vette LT1 conversion project . It's in a ' 76 . After not even 5 minutes of running time, the temp. gauge pins. But, at the same time, both fans kick on . The fans are mounted on a DeWitts radiator , and are wired with 2 relays ( one for each fan ). They temp. sending unit is in the passenger head , and the fans relays are connected to it . The temp. gauge is also connected to the temp. sending unit.
I've checked and rechecked all the wiring , and it is exactly as DeWitt's diagram . So, if anyone else has done this, or if anyone is really good with this set up, any and all suggestions are more than welcome !
I've checked and rechecked all the wiring , and it is exactly as DeWitt's diagram . So, if anyone else has done this, or if anyone is really good with this set up, any and all suggestions are more than welcome !
Burning Brakes
Joined: Jul 2001
Posts: 1,038
Likes: 3
From: Clinton IL
Need a bit more info.
Are you just now getting the whole thing up and running?
If so I would suspect you still have air trapped in the system. It is hard to get out of the LT1. The best way is to use the bypass line between the heads that goes to the throttle body as a bleeder. Fill and run the car until you get a steady stream of water out of that line. I would suspect you have capped it off to avoid heating the throttle body. Most people do.
Next issue is your temp sending unit MIGHT be bottoming out in the threads/head. DId you use an adapter bushing in the head that the temp sender runs in? If so, pull it out and inspect it off the car. Run the temp sender into the bushing and make sure the tip does not make contact with the sides of the thread bushing/adapter.
My money is on air in the system. Let us know what you find.
Are you just now getting the whole thing up and running?
If so I would suspect you still have air trapped in the system. It is hard to get out of the LT1. The best way is to use the bypass line between the heads that goes to the throttle body as a bleeder. Fill and run the car until you get a steady stream of water out of that line. I would suspect you have capped it off to avoid heating the throttle body. Most people do.
Next issue is your temp sending unit MIGHT be bottoming out in the threads/head. DId you use an adapter bushing in the head that the temp sender runs in? If so, pull it out and inspect it off the car. Run the temp sender into the bushing and make sure the tip does not make contact with the sides of the thread bushing/adapter.
My money is on air in the system. Let us know what you find.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
OK, here is a clue, the guage pegs and the fans come on at the same time. The guage is supposed to be on a sensor that provides a variable signal and the fans need a switch. You have a switch installed and are trying to run a guage of it. It will work fine for the fans, but not for the guage.
Burning Brakes
Joined: Jul 2001
Posts: 1,038
Likes: 3
From: Clinton IL
Originally Posted by SIXFOOTER
OK, here is a clue, the guage pegs and the fans come on at the same time. The guage is supposed to be on a sensor that provides a variable signal and the fans need a switch. You have a switch installed and are trying to run a guage of it. It will work fine for the fans, but not for the guage.
Since the fan sensor is designed to be on/off and a gauge sensor is designed to be a spectrum of resistance across the board, it makes sense. The point is you are most likely not overheating at all.
One trick you might like to know. If you get a scanner for the LT1 it will read out the engine temp as seen by the computer on the front of the water pump housing. It is always nice to have that to compare if you have any doubts about what you are seeing on your gauge only that is screwed into the head.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 110
Likes: 0
From: FRANKLIN SQUARE NEW YORK
Thanks guys !!! It seems I did make a bonehead move by putting the gauge and fans on the same sensor So now, in your opinion , should I put the gauge to another sensor in the head, or, to the water pump ? If the pump, I understand the reading will be 10-15 degrees lower than the head ? Many thanks for the heads up guys !! Always good to go to the guys with more experience !! 
So now, in your opinion , should I put the gauge to another sensor in the head, or, to the water pump ? If the pump, I understand the reading will be 10-15 degrees lower than the head ? Many thanks for the heads up guys !! Always good to go to the guys with more experience !!
4th Gear
Joined: Apr 2006
Posts: 4
Likes: 0
Need some more info on conversion
Hi, i have a 78 vette and a 1993 LT1 out of a camaro with the auto tranny im going to be doing the conversion and was just wondering what problems you ran into any hood clearance problems, which radiator do i use? do stock motor mounts work? i havent measured up the LT1 yet, sorry to sound dumb about just want to know what im in for. Also can i use all my stock gauges and speedo if so how do i do it?
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