coolant sensor and electric choke thermostat

[capev86]

i managed to get my 72 burb running after the 80's Q-jet swap, but.....

hoping to use the electric thermostat and wiring from my dad's 84 burb in my 72. can i use the 2 prong coolant temp sensor from the 84 to power the stock 72 temp gauge or is the resistance range different? it looks like i will have to leave excess wire when i splice it in so i can swap the 406sbc which has the sensor near the back end of the driver side whereas the stock 307 has the sensor mounted between cylinder 6 and 8. also, how do i wire in the 2 wires to a system that only has one wire to begin with. any and all input would be great....

thanks!

[JimKshortstep4x4]

The 84 sensor resistance range will not match the 72 dash gauge.

I don't know what year small blocks you have but by convention, the coolant sensor was mounted between 1 and 3 on the left side. The right side head has a spot for the sensor between 6 and 8 but was usually plugged.

Jim

[capev86]

the 307 is the original '72 power plant

the 406 is a '77 model but with replacement heads on it because the original ones didn't have the cross drilling like the block has and the heads cracked while trailer towing (the correct heads fixed that problem).

my dad put this engine in his '84 burb in 1995 to replace the worn 350 and so we'd have plenty of power to pull our trailer out to yellowstone and back on a month long trip. it had about 10,000 miles on it since it had been rebuilt at that time (now about 30,000 miles on it). he used the stock '84 350 harness and even swapped over the q-jet and intake manifold. as far as i recall, only major mod he had to do was drill and tap an extra hole on the driver side to mount the exhaust manifold because the forward most stud was in a different spot.

other than the shot of chevy orange i gave it while on the engine stand it looked like the factory engine once installed....complete with the miles of smog equipment. i will use the ram horns from my 72 when i do the engine swap in the next couple years. right now i want to get the 307 running right with the edelbrock intake and reman q-jet i put on it in place of the original 2bbl. i will keep the 72 accessories when i do the swap and want to set up the electric choke t-stat and wiring i scabbed from the '84 harness which is still on the 406.

when my dad and i pulled that bad boy a few years ago we cut the harness at the firewall and then junked the truck. i am just trying to figure out what to do based on visual observations and a chilton's manual that covers '80-'87 gm trucks.

-thank you for the input.....keep it coming guys and gals!

[capev86]

The 84 sensor resistance range will not match the 72 dash gauge.

ok.....how do i get around this problem and still keep my factory gauge and run an electric choke t-stat? do i have to use a seperate e-stat add on kit or can i put a converter on the lead to the gauge?

[frog trucker]

Why can't you put the '72 temp gauge sender in the left head & the late-model coolant sensor in the right head?

[capev86]

i would use separate ports....if the 307 had them. only coolant port i can find is on the right bank between the #6 and #8 plugs.

on the 406.....the port is on the way back driver side just as it was on the original '84 350, lower than the plugs and right ahead of the bellhousing. i looked for a port between any of the plugs and i didn't find one where the 307 has one....likely because the 406 doesn't have water jackets (thankfully mine is cross drilled so cooling is not an issue).

[capev86]

could i possibly use a port in the intake manifold below the t-stat housing?....it should theoretically be close to the same temp as lower in the blow if it is before the thermostat....

[mclairmo]

Read the below that I found from Corvette Specialties of Maryland, Inc.

Can you repair my temperature gauge?

It reads high, but my 'Vette is not actually overheating.

COMMON CUSTOMER COMPLAINT: (Applies to all Corvette electrical temperature gauges from 1955 to approximately 1972.) Customer will usually add the following: I know it's not the sending unit. I've already replaced that.

REALITY: ALL, (I mean ALL), each and every new sending unit that is sold presently is wrong. I don't care what the parts guy tells you or what the parts manual says, they are wrong. There is an exception to this, which is to find a New Old Stock (NOS) part. To my knowledge, these parts have not been available for at least 20 years. Our testing of a known good original sending unit and the currently available part, shows that both units read nearly the same - until the water temperature reaches approximately 180 degrees. From that point and higher, the correct sending unit will maintain accuracy, but the replacement unit will give you a reading that is approximately 30 degrees higher than the actual temperature. Unfortunately, in our opinion, the addition of a resistor (to alter the reading of the replacement part) is inappropriate. The readings are not consistent throughout the normal temperature scale. They do not vary (enough to be a problem) until approximately 180 degrees. For those of you that have a car that rarely exceeds 180 degrees, you will not notice an inaccurate reading with the replacement sending unit.


SOLUTION: We currently have a GM licensed reproduction sending unit with correct calibration for $22.00 each. The appearance is like the original, including the wording "A.C.- Made in USA.-12 Volt". You may also replace the sending unit with an original type. It may sound difficult but through research, we have found that many GM products from the 50's and 60's used a sending unit that will work in your Corvette.

I also read another article that explains that the newer AC Delco G1852 water temp senders are the same as all the aftermarket one and are wrong. As such, if we are using these new aftermarket units, our guages will be wrong. I am going to buy the repro Corvetter one and see if that is accurate.