Dash Gauges

[71MoneyPit]

hey everybody,

finally getting the Money Pit all finished up, but im having a problem getting the gauges to work with the caddy. What I am wondering is if any of you know where the sending unit for the water temp is and where the sending unit for the oil pressure is. There is one right above the front spark plug on the pass. side cyl head, and another one in the back of the driver cyl. head. and there is also one right on the front of the engine that is threaded in right below the intake. I have no idea which ones im supposed to use or if they will even work with the trucks gauges

Also, can't I just thread a fitting in where the oil pressure sending unit is and hook that up to the mech. gauge in the dash

And one more thing, what would be making my fuel gauge read empty when it is at least half full

thanks in advance

[Project1970]

Originally posted by 71MoneyPit

And one more thing, what would be making my fuel gauge read empty when it is at least half full

That'd be the Cadillac

[Longhorn Man]

The fitting in front by the T-stat with teh green wire is for the temp guage...Dunno if it is compatable or not.
There should be an electric sending unit in the back on top for the oil pressure light. I have not looked into the mechanicle guage possability on tat fitting yet, but I'm sure there is a way with a brass fitting or two.
The two sending units on the heads...I have no idea what the heck they are for. They look to go into he water jacket, but I have not looked into it. I have a couple 472 heads sitting in the back of the Longhorn as we speak...I can try to look at them in the A.M.It is too dark and cold to bother at the moment.
As for the fuel guage...I'm willing to bet you are not getting power to the guage. If the sending unit wire is unplugged, it'll go to the 3 O'clock position, if it is grounded, it'll go to the 9 O'clock. (I may have that backwards..its been a while) However, ig there is no power going to it, it'll stay in it's last powered position.
I went through all this on my GMC.

[Ironhorse]

Another suggestion for the fuel gauge reading empty when half full is to pull the sending unit and make sure the brass float is not full of gas. I had this problem on my 4x4 when I moved the tank from the cab to under the bed. GM should have put them back there to begin with in my opinion. Anyway, after first actual "full fill" of the tank the gauge initially registered "full". Next morning right after starting the truck the gauge went to rock bottom empty and stayed there. Run my wires, checked my grounds several times, made sure the gauge itself was good. Next item was the new sending unit that came with the tank kit. I ran the truck until I thought it was close to empty (carrying 2 gal. can with just in case I mis-calculated). Dropped the tank and pulled the sending unit. Brass float was "FULL" of gas causing it to sink and give an empty indication at the gauge. Float had numerous cracks in it leaking fuel in. Contacted the vender, told him the problem and he "Overnighted" me a new float along with a big apology for my trouble. Put it all back together and no more empty! A long post I know but something to consider. Is your tank in cab or under the bed? I like under the bed but a pain to pull the sending unit. Hope this helps and Keep On Truckin'

[71MoneyPit]

do you think there is a way I could use the factory sending unit for the chevy dash in the caddy motor?I was thinking if I figure out a way to match the threads it might solve it.

[Longhorn Man]

I have never seen a stock sending unit, so I am of little help there.

[cableguy0]

u should be able to buy a little kit for that oil pressure guage that has the copper tubing and an assortment of brass fittings.if not go to www.summitracing.com im pretty sure they have the kits im talkin about

[71MoneyPit]

thats what I was thinking of doing with the oil gauge,
Longhornmail- i forgot to say in the post.I meant the stock temp. sender for the Chevy

[Longhorn Man]

Yeah, i figured thats wht you ment. 2 of my 3 trucks had aftermarket guages, and the third had a Pontiac engine.

[71MoneyPit]

well,

i got the temp sender in, i was able to find the stock sender for a 350 in a 71 c-10 and it was even the same thread!

but I have a problem....., i bought some tubing and all the fittings, and ran the tubing for the mech. oil press. gauge in my dash, tightened it all up started the motor, let it run and shut it off. My oil gauge never even moved. I loosened the fitting from the gauge and it is completely dry do you think that the fitting at the back of the 500 is for something else, or maybe your'e supposed to use one of the holes in the heads . Im at a loss now, i can't figure out why it wont work, or is there something im missing

[Longhorn Man]

Hmmm, interesting. I had been told (I noever verified it though) that was the oil pressure port.
With any luck, I'll be able to look into it later on today and this weekeknd.

[71MoneyPit]

thanks man

[Longhorn Man]

Looking at my engine...(still not fired up naturally) I'm willint to bet that if you removed the sensor by the thermo stat...the one facing forward, it might be the one you are looking for. (I know what I said before....I had been lisntining to some one else instead of verifying stuff)
I was looking at mine, and that sensor is right over the oil pump drive shaft rod deal. Pop that out and see what comes out of it...coolant or oil.
Let me know what you find out if you could too please.

[71MoneyPit]

that's what's got me confused... the one facing forward right under the t-stat has coolant in it, thats the one that i put the sender in( the 71 350ci temp sender). One thing i was wondering is there a way that it could have an air bubble in the line that is not letting any oil through Maybe if I disconnected it from the gauge and tried to crank it to see if any oil comes out...

Those two that are in the heads have me stumped. Iv'e been to the library to see what the wiring diagrams say but you need super vision to be able to read the small print

it's always these little things that you never worry about while your swapping the motor that come back and bite ya in the

[Duallie]

The two sensors in the heads are actually "high metal temp: stop engine now" temperature SWITCHES that don't contact coolant. They trip at like 300 or so degrees and light up a "stop engine now" idiot lamp and make the key buzzer sound until the engine cools, and you CAN'T SILENCE THE BUZZER. You'd have to wait until the engine cooled to quiet the buzzer.
Regarding oil pressure: What I did was but a 100 psi gauge into the 1/4 npt port just above the oil pump, and just above the bellhousing behind the intake manifold a tee for both a low oil pressure switch and the factory oil line to the mechanical dash gauge. That way I knew I had oil pressure during the initial fire off. You do have oil pressure, right?
The reason I put the dash gauge tap at the back of the block was to see worst-case oil pressure, and to give me the most time to see a sudden pressure loss before the engine could sieze, since I was seeing pressure at the end of the engine opposite the oil pump.
Hope thats clear...

[Longhorn Man]

Money pit, did you ever figure out the oil pressure port?
Talk about digging one out from the grave huh?

[FormerMember]

oil pressure port on most GM's is in back, near the distributor.

At least, that's where I've always run mine.

Or you can go to the base of the block, driver's side near the timing chain cover.

Should be smaller NPT.

[GMC AMI]

Make sure you have oil pressure before running that caddy engine! It is harder to prime
the external oil pump than on a internal chevy engine if you had this apart or have put a new one on. Also the oil pickup has a seal that is very important! If not there or bad the oil pump will not hold the prime or pick up and you will put the center thrust bearing of the caddy motor at risk due to the tighter clearance with low or no pressure.

[71MoneyPit]

Hey Longhorn Man,

Ya i figured Out the oil pressure port, it wasn't a problem with the tubing or the location(by the way the location I used is where the stock Electrical Oil Pressure sending unit was) the problem was with my gauge . It had frozen up with rust from all the years of just sitting All I done was hit it with some penatrating oil and it freed right up. It works fine now. The 500cad runs right in the middle of the oil pressure gauge.

Boy its been awhile since I posted on here. I've been lurking around just not posting.I kinda had to take a break from working on the Money Pit.(I had been working on it every day almost for about a year) I have just been driving it just the way it is, Primered and ugly I have just been driving it downtown every once and awhile and screwing with the little ricers(they think its just a typical piece of crap old truck,boy do they get a surprise) With gas at $2.09 a gal. it gets expensive to drive it any more than that. About the only problems I have had with it are the brakes(bad brake lines and prop. valve)


I also kinda got into another hobby that is just about as much fun as driving the old truck. ATVs. Ill enclose a pic of them (the one on the left is mine ,middle one is my mothers, and the right one is my dads)I kinda put the truck on the backburner after we bought them. I still work on it just not all the time like I used too.