Thread: Cooling lines on turbo 350-which is oil out, which is return?

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I have just purchased an external transmission oil cooler for the roadster pickup, and the recomendation is that it be hooked in series with the cooling loop in the bottom of the radiator, downstream from the radiator, which would be in the return line leading into the turbo 350. On a turbo 350 the 2 oil cooling ports are vertically aligned, one above the other. Does anybody know which of these ports is for the return line?

Originally posted by DennyW
Bottom.
The top is the same as the radiator. It's hot, and the bottom in when the air cools it for inlet or return.

Mike ??

the bottom one.

ps, or trace it from the trans. the top line on the trans. is the pressure line and the bottom line is the return.

Is the 700r4 the same?.......Don

Originally posted by Don Meyer
Is the 700r4 the same?.......Don

as far as i know all of the GM alum. trans. the top line coming out of the trans is the pressure line which goes into the top of the radiator and the bottom line is the return line coming out of the bottom of the rad. going back to the lower fitting in the trans. the external cooler would go into the bottom line. i have put them in the upper line and didnt see a dif. that i could tell. but i guess if they say put it there then you should.

According to the website Denny posted, the upper fitting is the return line.

That is what I thought for the 700r4............

Originally posted by Don Meyer
That is what I thought for the 700r4............

i dont see what youll are reading, but the top line coming out of the trans is the one coming from the pump so i would think that would be the pressure line. what part of that websit says that.

i see what your talking about now but i dont have a trans to look at now and havent looked at one in a while, but that would be news to me. i will put my hands on one tomorrow, but if thats wrong then its a lot of them running wrong.

brianrupnow, you are looking at your trans, which line is closer to the front. the pressure line should be the one closest to the front of the trans. which is where the pump is. the return just run back into the pan.

just looked at a pic of a 700r4 and cant tell much from it so im gonna look at a real one just to be sure, but the lower is mighty close to that servo and there is open case around the servo on the inside. i still belive the upper fitting goes to the pump, but they should know.

ps the more i look at it they may have the top line in the top like that so the cool oil will spray over the inside of the trans to help cool it down. i am now.

i guess you can come up with most any thing you want to, but the thruth is it dont make no dif.

It1S10---thank you for all of the input. Like you, I don't think it really makes a darn bit of difference.---Thing is, if I am going to do a new installation from scratch, I would prefer to do what the people marketing the product recomend. The only reason for my doing this at all is that I used the bottom tank off a 6 cylinder Chrysler car, and the radiator builder mentioned that the cooling loop might be marginal, as it was not built for an 8 cylinder car. Personally I think that is a lot of hooey, as I am running a bone stock 305. The external cooler I bought is only a little one, at 4" x 11" x 3/4" thick. I will make a set of stand-offs and mount it about 1" off the inside of the passenger side frame rail, with the 4" vertically aligned and the 11" length parallel to the framerail. There is no fan on this thing, it depends on air flow generated by moving down the road. I very seldom have slow in-town traffic to contend with.

Originally posted by brianrupnow
It1S10---thank you for all of the input. Like you, I don't think it really makes a darn bit of difference.---Thing is, if I am going to do a new installation from scratch, I would prefer to do what the people marketing the product recomend. The only reason for my doing this at all is that I used the bottom tank off a 6 cylinder Chrysler car, and the radiator builder mentioned that the cooling loop might be marginal, as it was not built for an 8 cylinder car. Personally I think that is a lot of hooey, as I am running a bone stock 305. The external cooler I bought is only a little one, at 4" x 11" x 3/4" thick. I will make a set of stand-offs and mount it about 1" off the inside of the passenger side frame rail, with the 4" vertically aligned and the 11" length parallel to the framerail. There is no fan on this thing, it depends on air flow generated by moving down the road. I very seldom have slow in-town traffic to contend with.

i dont blame you brianrupnow, for wanting it right, but i checked and i dont have one and i called 2 dif. shops and both said the top is the pressure they thought, but was something they hadnt thought much about and didnt think it would make a dif. if you really wont to know take your air hose and blow into the lines and the return line wiil be open and you cant blow through the pressure line. dont use a lot of pressure like 5-10 lbs and then youll know. let me know.

Got yer info right here, straight from a 1980 Chevrolet Light Duty Truck Service Manual:

page 7A-17, upper left hand corner, shows a picture of a Turbo 350, with a label for the upper port as the pressure line to the radiator, and the lower port as the suction line (return) from the radiator.

So there's a bonafide reference to back up what the other guys have already told you.

Randy

Originally posted by vurtok
Got yer info right here, straight from a 1980 Chevrolet Light Duty Truck Service Manual:

page 7A-17, upper left hand corner, shows a picture of a Turbo 350, with a label for the upper port as the pressure line to the radiator, and the lower port as the suction line (return) from the radiator.

So there's a bonafide reference to back up what the other guys have already told you.

Randy

thanks randy, i have found around here there is 2 sides to every story and without proof, nobody known for sure, and thats a good thing.