13sec83trans

I have a 73 chevy 400 motor that I cannot get in optimal temperature range, after the thermostat opens and has its initial drop in temp it never comes back down and just keeps going up...I always cut the engine before it hits 230. It does its overheating in the 40mph and lower range and stays good on the highway. I changed out the stock 305 radiator with a champion 3 core, the fan is a flex a lite syclone s-blade 16 in. I did the troubleshooting with the radiator cap off and waited for the thermostat to open....watched the coolant level go down, then had my dad rev it a couple times and watched it get sucked down pretty good each time ruling out the water pump and t-stat. after that I put the cap back on and observed the lower rad hose and it was gushing through the hose when it was revved and showed no signs of collapsing. my water pump pulley is a good bit smaller than the crank pulley so I should have a good ratio there. I made sure the fan is blowing towards the engine it is wired to be constantly on with no switch. the air dam is slightly damage but my overheating is in the lower speed range so this really shouldn't matter and its only slightly damaged. the temp gauge is aftermarket and should be reading correctly, I'm going to barrow a temp gun to make sure but the radiator and everything else is extremely hot so I am 99% sure it is right.


so I've covered the radiator, fan, t-stat, water pump and pulley, and lower rad hose I'm at a loss and starting to get frustrated that I can't drive it more than 2 miles.


here is some specs for a better idea
forged flat top pistons bored .30 over, 9.5 compression (not 100% on the compression but its definitely not higher than that)
mildly lifted cam
750 quadrojet carb
some big headers they barely fit have a lot of heat tape on stuff around them
the heads are stock 76 cc heads they should have the steam holes being stock but I've never taken the manifold off.
has no computer, no emissions control and no ac/heat/defrost although I think the hose to the heater core is still being used in the routing of the coolant
my next step right now is to change out the 170 t-stat with a 180 high flow, change the fan over to a proper fan tstat that turns on around 170ish and retard the timing a bit to see if that helps (I don't know how advanced it is or if it even is but I guess ill find out) if all else fails does anyone have a suggestion what I should try next? me and my dad really don't know what to do next if this last effort fails and I have a good feeling it will.

NoEmissions84TA

iTrader: (1)

Was it ever running right, or did this just begin recently?
Where is the temp sending unit screwed in?
V-belts or serpentine? You might have the wrong rotation water pump.

It sounds like you are not getting enough airflow at idle/slow speeds.
Is that fan properly shrouded?
When you go over 40 mph, you get enough air to cool the engine.

Incorrect timing can contribute to this problem.

Tootie Pang

iTrader: (2)

^^^ all good points to check.

Particularly the water pump rotation

While that fan is a mild 2500 cfm, it should be plenty to keep that engine cool.

My factory temp gauge is outta whack and was driving me nuts so I bought a Holley radiator cap with a temperature gauge built right in. Very helpful as a sanity check.

dlipka

Do the radiator hoses get hot?

13sec83trans

The fan is shrouded and it is a v-belt setup. It always overheated but before I changed the radiator it would only get hot sitting at a light and would cool down just cruising at 35 now I need to be at 45+ to get any cooling. I will look into the water pump is there any easy way to tell the difference between a v belt and serpentine belt pump? the hoses do get to hot to touch.


I took it out after I got home from work is was dark and 50 degrees. it stayed at 165 the entire time I was on the highway but I got off and took a side street back and it climbed the whole way back. I was thinking my t-stat might be a big problem only being at 170 and maybe the 180 I got would not be high enough either to give the coolant time to cool. I'm going to pick up a 195 as well and try both of them.

NoEmissions84TA

iTrader: (1)

It still sounds like you are spinning your water pump in the wrong direction -
or the wrong water pump in the correct direction.
If you are not completely sure, the only way to tell is to remove the WP
and take the back cover plate off to look at the impeller.

13sec83trans

that sounds like a lot of work, do you know if the 305 motor on a 83 trans am came with serpentine belts at all? i can't see the person before me buying the wrong pump for such an old motor but if he reused one from the original motor i could see it. I tried looking it up but to much nonsense exists in google. I am inclined to believe that would be the problem as I don't really know what else it would be. 100 bucks for summits long style clockwise pump doesn't sound to bad i might just pick that up and call that a day if I'm going to go through the trouble of taking the old one off anyways.

Galaxie500XL

iTrader: (1)

IIRC, serpentine belts didn't come out until 1988...but not everyone realizes at the parts store that there are two different pumps. Not long after I bought my IROC, I discovered the previous owner had installed the wrong pump.

13sec83trans

alright I bought a flowkooler hi flow long clockwise pump should be here by Friday I live like 45 minutes from the summit warehouse in Ohio. I will install it this weekend with the hi flow 180 t-stat and let you guys know if it worked.

13sec83trans

well this is extremely embarrassing but I put the new water pump and t-stat in and it was still just as bad....I pulled in the driveway and looked at it for a minute and I was like you know it has to be this fan then. Every time I tested the fan's direction before I only put my hand in front of it as did my dad and we thought it was right but today I decided to use a piece of paper and sure enough it was going the wrong way. So I reversed the polarity on it and now it runs between 170-190 now. I am so embarrassed that I didn't use a piece of paper to test that fan I genuinely thought that it was blowing the right way with using my hand but apparently that is not good enough. I can't believe I bought this car with the fan blowing the wrong direction that is mind-blowing to me. so ya I face palm x100 times after wasting 300$ on stuff I didn't need on such a stupid and easy fix. I apologize for wasting everyone's time.

NoEmissions84TA

iTrader: (1)

That's OK. You stuck with it to the end.
Now it's fixed, and you have a new WP that you shouldn't have to worry about it for a long time.

LiveIt!

Don't let it get to you, I spent months and $$$ buying stuff my car didn't need trying to get it running, in the end it was just a power wire I overlooked!

LiveIt! And Learn... :P

Tootie Pang

iTrader: (2)

We've all been there. The important thing is you won the war.