All,
I recently installed a new GM crate engine, the 330 HP 350 with the vortec heads. I got everything assembled, new edelbrock performer intake, new holley 650 carb, put on a new serpentine belt system, (had to do alot of modification to get it to work right, clearance issues to the frame, etc) and installed a new MSD ignition system. I was able to get it to crank up easily, adjusted the timing, made slight adjustments to the new holley 650, etc. But now I have a serious overheating problem. I cant drive the car in town, (stop and go) for mor than 20 mins or so before i have to turn the car off to let it cool down. I tried installing a 150 degree thermostat, drilling 2 tiny holes in it, etc, and installed a cheap generic coolant overflow tank, because it was spewing all over the place when you turned the car off after it was hot. Anyway, after doing all that, it is still giving me overheating problems. Can anyone provide some suggestions as to what I can try next?

When you installed the Serp system, did you put on the correct water pump?

The serpentine system came with a waterpump of its own, along with an idler pulley for the ac, alternator, etc.

You didn't comment on the radiator. Is it original? What condition? Have you used an IR gun to shoot the radiator to see if there are cold spots, indicating a blocked rad?

In my experience, overheating in stop and go driving can be caused by a bad fan clutch. How is your fan set up?

is radiator good?
is fan and fan clutch good?
if electric fans, is it/they running?

may be air in the system

does 71 have the expansion tank? others will chime in on its proper setup.

i could talk about overflow system if that's what you have . . .

Are you using a distributor with vacuum advance? If so, do you have it hooked up to manifold vacuum (not ported)? If you don't have vacuum advance, you're going to overheat that engine in stop & go traffic unless you change the curve to run a bunch of initial timing.

I just had the radiator overhauled by a reputable radiator guy locally. As far as the fan clutch, it is also new, but it is not the "correct" one, the original fan clutch would not fit on the new water pump, I hope that isnt the cause, cause im not sure where i will have to go then. if that could be the problem, can i remove the fan altogether and invest in an aftermarket electric fan system, something that wont break the bank? any other options?

and as far as an overflow system, i have a rigged up temp overflow tank on it, just for the time being. I would like info on how i can rig up something more permanent in terms of an expansion/overflow tank, im all ears

"Lars" wow, honored. yes, i am running vacuum advance on the new msd tach drive distributor , and i do believe it is hooked up to manifold vacuum, but could be wrong.

What fan blade are you using? Did the serp system come with a fan blade?

No, it didnt, i am using the original fan blade on the "improvised" fan clutch

Artsvette73 may be onto something. see if the fan is blowing air out the front of the radiator!!!

Your fan is running backwards. Serp kits use a reverse rotation waterpump. You need to either go electric, or get a reverse pitch fan

also does the lower hose have a spring in it ?

you know, i had been thinking of that very thing for quite some time, but just didnt really take the time to double check. ill check it out, great input folks, and anything anyone else can think of is welcomed!

Yup, i took the one out from the old hose

My advice is go electric, nice clean install and better cooling than stock and looks great with the serp kit

A reverse pitch fan looks like the initial direction i will try to go , at least initially. Anyone know what i should ask for, or where i might find one, understanding that this is an aftermarket engine with a waterpump that wasnt really designed for this car?

If electric is the direction you would go, can you suggest a website or a model i could look at?

surprising how often this is overlooked