Overheating!! - Troubleshooting not going well, need input
 

swapped a '90 350 stock tbi into a 91 S10 Blazer. swap went without incident, but having issue with operating temp. so far we have upgraded to 82-89 corvette radiator, & derale 15" Hi-Perf fan. the temps hover at 210 and will go to 230 in traffic (w/o AC). i even installed 2 electric pusher fans without improvement. been thinking maybe the water pump not flowing enough and or fan not big enough. don't know if the water pump is new or rebuilt. impeller clearance may not be right. i have access to a 17" flex fan so water pump and fan swap is next steps. i welcome any wisdom and/or input.

Re: Overheating!! - Troubleshooting not going well, need input
 

How did you fit a mechanical fan to it? Did you move the engine back or move the radiator in front of the core support? Do you have a fan shroud?

Re: Overheating!! - Troubleshooting not going well, need input
 

moved the radiator forward. yes it is shrouded, about 1.5" between rad and fan. i also tried swapping the t-stat and drilling 2 - 1/4" bypass holes in the t-stat w/o improvement. gonna try a diff water pump & fan next (larger diameter) as i'm out of options. i've been more leery of elec. fan setups lately. swapped back to a belt driven fan on my GTO that dropped temps from 205 average to 180-190. i wasted several hundred dollars on a elec. rad/shroud/fan system made for that car with dismal results.

Re: Overheating!! - Troubleshooting not going well, need input
 

Are you sure the fan you used is for a reverse flow water pump? I like using a stock type fan with clutch, I never had any luck with electric fans either. I recently changed the water pump on my truck and it brought the temperature down, I was thinking maybe the impeller was rusted out. I had a van I rigged up with a smaller radiator with no shroud and didn't have cooling problems.

Re: Overheating!! - Troubleshooting not going well, need input
 

WP and fan is correct reverse flow. gonna install a larger diameter fan and change the WP this weekend. the problem is that the temps dont go down even at highway speeds which is indicative of a water flow problem. if temps go down at highway speeds then there is a air flow problem. wish me luck.