3 Blade Clutch Fan Question

[trucknut85]

When i got my 85 Chevy K10 it had a 305ci engine with a 3 blade clucth fan. But when i swapped out the 305 to a 350 i went with a 6 blade flex fan from the auto store cause i was young and it was shiny and cool. I'm now trying to restore my truck back to more of a stock look. I'm curious if the 3 blade fan was stock on a 305 at the time, or was it a replacement as i'm not seeing a replacement 3 blade fan on any of the major 73-87 parts sites. Should i just upgrade to a 5 or 6 blade clutch fan? Any input would be appreciated.

[Nick_R_23]

It was stock, but many people upgrade to the 5, 6, or 7 blade clutch fans.

[MikeB]

Originally Posted by trucknut85

I'm curious if the 3 blade fan was stock on a 305 at the time, or was it a replacement as i'm not seeing a replacement 3 blade fan on any of the major 73-87 parts sites. Should i just upgrade to a 5 or 6 blade clutch fan? Any input would be appreciated.

I think a 3-blade fan and tiny fan clutch are what my 82 had on its 250-six. I certainly would NOT use either one on a 350. A 5 or 6 blade fan will probably like a heavier duty clutch to dissipate the extra heat.

On another note, I ran a 17" Derale flex fan with big rectangular blades on a 350 with AC for many years with no overheating issues. However, I wouldn't run one with the type blades that narrow down towards the ends.

[Pontiac1976]

So I bet you most likely had a single core rad w/ 3 blade small clutch, no a/c 305 Trans TH350 ?
would that be close.
If your towing you might have two core rad 3 or 5 blade fan med clutch. If you had a M/T you would most likely have a smaller rad cooling.
what do you use the truck for mostly, what temp seem to be the normal in your area.
If your drive it like a car. All most never load it up, you would not need extra cooling.

[Matt Man]

My truck had a 3 blade fan clutch on it, my truck also had the 350 with HD cooling, but no AC.

[trucknut85]

Truck came factory with a 305, 700R4, and no A/C. I believe the radiator is a two core. The truck is just a summer cruiser, occasioonal wood hauler, don't really tow anything with it. The temps here in the summer range from the 70's to 90's usually. Truck seems to run about 210 deg with a 195 thermostat in it, but does heat up a little if it sits in traffic for a bit. But cools right back down once it starts moving again. Mainly just want to replace the flex fan to get it back stock looking and to remove the parasitic drag. I'll start looking for 5 or 6 blade clutch fan.

[blazer2007]

rodkill engine masters had a good episode on fans

[trucknut85]

Just watched that episode, yet another reason to ditch the flex fan.

[Pontiac1976]

To make sure the fan pull the best amount of air, the fan blades should be 1/8" to 1/4" passed the lip of the fan shroud.

[trucknut85]

Went to a swap meet this weekend, picked up a 7 blade clutch fan, a 3 blade clutch fan, and an original looking fan spacer. I paid $5 for the 7 blade fan, and a $1 each for the 3 blade and the spacer. I didn't need the 3 blade fan, but the clutch on it looked almost new, so i figured for a dollar i'd have a spare clutch in case the other one was junk. Now i just need to find some correct studs, as i don't believe i kept the originals.