Just get a heatsink that fits. They don't cost much at all.

Here is one for 3$
http://m.ebay.com/itm/Socket-370-cpu-fan-/162 … 6%257Ciid%253A3

Not the best heatsink but just a reference.

That being said why not try the two and find witch works best? Also keep an eye on your PSU temperature when sucking air in the back.

The best thing to do would be to buy a heat sink that actually fits (or a fan for the heatsink you're trying to use passively).

If you're the crafty type you could keep the rear fan as exhaust and make a duct out of corrugated plastic or cardboard to force the the fan to suck air up from around the passive heatsink. If you google "Dell Dimension 2350" and find an internal picture that's what I mean.

Just make sure the heatsink you're trying to use passively has somewhat wide fin spacing.

If you really want to go passive zalman made a bit copper heat sink for sk370 I forgot the name but it was one of these flower heat sinks.

Jade Falcon wrote:

If you really want to go passive zalman made a bit copper heat sink for sk370 I forgot the name but it was one of these flower heat sinks.

If you're talking about the Zalman CNPS3100, those are not designed for passive use and still rely and a large low RPM fan pointed directly at it.

If you don't want a fan on the heatsink the best thing to do would be to introduce airflow into the case. Use an intake fan at the bottom near the psu and an exhaust fan on the back. Just be sure to not put the PC on carpet and make sure there is enough clearance underneath it to pull in air.

EDIT on a second look I realized your PSU is up at the top, can you post pictures with both fan ports so I can get a better idea how airflow would work in that chassis? If you only have the one fan spot passive cooling will not be enough to keep your CPU cool.

There's a picure at http://www.overclock.net/t/1336501/fan-air-flow-disruptions
It shows the air flow inside of a PC. Esentially, the fans at the front side are intake and the fans at the (upper) rear are exhaust.
This unburdens the PSU from exthausting all the heat on its own (which is both good and bad; the PSU requires a bit of the
air flow for its own purpose. Anyway, a little bit of cool or medium tempered air flowing through the PSU is better than lots of hot air ;) ).

Gatewayuser200 wrote:

[…]
Show full quote

Jade Falcon wrote:

If you really want to go passive zalman made a bit copper heat sink for sk370 I forgot the name but it was one of these flower heat sinks.

If you're talking about the Zalman CNPS3100, those are not designed for passive use and still rely and a large low RPM fan pointed directly at it.

Yes that's one of the two. Its alright for socket 7 and most 370 CPU's provided you have good case flow.
I had one on a overclocked AMD k6-3+ and it did fine.
Its socket A CPU's that need the 80mm fan, I'm sure a stock Piii without overclocking would be fine.

Well I've tried another socket 370 cooler and it's just as loud 😒 Maybe the bearings in the fans are going because of age? Anyway, without a CPU fan, I'm hitting 55 Celsius under load, and with the latest fan I've tried, it was 47 Celsius under load.

Well I bought a Noctua 6x6mm fan and that runs at half the speed of the previous fan (which was 6000RPM - no wonder it was so noisy!), so that's the noise issue sorted. But just to clarify, should both my CPU fan (the Noctua) and the larger case fan at the back be on Intake, or Exhaust? My Case fan is on Exhaust and my CPU fan is on intake. Which should it be?

bergqvistjl wrote:

My Case fan is on Exhaust and my CPU fan is on intake. Which should it be?

That's how I do it. I'm not big on too many fans--I never use a front intake fan and rarely use side fans, just the rear exhaust + PSU exhaust. I always have cpu fan blowing towards the cpu.

A single heatsink fan would always be set to blow into the heatsink, as the air stirred by the fan will cool better and pass deeper than the lazy flow of air sucked in.

Ideally. if the heatsink can be mounted in in front to back orientation, then the heatsink fan is at the front, blowing through the heatsink toward the case extraction fan, otherwise it runs bottom to top.

For what I call "downdraught" heatsinks, as they would be when flat in a desktop, the fan blows into the heatsink and air escapes toward motherboard components

As Jo22 already said, its best if both intake & exhaust are there, airflow is very important in cooling procecss.

To clarify, my CPU fan is on the top of the heatsink (cant mount any other way) and my single case fan is on the rear of the case, and I can't fit another.