Not to any noticeable extent.
But the advantages are:
Quieter, because most of the time the electric fan doesn't need to cut in
Less wear on belts
Engine warms up more quickly.
You have the option to turn on manually, eg in anticipation of hill.
Improved access at front of engine


disadvantages:

dependence on electric motor

I've found that my '84 has more power than I thought. Maybe you aren't as inhibited as I was and already know this, but I followed the Board's advice and when I want to go fast I really stomp on it and keep it down. Starts to come alive in the upper RPMs and I enjoy it much more now that I've been reassured that the noise I hear doesn't mean it's gonna blow!

Steve

I removed the fan on my 242 completely and drove around without it for a couple of days, thinking that I would see some improvement. Considering I spin the engine to 6500-7000 I figured it would do something. All it did was promote heating in traffic. The noise level wasn't even reduced.
The Volvo clutch fan is actually very good, and the temp needle never moves. The electric fan will accomplish nothing.

Remove the fan (4 10mm nuts, I think), hop in, and see if it accelerates any faster. I can't imagine hurting anything in a few minutes of driving without a fan (just keep an eye on the temp needle) and it will give you the chance to see what difference it'll make without a possibly long and expensive project.

Some here have reported a slight increase in fuel economy in highway driving. Since the stock fan has a thermally activated clutch that only fully engages the fan when the radiator is getting too hot, it's hard to see that you would experience enough gain to make it worth the trouble. As for power increase at the rear wheels, I doubt that a stopwatch would see any difference, let alone the seat of one's pants. But it probably makes for a fun project.

It's pretty well impossible that the fan absorbs 10HP from the engine, but let's say if it does, it's because that's needed to get enough air through the rad to keep temps down. No electric fan that would fit in the car can produce 10HP. That's equal to 7460 watts or 574 Amps at 13Volts. Er....don't think so.

Typical electric cooling fan load is ~30Amps in continuous operation; that's about 1/2 HP. If we say the engine-driven Volvo fan is 3 times as 'powerful', it's only drawing about 1.5 HP.

Anyone who can "feel" that difference should rent their butt out as a dynamometer!

My 745 V8 has a 960 Volvo electric fan, but that's because the engine never had provision for a belt-driven fan. Its original application (Firebirds and Camaros) used dual electric fans triggered by the engine computer. It seems to do the job, with the huge, 3-inch, custom aluminum rad.
--
Bob (son's 81-244GL B21F/M46, my 83-244DL B23F/M46 and 89-745(LT1 V8): dtr's 94-944 B230FD; hobbycar 77 MGB, and four old motorcycles)

Clearly the engine driving the cooling fan requires power, but I seriously doubt it is anything like 8 to 10 HP. You certainly won't notice the difference when driving the car in terms of acceleration.

Realistic estimates I have seen are in the 3 to 5HP gain, without AC (and fan clutch), it might be a bit more. Unreasonable estimates are in the 10 to 12HP range, if you look back far enough in my posting history, you might find a post where I mentioned 12HP... I am correcting that here and now.

I have done the mod and like the results very much, may I suggest though that you use a fan from a 940 or 960, I took the option of modifying a fan from a Mitsu (since I had one)... very painful... but in the end successful.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!