Slimmest engine driven fan on Rover V8?

[twodoorgaz]

Been getting some great advice on the planned Rover V8 conversion into my SIIA.

 

I picked up the engine this weekend and am off collecting various bits to reduce the length.

 

it is being converted to a P38 distributorless setup with serpentine belt/pulleys. As far as I’m aware that results in the shortest possible RV8 - much shorter than the traditional mix of SD1 and P6 parts.

 

But, I’d really like to keep a mechanical fan and I think I have space to fit one neatly.

 

does anyone happen to know the slimmest possible engine-driven fan setup that can be fitted? I’m happy to go all the way back to a fixed fan (with a custom boss to fit the 3-bolt serp water pump) or I’d look at any of the viscous fans too. There’s the width of the fan to consider as well as the length of the shaft that it runs on.

 

happy to track down obscure parts (101, LDV, etc) if there is a combination that keeps the fan as close to the block as possible.

[twodoorgaz]

Ps: I think that the serpentine waterpumps (as I’ll be using) might have run in the opposite rotation to the earlier bee-belt pumps. So if sticking with serpentine then an intermediate serpentine 3.9 V8 fan seems to be a lot tighter to the block than anything from the P38.

here’s some good pics of an intermediate 3.9:

https://www.simmonites.com/shop/engines/reconditioned/3-9-rover-v8-serpentine-engine-land-rover/

I’ve still got Disco IIs and 50th defenders to check.

 

guess if I go with a fixed fan then I’d need to flip it to run the opposite way.

 

[Snagger]

I don’t know anything about the depth of different belt arrangements, but certainly a fixed fan will be slimmer than a viscous fan.  As for flipping one if the rotation direction is wrong, that won’t work - the camber on the blades would be reversed, but not the direction of twist.  I think a better option would be to look at removing the viscous unit from the standard fan of the engine and fabricating a thin fixed hub for the fan to bolt to.  Such hubs may already exist and be a swap or adaptable fit.

Failing that, a large electric fan could be installed in front of the rad - there is a lot of wasted space there.  The fixed fan would be more reliable and almost certainly more powerful, but if you find a good enough fan from a decent large car, then an electric fan should be well up to the job and may be more powerful than the fixed unit when the engine is idling as it would be independent of engine RPM.

Edit - I can picture John smirking at me already for that second paragraph! 😂

[Escape]

Yes, there is a difference in direction. The water pump and thus the fan turn in the opposite direction to the crank on a serpentine V8, whereas on the earlier V-belts they turn in the same direction. So you do need to take that into account.

[Bowie69]

I doubt you'll get much slimmer than the P38 unit to be honest, if you haven't room for that a scrapyard electric fan arrangement is the next go to (90% of aftermarket fans are rubbish).

[Snagger]

1 hour ago, Bowie69 said:

I doubt you'll get much slimmer than the P38 unit to be honest, if you haven't room for that a scrapyard electric fan arrangement is the next go to (90% of aftermarket fans are rubbish).

Looking at the photos in the link, I think you are right; the back edge of the standard fan is only just ahead of the belt, and the viscous hub doesn’t appear to protrude much.  A fixed hub isn’t likely to help by any useful amount.

I agree about the aftermarket electric fans.  I have one on my 109, and it wasn’t even spinning the right way - it was a pusher labelled and boxed as a puller, so opposed the ram airflow through the rad and reduced cooling effort, blowing some hoses on a mountain.  Such is QC on Chinese tat.  A hefty OEM fan from any of the premium car manufacturers would be a far better bet.

[Landrovernuts]

Are the old Rover Vitesse fans not multibladed and very thin. May be this can be flipped for the correct rotation? 
Toby

[twodoorgaz]

Thanks all. The confirmation on the reverse running is very handy. Snagger thanks for the tip re: not simply flipping a fan - I'd need to find a generic fixed fan of the correct size that is designed for that rotation.

I did notice that the P38 fan is very very thin (or at least the band around the fan is), but as Snagger points out above, while the fan surround  itself is very thin, the blades flare forwards, sitting quite far away from the belts, whereas the 3.9 interim fan has the blades butting right back up against the serpentine belt. Its reminds me of the offset on road wheels - as if the 3.9 has a much higher offset than the 4.0, so it sits tighter to the block. I'm going off photos for this conclusion, it might all be an optical illusion, so I'll just have to find some engines and take a tape measure to them.

3.9 Intermediate Serp:

 

P38A 4.0 V8 (belt not attached):

 

Disco 2 4.0 V8 engine:

From those images, I would guess that a P38A distributorless timing cover, coupled with the viscous unit and fan from a 3.9 intermediate serp would be the fractionally tighter option.

 

I'll certainly have a look at the Vitesse fan to see if it can work.

 

On the electric fan, I know it is how V8 conversions have been done for a long time - but I really want to try and exhaust all options for an engine driven fan first. The engine I'm building is all about adding reliability, incorporating all the P38A developments (except the 92mm bore) so an electric fan doesn't quite align with all that, fine and everything, but not aligned with what I'm hoping to achieve.

 

 

 

Edited February 28, 2023 by twodoorgaz

[Landrovernuts]

Not a very good picture but it is off a 2.3 and 2.6 rover vitesse and stolen from EBay! Looks pretty thin if you can make it work.
Toby

[smallfry]

Maybe you could get a fan from and electric set up, cut the middle out, and adapt it to a viscous unit. Serpentine fan runs anticlockwise (I think) so this may be a challenge. I do like the idea of the ring though, having had me fingers chopped a couple of times.

[twodoorgaz]

thanks all. I have a lathe and access to a milling machine so making a hub should be no issue. It seems to be a threaded boss onto the serp water pump and I can cut such threads.

 

I think the best course of action may be to buy a series of fans off eBay with their respective hubs and measure them all up to find the closest fitting solution.

 

Edited February 28, 2023 by twodoorgaz

[Bowie69]

Worth saying an electric fan will be designed to run at probably 2500rpm, and not rated for more. If you bolt it to the front of your 5500rpm engine (and possibly higher speed water pump?) don't be surprised when it explodes showering your engine bay with shards of plastic.

There's a reason why engine driven fans are so much more heavily built than electric.

[twodoorgaz]

duly noted, thanks Bowie.

 

To be fair if I do deviate at all from a standard Viscous unit (matched fan and clutch) then I'd be buying a purpose build fixed fan and would most likely order one from the US that's intended for one of their domestic V8s.

 

For example, Flex-O-Lite stock a large number of fans in various sizes and widths that are intended for American V8s. This one caught my eye, its a reverse-rotation (so should be good for a Serp pump), it comes in a number of sizes (this particular one is 17inch to match the standard Rover size) and the description even mentions it being used to replace a factory clutch-driven fan. If I'm going 'custom', then a route like that seems the safest bet - at least I know the fan is intended to be mounted on the front of the engine and should cope with the correct rotation and RPM. I don't know whether the pump bearings would be happy with having a fixed fan, but I suspect it would make little difference to them when compared with a viscous unit. That particular fan is only 1-3/4" wide.

 

Having started down that path, there are others of course, from companies like Derale who make V8-type fans in reverse rotation at the correct sizes and their width comes down to as low as 1-1/8".

 

So, if I do go for a fixed fan, it looks like the American aftermarket is the best bet (none of them are very expensive and I have a PO box in the US that I use regularly, so shipping is nothing) - I can order a fan of the correct diameter that is intended for an engine of that size and, if I get lucky, I'm sure I could find one of them that could supply a fan on request with the centres drilled with a PCD and pilot hole to suit my needs. A fixed fan does have some additional appeal to me with less chance of failure and, as this engine bay is intended to look like its come straight out of the 1960s (the serp belt and lack of distributor being the only giveaway) then a fixed fan does remind me of the original Buick 215 design.

 

So - it looks like the slimmest reverse rotation viscous unit is going to be that from an intermediate serp 3.9. And that just leaves the question - if I do move to a fixed fan, provided it is mounted correctly on the water pump and spaced correctly/safely from the belt, does anyone see any pitfalls in mounting a fixed fan on a pump hub that was intended to receive a viscous unit?

 

When it comes to mounting a fixed fan on a serp pulley, I suppose there's two options:

1. I could bolt it onto the serpentine pulley using three bolts right through into the pump boss, I might make use of the redundant three holes as an alternative. This would effectively make the fan and pulley a solid unit - I do have concerns that any movement in the fan could affect the alignment of the belt.
2. I could turn up a threaded boss that engages onto the threaded shaft in the centre of the pulley just like the viscous unit did and bolts in turn to the fan. Provided it is properly balanced I would assume that that would be a far better solution from an engineering perspective? 

 

 

Edited March 1, 2023 by twodoorgaz

[Bowie69]

A fixed fan will be WAAAY more noisy, as well as hitting your power output at higher RPM.

Those metal ones you link to are notoriously bad.

 

[JeffR]

Have a look at VW passat pdi viscous fans (pre 2005) they are vey slim, plus the viscous gubbins are removable

Edited March 1, 2023 by JeffR

[FridgeFreezer]

I hate to start an internet holy war but in terms of reliability / survivability I don't see electrics as a disadvantage, I run twin electrics on both my V8's, one set are Saab (so that tells you how old they are) one set are Freelander 1 and they've been fine.

Conversely I've seen viscous fans fail, go weak, fall off and eat radiators, knock all their blades off in water/mud, etc.

I get that viscous is (by default) a simple & easy solution, but you are now into more convoluted/non-standard versions of this which are thus not simple and are harder to replace if they fail or are damaged.

If my electric fan dies I can pick almost any old thing off a scrap car and stick it in there, if your custom fan shipped from America fails you need another one shipped from America.

Electrics are also low-profile, easy to package, and more efficient. I can turn them off for wading, I can force them on if the truck's working hard, I have a warning light that tells me they're working.

[twodoorgaz]

Sorry Fridge, that'll be my fault for groundlessly mentioning reliability - wouldn't want to give the impression I thought that there is anything wrong with that approach. I simply meant that a fixed fan is simpler (to my simple brain) and has fewer failure points than viscous and certainly not that electric is inherently unreliable.

 

The vehicle I'm building is a bit of a passion project to see if I can assemble a SWB V8 with parts choices that are close to those the factory would have considered acceptable in a production vehicle - had they stuck with selectable 4x4 and had access to the same parts bins we have today, and doing so without chassis mods and to try and have the engine bay appear period -at least at a passing glance. Land Rover have always used engine driven fans on their production utility models so I'm hoping to retain that feature as part of the build - even though it would be far, far easier to just use electric fans.

 

Taking on board all the advice above (and the video, which was great) - I think its now a case of dry building the thing up in the chassis with the radiator in situ and trying a combination of factory viscous setups as a starter to see how close to a nice fit I can get. I understand that the fan design is optimised to set distances between the blades and the radiator and that where the cowl sits in relation to the blade tips is also relevant, so I'll pick up a few serpentine fan/viscous hub assemblies, will grab some measurements off the family P38/Disco II and anything else I can find with a Serp front end and try them and work out where I need to lose any dimensions to make it all work well. The cowl will be a nice complex bit of metal shaping, so that'll be a nice project to look forward to. If I can't make it work, I'll revert back to electric fans and call it a day.

Edited March 1, 2023 by twodoorgaz

[Bowie69]

The P38 fan doesnt need a cowl, just be close to the rad.

 

 

[twodoorgaz]

That’s a really nice bit of info, thank you. I’ll add one to the spares pile to trial.

Edited March 1, 2023 by twodoorgaz