How hot do the heater tubes from the heat exchangers to the blower fan get? I have a '72 1.7L. I'm referring to the "J" tubes that come up from the heat exchanger and go to the fan that blows air.

I want to know how hot those tubes get on the warmest day with the engine at the highest temp it operates at.

I need to get the flexible hose that joins these items, and have some shop vac hose that fits. It's PVC, which melts at 140 Celsius (284 F).

I want to use the PVC hose until I can get some of the proper hoses from 914rubber. BTW, do these fit? The outlet on one side of the fan is 60mm and the j-tube is 55mm. The other fan outlet is 55mm and the j-tube is 55mm.

Plastic will not last in that location.
Consider muffler pipe, possibly custom made for you at a muffler shop.

Silicone hose the kind used for intercoolers and such would probably hold up better than PVC.

If you are talking about the flapper valves, you need high temp silicone. You sould use rubber, but it will get brittle eventually. May be a little smelly, but could work in a pinch.

Definite no to PVC, it will not last long and potentially cause a fire (more likely it would just melt, but possible).

Think he's talking about the hoses in the engine bay between the fan and the j-tubes through the engine tin.

I thought about the hose to the passenger side for quite awhile for my new fan dual outlet - ended up buying the hose from AA (their part# B461261235A for $20)

If I understand your ? correctly, the j tubes see air FROM the aux electric fan in the engine compartment and pushes thru the tubes to the heat exchangers to the flapper valves. This is 'supplemental' heat. Not the full force seen from the ENGINE cooling fan. As that air increases a set of little 'doors' on the fan shroud outlets open and the supplemental heat really doesn't come in to play. No need to re-invent the wheel. Just find a set of j tubes in the classifieds. The j tube tops can be closed with rubber caps (plumbing department of your hardware store) and a couple of stock large hose clamps if you should decide to eliminate the fan. With all other components in good working condition you'll have plenty of HOT air. The hoses from the aux fan see air that is about the same temp as that in the engine compartment for the most part.

If you're just replacing the hose from the fan to the J tube, PVC should work fine in the short term. I'm not sure I'd trust it in the long term, but for a little while during the coldest months of the year should be fine.

--DD

I've used shopvac hose on my VW bug and Bus heater boxes and fan to heater box for years with no problems.
The end on the box does soften and after a few years it distorts. When it gets to that point I just cut a piece of vac hose.
I found hose that went over the orange silicone part of the VW heater box OE tube and hose no longer distorts.

Never tried it on a 914, but I'd try it and keep an eye on it.
As long as it's not touching a header or rubbing on a sharp edge it should work.
If it works it works.

I'm talking about the ones from the blower fan on top of the engine that blow outside air to the heat exchangers, not the hoses from the flapper valves to the firewall.

I see you sell what I'm looking for. The attachment to the fan on one side is 60 mm and the attachment to the j-tube is 55 mm. For the passenger side, both ends are 55mm. Are the ones you sell sized to fit? I'd rather buy them from you than AA.

The hoses up top are fairly low temp.
The tubes are steel, which is what I thought you were asking about.

The ones that came on my motor were similar to shop vac plastic and lasted 40 years.

I looked into that. They only have 1.5", 2", 2.5" diameter tubing. The flexible stuff doesn't bend enough. The cardboard aluminum-coated pre-heater hose doesn't come long enough. Oh, sure I could notch it so it could be clamped, but that looks terrible. The muffler shop offered to swage out some tubing to the right diameter so I could make hose adapters, but I couldn't find hose long enough to work at any of my FLAPS. I even tried to find rubber radiator hose that was 2" but it won't stretch enough to fit.

I just replaced the hoses you're talking about. I used SCAT ducting, which is designed for aircraft use and it's good for temps up to 550F. I bought it cut to length. I recommend getting a few more inches than you think you need

http://www.aircraftspruce.com/catalog/appages/scat.php

Confused...what are you trying to accomplish? Simply putting hose/hoses from the aux fan to the j tubes?

Yes mine are sized correctly. Yes the blower hoses into the heat exchangers were paper and aluminum,so not a problem using a lower temp item here.

http://www.shop.914rubber.com/Engine-bay-b...m?categoryId=-1

Yes.

Which one did you get, the 2", 2.25" or 2.5" diameter?

Alrighty! I have some other stuff I need to get and I'm making a list. I'll be ready to order soon.