Has anyone used Clarks Pcv oval flex heater hose?

[BigGeorgesVair]

Just wondering if anyone out there has ordered/used the PVC version(pt#C3131R) of the oval heater hose from Clarks? I've seen the fabric version, in person, and it looks like good quality, but haven't seen the PVC version and sometimes it's hard to tell from a picture. It is about $10 cheaper, so if it is decent, I'm ok using that one. But I bought one from The Corvair Underground a few years back (they called it Super Silver) and it was TERRIBLE. Not even usable, had to throw it away. Don't want to make that mistake again by trying to save a few bucks.
Here's the 2 choices I'm talking about from the Clarks catalog.

[MCataldo]

The PVC hose is decent, but there is active discussion on the need/value of that hose. This hose is part of the Fresh Air system. It connects to the rear of the upper shroud and ducts away a significant amount of cooling air from the #5 (right rear) cylinder before it reaches the cylinder and head. This can have a detrimental effect on valve and valve seat life of the #5 cylinder. Many have chosen to remove the hose and close the opening on the shroud with a block-off plate. Some block the opening on the fan (heater) housing and others install a separate air filter next to the housing that the heater fan can draw through. I chose to remove and block the hose port and haven't missed not having access to air through that system.

[66vairguy]

Just my 2 cents worth -- but the original pre production 65 heater design had a fresh air inlet to the atmosphere, only one problem, the hot air from the heater hoses was pressurized so they had to hook the fresh air (cool air) inlet to the fan shroud to equalize air pressure at the heater box to mix cool air with the hot air off the engine via the heater cable. Before production began Chevrolet installed a square plate to cap the early design (when they found the problem the early heater boxes had already been manufactured) heater boxes and installed the fresh air heater hose. There is a persistent myth that the fresh air hose off the fan shroud causes the #5 cylinder to run hot. This is ONLY TRUE if the fresh air hose has a leak!!! Unfortunately the hose is hard to inspect with the drivetrain in place and it's not unreasonable for the hose to be split and leaking air after many decades.

Bottom line --- the engineers knew what they were doing and if the hoses are intact there is NO problem. So replace all the hoses and the heater and engine will be fine. NOTE: This assumes the heater mix box rubber flapper seals are intact.

Whenever I pull a drivetrain I remove the heat box and clean it and inspect it. The rubber air mixing flap is very durable and usually are serviceable. If not fine a replacement.

[MCataldo]

Just my 2 cents worth -- but the original pre production 65 heater design had a fresh air inlet to the atmosphere, etc...

Excellent explanation and information I was not aware of. Thank you for posting it.

Mark

[azdave]

...the original pre production 65 heater design had a fresh air inlet to the atmosphere...

When you hear people discuss the "mystery box" in the engine compartment of a 65 Corvair that is what they are talking about. The abandonded fresh air intake that is covered with a metal plate. This is seen only on 65 models.

See photo.

[BigGeorgesVair]

Actually, I am not asking about the fresh air hose that Mark describes bypassing (for potential cylinder #5 issues, btw, I did had already done exactly as Mark described and installed a filter element)
I am referring to the hose that connects the fan box to the tunnel. ( item #3 - large oval hose, on the following page in Clarks catalog)

[64powerglide]

Clark's says the original style is preferred so that should be your choice.