What do you when you remove heater, but not heat exchangers?

[Hotwatermusic]

So I am about to re-install the engine and transmission, which I am deathly worried about (but that's a whole 'nother thread).

Anyway, since I live in Texas, and haven't once turned the heater on in my car, and the hoses in the engine bay were pretty grungy anyway, I removed everything (I think) heater-related on the engine. I'm not however, removing the heat exchangers, simply because I have nothing to replace them with. What then do I do with the open holes that once belonged to heating equipment? I've included some pictures, indicated with places I am talking about exactly. What do I do with these open holes if I'm going to use them once the engine is back in? Also, is there something I'm not considering in removing the heater-related stuff like I have?

[DRACO A5OG]

Hmmm, Reconnect the hoses from the heat exchangers, just incase you may want some heat, better to have it then not, like defrost the front windshield, when it rains, I know it rains in Texas

Find some Hi-Temp hose and plumb the two holes together so when you want heat all you have to do is pull up the levers. I have seen pics of other that did the same.

Not only that, since it is hot there keeping it plumbed will help cool her by slightly lifting the lever so the hot air can blow down the heater flaps.

Jim

As far as Engine/Trans re-install, go slow and watch the CV's, all hoses once you get them under the car, lower the car to them, the angle of attack is less steap that way. I did this myself twice in recent months and I found it much easier and safer for you and your baby.

Remember you want to re-torque (gradient star fashion) the CV after about 500-1000 miles, use new gaskets if the are questionable.

[DRACO A5OG]

Also remember to hand crank the engine couple of times to get oil to all parts prior to starting her up the first time from being dry so long.

[Eagledriver]

You can cap off the hole in the fan shroud and the hole in the sheet metal at the back of the engine. There are also block off plates available to replace the part on the fan shroud. Leave the holes in the heat exchangers open. There are those who worry about the headers getting too hot with no air flowing through the heat exchangers, but plenty of people run that way with no issues.

-Andy

[will hung]

If the engine oil gets too hot from leaving the heat exchangers in tact but no heat attached to evacuate the heat in the exchangers, you can cut off the sheet metal for the heat exchangers so that they no longer hold heat underneath the engine.

[Mountainman]

I went the same route you are going down until I talked to a true expert.
I'll withhold his name since he is not posting this himself.
He said that the heat exchangers will get too hot if there is no positive pressure
air movement through them, hot enough to ignite dripping oil. So I backdated my system and used orange aircraft flex tubing to make the connections. Took out the electric fan, cruise control and AC too. The engine compartment is now neat and tidy, I have heat if I need it, air through the exchangers - everything worked out well.
I'm not too good with pictures and computers to show you mine but if you search for something like
"SC heater backdate" or "backdating heater" there are some nice pictures to guide you. If you need a parts supplier for the backdate pieces you can search that as well or pm me for the info. Good luck -

[Grady Clay]

Mountainman has it correct.

There are two acceptable choices:
Use the heater systems as designed with the proper air flow through the heat exchangers
OR
install ‘headers’ (exhaust pipes without heat exchangers) and cover the openings from the fan shroud.

The worst possible is to leave the openings from the fan shroud open (wasting necessary cooling air) and have heat exchangers with no air flow (allowing the exhaust pipes and tin to get so hot as to ignite residual oil).

With original heat exchangers, it is also important to have the heater control ‘flapper’ valves in place as they provide design restriction to the air flow through the heat exchangers.


Even in Texas, there are days where heat (windshield defrost) is necessary.
The Factory heat exchangers are very good performance parts. Use them as intended.

There are situations where not using heat exchangers is appropriate.
Those include some racing in warm weather.
It also includes situations where the engine cooling system is stretched to the limit of capacity (117F in Houston with the A/C on).
Here, you want every single molecule of cooling air to cool the heads and cylinders.

Best,
Grady

[porschenut]

I completely removed the heater components from my '86 Carrera, and only installed the left side blockoff plate on the fan shroud. For 4 years, I've been running with the heat exchanger holes wide open with no forced air flow through them whatsoever, and my oil hardly ever reaches 210 degrees. I too have heard the warning about airflow through the exchangers, but I've got 4 years of real world experience to disprove that theory.

[wwest]

Originally Posted by DRACO A5OG

Hmmm, Reconnect the hoses from the heat exchangers, just incase you may want some heat, better to have it then not, like defrost the front windshield, when it rains, I know it rains in Texas

Find some Hi-Temp hose and plumb the two holes together so when you want heat all you have to do is pull up the levers. I have seen pics of other that did the same.

Not only that, since it is hot there keeping it plumbed will help cool her by slightly lifting the lever so the hot air can blow down the heater flaps.

Diverting airflow from cylinder head cooling so as to "cool" the exhaust manifold makes NO sense.

Jim

As far as Engine/Trans re-install, go slow and watch the CV's, all hoses once you get them under the car, lower the car to them, the angle of attack is less steap that way. I did this myself twice in recent months and I found it much easier and safer for you and your baby.

Remember you want to re-torque (gradient star fashion) the CV after about 500-1000 miles, use new gaskets if the are questionable.

...

[Gunter]

Originally Posted by Grady Clay

Mountainman has it correct.

There are two acceptable choices:
Use the heater systems as designed with the proper air flow through the heat exchangers
OR
install ‘headers’ (exhaust pipes without heat exchangers) and cover the openings from the fan shroud.

The worst possible is to leave the openings from the fan shroud open (wasting necessary cooling air) and have heat exchangers with no air flow (allowing the exhaust pipes and tin to get so hot as to ignite residual oil).

With original heat exchangers, it is also important to have the heater control ‘flapper’ valves in place as they provide design restriction to the air flow through the heat exchangers.


Even in Texas, there are days where heat (windshield defrost) is necessary.
The Factory heat exchangers are very good performance parts. Use them as intended.

There are situations where not using heat exchangers is appropriate.
Those include some racing in warm weather.
It also includes situations where the engine cooling system is stretched to the limit of capacity (117F in Houston with the A/C on).
Here, you want every single molecule of cooling air to cool the heads and cylinders.

Best,
Grady

+1

Heat is the enemy for aircooled engines, especially in hot climates.
Premature valve guide wear is one negative aspect along with a few more.
Either do correct "back-dating" adding SSI's (which you want anyway) or ensure some way of airflow with the stock set-up.

BTW: For the 964/993, it is recommended to remove the engine under tray for increased airflow helping with cooling and extending valve guide life.

It only makes sense when considering the high air temps in certain areas.
Just because the oil temps stay within limits doesn't mean that the exhaust ports on the heads don't get hot as hell without airflow.

[Grady Clay]

Dave,

I suspect your engine already had a right-side block-off plate at the fan shroud.
You blocked off the air at the left-side where the air would have gone to the heater fan.
This means you have no wasted air from the fan shroud.
Good.

You are fortunate to not have oil accumulation in the heat exchangers.
If you had, there was the possibility of an oil fire.
If you measure the temperature inside your heat exchangers, you will be appalled at the heat.
Consider the alternatives.

Porsche designed the system where the exhaust heated air was either wasted (out the ‘flapper valve’) or used to heat the cockpit and windscreen.
If we choose to not use cockpit heating, then we need to pay attention to the complete system.
Race cars (911R, 906 and others) sometimes choose to abandon cockpit heating in favor of increased engine cooling.
This was an event-by-event choice, not regular practice.
You can make similar choices.

The important issue here is having heat exchangers without air flowing through.
In spite of Dave’s experience, no air flow is bad practice.
Sure, without oil leaks and others you can ‘get away with it’.

A significant clue as to Porsche’s inclination is their 901 engine dyno air restrictors on the outlets of the heat exchangers.
There are pictures in the 911 Workshop Manual, Volume I, p.p. E119-E121.
This indicates how important having (restricted) air flow through through the heat exchangers is.

Best,
Grady

[porschenut]

Grady, your explanation certainly makes sense, and it sounds like I've just been lucky not to have experienced any problems. I've wanted to replace the stock HE's for a set of regular headers, but it's a street car and I can't get out from under the Colorado AIR program requirements for a catalytic converter. What I may do is simply cut off the sheet metal around the headers and leave the crossover and emissions equipment as they are (if that's possible). That might make a good spring project.

[Hotwatermusic]

Ok, so the main priority is to cap off the left side of the fan shroud so none of that cooling air goes to waste. Then reconnect the hoses at the transmission end of the heat exchangers. Do I have to reinstall the blower motor and hosing that runs over the top of the engine to achieve the required cooling action on the heat x'ers?

[will hung]

You need to have air traveling through the heat exchangers to shed the exhaust heat stored in them. You can achieve that in 2 ways.

1 is to reattach all the factory plumbing and blower motor.
2 buy heat backdate ducts. These would replace the duct off the left side of you fan behind the distributor and the block off plate on the right side. You then run tubing from the ducts to the exhaust exit end of the heat exchangers. Then the cooling fan will force air through the heat exchangers. For both scenarios, you still attach the transmission side of the heat exchangers to the flapper valves.

[wwest]

Originally Posted by Grady Clay

Dave,

I suspect your engine already had a right-side block-off plate at the fan shroud.
You blocked off the air at the left-side where the air would have gone to the heater fan.
This means you have no wasted air from the fan shroud.
Good.

You are fortunate to not have oil accumulation in the heat exchangers.
If you had, there was the possibility of an oil fire.
If you measure the temperature inside your heat exchangers, you will be appalled at the heat.
Consider the alternatives.

Porsche designed the system where the exhaust heated air was either wasted (out the ‘flapper valve’) or used to heat the cockpit and windscreen.
If we choose to not use cockpit heating, then we need to pay attention to the complete system.
Race cars (911R, 906 and others) sometimes choose to abandon cockpit heating in favor of increased engine cooling.
This was an event-by-event choice, not regular practice.
You can make similar choices.

The important issue here is having heat exchangers without air flowing through.
In spite of Dave’s experience, no air flow is bad practice.
Sure, without oil leaks and others you can ‘get away with it’.

This is nothing less than PURE BS

Why divert engine cooling airflow in favor of cooling the exhaust manifold rather that having FULL engine cooling airflow AND cooling the heat exchangers in the same process...?

A significant clue as to Porsche’s inclination is their 901 engine dyno air restrictors on the outlets of the heat exchangers.
There are pictures in the 911 Workshop Manual, Volume I, p.p. E119-E121.
This indicates how important having (restricted) air flow through through the heat exchangers is.

Best,
Grady

...

[Gunter]

Quote by wwest:

"This is nothing less than PURE BS"

Why divert engine cooling airflow in favor of cooling the exhaust manifold rather that having FULL engine cooling airflow AND cooling the heat exchangers in the same process...?

Grady never said to just cool the exhaust manifold without full airflow for the engine.

Consider more carefully before calling the input from a very experienced and helpful contributor pure BS.

It goes without saying that the cylinders need aircooling before anything else and the design by Porsche was always to have full airflow for the engine.

The auxiliary blower is not absolutely necessary but was added to supply extra heat for the cabin at idle, AFAIK. Main airflow has always come from the big fan supplying aircooling whether the flappers are open or closed.

So, whether using the air for the cabin or just have it diverted into the void, the design calls for full airflow through the HE's either way and I'm sure Grady knows that.

If the extra blower is removed, a block-off plate is used and a hose is re-routed to ensure that full airflow is maintained as intended by design.

When adding SSI's, the auxiliary fan and hoses on top of the engine are removed and different plates left and right of the fan are installed with short new hoses to the SSI HE's.
That's "back-dating" and actually gives more heat as experienced by this old ME.

[wwest]

Originally Posted by Gunter

Quote by wwest:

"This is nothing less than PURE BS"

Why divert engine cooling airflow in favor of cooling the exhaust manifold rather that having FULL engine cooling airflow AND cooling the heat exchangers in the same process...?

Grady never said to just cool the exhaust manifold without full airflow for the engine.

You can't have FULL airflow through the engine's cylinder cooling vanes while diverting a portion of the airflow to "cool" the heat exchangers, exhaust manifold.

Plus...It seems to me that the extra cylinder cooling you get by using ALL of the airflow might result in the exhaust manifold being just as cool as otherwise, diverting a portion of the airflow to directly cool the exhaust.

Consider more carefully before calling the input from a very experienced and helpful contributor pure BS.

It goes without saying that the cylinders need aircooling before anything else and the design by Porsche was always to have full airflow for the engine.

Exactly...!!

Just another way, quite FACTUAL way, of calling Grady's input BS.

The auxiliary blower is not absolutely necessary but was added to supply extra heat for the cabin at idle, AFAIK. Main airflow has always come from the big fan supplying aircooling whether the flappers are open or closed.

So, whether using the air for the cabin or just have it diverted into the void, the design calls for full airflow through the HE's either way and I'm sure Grady knows that.

If the extra blower is removed, a block-off plate is used and a hose is re-routed to ensure that full airflow is maintained as intended by design.

When adding SSI's, the auxiliary fan and hoses on top of the engine are removed and different plates left and right of the fan are installed with short new hoses to the SSI HE's.
That's "back-dating" and actually gives more heat as experienced by this old ME.

"...The auxillary blower is not absolutely necessary.."

Yes, I suppose in the alternative one could always push in the clutch and use the gas pedal to elevate the cabin heating airflow enough to be comfortable on a COLD day/night when the engine might otherwise be at idle. My experience was that the auxillary blower required a modification in order to keep a reasonable cabin comfort level on a cold day, "Seattle" cold day.

Oops, correction..

The blower/fan modification resulted from not being able to keep the interior surface of the windshield defogged consistently.

[Grady Clay]

This should not be a contentious issue.

Porsche engineering staff made ‘engineering decisions’ balancing the cooling airflow through the engine (heads, cylinders and engine oil cooler) vs. the airflow through the heat exchangers.
Keep in mind that the airflow through the heat exchangers takes away cooling air from the engine.
This air is NOT previously used for engine cooling (Porsche didn't want the additional oil-leak smells).

With the air through the heat exchangers, the engineers restricted the airflow when wasting the heated air (hot weather, cockpit heating off).
This restriction was provided by the heat control ‘flapper’ valves.
The purpose of continued airflow is to maintain cooling of the exhaust inside the heat exchangers (preventing fires and over-temperature damage).
Porsche had a lot of experience with this system with “European heaters” fitted to 356 since 1963 when the 911 was being developed (and eventually 912s ).

When originally developed, the 911 heat exchangers had a fabricated exhaust system inside the heat exchangers.
This was quickly removed (recalled, thanks to Corvair experience) and substituted with the ‘S’ heat exchangers we all know and love (’64-’74) and more modern aftermarket SSI.

The more modern Factory systems have restricted airflow through the heat exchangers but enhanced with electric fans when cockpit heat is necessary.
This allows some air through the heat exchangers in hot weather (when cockpit heating is off) in order to protect the system from heat damage while not wasting too much cooling air.
In cool weather (when engine cooling is less significant issue), more air is forced through the heat exchangers by the electric fans (including the two in front starting in ’84) to the cockpit.

When you choose ‘headers’ (exhaust without heat exchangers), it is assumed that you are almost always ‘at-speed’ on track.
The airflow under the car keeps the exhaust within ‘reasonable’ (race) temperatures.

Anyone who doubts these issues should observe a 911 engine at full power on an engine dyno.

These issues resulted in the use of the “Rubbermaid Solution”.

Best,
Grady

[porschenut]

I'm about to show some additional ignorance here, but I'm not sure I understand the need to keep the exhaust manifold cooler, aside from possibly preventing a fire in the event of oil dripping on to the HE's. Is there another reason?

The headers (whether surrounded by heat exchanger sheet metal or not) are connected to the heads. So if 100% of the fan output is directed to the heads and cylinders, won't that help keep the manifolds cooler too (especially with the Rubbermaid Solution)? Or, at the least, won't it direct the cooling air where it's most critical?

[wwest]

Originally Posted by Grady Clay

This should not be a contentious issue.

Porsche engineering staff made ‘engineering decisions’ balancing the cooling airflow through the engine (heads, cylinders and engine oil cooler) vs. the airflow through the heat exchangers.
Keep in mind that the airflow through the heat exchangers takes away cooling air from the engine.
This air is NOT previously used for engine cooling (Porsche didn't want the additional oil-leak smells).

With the air through the heat exchangers, the engineers restricted the airflow when wasting the heated air (hot weather, cockpit heating off).
This restriction was provided by the heat control ‘flapper’ valves.
The purpose of continued airflow is to maintain cooling of the exhaust inside the heat exchangers (preventing fires and over-temperature damage).
Porsche had a lot of experience with this system with “European heaters” fitted to 356 since 1963 when the 911 was being developed (and eventually 912s ).

When originally developed, the 911 heat exchangers had a fabricated exhaust system inside the heat exchangers.
This was quickly removed (recalled, thanks to Corvair experience) and substituted with the ‘S’ heat exchangers we all know and love (’64-’74) and more modern aftermarket SSI.

The more modern Factory systems have restricted airflow through the heat exchangers but enhanced with electric fans when cockpit heat is necessary.
This allows some air through the heat exchangers in hot weather (when cockpit heating is off) in order to protect the system from heat damage while not wasting too much cooling air.
In cool weather (when engine cooling is less significant issue), more air is forced through the heat exchangers by the electric fans (including the two in front starting in ’84) to the cockpit.

When you choose ‘headers’ (exhaust without heat exchangers), it is assumed that you are almost always ‘at-speed’ on track.
The airflow under the car keeps the exhaust within ‘reasonable’ (race) temperatures.

Anyone who doubts these issues should observe a 911 engine at full power on an engine dyno.

These issues resulted in the use of the “Rubbermaid Solution”.

Best,
Grady

I do not disagree, dispute, that if you sometimes HAVE/NEED cabin heating it is best to continue the airflow through the heat exchangers even with cabin heating OFF. With this heating arrangement you ARE diverting/bypassing a portion of the engine cooling airflow around the engine so it can do no harm, only good, in provided some amount of cooling "downstream".

But the question here is whether are not you can eliminate the need for cabin heating airflow completely. In that case the engine would always get the FULL cooling capability of whatever level of airflow the engine driven fan can "pump".