MFI and SSI

[Gene Smith]

When restoring a MFI car to original from Weber carb converted MFI, what is the difference in the SSI HEs.

When I bought my SSIs over 12 years ago to install on my MFI engine with Webers installed, I thought I bought a pair that were compatible in the future with MFI. I remember the MFI versions had a fitting that was just unused with Webers?????

Now I see SSIs that have a complete "stove" around the exhaust in addition to the cabin heat exchanger that I guess is for MFI preheat?

If I decide to return the MFI to my engine, must I buy new SSIs (of questionable DANSK quality) or is there a work-around to using the SSIs I currently own?

Gene

[kenikh]

Pre heat isn't necessary and didn't work that great anyway. Supertec's rack enrichment lever works miles better.

[Porboynz]

The lhs heat exchanger has a pipe to feed heated air to the MFI unit via an insulated hose. Its about 3/4 inch diameter, on the LHS and aiming to the rear, maybe 1.5 inches long. Simple to add if your SSI's do not have this pipe which would be blocked off with Webers.

I never had a problem with the MFI thermostat but plenty of folk do replace it with a pull cable or just fix it in the warm/hot position. I left the hose off once, the engine ran rich, really rich.

[Gene Smith]

Thank you- Yes Porboynz that is what I remember-

I have the fitting you describe- labeled A in this photo.

But I DO NOT have the apparatus labeled B

I would love to keep it simple and have a manual enrichment, the car is a '69. I'd also love to have a nice old school exposed K&N. I think seeing the stacks and linkage is fun. I also won't want to miss the fantastic intake sound I now have hidden by that big ol' stock air cleener...

I saw a reference to a thread by the late Grady Clay about "waking-up" a MFI pump that has sat a long time. Many, MANY years ago I read a piece in Pano about "pickeling" a MFI pump for storage. Unfortunately mine was just plugged-up and stashed away by PO when Webers were installed.

Does anyone know of a link to the pump storage post by Mr. Clay?

Thanks again,

Gene

[kenikh]

I remember that thread, too

[tobluforu]

I'm pretty sure it was early_s_man that stated to take the pump and soak it in Berrymans for 7 days????

[kenikh]

Warren... Grady, gone but not forgotten.

[Porboynz]

Originally Posted by Gene Smith

Thank you- Yes Porboynz that is what I remember-

I have the fitting you describe- labeled A in this photo.

But I DO NOT have the apparatus labeled B

I would love to keep it simple and have a manual enrichment, the car is a '69. I'd also love to have a nice old school exposed K&N. I think seeing the stacks and linkage is fun. I also won't want to miss the fantastic intake sound I now have hidden by that big ol' stock air cleener...

I saw a reference to a thread by the late Grady Clay about "waking-up" a MFI pump that has sat a long time. Many, MANY years ago I read a piece in Pano about "pickeling" a MFI pump for storage. Unfortunately mine was just plugged-up and stashed away by PO when Webers were installed.

Does anyone know of a link to the pump storage post by Mr. Clay?

Thanks again,

Gene

I have the exhaust below that has just the one hot air bleed for the MFI, yours will be fine.



My pump sat for 10 years without any special attention, no problem on restart. If you can turn it by hand it will likely be just fine, you can always squirt some oil in via the drain pipe if you are concerned. Its easy to remove a side cover and inspect for added reassurance, I bet its all nice and oily in there.

[mobius911]

I believe John Daniels of SSI made a decision not to include the clamshell and "B" connections shown above. I recall that this was based on a technical bulletin from Porsche claiming that they weren't necessary. AFAIK, the connections were there just for pollution control at idle during warm-up.

The Dansks for MFI do include it now, but you certainly can run without. You may want to block off the opening through the rear engine tin if you run without.

[Gene Smith]

Great! Thanks Guys.

[webco]

I know this thread is getting a bit old, but I'm also trying to figure what the "B" connection is for and what it connects to. I have a '71 911E that is slowly going back together. Was the "B" hose fitting only for the carburetored cars? Some sort of pre heater?

Bill

[mobius911]

"B" on the driver's side heat exchanger connects to a vent connection through the left side engine tin. It just dumps the air into the engine bay; no additional routing. The opening into the engine bay has a screen on it to prevent crap from falling into the hole.

The third outlet at the back of the heat exchanger connects to the circled "flapper" in the photo. These often got tossed. I happened to hang on to my mine and just reinstalled it after not running it for 20 years. Doesn't really do much but I decided to go "original".

The flapper has a heat-activated door that lets in heated air from the H.E. at idle during wam-up, and then switches to cold air after the car is warm. A separate flap activated by the throttle assembly opens and bypasses the pre-heat air circuit as soon as the throttle is at about 1/4 position. I like hearing the flap snap open and shut as I'm driving, although that will get old. The thing is a Rube Goldberg delight.

If you find a flapper- and they come up on Pelican- make sure that the heat-activated door is working properly. They can get stuck after all these years.

One final edit: The 'B' connection and the "flapper" were for 72/73 only, so a 71 wouldn't even have it. These additions were right at the beginning of the emission control era.

[Dodge Man]

I know that this is an old post but MFI info is not that common. My 72 MFI 2.4 time capsule on the stand has a thermal heat riser only hot air for the intake. Many variants for early 70's so Dansk says you may need to plug the fan air intake "B" exchanger port on some models. Very common on early 70's 911s to have several variants for MFI, CIS, and ROW carbs. Many just put the hot air parts on the shelf. It looks like my 72 MFI uses the left tin for only the small hose pass thru. PET illustrations can be confusing showing a pass thru on the carb & CIS left tin. Cheers!