Heat exchanger swap out

[sundlh]

I am the original owner of a 1979 911SC with 75K miles on it. The original HE's have some rust so I bought a used pair in great condition but have not yet pulled the originals off the car. Ordered all new gaskets and hardware from the host, tried to fit the new manifold gasket to the replacement HE and found that the stainless gasket for my year doesn't fit: ......just a wee bit to small on the hole ID to fit over the tube that goes into the head.
Here is my concern......if my replacement HE's are from a 1983 or later 911 are the ports in the head a larger size than on my my 1979 911SC?

When I bought the new/used HE's I was told they came off a 1978 SC.

Given that the new gaskets are a wee bit too small I am now concerned that the exchanger won't mount onto my engine do to larger tubes at the flange site.

Any help or insight is welcome before I begin to dismantle my heat exchangers.

FYI the numbers on the new/used HE's is 93021102901 and the number above that is 911/122

Many thanks for any help!
sundlh

[snbush67]

Your 79 heads have 35mm exhaust ports. The later SC's have 35 mm exhaust ports as well exept they have a 39mm step to accept the gasket blow out sleeve so the ID of the sleeve will still be 35mm.

This means that you can cut of the sleeves from the later heater exchangers, and change the headstuds to the later, longer ones if you want to use those later thick flange exchangers. Then you can use the 78-79 gaskets.

Most people break a few headstuds while removing the old exchangers. Be prepared for this as it will require some skill in extracting broken studs. Also have your new studs, barrell nuts and copper nuts ready to go.

[Flat6pac]

Youre mixing and matching different year stuff.
79 has thin flanges, 80 to 83 has thick flanges with a head insert. You can remove the insert section by driving a chisel into the insert , collapsing it. there is 3 spot welds holding it in place.
You still have to change out the 12 studs..can you say nightmare
I would recommend you spend some more time and locate heat boxes that will work for you.
75/76/78 and 79 are thin flange units.
With a torch, you should be able to swap out the boxes in the car.
Bruce