Which SSIs for a '77 motor in a '71?

[MrBonus]

I feel like this is a stupid question but which SSIs would I need?

The engine is coming down for a reseal and Weber rebuild in the spring and I figure this is as good a time as any to remove and replace my rusty heat exchangers.

[drtyler]

Probably need thick flange, but it all depends what is installed now. Really need to add picture or verify from previous posts & pictures whether your engine has thin or thick flanged heat exchangers.

[MrBonus]

Originally Posted by drtyler

Probably need thick flange, but it all depends what is installed now. Really need to add picture or verify from previous posts & pictures whether your engine has thin or thick flanged heat exchangers.

Thank you. Second-owner hot rod problems.

I'll snap some pictures this weekend. Please ignore the thin coating of oil on them.

[75 911s]

all comes down to the studs. That 77 likely would have the longer studs on it, so you would need the thick flange with the smooth top. I want to say there was a carrera thick flange with raised center pipe on the flange, so don't get that one or you'll be cutting off the center pipe sticking up out of the flange. I don't even know if they make that version anymore. But maybe if you buy a used set.

Of course you can always adapt with spacers on the longer stud if you end up with thin flange SSI, but be advised that adding 12 spacers is a royal PITA given the working clearance between the ssi and the bottom of the engine. Swapping to shorter studs is a dangerous idea too as those studs are brittle from heat cycle and likely to snap.

[MrBonus]

Originally Posted by 75 911s

all comes down to the studs. That 77 likely would have the longer studs on it, so you would need the thick flange with the smooth top. I want to say there was a carrera thick flange with raised center pipe on the flange, so don't get that one or you'll be cutting off the center pipe sticking up out of the flange. I don't even know if they make that version anymore. But maybe if you buy a used set.

Of course you can always adapt with spacers on the longer stud if you end up with thin flange SSI, but be advised that adding 12 spacers is a royal PITA given the working clearance between the ssi and the bottom of the engine. Swapping to shorter studs is a dangerous idea too as those studs are brittle from heat cycle and likely to snap.

Thanks for the detailed explanation!