74 versus 75 engine cooling differences

[Opelmn70]

I don't think this question has been asked or answered in the past forums, or at least in my search. Some background: A friend's 75 Manta with fuel injection. Wiring was unrecognizable from previous owner. Friend decided to go with carburetor and give injection set up to me. Regarding the cooling, he replaced thermostat hoousing, fan and hose set up for 75 and is using 74 and earlier housings. 75 original heater hose comes from passenger side rear plug to heater core instead of coming from 74 thermostat housing in front passenger side outlet. If we plugged the rear outlet in favor of the front outlet, would this change the cooling of the engine? ie. is the reason for the different outlet designed specifically for the 75 because of greater need (cooling) or for space efficency? Are there any other issues with cooling of the 75 engine with the 74 set up?
Thanks,
Gerry

[opelnut10]

The only differance in the 74 and 75 is the water inlet on the side of the head. If you use the 74 on the 75 and plug the port on the side of the blockc you will be fine. Be sure you use the 75 thermosrat with the FI because the module is set up to operate at that temp. You woll also need all the electronics to go with the FI including the fuel pump. Your friend will have to use a low pressure electric fuel pump as the 75 front cover does not have provisions for a mechanical pump. You will have to make a fuel pump block off plate and use yhe 75 pump.

[tekenaar]

Originally Posted by opelnut10 The only differance in the 74 and 75 is the water inlet on the side of the head. If you use the 74 on the 75 and plug the port on the side of the blockc you will be fine. Be sure you use the 75 thermosrat with the FI because the module is set up to operate at that temp. You woll also need all the electronics to go with the FI including the fuel pump. Your friend will have to use a low pressure electric fuel pump as the 75 front cover does not have provisions for a mechanical pump. You will have to make a fuel pump block off plate and use yhe 75 pump.

Let me just add that if that '75 FI is to be used in a different car, make sure you get that water hose nipple from the original car as well as the T-stat housing with its 3 hoses, that's right, all 3! They are unique to the FI setup.

Here's a list of the things needed for installing the '75 CIH FI.