I am looking at a 74 that had its 1.8 engine switched-out for a 75 2.0 engine. How big of a task is it to backdate a 75 2.0 engine so that it performs and has the characteristics of a 74 2.0? Would the extra 7 hp that might be gained even be noticeable?

If it still has all the smog take it all off. Block of the ports on the motor. Pretty easy & worth the time. I'm not sure that gets the 7hp you mention but is probably close depending on your muffler & Exhaust. The 75 HE do not flow that well. Your definately better off with early 2.0 Heat Exchangers. Good luck

They are the same except for:

1.) Restrictive exhaust

2.) Lack of head vents (which can be added)

3.) Addition of air injection holes into the exhaust ports (which can be plugged)

4.) Lack of tapped screw holes to secure the engine tin (screw holes would be where the air injection holes are.

Same crank, same pistons, same heads. The exhaust probably accounts for the greatest loss in HP.

That's almost 10% power gain! (7.95 to be exact)

Yes, you'll be able to feel that.
Andy

PS: And if you upgrade to Euro Spec while you're in there you'll get a 13.63% power increase.
Make that a 2056 with a modded Cam and now you're getting close to 30% power gain.

I agree with everything above.
I want to stress, get RID of the 75 HE setup.
It not only is a lower power system, it is also a heat issue.
The 75 setup routes the tubing forwards and then back, thus there is more heat under the head for alot longer....motors run hotter.

Its also a total bitch to do valve adjustments or anything else with that system up in there.

Rich

Acording to spec book. 75 had 88 hp and the 74 had 95 hp.

And, if you drop in a SBC that will be a 300% gain...kind of. And yes, you can "feel that"

Thanks everyone -- that's really useful info.

WooHooo!!!!