914World.com [Powered by Invision Power Board]

Posted by: Panamericana Apr 29 2009, 08:42 PM

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?

Posted by: JRust Apr 29 2009, 08:57 PM

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

Posted by: SLITS Apr 29 2009, 10:13 PM

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.

Posted by: SirAndy Apr 29 2009, 10:18 PM

QUOTE(Panamericana @ Apr 29 2009, 07:42 PM)

Would the extra 7 hp that might be gained even be noticeable?

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

Yes, you'll be able to feel that.
popcorn[1].gif

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.

Posted by: r_towle Apr 30 2009, 05:54 AM

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

Posted by: 914Sixer Apr 30 2009, 06:51 AM

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

Posted by: computers4kids Apr 30 2009, 07:41 AM

QUOTE(SirAndy @ Apr 29 2009, 09:18 PM)

QUOTE(Panamericana @ Apr 29 2009, 07:42 PM)

Would the extra 7 hp that might be gained even be noticeable?

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

Yes, you'll be able to feel that.
popcorn[1].gif

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.

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

And yes, you can "feel that"

Posted by: Panamericana Apr 30 2009, 09:13 PM

QUOTE(r_towle @ Apr 30 2009, 07:54 AM)

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

Thanks everyone -- that's really useful info.

Posted by: Sleepin Apr 30 2009, 10:14 PM

QUOTE(computers4kids @ Apr 30 2009, 07:41 AM)