Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ Converting 1975 exhaust to pre 75 exhaust

Posted by: Geezer914 May 6 2009, 02:03 PM

How much horse power will I gain by switching out the heat exchangers from a 1975 to the pre 75 dual exit heat exchangers and adding a Monza muffler?

Posted by: SLITS May 6 2009, 02:06 PM

3 - 5 maybe.

Horsepower is not the only consideration though.

Posted by: maf914 May 6 2009, 02:44 PM

I backdated the exhaust on my 76 from completely stock to 74 style SS heat exchangers and a Bursch quiet extractor muffler. I liked the result but I can't really say I felt a big increase in power. It may have just been the exhaust note but it felt as if the engine was a bit more lively above 3500 rpm.

I will say that many years ago I tried a Monza 4-tip muffler on my stock 76 heat exchangers. I found it to be too noisy for my taste. At first it was fun but after a couple of months I found I was driving to reduce the noise. I would coast into my driveway because I didn't want to annoy the neighbors. I know, what a wimp. But in less than a year I had replaced the monza with the stock muffler system (had to buy a new secondary muffler which are now NLA I think) and thought good riddance. Several years later when I went to the Bursch quiet I was a little wary, but I found the sound to be reasonable. IMHO, if you go with a Monza just be prepared for some noise.

Posted by: Drums66 May 6 2009, 03:15 PM

I will say that many years ago I tried a Monza 4-tip muffler on my stock 76 heat exchangers. I found it to be too noisy for my taste. At first it was fun but after a couple of months I found I was driving to reduce the noise. I would coast into my driveway because I didn't want to annoy the neighbors. I know, what a wimp. But in less than a year I had replaced the monza with the stock muffler system (had to buy a new secondary muffler which are now NLA I think) and thought good riddance. IMHO, if you go with a Monza just be prepared for some noise.
[/quote]

everytime I drove through Apt complexes........I would set
off all the car alarms.....I got tired of that!!!(went back to stock)

Posted by: Jerry75914 May 6 2009, 06:01 PM

I actually just did a 2.0 backdate to my 1975 1.8L. It seems much more lively, and a step or two quicker according to my butt-dyno. Then again, I also had the valves, dwell and timing adjusted at the same time, so it could be a combination of several things. I did notice that it ran much cooler than the stock setup.

Thanks again to everyone at the Sacramento swap meet for setting me up with parts and advice!