I just installed the Corvette Central true dual exhaust system with the Magnaflow mufflers in my 1974 auto L48. I went with the 2 1/2" system, which was an upgrade from the old 2" stock pipes I had on the car originally. I searched for information on installing the system, but couldn't find any youtube videos or walk throughs on it, so I thought I'd try my hand at making one.

https://www.youtube.com/watch?v=VRuqak9O0Bk

The end results of the system is that my car is... smoother. That's the best way I can describe it. It seems to have a better power curve, it's quieter and more predictable, and seems to have a little more oomph. Of course, all of this might be the placebo effect, but that's my impression based on my experience since installing it.

One item I noted in my video and wanted to call attention to was that when I pulled off the front pipe on the passenger side, I discovered that my heat riser had kicked the bucket. It had turned from a flat flapper valve into a twisted piece of metal that was frozen in place. It was probably restricting the exhaust out that side of the engine by at least a third. So I chiseled the valve out with a screwdriver and hammer and just left the heat riser's center rod in place. It wasn't doing me any good anyway.

I had a bit of a struggle trying to figure out how to remove the exhaust bracket from the transmission - it was due to lack of understanding how everything went together. Once I figured that out (and realized my crossmember was removeable) it all came apart just fine - see the thread link below for that challenge.

https://www.corvetteforum.com/forums...2-problem.html

Now that the new system is in, the only issue I'm dealing with is an issue of drone. I have a strong drone from just about 30mph to 40mph under any load. It's absent when I'm completely off the throttle. I also get a drone when I'm at idle in neutral (not in gear) when the car is warmed up, and when at idle in gear when the car is cold. That one doesn't bother me as much as the cruising drone. I've tested the car up to about 80mph, and there's no drone at higher speed. It's not unmanageable, but it's a little annoying, and I need to research whether it's an easy thing to get rid of.

One last item of note, also covered in the video, is that one of the pipes doesn't seem to be quite long enough. With the system assembled, one of my muffler hangers is under tension, trying to pull the exhaust out far enough. I'm pretty sure it's going to cause premature wear on the bracket, so I need to figure that one out as well.

 

Nice video and good work. I plan to do this during the winter.

 

Check to see if you have the pipes slip fitted the same depth on both sides.

 

I have the 2" system from Corvette Central on my '77 L-48 and had a noticeable drone around 1700 RPM. Strangely enough I did a tuneup and advanced the base timing from 8 to 14 degrees, recurved the distributor mechanical advance and the drone is almost completely gone. I didn't have any length issues with the pipes on my system, but will look in a few minutes to verify as I drove the car into work today with our great weather.

 

Enjoyed your video, very informative. Thanks for posting.

 

Make sure the pipe are not touching the through tubes in the crossmember.....this can cause a drone when stopped or running.

Jebby

 

I just peeked under the car and while the clamps might be slightly forward of the center of the hangers, the rubber rings in the hangers form an almost perfect circle.

 

The hangers can be rotated 180*. That will move the attachment point about an inch.