LS1 Conversion, A Retrospective Build Thread Options

[andys]

Here's the start of a retrospective build thread of my LS1 conversion. It took a few years to get it done mostly due to not wanting to be a slave to the project, and work on it for the enjoyment; and of course when family obligations allowed......teen daughter and high maintenance wife (IMG:style_emoticons/default/biggrin.gif)

What I started with was a local orignal owner '75 2.0 with 139K miles. The original owner "drove the heck out of it" until something died in the electrical system and he parked it in the garage for 14 years, as evidenced by the renewal tags. Only body damage was when he submarined the rear of a Mustang and creased the hood and flattened the left signal light pod. Otherwise, it was a good condition rust free (SoCal) car.

Brief specs are: '01 LS1 Z28 motor, Audi 01E 6 speed tranaxle, 911 front suspension, custom made rear trailing arms, Koni shocks, 993 wheels, and AC.

Below, are photos of what I started with, and what I ended-up with. I'll do my best to re-trace the build process, so if you have any questions along the way, please ask.

BTW, how does one place text between photos in the same post?

Andys

[andys]

Time to get back to posting more retrospective build photos, so I decided to show the exhaust sytem next.

The stock LS1 headers exit in the wrong place (pointing straight at the axles), so after a little digging, I decided to go with stock LS6 Vette headers. They are thin wall cast iron, tri-Y design, and surprisingly light weight. What I like about these headers, they have some real nice heat shields, aren't prone to leakage like tubing headers, suppport 405HP (which is plenty good for the LS1), and dump on an angle somewhat centered so it's perfect for my application.

The exhaust pipe routing is up-over the axles, which I made from some 2 1/2" stainless mandrel bends from Summit. The flange that bolts to the header wasn't available as an aftermarket part, so I made my own such that it will sandwich the stock Vette donut gasket. The flange is made of mild steel, so I used some 312 stainless rod that's recommended for carbon steel to stainless welds. As an aside, I found this rod is very nice to work with, and I used it on a few other dissimilar welds.

For mufflers, I decided on Flowmaster three chambered stailnless. The three chambered mufflers, according to the Flowmaster noise graphs, significantly reduce the interior noise level; that is something I really wanted. Actually, I needed to determine the available space first, so I mocked-up mufflers from cardboard from the advertised dimensions and moved them around until I got them where I wanted. Since the 01E transaxle is fairly long, there was no space between it and the rear of the car to fit the Camaro style dual inlet/dual outlet muffler that some have used....I think it's a nice solution, but unfortunately not for me.

Once the mufflers were welded in place, I made a brace off the transaxle to mount some rubber isolators to support the weight at the rear. I did add some heat shielding in strategic areas so as to manage the heat. First, I shielded the area adjacent to the shocks, since the muffler and inlet pipe was a bit close. I then added a heat shield where the pipe runs close to the shifter cables. Finally, I installed heat shields to the top of the mufflers to keep the trunk floor from getting too hot; these are made by Flowmaster specifically for the three chambered muffler.

After driving the car, it is a bit loud (exterior noise), but I'm not surprised due to how short the exhaust system is. I know I can quiet it down by adding a cross-over pipe, but there's so little room I'm not sure yet how to route the pipe; I'll have to chew on this for a while. There's also a drone under load from about 1800 - 2000 RPM. After some research, I found that a Helmholz chamber can cancel out this drone. A closed end pipe, regardless of routing, placed preferably just ahead of the muffler, calculated to the proper length (wave speed, number of pulses, frequency, etc) can cancel out the resonance (drone). It's a tidy solution that I may employ once I figure out the cross-over pipe.