Tuesday, June 12, 2018

MGB muffled

Continuing the saga of getting the MG summer-weather ready, today's post covers some fun with the exhaust system. I started this post a few months ago and forgot about it, so recognize this was before I got through DEQ. So, I was doing things that were lowest possible cost in case I needed money to get through DEQ (think engine rebuild, etc).

Quiet You
In each of the test drives where I verified my fixes, I couldn't help but notice 2 things. First, the MG was loud as #$%!. Second was the unmistakable sound of an exhaust leak (pop pop pop). Out of curiosity, I pulled out a decibel tester app on my phone and checked. Parked in the garage with the doors open, sitting in the driver seat, I started the engine, and pushed the revs up to 3k and back down. I peaked at just shy of 100dB. According to the application, that's as loud as a blender. In the driver seat.

When we had the donorZed, I noticed that the exhaust was the same smaller-diameter piping as the MG had: 2". In the interests of getting every usable part off that thing, I cut off the rear muffler (which was surprisingly not that rusty), and the catalytic converter (cat). I figured that one of the two cars could use one or both of those parts, and with DEQ smog a part of ownership of these cars for the foreseeable future, one of them would eventually have use for the cat.

So, with the blender-loud exhaust reality in my face, I decided to start with the muffler going onto the MG. One would reasonably think that the crazy-bending exhaust plus muffler wouldn't "just fit". And, it sort of did.

Soup Can Exhaust
Most of the exhaust system on the MGB is coated with rust. The pipes, the little cherry-bomb mufflers, even the exhaust manifold. There is deep rust everywhere. This makes welding replacements all the more difficult because you have to get to clean steel to have a good strong weld. Fortunately, there are no-weld joiners available for most standard diameter sizes. These are somewhat simple in their design with a straight section of pipe with an integrated band clamp at each end. You put 2 cut ends of pipe into each end of this thing and tighten. Simple. It reminds me of the old-skool way to patching a hole in the exhaust: cut a soup can into a patch and get it to hold on with hose clamps.

All of this leads us to my noise reduction. The MGB had 2 cherry bomb mufflers in sequence which were not really muffling noise at all. So, I cut off the one on the back and fitted the one from the donorZed. With some careful cutting, I was able to get the 2 straight sections to abut, but there is not an off-the-shelf no-weld joining thing to connect them. So, I went back to the old-skool roots and cut up a small can, and hose-clamped it together. Yeah, I'm not that proud of that, but remember, this was done before I got through DEQ.

I re-used the hangers that were there from the cherry-bomb muffler, and it was ready for testing. Total cost: $0. I tested the noise level the same way: car in with the garage doors open. dB levels hovered in the low 90's, so I shaved up to 10% of the noise just by putting a bigger muffler on. Truth-be-told, the muffler from the donorZed looks an awful lot like the stock MGB muffler. During the test-drive, it became clear that the rubber had completely dried up, so I had to resort to holding the center section of pipe off the ground with bailing wire. Yeah.. not too proud of that either.

I'll get after the backfire in another post. For now, the exhaust is quieter, if not in a better long-term disposition. My thinking: don't attract unwanted attention by the tester at DEQ. That includes disconnected things under the bonnet and a super-loud exhaust which might imply something non-stock is going on.

Anyway, that's it for today. I'll post on my attempts to solve the backfire and other developments as I do. Thanks, as always, for following along-

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