We're putting a complete new exhaust system into our '73 LeSabre. New headers, all new pipes and mufflers etc., from head to tail. In the past, I've had issues with gasket sealing (who hasn't?)... And we got to thinking that maybe it's not a good idea to have a very rigid support for the exhaust, since the engine moves around. On some newer cars, I see a lot of rubber hangers and flex-pipes and whatnot, but on the old cars there isn't much flexibility in the system. Could a too-rigid support cause gasket issues (i.e. collector gaskets especially)? Has anyone used any newer-style rubber hangers, so the exhaust can move around a bit? -Bob C.
For some additional info, the old system was held up by flat steel brackets with some polyurethane bushings bolted to the frame, you could do pullups on the pipes and nothing would move, and header gasket replacements felt like a monthly item. We are thinking about something a bit more flexible, like this kind of hangar with steel rods attached to the frame instead: Also curious how much support the system would need. The old system was only supported by a couple hangars on the tailpipes and by the headers bolted to the engine. I'm thinking we should add some kind of midway support - the mufflers are heavy! Thanks! (Bob C's brother)
You could add a flex pipe like the new cars have:https://shop.advanceautoparts.com/p...gclsrc=aw.ds&dclid=COa-lqq3jt4CFYGtaQodmmcFug Find one that fits and weld it near the collector.
Rubber hangers are a good idea, but I also strongly suggest remflex header gaskets. They came strongly recommended by many here, and I can say I've had zero issues with them. Maybe a complete answer to your issues, maybe not, but they've proven their worth to many here (myself included) and seem to be a good choice for the relatively small additional investment.
Over the years my concern has been rattles not leaks. We put an exhaust system on, figure out where it fits then make it as stationary as possible. This has usually been performance oriented so larger pipe diameter and less clearance. In this scenario you don’t want it to move too much or it’s going to start rubbing somewhere. And Nobody likes to have a new exhaust system rattling on the floorboards, quarter panel, gas tank, springs, etc. And I second the vote for Remflex! They compress enough to fill any small imperfections or variations in the surfaces. They seem to be pretty near fire proof as well so they should never burn out, and the small compression they provide seems to keep constant pressure on the hardware so nothing can loosen up and back out.
That looks great, Matt. I am fine with compressible gaskets, except I've never heard of one that also decompresses- so after it flexes around it also leaks. I'll consider Remflex for sure, but a better solution in my mind is to prevent stresses on the gasket areas in the first place. A flex pipe is also an interesting idea, but we've already put the pipes in and welded everything together. -Bob C.
Thanks for the input all. Matt, I really like those hangars - that was what I wanted to do. The old system used steel brackets with a polyurethane bushing where it bolts to the frame. I had a lot of trouble coming up with something like this on short notice so I ended up grinding the brackets off the old pipes and re-using them. The system seems solid enough. It's supported by the engine, at the rear of the mufflers and the rear of the tailpipes. To help with the header gaskets I have stage 8 locking header bolts - a bit of a pain to remove later but should stop the bolts from loosening up, which has been the cause of a lot of our issues in the past. Now the collector gaskets... we'll see about that. In the past I've cut the collectors off and had them welded solid. I'd like to keep the system so that I can unbolt it from the headers. I've seen a 'ball and socket' header reducer that's supposed to work better. We finished the system today, here's a video of it. Flowmaster 70-series big block mufflers and an H-pipe. Not too loud, nice burble, you can hold a conversation next to the car which was hard to do before!
I like those - that's what I was thinking of using when we posted this. My concern with those is that the newer cars that use them are mostly FWD and those get flexed front to back squeezing them lengthwise - underneath that braiding is an accordian shaped piece that seems like it was meant to squeeze and expand, I don't think they were meant to flex side to side. Also I'll need to support the front of the system some other way. If we continue to have gasket problem I'll give something like this a try.
Just to wrap this up, I thought I'd post all the pieces we used to make the system. It took me a while due to my own time constraints, being a novice/intermediate welder, and wanting everything to be just right... It took me a few weeks from having the exhaust finished to actually being able to drive the car (had to do some other work before it was roadworthy again). Now that I've been driving it, I love the sound even more! It's burbly, but mellow and not too loud. The video has a bit of echo to it from the car being inside the garage, out in the open it sounds much deeper and richer and doesn't have any of the tinny sound I picked up in the video. It's very quiet inside while driving (until you floor it), I'm still really excited about the finished product. We bought all of the pipes we used from Flowmaster, besides the headers (TA Performance on those). The tailpipes were my biggest challenge, since these were made for an 80's G-body and I wanted them to fit in a 70's B-body... the S-pipe kit was my savior, just invaluable to the finished product. I used the S-pipes to get from the header reducers in under the crossmember to the H-pipe, then used additional curves from them in the tailpipes (scroll to the end to see what I had to do to them!) Flowmaster 70 series big block II mufflers https://www.flowmastermufflers.com/flowmaster/street-mufflers/70-series/ A note - these are REALLY FREAKIN BIG and probably wouldn't fit in a skylark. No worries though, the LeSabre is also really freakin big and they fit perfectly. The muffler body is 22" long, 28" long with the inlet and outlet pipes! But without these I'm sure we would not be as pleased with the sound. S pipe kit https://www.flowmastermufflers.com/...ent-2-50-in-tubing-various-offsets-set-of-6/? H pipe kit https://www.flowmastermufflers.com/product/flowmaster-15920-balance-pipe-kit-for-2-50-in-tubing/? Tailpipes https://www.flowmastermufflers.com/...17-prebent-tailpipes-2-50-in-rear-exit-pair/? And the tailpipes ... this is what they looked like after my cutting and splicing... A LOT different! I ended up painting them (see video a few posts above) to protect the welds. Hopefully this is a lifetime system! Most importantly, regarding the header gasket issues we've had. I believe our problem is that the engine rocks side to side, while the exhaust system tries to stay still. This constant flexing of the headers causes the flanges to move and eventually the header bolts to back out. I installed a set of these Stage 8 locking header bolts to try to address the issue, I'll report back in a few months if it's holding up or not: We'll see how they hold up over time. I've had good luck with them in the past on other vehicles. https://www.stage8.com/gm-performance-locking-fasteners/gm-locking-header-bolt-kits/ Editing to add one more pic - the front S-pipes, H-pipe and mufflers: I tack welded together in the car and removed to do the full welds. I also painted the H-pipe and front pipes with high temp exhaust paint.
No drone - and almost no "deep rumble" (but after all, it's a 455 and you can still tell that by the exhaust note). I thought it would still be too loud for me, but I like how it sounds. Not quite a Toyota Corolla, but it's very tolerable and drivable. No performance comparison yet - with the old system (crappy bends, leaky muffler, no h-pipe, etc.) we got s a bunch of 13.9's but the track is closed for the season now. Good performance for a totally streetable 5,000 pound car. It seems in the world of performance mufflers, you only get to choose only two of Quiet/Fast/Small. -Bob C.
