Exhaust question

[Recian]

Are the exhaust systems for all 73-87 sbc's the same? I've got an 81 and I'm looking to add a dual system to eliminate the cat and pick up some power. I'm looking at this set

http://www.lmctruck.com/icatalog/cc/full.aspx?Page=159

Muffler shops in my state won't remove cats. They can only add new ones in. That being said it's cheaper to buy this set and have it shipped (about $330) than have a local shop build a system and pay for 2 new mufflers and 2 high flow cats. The only thing is LMC lists them up to 78 since after that they went to cat. converters and legally LMC can't sell them as a removal of cats. Manifolds on the SBC should be the same regardless of year correct?

[motornut]

most won't remove them,but if they can fall off on the way.....they will fix the leak lol

[07XCSBZ71]

It doesn't say it won't fit, just that it is only legal on year without a cat.

Summit offers this kit, It might be a cheaper option, even having to buy mufflers. It is designed for trucks that came factory cats.
http://www.summitracing.com/parts/wl...olet/model/c10

You can get the correct style mufflers for about 34.00 each.
http://www.summitracing.com/parts/wlk-17655/overview/

[Tx Firefighter]

Originally Posted by Recian

. Manifolds on the SBC should be the same regardless of year correct?

No they are not. I just learned this a few days ago. My truck is a 78 model. My buddy gave me a decent exhaust he pulled off of an 86 model truck he's parting out. I figured it would be a slam dunk since the trucks are basically the same. What I found was that while the pipes are oriented the same and everything, the flanges on the ends where they bolt to the manifolds are different between different years. They looked the same, but the 86 model flanges were larger overall than the 78 ones. I wound up cutting the stubs off my factory 78 y pipe and welding them into the new dual exhaust so it would all bolt onto my older manifolds. I didn't want to use those manifolds in the first picture since they had smog tubes and my 78 model ones don't. The angles and everything else were perfect, just the flanges on the ends and stud spacing on the manifolds.






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[Recian]

I've actually had the cat fall out before. On my sentra the muffler shop wouldn't even weld on a muffler downstream if the manifold cat AND downstream cat (not monitored by the ecm) wasn't installed. Now my exhaust manifolds are different than yours in the pic. The driver one dumps between 5/7 and the passenger side dumps between 4/6. They come out of the head and curve up not down. Wires are under the manifolds. It also has a vacuum actuator on the passenger side. I'm also not sure how its assembled. If its in peices like the dynomax then I can cut my old pipes and remove the flanges and use them on the new system as long as lengths are the same since yours are rear dump. That would make all the angles and length at the manifolds different.

With the summit kit will it allow room to clamp in the mufflers? No need to weld or cut

[Tx Firefighter]

Originally Posted by Recian

I've actually had the cat fall out before. On my sentra the muffler shop wouldn't even weld on a muffler downstream if the manifold cat AND downstream cat (not monitored by the ecm) wasn't installed. Now my exhaust manifolds are different than yours in the pic. The driver one dumps between 5/7 and the passenger side dumps between 4/6. They come out of the head and curve up not down. Wires are under the manifolds. It also has a vacuum actuator on the passenger side. I'm also not sure how its assembled. If its in peices like the dynomax then I can cut my old pipes and remove the flanges and use them on the new system as long as lengths are the same since yours are rear dump. That would make all the angles and length at the manifolds different.

I know the ones you're talking about. I had an 83 model truck with a factory 305 that had ones like that. I had forgotten about that style also.
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[bnoon]

On my '86 blue Chevy I sold back in February/March I got the dual pipes from a salvage yard, bought new Summit chambered mufflers (Flowmaster type), and spent something like 65 bucks TOTAL out of pocket including the pipes, new mufflers, a $20 Summit Bucks coupon and free shipping code. Hopefully I can find a set of 2.5" or 3" duals for the 454 now because the dual cherry bombs and dumps sound like crap to me.

[Recian]

I wouldn't mind some shorty headers but the only ones I can find are turbo mount center dumps. They don't fit to these pre bent systems well
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[07XCSBZ71]

Originally Posted by Recian

With the summit kit will it allow room to clamp in the mufflers? No need to weld or cut

As long as you get the mufflers with the correct inlet and outlet location, you should be able to run clamps.

After talking to a few exhaust shops, I think I going to order both the links for my 77 that I posted. The local shops are nuts! They want 450-500 plus tax for the same exhaust.

[Recian]

Exactly why I figured 300 or so would be good. I ended up putting my exact truck info in and that kit still comes up. That kit lists for all 73-87s so I assume it'll fit early and late models with slight adjustments depending on model. just re-use your existing flanges, just cut the original exhaust pipes, remove flanges and install the flanges to the new ones before assembly.

I'm going to the junkyard tomorrow so MAYBE I'll come across something there that I can remove and put on my truck even if I have to take the manifolds with it. (cheaper when you don't disassemble)

[cory d]

the dynomax kit is a good deal, cant do it much cheaper yourself. unless you can bend it

[Recian]

The dynamax looks to be a stock exit system not a rear exit
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[baclay9]

Wow, I hate it for you guys they are so stringent on the emissions on your trucks. Even when we had inspections as long as the cats were already cut off they would do any exhaust you wanted. The same shops installing the exhaust for you were the same ones doing the inspections though. Since they quit doing inspections it is pretty well a free for all here now. Not bragging, I just can't imagine having to deal with this.
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[Recian]

Sad thing is in 3 years my truck will be inspection free. No more inspections but legally the shop can't take my cats out or even work on an exhaust that has no cats. It's like a federal law but I'm sure states without big emissions regulations don't enforce it.

[Recian]

The more I look at the pic on LMC's site I think it'll still fit my 81. The pass. side has a 45 degree header rear dump angle and the driver side is a straight down dump that leads into a 90 degree bend a bit more forward of the passenger side's dump. My only worry is the heat riser and how it'll fit around that. Now that I think about it that could be causing me some power issues too since my engine seems to bog at random times and usually under heavy throttle

[07XCSBZ71]

Originally Posted by baclay9

Wow, I hate it for you guys they are so stringent on the emissions on your trucks. Even when we had inspections as long as the cats were already cut off they would do any exhaust you wanted. The same shops installing the exhaust for you were the same ones doing the inspections though. Since they quit doing inspections it is pretty well a free for all here now. Not bragging, I just can't imagine having to deal with this.
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Same here. They don't care as long as you aren't making ears bleed as you pass by.


I just ordered the summit/dynomax kit with the welded thrush mufflers, 223.91 to the door. Summit has free shipping for anything over 100 bucks.

[nheller76]

I've got the thrush mufflers and YEA! FUN!!! U could weld one up yourself. Welding is a lot easier then it seams and u can get what u want for cheaper.
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