Exhaust ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bowtier · 08-09-2005, 07:09 AM

Hey all, I've got a question for you. My '71 c10 is due for inspection end of Aug. & I need new headers & mufflers. I think I've decided on Hedman ceramic coated headers, & Flowmaster delta 40's. My dilemma is, I already have all stainless pipe that is still good but it's 2 1/4" dual & the headers are 3" out & I only see the flowmasters in 2 1/2" or 3" in the stainless ones. So I don't know if I should just scrap my good pipe & get dual 3" (my buddy's suggestion) or have the guys @ the ehaust shop use my pipe where they can & scab it all together in 2 1/4". I've been reading old threads tryin' to come up with something but just can't decide, I read somewhere 3" duals would be too much for a mild 350.... but this is a pretty stout 400sb so would it be ok? Any help would be appreciated.

mplex2000 · 08-09-2005, 08:55 AM

Unless you're running a ton of power, I would not recommend 3 inch. I would say at LEAST 500 whp. If you're not there, you'll probably lose quite a bit of bottom end power.

Here's what I'd do: Have the shop expand your 2.25" pipe out where it mates to the nw 2.5" muffler. If you have dumps, replace them with 2.5", otherwise they can expand the pipe on the exit as well.

When I upgraded from 2.25" to 3" on my Civic, it made a tremendous difference, but I was putting out a little over 300 whp on 4 cylinders. I guess that'd be about equivalent to about 600 whp on a V8

tomatocity · 08-09-2005, 11:37 AM

If you splice your 2.5" headers to a 2 2.5" tailpipe you effectivevly have a 2.25" exhaust system. If you want to do it once and do it right then build a new 2.5" system. If you want you can go to 3" after the mufflers. If you want performance you should consider an 'X' pipe, not an 'H' pipe. An 'H' pipe is manily for balance and tone. An 'X' pipe will add a little bit better performance if you like to challenge your engine plus it looks killer.

Summit online catalog

2.5" X pipe
http://store.summitracing.com/defaul...=egnsearch.asp

3.0" X pipe
http://store.summitracing.com/defaul...=egnsearch.asp

H pipe
http://store.summitracing.com/defaul...=egnsearch.asp

bowtier · 08-09-2005, 01:08 PM

Is anyone with a 400 sb running a 3" system?
I just don't want to pay more for the 3" and then have it bog my low end. Will I notice a difference? Will it harm the engine in any way? I guess I just don't really understand what the advantages & disadvantages are. I'm thinking @ this point I'd be best to get the 2.5" headers & muffler & have the shop adapt them to my 2.25" pipe I have now.??? Feed back please.

72BlckButy · 08-09-2005, 01:19 PM

I'm in the same situation, except, my engine is not built yet...

I also have a sb400, and am considering exhaust. I'm considering 3" as well, but I've read on the board that 3" might be to much. So now I'm leaning to 2.25" or 2.5" exhaust pipe. I'm considering an X pipe, but I'm not sure how to it since I am also planning on running electric cutouts, and possibly turn downs or go an ahead and run it out the back. It will be kind of a confusing exhaust system to build, if it's even possible. Good luck bowtier.

bowtier · 08-10-2005, 04:59 PM

Good luck to you too 72B.B......
So, anyone else able to offer some advice?????????????

LUV2XCLR8 · 08-10-2005, 05:25 PM

Some advice to go by, look at this HP chart (Flowmaster's chart from their Dealer book)

72BlckButy · 08-10-2005, 05:45 PM

So GQ, if I'm running a SB400, and I want to run in the future at least 400HP, should I go with 2.5" or 3"?

LUV2XCLR8 · 08-10-2005, 05:54 PM

Quote:

Originally Posted by 72BlckButy

So GQ, if I'm running a SB400, and I want to run in the future at least 400HP, should I go with 2.5" or 3"?

Your right on the edge, you could go either way, 3" sounds mean, but it
cost more than 2.5" if it is a P/U I say go 3", 2.5" if it is a BLAZER, only
because a Blazer has alot less room to run tail pipes out the back in 3"
it can be done, I have seen it, but it just looks 2 cramed to me, JMHO

bowtier · 08-11-2005, 08:00 AM

Thanks a lot LUV2XCLR8. It's much easier to make a decision when I can see it in black & white. I don't think I'm makin' enough power right now to justify a 3", maybe I will in the future though..... Guess I'll just check out the price diff. & then maybe flip a coin.

I hate having to make such important decisions.

08-09-2005, 07:09 AM	#1
bowtier Nobody rides free Join Date: May 2005 Location: PA Posts: 1,076	Exhaust ? Hey all, I've got a question for you. My '71 c10 is due for inspection end of Aug. & I need new headers & mufflers. I think I've decided on Hedman ceramic coated headers, & Flowmaster delta 40's. My dilemma is, I already have all stainless pipe that is still good but it's 2 1/4" dual & the headers are 3" out & I only see the flowmasters in 2 1/2" or 3" in the stainless ones. So I don't know if I should just scrap my good pipe & get dual 3" (my buddy's suggestion) or have the guys @ the ehaust shop use my pipe where they can & scab it all together in 2 1/4". I've been reading old threads tryin' to come up with something but just can't decide, I read somewhere 3" duals would be too much for a mild 350.... but this is a pretty stout 400sb so would it be ok? Any help would be appreciated. __________________ '71 C10 LWB 400SB/350TH '86 K2O LWB 350SB/400TH-6" tuff country lift, Shackle flip - plow truck '06 HHR - wifes wheels '01 Blazer - daily driver "It's better to burn out than it is to rust." -Neil Young

08-09-2005, 11:37 AM	#3
tomatocity Registered User Join Date: Jun 2005 Location: Sacramento CA Posts: 1,255	If you splice your 2.5" headers to a 2 2.5" tailpipe you effectivevly have a 2.25" exhaust system. If you want to do it once and do it right then build a new 2.5" system. If you want you can go to 3" after the mufflers. If you want performance you should consider an 'X' pipe, not an 'H' pipe. An 'H' pipe is manily for balance and tone. An 'X' pipe will add a little bit better performance if you like to challenge your engine plus it looks killer. Summit online catalog 2.5" X pipe http://store.summitracing.com/defaul...=egnsearch.asp 3.0" X pipe http://store.summitracing.com/defaul...=egnsearch.asp H pipe http://store.summitracing.com/defaul...=egnsearch.asp __________________ Got bored, sold everthing. Got bored, looking for a 1960-66 C-10. Want to build my last truck.

08-09-2005, 01:08 PM	#4
bowtier Nobody rides free Join Date: May 2005 Location: PA Posts: 1,076	Is anyone with a 400 sb running a 3" system? I just don't want to pay more for the 3" and then have it bog my low end. Will I notice a difference? Will it harm the engine in any way? I guess I just don't really understand what the advantages & disadvantages are. I'm thinking @ this point I'd be best to get the 2.5" headers & muffler & have the shop adapt them to my 2.25" pipe I have now.??? Feed back please. __________________ '71 C10 LWB 400SB/350TH '86 K2O LWB 350SB/400TH-6" tuff country lift, Shackle flip - plow truck '06 HHR - wifes wheels '01 Blazer - daily driver "It's better to burn out than it is to rust." -Neil Young

08-09-2005, 01:19 PM	#5
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	I'm in the same situation, except, my engine is not built yet... I also have a sb400, and am considering exhaust. I'm considering 3" as well, but I've read on the board that 3" might be to much. So now I'm leaning to 2.25" or 2.5" exhaust pipe. I'm considering an X pipe, but I'm not sure how to it since I am also planning on running electric cutouts, and possibly turn downs or go an ahead and run it out the back. It will be kind of a confusing exhaust system to build, if it's even possible. Good luck bowtier. __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package)

08-10-2005, 04:59 PM	#6
bowtier Nobody rides free Join Date: May 2005 Location: PA Posts: 1,076	Good luck to you too 72B.B...... So, anyone else able to offer some advice????????????? __________________ '71 C10 LWB 400SB/350TH '86 K2O LWB 350SB/400TH-6" tuff country lift, Shackle flip - plow truck '06 HHR - wifes wheels '01 Blazer - daily driver "It's better to burn out than it is to rust." -Neil Young

08-09-2005, 08:55 AM	#2
mplex2000 Registered User Join Date: Jul 2005 Location: DFW Posts: 463	Unless you're running a ton of power, I would not recommend 3 inch. I would say at LEAST 500 whp. If you're not there, you'll probably lose quite a bit of bottom end power. Here's what I'd do: Have the shop expand your 2.25" pipe out where it mates to the nw 2.5" muffler. If you have dumps, replace them with 2.5", otherwise they can expand the pipe on the exit as well. When I upgraded from 2.25" to 3" on my Civic, it made a tremendous difference, but I was putting out a little over 300 whp on 4 cylinders. I guess that'd be about equivalent to about 600 whp on a V8

08-10-2005, 05:25 PM	#7
LUV2XCLR8 The LuvShack Garage Join Date: Jan 2004 Location: Maple Grove, TN (West Side) Posts: 30,484	Some advice to go by, look at this HP chart (Flowmaster's chart from their Dealer book) Attached Images __________________ Owner/Op: "TN Classic Transport Carriers" The Toy: "Square Vette" 72 Hybrid Blazer Toy Barn: "LuvShack" 40 x 60 x 20 Shop Tow Piggy:"Maddy" 88 Silverado 3500 Hauler: "Feathers" 14 Aluma 8218T

08-10-2005, 05:45 PM	#8
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	So GQ, if I'm running a SB400, and I want to run in the future at least 400HP, should I go with 2.5" or 3"? __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package)

08-11-2005, 08:00 AM	#10
bowtier Nobody rides free Join Date: May 2005 Location: PA Posts: 1,076	Thanks a lot LUV2XCLR8. It's much easier to make a decision when I can see it in black & white. I don't think I'm makin' enough power right now to justify a 3", maybe I will in the future though..... Guess I'll just check out the price diff. & then maybe flip a coin. I hate having to make such important decisions. __________________ '71 C10 LWB 400SB/350TH '86 K2O LWB 350SB/400TH-6" tuff country lift, Shackle flip - plow truck '06 HHR - wifes wheels '01 Blazer - daily driver "It's better to burn out than it is to rust." -Neil Young



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