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#1
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3” Pipes too Big for 408
I have a 408ci Edelbrock headed 4spd Duster and TTI’s with a 3” output. I was thinking:
Would the TTI’s with 3” pipes and glass backs exiting to the side of the car be too much? That will probably kill almost all backpressure right? - |
#2
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The step headers would probably help.
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#3
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And the glass packs hurt. Look inside and see how the neck down a tad.
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#4
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Go with a better muffler and you should be good, there is to much emphasis on back pressure.
Steve |
#5
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What are you doing with the vehicle? I would go with the BIGGEST header you can get in the engine bay. Would you put 1" 5/8 headers on a big block?-I wouldnt. So why even think about it for a 408 which basically is a big block. Going from 1"5/8 to 1" 3/4 dropped me about 3 tenths on my 340. I wouldnt even put the smallies on my 416. But even if you are running a ported iron head (X or J) you wont benefit from a bigger header reguardless of the cubes. Forget backpressure, unless you have an 1000 converter or something and you want your car to be like grandpa's
Same with tailpipes, go as big as you can,( just my 2 cents) The 4 speed will work great with the big tubes. |
#6
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3" inch is too much unless you making well over 600hp. And don't use a side exit on a street car. It will suck the fumes back inside the car and put you right to sleep. Bad idea.
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#7
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3 is too big. Look at a header website and read some of the tech articles. Flowmaster, I think, has a great tech library and sums up the HP/size chart. Think of the extreme, open header, No balls off the line except for a high stall convertor auto. Scavenge works with a appropriate sized collector and pipe.
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#8
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DWC? Do you sniff glue?!!
Quote:
Also, only an idiot would fall asleep with side exit exaust. My Fury exaust ran out the side just in front of each rear tire, and I drove the car every day for 4 years. Never once did I fall asleep. |
#9
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Quote:
BTW, I have 3" TTI's on my Demon and love em. They look great too. (for as much as they cost they better look good) |
#10
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For comparison, 3 weeks ago I did back to back tract test with my exhaust.
400BB with 1 7/8 headers, 3" X pipe off the headers into 3" race bullets into 2.5" dynomax super turbos into 2.5" tail pipes. Like that the car went 1.58 60' 11.37@117.5. I dropped the 2.5" mufflers and ran through the 3" only and it would no longer hook but ran 11.29@120.5 spinning with a 1.60 60'. The engine has no stroke but hates back pressure. 4.38 bore with 3.38 stroke. I did not try open headers. The car weighs 3615 with me in it, not bad for a mild 400. |
#11
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I'm going with 3" on my 408. Projected hp should be around 500 hp. since it's a fairly mild engine. The hedders are Hedman Husslers with 2&1/2" primaries. I had 3" on my 340. Didn't seem to hurt it. A few pics..
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#12
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Agreed biggest header possible...And what does Dcw know?
Steve |
#13
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WOOPS! Typo. I ment 1&7/8" primaries.
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#14
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Thanks for the info guys. Seems that all the 'tests' I read about say that bigger/more flow is better.
Seems you guys don't really like the idea of using glass back? What's a good brand glass backs? I used Cherry-bombs and loved them but I'm told that they 'blew out' and are too loud now, driving my car on a daily basis, I did not notice the increase in sound... Thanks for the pictures Lenweiler, looks great! If i dont go with side exhaust then I'll probibly go the route you took, ( pipes to the axle ). -dust |
#15
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The Dyno Max welded muffs have a really nice sound.
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#16
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I used 1 7/8 headers and 3 inch exhaust with a x pipe on my 360/414 that went 10.60 spinning.
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#17
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I would like to hear some longevity stories on OEM small blocks that are driven frequently with over 450HP without fillers for additional strength. As all performance engines are a compromise it would appear that the limits of a factory small block would fit these parameters and live. 450HP max, 1 5\8" headers, 2 1\2" exhaust out the back, max decibel 95db. Frame connectors, good brakes and suspension. The small block Mopar engines have oiling issues and if driven at high RPM for prolonged periods modifications to the oiling system are warranted. dwc43 addressed a safety to life issue that should not be ignored or taken lightly, exhaust fumes will impair a vehicle operator and could potentially harm themselves or others. Maybe the source could be considered a 590HP daily driven OEM small block exceeds the expectations of the Chrysler engineering department and the tech editor of Mopar Action magazine.
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#18
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Quote:
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#19
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Quote:
heh.. |
#20
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I have the T/A style side exhaust on my Challenger for 5 years and have never had "sleeping" problems while driving it. The only time I even smell the exhaust is when I start it up in the garage. (I know the deadly part doesn't smell) I try to back it out asap or else I smell like exhaust for the rest of the day.
I'm also building a 416 SB and am trying to decide what size pipes to use. The engine is kind of like an air pump. You want more air in for more power, well you also need more air flow out to match (that's the BASIC idea). I'm thinking of 2 possibilities. 1) 1-5/8_1-3/4 step hdrs with 2-1/2 pipes or 2) 1-7/8 hdrs with 3" pipes. Option 1 for iron/stock heads/stock-med. flow intake or option 2 for alum. heads/high flow intake. I really like the T/A style exhaust so I'm leaning toward the 2-1/2" and using the Dynomax #17676 2-1/2" mufflers. I now have the #17675 2-1/4" and they sound sweet. |
#21
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Stepped headers in to a short 4" pipe turned out in front of the rear tire on a 90" wheelbase. Breaths well, but I do notice it has a very defined power band from 2500 on up. A 2.72 rear end doesn't help off the line either.
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#22
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With a 408 small block you have 4" or so of stroke. And the bore is 4" or bigger. Run the 3" pipes. You will have more than enough back pressure to prevent burnt valves or any other problem that might cause. People put WAY too much emphasis on back pressure because they read about it somewhere! In this case more power will be the result. Put on a muffler that has metal baffles inside it, not fibreglass or other "packing" style sound deadener. Take note, all else being equal, the 3" system will be noticeably louder than a 21/2" or smaller. Go big or go home, you'll be glad you did!!!!!!!!!!!!!!!!!!!djs
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