73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: The dream on September 22, 2011, 10:00:45 pm
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When is a 3" exhaust necessary? what can i expect?
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Are you talking a single 3" or duals? As to when it's really necessary depends on what your referring to. As in, what are you using the truck for? How are you measuring gain/loss, ect. A 2 1/2" pipe flows allot of gases, the bad bends or restrictive mufflers are really the problem if there is one. Not sure what you are referring to as far as "What can I expect?" Lorne
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I'm talking about duals with a probable "h" setup, 78' K20 with a 383, longtube headers and super 44's, street performer with very light offroad. No towing intended.
Just wanted to know what size i should use, 2 1/2 or 3"?
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I'd go 2.5" personally. A 383 doesn't need 3", and it'll just make it really really lound with the 44's.
I had a 2.5" system on my 79 with a 350/350 and Flowmaster super 44's, sounded plenty tuff and flowed really well.
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So aside from being loud at 3", performance wise I can expect good things/enough size at 2 1/2" ?
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Yeah. Performance wise you'll be just fine with that 383. Plus you'll get the cost savings over 3". I had a muffler shop quote me almost $100 more for 3" over 2.5"
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I hear you, 150 dolar diference between 2 1/2" and 3".
Besides i am a little worried about the noise, just that i didnt want to sacrifice performance.
Thanks a lot guys. 8)
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no benefit to go 3"
Your motor isnt big enough
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I'd go with the 2 1/2" also.
I was running 3" on my 1200 HP pro street ChevyII and it was a pain to install and hide.
Plus the downside is, if you go too big, it'll hurt your low end (talking motor). A little back pressure seems to make the low end a little snappy and crisper.
This is just my opinion of course.
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(http://www.naioa.com/v2/modules/Forums/images/smiles/iamwithstupid.gif)
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Built Big Block likes 3"
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If I remember correctly isn't dual 2 1/2 good to like 500-550 hp anyway?
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Well thats good to hear, i don't really know how much HP I'm packing in the 383, but i don't think I'm in does numbers (maybe i can do another post with my set up and somebody can give me an idea? is that possible?). Actually its been a learning nightmare. thats what you get when you don't have any experience. Ive drop a little over 3000 in the engine and i still need some accessories. So know I'm really tight on cash, and saving 150-170 dollars sounds good to me. I JUST NEED TO RIDE AGAIN !!!
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Some more info on the motor would be helpful.
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I wont hold anyone to their answer, so a good guess will be appreciated. ;)
350 block bored .060
400 crank with 3.75 rods/ 5.7 rod length
Flat top pistons
World SR torquer iron heads, 67cc, 170cc intake, 2.02 intake, 1.6 exhaust.
Thumpr Hydraulic Flat tapped camshaft, Op range 2000-5800, 227 241 @ .050, 479 465 @ 1.5:1, 107 lobe
Edelbrock RPM Performer Intake 1500-6500
Comp Cams Rocker arms 1.52 Rollertip
MSD Ignition Kit, 43TS ACDelco's
600 cfm Edelbrock Carb
B&M 2000 stall on a 400 auto (haven't figured out the gear ratio but it haves 14 bolt FF)
So what kind of torque/HP am i looking at?
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maybe in the 350-400 range? i could be way off but its a guess :) the setup i had on my old truck thats in my sig was an estimate of 300hp there is a member here cant think of his screen name right off though that had a similar build as mine but with vortec heads though and made 390ish hp at the flywheel on an engine dyno. maybe he will chime in. i dunno much about your heads and havent seen alot of builds with that cam.
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At least i have an idea now. I was really confused about that, because when i was picking parts for the build theres many parts that are HP rated. Luckily most of them are in the range you are talking about, other parts are 500+HP that i knew i wasn't going to reach.
Down the road i will dyno it, and share the info.