Exhaust..Power loss question........
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Melting Slicks
Joined: Jan 2005
Posts: 3,028
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From: Madison Ms
Exhaust..Power loss question........
After running open headers for a day or two, the power was unbelievable.........I just got the standard exhaust welded back up at a local shop, and it's a noticeable difference in loss of power. I'm true dual exhaust with no cat. I also lost that sweet lope......any suggestions?
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
You know Brett, I don't know, other than they are std. exhaust size. I have only replaced from the cat forward. I'm thinkin' go 3" all the way, where now I'm either 2 1/4 or 2 1/2.
Pro
Joined: Mar 2004
Posts: 686
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From: Southeast
Originally Posted by MsVetteMan
You know Brett, I don't know, other than they are std. exhaust size. I have only replaced from the cat forward. I'm thinkin' go 3" all the way, where now I'm either 2 1/4 or 2 1/2.
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Originally Posted by Fubba
You don't need 3". That's overkill. You do need a 2 1/2" system though if you're running the stock size exhaust. I think stock is like 2". That will help. What mufflers are you running?
The muffs....??? Don't have a clue. They just look like plain ole jain cheapos to me. They have seriously restricted my sound quality, and especially the lope which was quite noticeable with the open headers, and now I can't even hear it.
Melting Slicks
Joined: May 2003
Posts: 2,387
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From: Meriden CT
Originally Posted by Fubba
You don't need 3". That's overkill. You do need a 2 1/2" system though if you're running the stock size exhaust. I think stock is like 2". That will help. What mufflers are you running?
mandrel bent pipes is the key... not the kinked bends that most shops use.
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by MsVetteMan
You know Brett, I don't know, other than they are std. exhaust size. I have only replaced from the cat forward. I'm thinkin' go 3" all the way, where now I'm either 2 1/4 or 2 1/2.
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Le Mans Master
Joined: Jul 2005
Posts: 5,752
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From: Austin Texas
I had my '68 dyno'ed last year, 383. Almost no difference between open headers (cut-outs) and 2-1/2 exhaust with 40 series Flowmasters. I bet the sound of the exhaust was playing mind games with you...
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by MsVetteMan
lol.....cats are gone........long gone.....I guess I phrased that incorrectly......
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 3,028
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From: Madison Ms
Originally Posted by bobs77vet
perhaps the sounds made it seem faster.....my kids think i'm speeding inthe vette even when i'm going under the speed limit....it took the wife a lot of necking turning to get her to believe me that it just seems like we are going fast
I'll work on the fine tuning first, then see where that leads.....until then.......I'm burning some serious rubber......
Racer
Joined: Aug 2005
Posts: 308
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From: Salem MA
Originally Posted by MsVetteMan
I don't know about that. The "Viz" (David Vizard) says rule of thumb for 3" exhaust is about 360hp.......but then again, that's why I'm asking.
dual 3" exhaust is probably good for nearly twice that.
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Originally Posted by not a '76
maybe single 3" exhaust.
dual 3" exhaust is probably good for nearly twice that.
dual 3" exhaust is probably good for nearly twice that.
Direct quote from one of Viz's books....."A 3-inch secondary is only of advantage when the horse power is up past the 375 mark."
But in reading some more he says...."For good all -around street performance, a 2.5-inch secondary works well."
Le Mans Master
Joined: Oct 2004
Posts: 5,269
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From: Orlando Florida
St. Jude Donor '05
2 1/2" is plenty for a true dual system. I'd get two Dynomax Ultra Flow mufflers, these are 'straight thru' design but not too loud... if you're lucky you find them on sale for around $50 each. The local parts store should have these.
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Been using the shop up here on 51N in Canton......he's the guys that did my true duals last year!! He's pretty good! He recommended I stay away from the flowmaster because of the resonance factor because the vette sits so low to the ground. No hurry, I'm just fishing now!!
Safety Car
Joined: Jul 2002
Posts: 3,770
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From: St Louis MO
Originally Posted by MsVetteMan
Been using the shop up here on 51N in Canton......he's the guys that did my true duals last year!! He's pretty good! He recommended I stay away from the flowmaster because of the resonance factor because the vette sits so low to the ground. No hurry, I'm just fishing now!!
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Originally Posted by Brettmc
So he did the duals you have on the car now? Did you reuse the old mufflers or something? Dynomax Ultra-Flos have darn near the best flow rate on the market. Think about swapping over to them and getting rid of the no-names you have now.
I'll check out the Dynomax, but the Flowmaster super 40's look sweet, without the resonance.
Thread Starter
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Originally Posted by not a '76
but... flowmasters dont actually flow.
I do want flow as the #1 priority, but a good sound to bring that lope back out would be nice as well.
I'll look at the Dynomax......I need about 375 cfm of flow per each side....