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post #16 of 48 (permalink) Old Feb 12th, 20, 3:59 PM
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Re: 489 exhaust system

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Originally Posted by moncam View Post
Thanks for your input! I dyno tested 2" vs 2 1/8" and picked up on average 5-10hp and tq throughput the rev range.

What do you think of going down to 2.5" after the mufflers?
That will cost you HP so that is just the opinion of someone who's disappointed by the 2.5" system.

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post #17 of 48 (permalink) Old Feb 12th, 20, 4:52 PM
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Re: 489 exhaust system

Do the 3" all the way back.

If you have 2 1/8 headers run them, especially if they proved beneficial in power. However you may wish you had 2" headers when you go to change your spark plugs.

X vs H. X makes more power, is quieter, and changes the exhaust note. I will give up some ponies because I like how H pipe sounds.

As for muffler, pick your poison. There are those that say they picked up tons of ET and MPH by changing mufflers, but I've read a bunch of muffler comparos and usually the difference won't be noticeable. Go with the sound that you like, you'll be happier.
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post #18 of 48 (permalink) Old Feb 12th, 20, 4:54 PM
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Re: 489 exhaust system

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Originally Posted by Binford View Post
What size primary tube do you run?
I run a custom made 2 primary header. Two pipes are inside the frame rail and two are outside frame rail for each bank. Merge collectors with a 15 extension with cutouts and downturn.
Each side is split off to a 3 exhaust pipe.

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post #19 of 48 (permalink) Old Feb 12th, 20, 7:19 PM
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rick
 
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Re: 489 exhaust system

I installed a 3" Pypes X pipe system with violator mufflers in 2016 for a planned 496, it changed to a 489, I still have summit 1 3/4" headers but when I change from the 400ish hp 454 to the 489 in a month or 2 it's getting bigger headers, thinking 2" Hedmans ?


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post #20 of 48 (permalink) Old Feb 13th, 20, 5:31 AM
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Re: 489 exhaust system

540" running 3" exhaust through Flowmaster 70 Series, sounded great, relatively quiet, great for cruising and street use. Was stuck at 122-123 mph at the track. No other changes but swapped those out for set of Pypes 18" Race Pro (which is a straight thru design), car immediately went 125 mph, with additional tuning it hit 126 mph. Runs were made in back to back weeks at the same track in almost identical air.

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post #21 of 48 (permalink) Old Feb 13th, 20, 6:25 AM
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Re: 489 exhaust system

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Originally Posted by 71350SS View Post
That will cost you HP so that is just the opinion of someone who's disappointed by the 2.5" system.
Yup

Rick, the 1.75" and 2" "peak header torque" is only one parameter and a minor one. If the pipes are good, I'd use them.
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post #22 of 48 (permalink) Old Feb 13th, 20, 6:43 AM
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Re: 489 exhaust system

1 3/4" Summit headers are 7-8 yrs. old, blasted them and VHT painted them in 16, headers are still good


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post #23 of 48 (permalink) Old Feb 13th, 20, 9:05 AM
 
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Re: 489 exhaust system

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Originally Posted by moncam View Post
Hi all,

I'm going to be putting in a 602hp 600ftlb 489 BBC into my car and wanna know your opinions on what exhaust system I should go for.

2 1/8" headers into a 3" system. Should I go for H pipe or X pipe and why?

Also, to quieten the car down my exhaust guy has recommended I go down to 2.5" after the mufflers (magnaflows). What are ya'll thoughts on this?

Pypes is starting to come out with 3"/2.5" systems as we speak, but still waiting for a GM A-body system. So far they've come out with '65-'73 Mustang, '65-'70' GM B-body, '62-'67 Nova, & '67-'72 Mopar A-body. They use a 3" X-pipe system with a 3" muffler that has a 2.5" outlet and tailpipes. It's for cars with 600-750 hp and it make a lot of sense, especially for cars that are mainly street driven. Gases have cooled at that point, so 2.5" tailpipes are not a detriment to performance. The big benefits are reduced sound levels and easier fitment. Pypes has broken from their usual MO in that they're offering these kits with their Race Pro mufflers only. No 'no muffler' systems as they normally do. They made the first batch with Street Pro and Violator mufflers, but once they're gone, that's it. Only Race Pro after that. I'll call Pypes today and see if an GM A-body system is in the works and report back.


Fair amount of talk on this thread about mufflers. Obviously if you're in the 600-700hp range, you'll probably lean towards a straight through muffler. I've provided a Dynomax index of all their muffler SCFM and HP ratings (disregard the VT muffler as it's no longer made) here- https://classicmusclecarexhaust.com/i/exhaust-101. The "Loss Free" rating is the power level at which the muffler will start becoming a restriction and costing HP. You can see that the 'Ultra Flo's' have an incredibly high flow rate. Not the quietest muffler in the world, but there's a reason the F.A.S.T. class racers use them. For comparison sake, I've seen tests where your typical 40 series FM muffler will be good for 340-350hp before becoming a restriction, so if your engine is making less than that, FM's are not costing you power. As I said before, I'll let you know if an A-body 3"/2.5" system is in the works.
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post #24 of 48 (permalink) Old Feb 13th, 20, 9:30 AM
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Re: 489 exhaust system

That's good to hear, my full over the axle 3" system makes it really tight for wide tires, I have 255/50r17" 9.5" wheel w/5.5" b.s. on it now with (haven't measured yet) maybe an inch clearance, 68 malibu
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post #25 of 48 (permalink) Old Feb 13th, 20, 9:34 AM
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Re: 489 exhaust system

X or H make it more difficult to drop the trans and to unhook and add collector extensions for the track.


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post #26 of 48 (permalink) Old Feb 13th, 20, 10:34 AM
 
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Re: 489 exhaust system

In speaking with Pypes today, there's still a question mark as to whether or not to offer an A-body 3"/2.5" system. They're weighing whether to go ahead based on Mustang/Duster/Impala/Nova sales. I expressed my concerns that those 4 platforms are probably not the most accurate litmus test for a demand for this type of system. I would think the GM A & F body would be. I also suggested that if they did, could they offer a 'No Muffler' system too. Just mix & match 3" X-pipes with 2.5" tailpipes and throw in a couple of reducers and extra clamps so people can use whatever 3" mufflers they want.

As an exhaust system distributor, that's what I think. But the real question is, as a consumer, what do YOU think? Do you think there's a market out there for a system like this for the GM A-Body?
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post #27 of 48 (permalink) Old Feb 13th, 20, 12:09 PM
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Re: 489 exhaust system

Yes. I just purchased a full 2.5" X-pipe system from Pypes last year (2.5" tailpipes is what I needed.)

If they had this offering at the time (3" to the muffler, 2.5" tailpipe), it is what I would have purchased instead of a full 2.5" system.

Quote:
Originally Posted by CMCE View Post
In speaking with Pypes today, there's still a question mark as to whether or not to offer an A-body 3"/2.5" system. They're weighing whether to go ahead based on Mustang/Duster/Impala/Nova sales. I expressed my concerns that those 4 platforms are probably not the most accurate litmus test for a demand for this type of system. I would think the GM A & F body would be. I also suggested that if they did, could they offer a 'No Muffler' system too. Just mix & match 3" X-pipes with 2.5" tailpipes and throw in a couple of reducers and extra clamps so people can use whatever 3" mufflers they want.

As an exhaust system distributor, that's what I think. But the real question is, as a consumer, what do YOU think? Do you think there's a market out there for a system like this for the GM A-Body?
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post #28 of 48 (permalink) Old Feb 13th, 20, 2:47 PM
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Re: 489 exhaust system

What would be the downside to just running true duals all the way back?
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post #29 of 48 (permalink) Old Feb 13th, 20, 3:12 PM
 
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Re: 489 exhaust system

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Originally Posted by Rosinbluth View Post
What would be the downside to just running true duals all the way back?
General rule of thumb is that an X-pipe is worth about 20hp +/- at higher RPM on a 500hp engine. But there are many variables that go into that. A stock engine- not so much, but the more power you're pushing and the more RPM you're turning the greater the benefit of an X-pipe. H-pipes tend to help with lower RPM torque. For stock-ish street engines, true duals are fine.
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post #30 of 48 (permalink) Old Feb 13th, 20, 3:23 PM
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Re: 489 exhaust system

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Originally Posted by Jesse 496 View Post
I like x pipe ,Its possible H pipe can become ineffective at rpm.

Did a test one night ran 9.82 then pulled of the 3inch magnaflow system with x pipe this took 35Lb off of the car and it ran 9.85 next pass
Maybe it spun the tires a bit with the extra HP. A lot of things can vary the time .03 seconds; weather, track conditions, etc.

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