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· Young and learning
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46 Posts
Discussion Starter · #1 ·
Hey guys, new hotrodder here.


I bought my first classic car, a 69 corvette. Total project car. Has a 350 in it, don't know much about how it's built internally but it's a 010 block that's pushin about 140-150 psi compression w/ 461 heads.


Somewhat of a ways down the road but I'd like to put sidepipes on the car. However, I've read elsewhere that the quiet mufflers kill horsepower. Do any of you guys have any experience with this system, and which mufflers provide a good compromise between noise reduction and power loss?


Thanks for your time.
 

· Young and learning
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46 Posts
Discussion Starter · #9 ·
Thanks for the responses, guys.


In hindsight, I should've used the term "inserts" instead of mufflers, especially since the kit in particular that I had in mind (which, in my late-night state of weariness, also forgot to mention) was a Doug/ Hooker kit. Not sure if this will change anyone's answers.


As far as heat goes, they do sell heat shields for these pipes. If that ain't enough, I can heat wrap them, too.


Sorry for the lack of detail in my initial post, guys. Also, again, I greatly appreciate the responses. So far from what I've gathered, for my application, it looks like horsepower loss really isn't anything that I should be concerned about.
 

· Young and learning
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46 Posts
Discussion Starter · #10 ·
The amount of streetable horsepower that your going to loose is not even worth thinking about. Run a 2.5" cast "Corvette " ramhorns feeding dual mufflers and you will be good.


You dont need headers or a x pipe. It is a looks thing that is it. If you want side pipes then run side pipes just hide a muffler inside the heatshield.

Street rpm we are talking about never going above 3500rpm on a 250hp sbc.

You can dump $1000 into headers and straight sidepipes and may see a 10hp increase at 3500rpm over the simple cheap easy to work on and run setup I listed.

Until you get above 350hp most factory style dual setups are up to the task for street driven rides while giving a sound that won't set off car alarms each and every time you pull into a parking lot.

Been there. Run a 2.5" system with a idle you can talk to each other in front of the car and you will be good.

Its interesting that you suggest that. A personal friend of mine said something similar regarding running cast manifolds.
 

· Young and learning
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46 Posts
Discussion Starter · #13 ·
headers for sidepipes are different. Some road race headers are very long and pass where the sidepipes need to connect. 3" sidepipes are loud. No X pipe also makes them loud
What kind of headers do you have and what size

Not even sure what headers these actually are. I know they're a very old set of long tubes. But they've been on the car for a very long time; I suspect one of the previous owners built this engine in the 80s or possibly the 90s. Probably raced the car circle track, too.


That being said, the complete hooker kit includes a set of headers specifically for the side pipe tubes, so what I have right now really doesn't matter anyways.
 

· Young and learning
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46 Posts
Discussion Starter · #15 ·
Normally, I would. Both the Hooker and Doug kits have a Ø1.875 x 46" primary going into a 4" collector. Now I'll be the first to admit, I'm new to this stuff, so I'm not an expert by any stretch. But based on what I've read in HP Books's How to Hotrod a Small Block Chevy, that seems a little big on the diameter and long on the distance. Only option if I want to go that route. Otherwise I either go Cerial's route (admittedly I'm not a huge fan of the factory repro pipes, they just don't look as racey) or just run a traditional system.


All that being said, let's entertain for a moment that I bought a Hooker or Doug kit. Which muffler inserts should I run if I'm looking for a good compromise between noise reduction and top end power loss?
 

· Young and learning
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Discussion Starter · #20 ·
461 heads on a street friendly cam and 87 gas I am guessing it is in the 250 to 300hp range.

Thats probably about what it makes. I don't know much about this engine, as it was put together when I bought the car. What I do know is that it's a 010 block, likely a 2-bolt since it's out of a 1970 passenger car. Long tube headers. Went out and measured them, the primaries are Ø1 5/8. I notice that the heads have 202 stamped on the fronts and backs of the "camel humps" but I've yet to tear the engine down to verify if they truly are 2.02 heads or have any sort of porting on them (it runs just fine, why take it apart?) Vintage holley single plane street dominator spread bore manifold, I believe it's a 701R1-3001, and it's topped with a Holley 6210 carburetor. I run it on 91 octane to be on the safe side. Ignition is an old school Hays breakerless points conversion system. It doesn't have a big enough cam that it idles rough but it does have a little bit of lope to it; just enough to be noticeable.


Only data on compression I have are my 140-150 psi recordings with the tester but I haven't actually looked at the pistons to see if they're flat tops or not.
 
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