exhaust system
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Junior User
Joined: Oct 2004
Posts: 78
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From: South Williamsport, PA
exhaust system
I was just looking to get an dual exhaust system put on my truck. It's a 79 f-250 with a long bed. What size pipe would be the best to use? Are there any kits available that I can bolt on myself? Anyone from PA know how much I can expect to pay for a custom pipe job?
by the way, the motor is a 351m
by the way, the motor is a 351m
Cargo Master
Joined: Oct 2004
Posts: 2,148
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From: Seneca, SC
yeah a v-8 (especially a 351C or bigger) needs more like a three inch. You could probably do fine with a 2.5 for the small blocks, (302 and 351W) but for a bigger motor, or one that you are looking to hot rod, you may want to consider the full three inches.
EDIT:
oh, but in light of the administrator comment, 1&3/4 willbe closer to stock and allow the motor to be a bit more quiet. The only problem with the quietness is that the motor has a little more trouble breathing, making slightley less tourque and therefore slightly less resulting horsepower. But if you don't care about the power numbers, the 1&3/4 should also be a little cheaper (less for materials, and easier to fit for less labor)
EDIT:
oh, but in light of the administrator comment, 1&3/4 willbe closer to stock and allow the motor to be a bit more quiet. The only problem with the quietness is that the motor has a little more trouble breathing, making slightley less tourque and therefore slightly less resulting horsepower. But if you don't care about the power numbers, the 1&3/4 should also be a little cheaper (less for materials, and easier to fit for less labor)
Thread Starter
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Junior User
Joined: Oct 2004
Posts: 78
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From: South Williamsport, PA
Sounds like I will be going with the 2 1/2 or 3 inch. I would like to get some extra gas mileage by putting on this system. Also, I don't want it to be a quiet truck. THanks for your help
Postmaster
Joined: Apr 2000
Posts: 2,838
Likes: 6
From: SD
It all depends on the motor and what you use it for. In my opinion, there is no need for a stock motor in a daily driver to have larger than 2 1/2" dual pipes. The only time you need larger is a built high rpm motor (like runs over 5000 rpm regularly for an extended time). I think you'll be wasting you money if you go bigger than 2 1/2" duals. My stock 390 4v has long tube headers and 2 1/4 duals and I think it's perfect. But it's a daily driver that very seldom sees 4000 rpm and NEVER goes much higher than that.
My exhaust was custom bent at a exhaust shop, made from aluminized pipe (which lasts WAY longer), glass packs and exits behind the rear wheels. Cost me $200 total and took the shop less than 1 hour to install.
Marty
My exhaust was custom bent at a exhaust shop, made from aluminized pipe (which lasts WAY longer), glass packs and exits behind the rear wheels. Cost me $200 total and took the shop less than 1 hour to install.
Marty
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Elder User
Joined: Nov 2002
Posts: 620
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From: USA
Marty is right, it depends what your motor is used for. Smaller tube, 2-2.25" can help efficiency of the exhaust. There is a big write up somewhere on this site explaining all the mumbo jumbo, exhaust velocity, etc.
If you have a motor built for lower end torque you're going to be better off with 2 or 2.25" exhaust. 2.5" will work but might actually get you less performance in your application. I'm no expert though. I would recommend searching to find that post.
Jordan
If you have a motor built for lower end torque you're going to be better off with 2 or 2.25" exhaust. 2.5" will work but might actually get you less performance in your application. I'm no expert though. I would recommend searching to find that post.
Jordan
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Having the pipe TOO BIG is a problem.
Plus, that huge 351M only puts out 140 HP.
I have 2 1/2" true duals for my 429 and pipe is too large.
You will get a real tinny sound & the engine won't have enough back pressure to keep the exhaust valves stable.
Plus, that huge 351M only puts out 140 HP.
I have 2 1/2" true duals for my 429 and pipe is too large.
You will get a real tinny sound & the engine won't have enough back pressure to keep the exhaust valves stable.
Thread Starter
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Junior User
Joined: Oct 2004
Posts: 78
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From: South Williamsport, PA
what size will get me the best gas mileage and which would most likely give me the most power?
It's a daily driver but it is also getting some performance parts(Intake, carb, maybe a cam).
Million...where did you get the HP on the engine?
It's a daily driver but it is also getting some performance parts(Intake, carb, maybe a cam).
Million...where did you get the HP on the engine?
Last edited by snagmaster86; Feb 17, 2005 at 09:07 PM.
More Turbo
Joined: Nov 2004
Posts: 646
Likes: 0
From: Cleveland, TN
LMC Truck Magazine has a really nice true dual system for your truck....it comes with 2.25 inch pipes and your choice of glasspacks or turbo mufflers and its at a pretty good price $170 - $200
Posting Guru
Joined: Jun 2002
Posts: 1,214
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From: Rio Rancho USA
Originally Posted by Mil1ion
I have 2 1/2" true duals for my 429 and pipe is too large.
You will get a real tinny sound & the engine won't have enough back pressure to keep the exhaust valves stable.
Also, please explain how poor cylinder scavenging, poor flow, low efficiency and excess trapped heat keeps valves stable?
Not trying to be a jerk, but I would love to hear your opinion on this.
I'm glad I didn't say it! 