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stoney 81ta 12-02-2003 03:46 PM

how much extra power
reastoring a 81 ta 305 chev motor too bad like to keep it stock for now limited budget just want to add headers and true dual exhaust approx how extra horsepower will come from this if ant all replies thank you in advance. btw im monk 81ta from b4 puter crashed had to reregister new name.

KeithB123 12-02-2003 04:33 PM

Probably around 40 HP. I had a 86 305 and headers was the biggest improvement that I made. The true dual might hurt performance.

gt2betubbed 12-02-2003 04:49 PM


Originally posted by KeithB123
Probably around 40 HP. I had a 86 305 and headers was the biggest improvement that I made. The true dual might hurt performance.
Why is that?
I've never heard of a true dual being a hurt to HP. Just wanted to know...

stoney 81ta 12-02-2003 06:40 PM

if true dual will cut performance why? iam not a expert but i was thinkin headers with dual would be much better than stock set up with headers.also is heddman headers good quality.As u all can tell with my questions my experience with all this is new thanks for your inputs. Its nice to find a site that is really friendly and helpfull to others willing to learn.BY stockset up i mean factory

digitalfrek 12-02-2003 06:42 PM

i dont think it will cut power because i reduces back pressure but i dont know it might

lluciano77 12-02-2003 06:55 PM

Man I don't usually respond in run on sentences but here it goes single exhaust can flow as much or more than dual exhaust if you increase the pipe diameter to compensate I don't have the chart readily available but I have one that converts dual to single requirements and back.:sweat:

KeithB123 12-02-2003 09:05 PM

Some exhausts flow better than others.

It has also been said that " Smaller" Exhaust Header Tubes perform better on a Small Block Chevy. Example- 1 5/8. I agree with experience.

poncho62 12-02-2003 09:11 PM

The smaller header size will give you better bottom end torque. You will lose some on higher RPMs.

KeithB123 12-04-2003 04:19 PM

Yes Poncho thats what I was trying to say. With a a smaller displacement 305 or even a mild to mid 350 you do not want too much free flowing exhaust because all your performance gains will be too high and your bottom end will fall on it`s face. Now if you put together a 350 that has a huge cam and a high end intake then I could see a more free flowing exhaust. But with a 305....I would go with 1 5/8 "Shortie" headers and put on a Y-pipe. The 305 has it`s power on the low end...Why take away the power range? The 305`s power range is with the lower rpm`s ...if you take that away that 305 would be a dog.

Now if you don`t believe what I`m saying...try this.......( here`s a in-expensive test for you ) Put your headers on and then put on a couple of cheap flex pipes with the mufflers you were going to put on....just wire it up and Drive the car and you will see it won`t have any acceleration.

I have experimented with the 305 and 350 with a few different combos. I haven`t found a dual set up worth while for a "Street" set up. BUT...if you toss on your headers with some small tubes to give it some back pressure to help out the low end.

Like Luci touched on ...there are charts out there that tell you where your performance is. December issue of Car Craft touches on headers and it gives a chart, the bigger headers gives more higher end performance. It`s the same thing as your exhaust pipes.

I`m sure that 305 is not running at 4500 + rpm`s on a regular basis.

Good Luck

gt2betubbed 12-04-2003 05:34 PM

That makes a lot of sense Keith! Thanks for tha breakdown.

stoney 81ta 12-04-2003 06:00 PM

so what u suggest keith is to use headers and single exhaust what about a cat the car has one on now as far i know i have to use one in ontario if the car came with it. thanks all for your inputs.

KeithB123 12-04-2003 06:11 PM


Well. I`m originally from Buffalo.......soo ...if you like the Leafs keep the converter on. If you like the Sabres take the converter off.


stoney 81ta 12-05-2003 03:00 PM

tks for your reply and advice keith and all others btw i like the leafs so i guess it stays maybe?

lolathemustang 12-06-2003 02:31 PM

I have a 289 with dual exhaust and I think it helps. It is small 2" tubing that goes all the way out the back so as to build low-end torque, but I like it. It's probably not better than a larger single exhaust but I like the look of duals. I have full length headers (cheaper than shortys) and I think they helped a lot over the entire power range. Just my opinion.

badknuckles 12-06-2003 06:50 PM

i would run 4 inch pipes right to two 1 inch briggs and straton mufflers runs great on my lawnmower.
thats a joke im trying to lighten things up.
i would go with dual 2and1/4 inch pipes and dynomax mufflers with a 305

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