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I'm stuck and I can't seem to find a decent answer. I'll be honest...I hate it when I get the knee-jerk reaction of, "drop in a 460" or "add a 4 barrel and dual exhaust" without so much as knowing what the details of the engine/gear/tire combo or the type of driving I do.
-rant over-
I have a 77 F150 4x4 with a 4 spd granny gear and 3.55 rear end and 33" tires.
The engine is a 400M with aluminum intake and 4bbl edelbrock. Everything else is stock or really close to stock.
I am currently running a 'y' pipe with a single 2.5" exhaust through an open chamber muffler.
This is a work truck so mostly heavy loads, some off road and some longer road travel. Will I get any benefit from a dual exhaust or should I just leave it alone?
I'd vote dual 2.25 " with some reasonably quiet mufflers (like better Turbos at most) 'cause I just like duals on a V-8 ...... noise is stress and there's times I want quiet ..... like after a hard day's work.
Or you could look at the local muffler shop's pile of take off mufflers and get a late model stainless steel long truck muffler .... and build a nice long lasting single right rear exit 2.5"-3.0" system from that?
Question...does your current exhaust preform to your standards? Is it up to current tasks? Is there something its not doing or are you just wondering if you would get benefits from dual exhaust?
Dual exhaust at 2.25" would be great with a set of headers. This combo will help you tow, haul and keep exhaust gasses flowing easier. Might add a HP or two but don't expect huge gains. Add a X pipe if so desired and good mufflers.
If you are keeping stock manifolds, I'd go with replacing what you have currently.
Stock cam with aluminum intake and four barrel carb? Don't waste your money on noisy headers and dual exhaust. Keep the manifolds and a single exhaust with a good muffler. Sounds like you use your truck for truck reasons, not as a hotrod. Just my opinion.
Yeah, I just put the rebuilt 400M in it so I haven't driven it yet. I got rid of the 351M. I'm just at the point that, if I'm doing all this work, now would be the best time to put on a new exhaust.
I have heard that the stock manifolds and single exhaust can help with torque but I have not seen any data to back up the claim.
Myself, I'm a huge fan of dual exhaust.
But, if you are pulling a lot, you may want to stick with stock exhaust, or at least not a really verbal muffler, like Glass Packs, or Cherry Bombs. But I also think that dual exhaust foes help performance, but like was mentioned above, keep the exhaust pipe size to a smaller diameter, 2.25"/2.50". I went to 3" pipes on my 79 with the 400, and the loss of that back pressure really made a difference in the way the engine performed.
Let us know what you decide, and an audio clip would be nice too.
Unk Bob
I think duals would help performance a little but not worth the hassle to install and maintain. The stock system, which I think you mostly have now, is pretty tough and durable.
Personally, I would want a quiet(er) muffler. A big case turbo muffler or a big case standard muffler. Hearing that engine once in a while with open chamber could be fun. All the time in a work truck with 4.10's not so much fun.
Headers... needs headers. Then merge them with 2.25-inch tubes into a single 2.5-inch tube and a free-flowing muffler. Or just go to a dual 2.5-inch and headers.
I'm stuck and I can't seem to find a decent answer. I'll be honest...I hate it when I get the knee-jerk reaction of, "drop in a 460" or "add a 4 barrel and dual exhaust" without so much as knowing what the details of the engine/gear/tire combo or the type of driving I do.
-rant over-
I have a 77 F150 4x4 with a 4 spd granny gear and 3.55 rear end and 33" tires.
The engine is a 400M with aluminum intake and 4bbl edelbrock. Everything else is stock or really close to stock.
I am currently running a 'y' pipe with a single 2.5" exhaust through an open chamber muffler.
This is a work truck so mostly heavy loads, some off road and some longer road travel. Will I get any benefit from a dual exhaust or should I just leave it alone?
If it going to be used a truck and not spinning high RPM the Single 2.5" will be adequate for your use.
If you are pulling and carrying heavy loads and finding that you are using more than 1/2 throttle all the time dual 2.5"'s will be an improvement.
Since you already have a 2.5" Single it makes the most sense to go to 2.5" dual's. You will just need to replace the Y pipe and add the other side. Be sure to install a cross over this will help prevent you from losing low end torque .
The Dual's will help in the higher RPM range where you are moving more air or if you constantly on the throttle making the engine work. This also sets you up if you decide later on to do a cam swap to get more power. Headers are not necessarily going to help you until you start breaking that 300HP where the stock manifolds start becoming a choke point.
Headers will uncork horsepower and torque that is stifled by the use of manifolds.
Only if you exceed the stock manifolds ability to breath. The cost and aggravation to gain 5hp with headers is not always worth it.
It also very dependent on the engine. For example the small block Ford's and FE's will see a far higher percentage of gains with headers than say a 385 where the choke point is not is the exhaust manifolds but the exhaust ports.
The 335"s have pretty good flowing stock exhaust manifolds and are not much of an issue till you get nearer the 300 HP mark. By that time the big issue then starts to become the floor and of the roof of the exhaust port on the 335's, opening up the roof of the exhaust port will show significant gains.
Will headers help yes. Will they help on stock 335 engine not really and not as much a cam swap will. Headers should be the last step to squeeze the last few HP out of a 335 or 385 where they will then make the biggest difference in HP gains. Till that time more gains will be had spending that same money on cam and induction.
I have heard that the stock manifolds and single exhaust can help with torque but I have not seen any data to back up the claim.
Sure you have, almost every truck to roll off the assembly line.
Long tubes are proven to improve torque over factory cast junk.
Is the improvement gonna change your life and unleash a beast from within, no.
Dual exhaust is over rated, and just adds unnecessary weight.