so i'm gettin new exhaust, are 2 inch duals ehough?

[emoo99]

so i\'m gettin new exhaust, are 2 inch duals ehough?

i can go 2.5 inch duals all the way back but i'm thinking if the collector on the manifold is 2 inches i shouldn't waste my money on 2.5 inches. i have a stock 350 with a performer intake and carter comp 4bbl carb, now i have some elite ceramic headers but the collectors hang down too low and hit the shackle bolt, and there leaking so i'm going to sell those.. i want the ram horn manifolds but the 2.5 collectors are way more expensive than the 2 inch so how much will it effect my backpressure? will it be better torque? i plan on going: ram horn 2 inch exits, to cats to glasspacks, and from the glasspacks out i want to to 3 inch pipe to the rear. possibly instead of 3in pipe from glasspacks back i want 2 inch pipe with 5 inch tips tucked up by the tank so you can hardly see them.

 

[MudFrog]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

I would do a minimum of 2.25" possibly even 2.5" just in case you do any mods later on. Use this chart put out by MagnaFlow Performance Exhaust as a reference:
Exhaust Diameter Chart

 

[bablazer73]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

I just finished my duals on my 89. I used the stock exaust manifolds, The stock front pipe is 2 1/4, so i just went from there. I ran 2 1/4 to a pair catco high flow 2 1/4 cats, then went to 2 1/2 40 series flowmasters and 2 1/2 tail pipes. i want to put some 3" tips on it, but didn't have the funds now. The whole idea of running small pipes up front is to keep the back pressure high enough for proper cylinder scavaging. I looked at that chart from magnaflow, It's really just a guideline. Since most of the "stock" or mild k5 engines were low power, i would stay 2" or 2 1/4 tops. atleast to the mufflers, or cats if your gonna run them. I had to too keep it "legal"

 

[emoo99]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

thanks guys, i figured my theory is that manifolds will be 2 inch collectors so the point of larger pipe isn't worth it because the exhaust system is only as good as it's weakest link is that right?

 

[Blue85]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

It's not as though having a small diameter pipe for a few inches is the same as having your whole exhaust system that size. The total restriction is the sum of the restriction of all the parts. 2" pipe all the way back is too small. It sounds lousy, too. 2 1/4" duals is a pretty good baseline setup. For better sound, run pipes bigger than that back from the mufflers.

 

[6.2Blazer]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

Just as Blue85 mentioned, the total restriction in the exhaust system is also affected by the total length of the pipes.......so having the entire system only 2" will be more restrictive than just a short section of 2" followed by 2.25 or 2.5".

 

[84_Chevy_K10]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

[ QUOTE ]
The whole idea of running small pipes up front is to keep the back pressure high enough for proper cylinder scavaging.

[/ QUOTE ]

That is completely foolish. Close to the engine, the gasses are hottest and thus have the most volume. If anything you want the big pipe closest to the engine and run smaller tailpipes so that the cooler gasses with less volume can continue to flow.

The, "Megaphone" effect of building your exhaust system sounds great, but nothing you could have done would have hurt your performance more than that unless you went with even smaller pipe.

Backpressure is bad and will take power away from your engine reguarless of RPM range of operation. Although some backpressure is inevitable, it doesn't matter if you're idling or standing on it, anything that can be done to reduce backpressure will increase performance.

Personally, if I ever have an exhaust system bent, I will go 2 1/2". Nobody locally has a mandrel bender so I'm stuck with press bends. Going 2 1/2" will assure I get a full 2 1/4" all the way to the bumper.

2" duals are way too small and will result in far too much backpressure.

Putting duals on a truck with manifolds really isn't worth the money though.

Dynomax makes manifold dual kits that are cheap.

 

[Emmettology 101]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

Head out to www.flowmastermufflers.com There is a chart ont heir site that recommends exhaust size in relation to HP and cubic inches. But I agree, got at least 2 1/4" or even 2.5"

 

[Emmettology 101]

Re: so i\'m gettin new exhaust, are 2 inch duals ehough?

[ QUOTE ]
[ QUOTE ]
The whole idea of running small pipes up front is to keep the back pressure high enough for proper cylinder scavaging.

[/ QUOTE ]


Backpressure is bad and will take power away from your engine reguarless of RPM range of operation. Although some backpressure is inevitable, it doesn't matter if you're idling or standing on it, anything that can be done to reduce backpressure will increase performance.



[/ QUOTE ]

Some back pressure is good though... You dont want to rid the system of 100% backpressure. Just like they dont recomend runnign 3" duals on a stock-mild SBC because htere is not enough back pressure and also cause you could burn up valves.