Thread: 2.5" or 3"???

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I need to decide what size exhaust system for my Ranchero. It has a 429, Edelbrock 750CFM carb and manifold, CompCams X4270H cam and HEI ignition. I am shopping for headers although those from Crites seem good. I want the exhaust to include an X- or H-pipe. I can choose 2-1/2" or 3" pipes. What is the best choice?

Originally Posted by peteyx

I need to decide what size exhaust system for my Ranchero. It has a 429, Edelbrock 750CFM carb and manifold, CompCams X4270H cam and HEI ignition. I am shopping for headers although those from Crites seem good. I want the exhaust to include an X- or H-pipe. I can choose 2-1/2" or 3" pipes. What is the best choice?

On a big block, the smaller 2 1/2" pipe seems to help the low and mid range power with an H-Pipe... I'm sure the engine experts now why, I just know from my own experience that the smaller pipe makes better streetable power....

A smaller pipe will give you more velocity and help expel the gasses quicker.

If the gasses exit quicker, it can create a kind of mild super-charging effect, helping to fill the combustion chamber.

I'd go with the 2.5 inch myself.

That settles it. Thanks guys.

i allways thought the larger the exhaust pipe the faster the fumes would get out, what if you didnt have the H or x pipe then what ?

if you had shorty headers and coupldnt put long tube headers on, if you ran a 3" pipe to the muffler would that help to simulate longer headers ?

Originally Posted by lightning1901

i allways thought the larger the exhaust pipe the faster the fumes would get out, what if you didnt have the H or x pipe then what ?

The larger volume of the pipe would decrease the velocity of the exhaust flow..... Correct exhaust sizing is critical to get the right balance of volume and velocity.,....

Originally Posted by lightning1901

if you had shorty headers and coupldnt put long tube headers on, if you ran a 3" pipe to the muffler would that help to simulate longer headers ?

Nope, doubt it would do anything good for the engine. Again, increasing the size does not necessarily improve the exhaust flow because of the velocity. It would be better to use a large tube header (even shorties). When shopping for headers, avoid the cheapies with the super tight bends, spend the extra $$$$ and get some good ones. I've always had very good results with BBK headers... Hookers are good, too.

i got a set of JBA shorties,

Originally Posted by peteyx

I need to decide what size exhaust system for my Ranchero. It has a 429, Edelbrock 750CFM carb and manifold, CompCams X4270H cam and HEI ignition. I am shopping for headers although those from Crites seem good. I want the exhaust to include an X- or H-pipe. I can choose 2-1/2" or 3" pipes. What is the best choice?

I would run a 2 1/2 Mandrel bent system if you have the funds. The 2 1/2 pipe can really bunch up going over the axle restricting flow. Just had one done with Delta 50 Flow masters and a cross over. Sounds Badazz. An X pipe works better at high RPM than an H but causes more clearance issues. For your setup I would use the H it makes maintenance easy. Chris

i am running a ford truck, weight 3800, have a 460 bored 30 over, edelbrock rmp intake and cam, edelbrok 800 carb, d9 heads that have been gasket matched, bowl blended, 3 angle ground, with a set of tri y headers will be straight exhaust about 4 ft long including magna flow mufflers dumped after the cab have a 4.11 posi rear end, should i go with x pipe or h and what size pipe ?

I'd go with mandrel bend 2 1/2" pipe. As for the X or H pipe, not sure. Putting my first ever H Pipe on my pickup cuz everyone sez it will help the performance and sound..... We were having this discussion the other day, maybe some of the guys with more experience or dyno time with crossovers will chime in.....

Originally Posted by Dave Severson

I'd go with mandrel bend 2 1/2" pipe.

no bends, headers come out perfect, will be straight pipe, no cat's thinking of straight pipe with H pipe to mufflers and dumped off the mufflers,

i got a 78LTD2 with a 514 in it. i used a set of hedman headers and 2-1/2 exhaust with flowmasters. sounds good and runs good although i'm considering removing the flowmasters and using some magnaflows. its been found that the flowmasters might be a bottle neck as rpms increase. on 460.com there has been several people who gained more torque and horsepower with just a muffler swap. good luck with your Ranchero there are not many good looking big block examples out there.