Thread: Exhaust Pipe Size Considerations

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For a virtually stock SBC ZZ4 engine, automatic tranny, traditional exhaust running all the way out the back what size pipes would you consider to be optimal, considering that too big causes flow velocity to lag, and too small boosts back pressure. I'm hoping to add a crossover pipe to balance between the sides, but the ladder bar rear suspension is going to make things a bit tight.

My guess is 2 1/2. But lets see what the pros say.
My understanding is that true headers of about 24" with a collector of 3" diameter for about 18" before going to 2 1/2 would be ideal. All that was off the top of the head or as they say pulled out from my lower regions. But it should give enough targets for the pro's to shoot many holes in.

Should have mentioned that there's already a set of Edelbrock Street Rod Block Huggers (ED65752), 1 5/8" primaries into 3" collectors, ceramic coated that the PO bought, and that will be staying even though they are not the best performance choice.... They are like this, unequal primaries, tucked tight.

Roger, pipe size generally is dependent upon horsepower. THIS TABLE should be a good rule of thumb.

I have 3" pipes all the way back to the exit in front of the rear wheels. When I have the shop take those off and run them out the rear, I'm dropping to 2-1/4" pipes. I'm not worried about perfect tuning of the exhaust anymore. It's close to what's in that table, and I'm not drag racing or running at top RPM very often. That's my semi-scientific/kinda-practical approach. Works for me.

My point zero two.. 2 1/4" or 2 1/2", If I remember right, it's a driver that you are building for dependability / reliability.
You weren't trying to squeeze every ounce of power from it.. it may actually be sold off????

In that scenario.. "THE SOUND" will be more important!

Yep, it's just a driver. I've been kicking around whether 2 1/4" or 2 1/2" was better, and from the table Jack posted 2 1/4" should be about right unless something else biases the decision.

Well... as usual when it comes down to a choice like that. Then, bigger is better!


The 2 1/4 will give you additional room to squeeze the pipes in too. It's a good choice.

Speaking subjectively, and since objectivity has been well covered, 2-1/4 or 2-1/2 to the mufflers, then 2-1/2 to 3 for tail pipes. In my experience, the larger and longer the tailpipe, the deeper and more "Rrumbly" the sound, generally speaking.

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