What size exhaust pipe to run?

[BoneCollector]

Hi guys

I don't post on here much, but I hope you can help me out. I just installed a set of Summit Racing headers with 3" collectors on my small block. They included a set of 3" reducers.

The question is should I stay with the 3" pipes all the way back? Or should I run 3" to a muffler that exits at 2 1/2" or 2 1/4"? I plan on running pipe to the muffler somewhere below there the cab and the box meet and exit in front of the rear tire.

What should I do? What are the pros and cons between keeping the 3" all the way back or switching to a smaller diameter pipe.

Thanks in advance.

[cdowns]

the longer you run a 3" pipe the more you loose out on your torque curve of your ewngine// a 21/4 or 21/5 pipe will run much better

[70cst]

Mine was 2 1/2"

[gvw5400]

2 1/2" works well for me. All the best, Dirk

[Norcal72]

A lot has to do with the engine. Is it a fire breathing 11 to 1, 7500 rpm shift sbc? Then go with 3". If it's stock grocery getter, I would go with 2 or 2.25". If you have a mild build, headers, intake go for 2.5". Just my opinion.

[70blackfish]

2.5 for up to 500 hp

[findog78]

I just got new exhaust with x-pipe and magnaflow 3XL's exiting in front of wheels. I went from 2.25" to 2.5" and lost noticable tourque. Motor is not stock but not a fire breather. If there were do-overs I would go 2.25" again. Thats my $.02

[msgdsrf]

Originally Posted by Norcal72

A lot has to do with the engine. Is it a fire breathing 11 to 1, 7500 rpm shift sbc? Then go with 3". If it's stock grocery getter, I would go with 2 or 2.25". If you have a mild build, headers, intake go for 2.5". Just my opinion.

+1, too much exhaust equals too little fun to drive. Sound is different too. 3" without big air to push through sounds off too. And bigger pipes tend to add more drone in the cab. Food for thought.

[CC69Rat]

Tell us more about your motor (?)

[Stu Pidd]

Headers work properly only when they have enough velocity flowing through them.
Go too big on the exhaust, and velocity slows down, eliminating the header's scavenging ability.

[NONHOG]

Another thing to consider is as exhaust cools it needs less volume.
That's why many factory exhaust systems neck down as they go back.
Some say run as big as you can and adj. fuel accordingly. I say run what the experts call for. Plenty of charts online to help choose the proper size based on HP. And think about how often you will be at peak HP. Driver or racer?

[chevy72blu]

2.25" on a very mild 350 (vortec heads, cam, intake, headers) worked well for me. Caught some flack about my "pea shooter exhaust" but it pulled hard down low.

[Fitz]

Originally Posted by BoneCollector

Hi guys

I don't post on here much, but I hope you can help me out. I just installed a set of Summit Racing headers with 3" collectors on my small block. They included a set of 3" reducers.

The question is should I stay with the 3" pipes all the way back? Or should I run 3" to a muffler that exits at 2 1/2" or 2 1/4"? I plan on running pipe to the muffler somewhere below there the cab and the box meet and exit in front of the rear tire.

What should I do? What are the pros and cons between keeping the 3" all the way back or switching to a smaller diameter pipe.

Thanks in advance.

Run 2-1/2 using a reducer at the header collector.

[BoneCollector]

Its just a 307 or now. I plan on building a 350 or a 383 int the future when I start to rebuild the truck.

I decided to go with 2 1/2 inch all the way back. I'm going to run some 23 inch Thrush glasspacks on it and 45 it out before the rear tire.