2" or 2 1/4" 327 exhaust? need help/opinions...

[chewychevy67]

ok i have a 327 275hp from a 67 impala in my 67 truck. fresh stock rebuild. i talked to my exhaust guy today and he says do dual 2" exhaust cause my ramhorns have a 2" dump out. he says it will have more low torque and be quieter and i like quiet. almost all of my past trucks have had 2 1/4" duals. from your knowledge of experiences what is the best choice here. pros and cons. only want to do this once till it rots out at least lol. Rod.

[treeboy97]

This is a good reference article I found.

http://www.pontiacstreetperformance....p/exhaust.html

[BLOWN72]

Everybody has a different opinion on exhaust size. For me I have always gone 2.5" on every V8 I have owned. 2" is just to small and you lose a lot of tone with a smaller exhaust. It comes out to raspy. For example I had a 97 Sierra while a guy I worked with had a 96 Silverado both with 350, we both had true duals with flowmaster. He had 2" and I had 2.5". The exhaust note was totally different and it was not a comparison on which sounded better. And mine was barely louder when we would both get on it. I would go with 2.5" duals for the motor you have in there.

[chewychevy67]

would 2.5 in front of the muffler and a or 2 tailpipe hurt? i believe thsi is what the factory big blocks had but they also have larger manifold dumps. can you even run a larger than 2" off a stock ramhorn being that is the exit size?

[ProStreet68SB]

You can't go wrong with either size. If it was me I'd run 2" exhaust though.

[sir_talk_alot]

2.5, nothing i hate more then to here a v8 go by going "tatatatatatatatat", 2" makes it sound just like blown72 said, raspy. it wont sound very good at all, like its underpowered and a worn out old 305, lol . get on craigslist and buy some headers from somebody for like $50, at least go 2.25 on your truck, 2.5 sounds real good, nice deep tone.

[chewychevy67]

i cant use headers cause my alternator and my a/c brackets bolt to them and i am definately keeping my a/c.

[LEX]

2" pipes look like straws. I'd def go with 2.5..or at least 2.25 as mentioned above.

[paaw]

I run headers and still have factory ac. Took long bracket off on ac, one that hooks to manifold other two holds it fine and just put nut on back off alternator bolt .

[Beat68CST]

True 2" is plenty fine, it will have more low end too.

If you want more sound and close to the same performance, 2 1/4".

Don't go 2 1/2 on a stock SBC, they need some back pressure.

[VWBeamer]

2.5.

I just wrote and published an article on this very subject. back pressure is not a good thing in an exhaust system. Gas velocity, which will increase in a small diameter pipe, does help scavaging. This why smaller pipes help produce more torque.

But, without headers there isn't going to be much savaging anyways.

Yes, the smaller pipe might make a tiny bit more torque( and a tiny bit less HP) , but the 2.5 look and sound so much better.

[sir_talk_alot]

Originally Posted by paaw

I run headers and still have factory ac. Took long bracket off on ac, one that hooks to manifold other two holds it fine and just put nut on back off alternator bolt .

same, i have headers and a/c. hang on ill take a pic.

[sir_talk_alot]

this was already done on my truck. they cut the part that i guess in your case would mount to the manifolds, so that it would work. my a/c system itself is rough, and its later on the list of priorities for the truck.

[special-K]

I'd go with 2 1/4". It won't make it loud,it will have plenty of low end torque,it will flow a bit better,and there is absolutely no need for 2 1/2" exhaust on a motor under 300 hp. In fact,that could hurt your bottom end. A small step-up is good and bigger isn't always. I run 2 1/4" duals on my '72 with a healthy 350 and it runs fantastic.

[chewychevy67]

i have decided that i will use 2 1/4" from the manifolds to the muffler. Now if i ran 2" from the mufflers back would it still have that old tractor sound. would that hurt the flow. would i be better off to run 2 1/4 straight out the back? my tail pipe hangers are 2" and i would like to use the original style but not if it will hurt the flow. Rod.

[terry b]

ttt

[allchevy58]

I would do a minimum of 2 1/4 all the way out back. My 58' 283 2 barrel has dual 2 1/4 to muffler and then 2 1/2 to bumper. Runs just fine. My other small blocks with manifolds, I step it up to 2 1/2 just out of the manifold. If you run tailpipes all the way out back, they pretty quite.

[special-K]

I wouldn't reduce the pipes to 2". With exhaust you never want to reduce down. You'd be better off going 2" all the way. I'd go 2 1/4" all the way and if the OEM hangers won't work I'd make something that will work for the bottom 1/2 with the hangers. 2 1/4" dual exhaust isn't OEM anyway. Did big blocks run 2"?

[chewychevy67]

i bought some big block dual hangers from a member and the front hangers were 2 1/2" which i made work with 2 1/4" and the tail hangers are 2". thats why i was going to use those hangers. I guell i will have to find 2 more 2 1/2" hangers and modify them as well.

[70cst]

Lots of good opinions ...

[ttuch69]

Where are all the tough guys running 3 inch, i'm going headers into 3 inch dumping flowmaster 10's right under the box, and of course rocking those with my 327!!!!!

[chewychevy67]

Ok I'm bringing this to the top. Since this thread started I have found Nos mufflers for the big block that fit in the factory big block hangers and reproduction ones. The nos ones are 2.5" in and 2" out and 21" long but are 2" inside. The repo ones are 2.25" in and 2.25" out and are 16.5" long and they are 2" inside the muffler as well. So in reality does it matter what size the pipe is after the muffler being they are both 2"inside.

[Steeveedee]

I had a '64 Impala convertible with the SHP 327 (300HP). It had 2-1/2" pipes from the manifolds to the mufflers and 1-7/8" pipes all the way out to the back. I could pull 6 grand out of it, no problem. If you look around, you can find a video where a couple of guys hammer a set of headers full of an unbelievable number of dents without any reduction of HP on a dyno. I'll go look at my truck tomorrow (stock BBC) and see what size the exhaust pipes are. I know that they aren't all that big.

[chewychevy67]

That would be great. It's funny that you had a 64 because the mufflers I have are left and right 327 300hp mufflers for 64 passenger except wagons. . I just went out and checked and the I'd of the exits are just a hare shy of 2". How did the car sound?

[p0508]

https://www.hotrod.com/articles/what...pes-work-best/

2.5 is your bare minimum. Search hot rods and motortrend engine masters show. They debunk old myths all the time. Including losing power on bigger exhaust.

Less than 2.5 on a 300+ ci v8 is adding restriction peroid. I don't care what your seat of the pants Dyno says.

Myth: engines like backpressure and you lose torque with bigger exhaust