exhaust pipe sizes

1402 Views 7 Replies 2 Participants Last post by Guest, Apr 15, 2001

Discussion Starter · Apr 15, 2001

I am going to have a muffler shop fabricate an exhaust system for me probably within a month and its time for me to do my research (post questions for u guys to answer) /forums/images/icons/wink.gif I looked at flowmaster's application chart and it lists 2.25", 2.50", and 3.00" for 64-73. What are the advantages/disadvantages of each? I assume there is a difference besides looks, probably having to do with backpressure, but I can't translate that into something that means something to me. I was thinking 2.5" would probably look the best, but thats what u guys are for. What are the differences and/or advantages/disadvantages of each choice. Also, it has a "tail pipe/pipe kit" for the 2.5" setup. Is that kit just the pipes or something? It has a footnote that says "tailpipes do not fit cars that have staggered shocks." What are staggered shocks? One more thing. Do I just buy the muffler it recommends on the chart and the shop will work with it (inlet/outlet location) or I am supposed to get in contact with a shop and ask them which inlet/outlet configuration to get. Sorry for the length, but anybody got advice?

P.S. I am strongly considering the 50 series delta flow (3 chamber). I want a deep tone at idle and cruising where I can hear my radio, but something that sounds good under WOT.

~Chris
San Antonio, Tx
66 coupe 289
70 fastback done by may/graduation...hopefully

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Discussion Starter · #2 · Apr 15, 2001

i think you should go for 2.5" currently i have 2.25" and have noticed no power loss or anything, so maybe a little bigger won't hurt. I think that you choose the muffler, and then go to the muffler shop and have them fabricate the rest. My '65 289 was a single exhaust...i purchased a set of glasspacks and they fabricated the rest for around $100

College Station, TX

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Opentracker

· #3 · Apr 15, 2001

The hot set up is to have a bigger pipe in front of the muffler
than behind. I run 2 1/2" in front of the muffler and 2 1/4" after.
The reason is the heat from the motor slows down before the
muffler. Back pressure is the key to good torque. The gas from the
motor flows through the 2 1/2" to the "Flowmasters" and does
some cooling on the way, hits the muffler and cools some more.
The smaller tail pipes keeps the back pressure up.
I use this on our track cars and the street cars. Put a X pipe in front
of the mufflers, not a H pipe. The sound is fantastic and the performance
is substantial. If it is a race set up, use 3" to 2 1/2" but it is has to be a
"FAT" cam to need 3" pipe.

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beechkid

· #4 · Apr 15, 2001

The 3" would be most appropriate for 300 plus hp engines, which I kinda doubt fit your application and would probably not benefit the power range of the engine. Anywhere between 2" and 2.5" will be fine for your application. The only question you now have is which one looks visually best...

Jeff
Member: Flatheads ain't so bad association
Never trust an over 40 Chevy owner association (They have to cheat to win)

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Discussion Starter · #5 · Apr 15, 2001

I have 2.5" all they way back on my '68. I did 2.5, because I have a supercharger. I'd probably use 2.25 with a normally aspirated motor unless it's putting out over 400 hp.
I also have the 3 chamber Delta flows and the Flowmaster tailpipes. If I could do it again, I'd go with a quieter muffler though. M&F mag did a test a while back and another brand had similar horsepower ratings to the flowmaster, but less noise (the droning effect of the flowmasters can get on your nerves after a while). Also, the tailpipes are pre-bent with mandrel bends (prevents the "kinking" or "narrowing" effect you get when they bend the pipes at a muffler shop), but won't work on a car w/ staggered shocks, meaning one shock in front of the axle and one behind. I believe this was on some or all '69 and up models, but I am not sure. I don't believe any '65 to '68 models were staggered however.

'68 Coupe, Modified 289 w/ Holley blower
'65 Convertible (future 66 Shelby GT350 clone)
427 S/C Cobra Replica

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Discussion Starter · #6 · Apr 15, 2001

If I do that what kind of muffler do I buy? Do I need to find a flowmaster that has a different size inlet and outlet or does the shop somehow do this with a reducer or something? Thanks.

~Chris
San Antonio, Tx
66 coupe 289
70 fastback done by may/graduation...hopefully

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Opentracker

· #7 · Apr 15, 2001

You would get a muffler with 2 1/2" in/out. The shop will do the
reducing for the tail pipe. The shop I use makes there own X
pipes. They charge an extra $40.00 for the X. To me it is well
worth the money. They make the car quieter and give a nice
"Indy Car" sound. It raises the pitch of the exhaust note.
We run Flowmasters on all of our cars. I get them used at
the swap meets, usually for $50.00 a set.

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Discussion Starter · #8 · Apr 15, 2001

So the X pipe raises the pitch of the exhaust? Hmm, I was looking to keep it as deep as possible. Well, I still have to price the system and find out how much it would cost to buy/have fabricated an X pipe. Thank you very much for your help. I dont know what I would do without VMF.

~Chris
San Antonio, Tx
66 coupe 289
70 fastback done by may/graduation...hopefully

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