I have a silly question If I go to a 2 1/4 or 2 1/2 exhaust on my 1 barrel maifold will it help it breathe better I'm also getting the distributer recurve here next week will it make notable difference with my slant six just wondering and thanks again

Enlarging the pipe will improve performance some and deepen the exhaust tone. If you're not doing something with the exhaust manifold, you're leaving power on the table. The system is only going to be as good as its most restrictive component.

It is possible to go too large on the pipe. The exhaust provides some scavenging of the cylinder. The larger the pipe, the lower the exhaust speed, which lessens the scavenging effect.

The dizzy recurve should provide more power if its done right.

FWIW, I'm running an oversize exhaust manifold and a 2¼ pipe end-to-end with a "Turbo" muffler. It makes nice sounds at idle and is nearly silent at steady highway cruise (easily masked by radio).

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You can't fix stupid. - Ron White

Bill
I agree mostly with 2Darts. Unless your running a spruced up engine I think the stock exhaust manifold with 2 1/4 to the muffler is more than enough. Any bigger and it will hurt your changes like your recurve and HEI (right).
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

backwoodsbill,

I installed a stock SL6 a few weeks ago while my "Torque and Mileage" motor is being upgraded with a crank scrapper, double roller timing chain and one of Doc's HV pumps.

I must say that a pure stock motor with my recurved distributor and 2 1/4 exhaust is surprisingly pretty snappy!
Stick with 2 1/4" head pipe and a 2" tail pipe for best performance.
I am running a very free flowing system using a long body MagnaFlow muffler with a 2.5" core and a 22" long 2" diameter resonator. The system is nice and quiet.

It is an 1980 SL6 engine from a Dodge Diplomat with 85,000 miles on it. It had been setting in a barn the last 6 years, very rusty and covered with junk with no fuel pump or distributor. I am getting 22.5 to 23 mpg with it on my daily commutes running 5-30W Valvoline and a quart of Rislone. Rislone helps to clean it out and free it up so I can switch to 0-30W Mobile 1.

So I would recommend doing the upgrades.

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Aggressive Ted

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74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG