Slant Six Forum :: Bigger exhaust....jetting changes?

simply fattening the main jet will not make you go faster unless you are already running lean.

go out and enjoy your new exhaust for a while, then come back and read your plugs. go up or down depending on what they tell you.

I went up to a #60 and played around with the emulsifier screw. Car seems to like it, with a little more umph in the mid range.

Everything on the carburetor is stock Ted, so I don't know the size.

It is surprising how much more power you unharness with a little bigger exhaust pipe!

Quote:

Everything on the carburetor is stock Ted, so I don't know the size.

Eric,

Ok, how many turns out on the brass idle air bleed screw did you go? I will compare with one of my other carbs down stairs.

Author:	Eric W [ Sun Nov 09, 2008 12:30 am ]
Post subject:	Bigger exhaust....jetting changes?
I finally got a 2 1/4" pipe from the manifold to muffler (a Magnaflow) today, keeping the 2" tail pipe. Will I need to change the jetting on my Holley 1920 to compensate for the larger diameter exhaust pipe? I'm running a #58 jet now.

Author:	THOR [ Sun Nov 09, 2008 1:00 am ]
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Naw.... but you may be tempted to go larger... make it go faster! ~THOR~

Author:	steponmebbbboom [ Sun Nov 09, 2008 5:59 am ]
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simply fattening the main jet will not make you go faster unless you are already running lean. go out and enjoy your new exhaust for a while, then come back and read your plugs. go up or down depending on what they tell you.

Author:	Aggressive Ted [ Sun Nov 09, 2008 10:21 am ]
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Eric, No, you don't need to go fatter. Stick with the #58. I have gone as low as a #55 just to see what would happen. A #57 is what I am running which is right on the edge, the #58 gives much better vacuum readings and keeps you out of the power valve a little more.

Author:	68barracuda [ Sun Nov 09, 2008 11:09 am ]
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Hi As I understand it the moment you go from stock to headers with free flow system there is sometimes an enrichment needed

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Author:	kesteb [ Wed Nov 12, 2008 9:49 pm ]
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Depends, if your car starts to surge, then you need bigger main jets.

Author:	slantfin [ Thu Nov 13, 2008 10:53 am ]
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Quote: simply fattening the main jet will not make you go faster unless you are already running lean. go out and enjoy your new exhaust for a while, then come back and read your plugs. go up or down depending on what they tell you. What he said.

Author:	Eric W [ Thu Nov 13, 2008 11:15 am ]
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I went up to a #60 and played around with the emulsifier screw. Car seems to like it, with a little more umph in the mid range. Car is louder with bigger pipe, thats for sure.

Author:	THOR [ Thu Nov 13, 2008 3:43 pm ]
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See, toldya you wouldnt be able to resist putting a fatter jet in there! Goes faster! ~THOR~

Author:	Aggressive Ted [ Thu Nov 13, 2008 3:49 pm ]
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Eric, Quote: I went up to a #60 and played around with the emulsifier screw. Car seems to like it, with a little more umph in the mid range. How big (in drill size) would you say your idle air bleed is now that you opened it up with the brass screw adjuster? I have gone as high as a 61-2 with out going below 23 mpg with a .035 diam. hole which is the same as a #65 drill bit. It is surprising how much more power you unharness with a little bigger exhaust pipe!

Author:	Eric W [ Thu Nov 13, 2008 4:03 pm ]
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I get a bigger oil smoke screen also.... Everything on the carburetor is stock Ted, so I don't know the size.

Author:	Aggressive Ted [ Thu Nov 13, 2008 6:10 pm ]
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Quote: Everything on the carburetor is stock Ted, so I don't know the size. Eric, Ok, how many turns out on the brass idle air bleed screw did you go? I will compare with on of my other carbs down stairs.

Author:	DusterIdiot [ Thu Nov 13, 2008 6:51 pm ]
Post subject:	Like...
Quote: It is surprising how much more power you unharness with a little bigger exhaust pipe! Like what 10-15 hp tops with the stock cam, and maybe about 10 ft/ lbs of torque....just enough to shift the torque curve a bit, and make a little better mileage... -D.idiot

Author:	Eric W [ Thu Nov 13, 2008 8:59 pm ]
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Quote: Quote: Everything on the carburetor is stock Ted, so I don't know the size. Eric, Ok, how many turns out on the brass idle air bleed screw did you go? I will compare with one of my other carbs down stairs. Only about three quarters of a turn. It's really sensitive. If I just turn it out a tiny bit the vacuum and idle quality goes down. If I turn it in all the way, it will still idle fine but the engine starts shacking a little bit. Like I said, real sensitive.

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Author:	Eric W [ Fri Nov 14, 2008 12:32 am ]
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Its a bitch keeping my foot out of it....burn more oil ya know.