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Old 03-01-2011, 06:49 PM
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Exhaust Upgrade?

How much is stock manifolds and exhaust killing my engine? I have an 85 pickup with a 350 vortec heads rpm air gap intake .447 cam 223 duration with a 600 edelbrock. You cant here the cam at all until you bring the idle way down. I am wondering if a set of headers would bring the lope out more? Also how much vacumm should i have? I am at 14" at idle.

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Old 03-01-2011, 07:54 PM
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Headers make a world of difference. 2.5" exhaust with chambered mufflers or turbo mufflers would really bring out the power and the sound of the cam.
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Old 03-01-2011, 11:04 PM
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I am looking at buying either hedmans or hookers...i like the hooker better but they have 2.5" collector with 1 5\8 tubes and the hedmans have 1 5\8 tubes and 3" collector. Is the collector size going to make much difference?
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Old 03-01-2011, 11:25 PM
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Quote:
Originally Posted by hobby28
I am looking at buying either hedmans or hookers...i like the hooker better but they have 2.5" collector with 1 5\8 tubes and the hedmans have 1 5\8 tubes and 3" collector. Is the collector size going to make much difference?
The 2-1/2" collectors are fine unless you want to run 3" pipes straight off the headers.
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Old 03-02-2011, 06:00 AM
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I have had #11500 Flowtechs on my 85 K10 for going on six years now,uncoated and they have held up fine,fit good,albeit the drivers side header goes on from the bottom. Pypes has some great quality mufflers also.
I'm running a 3 inch stainless system with an h pipe and Pypes Violator mufflers.
Shane
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Old 03-02-2011, 02:30 PM
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Quote:
Originally Posted by hobby28
How much is stock manifolds and exhaust killing my engine? I have an 85 pickup with a 350 vortec heads rpm air gap intake .447 cam 223 duration with a 600 edelbrock. You cant here the cam at all until you bring the idle way down. I am wondering if a set of headers would bring the lope out more? Also how much vacumm should i have? I am at 14" at idle.
How much you hear the cam depends on several other things:

- If the duration is measured at .050 inch lift then you should hear it, if the 223 degrees is measured from zero or .006 inch lift, then this is a mild can and won't show much idle.

- If the compression is low the effect of the cam timing on idle is reduced. While Vortec heads usually move the compression up even with stock pistons, the end SCR will be very dependent upon the head gasket thickness. The typical SBC ranges will give compression from about 8.8 to 9.5.

- The cam's Lobe Separation Angle (LSA) which is the distance between the intake and exhaust lobe centers in crankshaft degrees has an effect on idle sound where a wide LSA makes for higher idle manifold vacuum and a calmer idle and a tight LSA just the opposite.

- Headers have an overall effect on an engine and that effect is more pronounced as the engine is tuned more radically. So the answer here is yes they will add to the rough idle sound of a long duration cam. They may also cause you to richen the mixture to compensate for greater mass flow through the engine and the effects of strong tuning waves.

Bogie
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Old 03-02-2011, 05:20 PM
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Here are the cam specs


cam lift .298 valve lift .447 adv duration 290 duration @.050 223

intake lobe 110
exhaust lobe 118
overlap 52
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Old 03-02-2011, 09:26 PM
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That's a fairly mild cam, the 114 LSA will tend to smooth the idle, too. Use headers anyway, regardless if the cam has much noticeable lope to it- it will make better power w/headers than w/o- by a good margin.

Use low restriction mufflers and a connector pipe between the two sides of the dual exhaust, after the collector and before the mufflers. Mount the mufflers as far aft as is practical. Then let the sound fall where it falls. At least you'll be getting all the cam has, performance AND sound-wise.
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