Do shorty headers add any tone and power to a stock l31 with a super 40 2 into 1 muffler?

[0xDEADBEEF]

Have you ever put a cam, nitrous, blower, stroker, etc. on stock manifolds? Did it make more power, or was it the same as before?

In terms of flow/restriction, the stock manifold flows more than enough.

 

[L31MaxExpress]

Have you ever put a cam, nitrous, blower, stroker, etc. on stock manifolds? Did it make more power, or was it the same as before?

In terms of flow/restriction, the stock manifold flows more than enough.

I have done that once. I went with a larger cam, better heads and a larger engine of the same family on stock manifolds and exhaust. Power was nowhere near what it should have been for the engine build. I wanted my 88 Cadillac whisper quiet at the time for some reason. I then swapped to headers and a halfway decent Caprice LT1 9C1 dual exhaust. I gained as much power adding headers and exhaust as I did swapping from a swirl port head HO Vin9 307 to a 403 with W31 heads, intake and a Mondello cam. Since that build, I have never tried to add power keeping the stock exhaust system especially on older vehicles.

Exhaust makes as much of a difference as a cam does on a L31 and the two together combine to make both work even better. The factory exhaust in decent shape on the 1500 L31s peaks over 5 psi backpressure measured at the EGR port. That is what it measured on my 99 Tahoe with a L30 305 that had a 218/218 cam. Swapping the muffler alone made very little difference. The 1-ton (2.75" dual) and Van (3" dual) exhausts peaks at ~4 psi with the factory muffler and a magnaflow dropped that to 1.5 psi, larger 454/8.1L cats and larger piping reduces the backpressure once you ditch the restrictive OE muffler. I have a 0-10 psi gauge that I specifically set up to measure exhaust backpressure and typically I measure it at the 02 sensor port or EGR port. I have fittings to convert the metal line to both.

 

[0xDEADBEEF]

I'm not saying manifolds are good for any amount of power, they aren't, but neither are shortys.

The last old engine I did headers on I fought 3 broken bolts for ~8 hours (before I had a welder). I wouldn't do that for 8 HP. People can do what they want though.

 

[L31MaxExpress]

I'm not saying manifolds are good for any amount of power, they aren't, but neither are shortys.

The last old engine I did headers on I fought 3 broken bolts for ~8 hours (before I had a welder). I wouldn't do that for 8 HP. People can do what they want though.

I have fought broken bolts, repairing broken manifold bolts on too many engines to count. The LS and Hemi are terrible for it. I typically weld a nut on them, then quench with a penetrating catalyst oil, and they come right out. Small blocks are not usually prone to breaking their manifold bolts when you attempt to remove them though. I have taken manifolds off 40 year old engines here with zero issues.

 

[0xDEADBEEF]

I have fought broken bolts, repairing broken manifold bolts on too many engines to count. The LS and Hemi are terrible for it. I typically weld a nut on them, then quench with a penetrating catalyst oil, and they come right out. Small blocks are not usually prone to breaking their manifold bolts when you attempt to remove them though.

The engine I'm referencing above was a 5.9 Magnum. Every junkyard 5.3 has at least one broken bolt though.

 

[L31MaxExpress]

The engine I'm referencing above was a 5.9 Magnum. Every junkyard 5.3 has at least one broken bolt though.

The 6.0L I had in the G20 van had 5 broken bolts when I acquired it. I did not bother extracting them. I was putting a pair of Lloyd Elliot ported 2.00" valve 862s on it anyway.

 

[Orpedcrow]

So… do shortys change the way the exhaust sounds? If so, what kind of difference is it?

 

[L31MaxExpress]

So… do shortys change the way the exhaust sounds? If so, what kind of difference is it?

They make the exhaust tone a bit throatier, deeper and smoother.

 

[L31MaxExpress]

Manifolds

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Shorties

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Tri-Y (had the 4L85E by this time where the first 2 were with the 2nd transmission, the 4L65E)

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All 3 had the same magnaflow muffler.

 

[Orpedcrow]

Manifolds

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Shorties

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Tri-Y (had the 4L85E by this time where the first 2 were with the 2nd transmission, the 4L65E)

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All 3 had the same magnaflow muffler.

That’s a good comparison. You can hear the engine trying to force the air out of the manifolds. I like the deep throatiness of the shortys. The Tri-ys make the engine almost sound effortless. Very smooth.