Horse Power gain from Stock Headers to Shorty Headers

spirockp · Apr 19, 2010

I am currently running a stock 302 with stock headers and Magnaflow mufflers. I was thinking of upgrading to shorty headers. Can any one give me an expected horse power gain that I may expect. Current horse power with my stock 302 is estimated at 225.

Thanks.

hhead · Apr 19, 2010

I don't think it's going to give you the boost you'd like it to. I believe they don't make hp, just frees up what you got. And being stock, I don't think it'll free up 10hp. It might sound better. But if hp is what you're looking for, I think your money would be better spent elsewhere.
Looking back, I see you already have headers, not stock manifolds. I think your gain will be zero. They will however move your power band, if that.

spirockp · Apr 19, 2010

On a side note I see that Stainless Steel headers are much cheaper than Ceramic Coated ones. Any reason why?

rbohm · Apr 19, 2010

spirockp said:
On a side note I see that Stainless Steel headers are much cheaper than Ceramic Coated ones. Any reason why?

the higher cost indicates the amount of work needed to coat the headers, as opposed to stainless steel.

D.Hearne · Apr 19, 2010

spirockp said:
I am currently running a stock 302 with stock headers and Magnaflow mufflers. I was thinking of upgrading to shorty headers. Can any one give me an expected horse power gain that I may expect. Current horse power with my stock 302 is estimated at 225.

Thanks.

What vehicle and what "stock headers" do you have ? I wasn't aware the late 80's Mustang stock headers would fit classic Mustangs. The only "stock headers" that'll fit a classic Stang are the 289 Hi-po manifolds (cast iron shorty headers) Going from these to steel tube shortys might net you a few ponies, but nothing you'll be able to feel in the seat of the pants meter.

spirockp · Apr 23, 2010

D.Hearne said:
What vehicle and what "stock headers" do you have ? I wasn't aware the late 80's Mustang stock headers would fit classic Mustangs. The only "stock headers" that'll fit a classic Stang are the 289 Hi-po manifolds (cast iron shorty headers) Going from these to steel tube shortys might net you a few ponies, but nothing you'll be able to feel in the seat of the pants meter.

I'm running a 1990 302 block and 66 original headers.

D.Hearne · Apr 23, 2010

There were no headers (as such) for a 289 in 1966. The closest thing was the manifolds made for the 289 Hi-po.

grainboy · May 6, 2010

Spiro, I think we can all assume you have the log style exhaust manifolds. With the swap to shorty headers, you may give up a touch of torque on the bottom end, but will expand the top end rpm, and add a few hp. You will experience more noise, burned plug wires, and leaks to the head. Is it worth it? Only you can answer that, after the swap is done. I rarely see rpm over 5000, and am quite happy with manifolds and flowmasters behind them.

2+2GT · May 6, 2010

D.Hearne said:
There were no headers (as such) for a 289 in 1966. The closest thing was the manifolds made for the 289 Hi-po.

The 289HP manifolds will increase power a bit, and 'shorty' headers a bit more, but if you leave the heads untouched with the horrible stock exhaust ports, the improvement won't be worth the trouble of installing them.

You need to clean out the ports-and port-match them to whatever headers or manifolds you use.

This head had all of the excess flash, shown shaded, and the smog injector 'nose' removed, and afterward (using a C9OZ-C hydraulic cam) turned 321 hp on the dyno. With all that junk in the ports, no way could it have done that.

Don't even bother with headers or dual exhaust with crappy stock ports.

jonfor · May 6, 2010

i'm dealing with the same basic issue.... my engine is terminally weak and i have rusted, long tube headers dragging the ground (shelby drop) and the smallest diameter pipes going back i have ever seen on a V8. i want more ground clearance, more aggressive aesthetic diameter, and a better sound without an obnoxious drone.

2010 will be a beans & bologna year for me so i'm not looking to drop a lot of money. i was thinking HiPo manifolds and 2.5" pipes with cheapo turbos. i would love side exit, but?????

2+2GT · May 6, 2010

jonfor said:
2010 will be a beans & bologna year for me so i'm not looking to drop a lot of money. i was thinking HiPo manifolds and 2.5" pipes with cheapo turbos. i would love side exit, but?????

I have the repro GT dual with the tailpipe resonators, resulting in no drone. 289HP with 289HP manifolds. I cleaned up the inside of the manifolds, and port matched the heads to them. Took out a lot of iron, since the manifolds are quite generous, but the heads were no better than the pitiful 2V heads. Runs like a scalded dog, now.

My exhaust is 2", and works great, the restriction on these engines is not the exhaust pipe, it's the lousy ports on the heads. Two and a half is excessive, anyway. Two and a quarter on a hard-core 289/302 is plenty, and it would take a lotta cam to need that.

I have driven side exhaust, and it's a lotta fun for the first half hour.

D.Hearne · May 6, 2010

grainboy said:
You will experience more noise, burned plug wires, and leaks to the head. .

Sounds like you did everything wrong. And nothing right. I have none of that with any of my headers.

grainboy · May 7, 2010

you dont have windsor jr heads. And this isnt my first experience with headers, thank you.

D.Hearne · May 7, 2010

grainboy said:
you dont have windsor jr heads. And this isnt my first experience with headers, thank you.

No, but I've had headers with many different heads, both aluminum and iron and, yes, if you use cheap header gaskets and don't tighten them occasionally, you will have leaks. But if you invest in a quality aluminum sandwich gasket(Percys), you eliminate all that, regardless of the heads. No more problems than iron manifolds.

Horse Power gain from Stock Headers to Shorty Headers

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