Headers or not

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mpbsr

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Since it's the Fall, been thinking about a Spring project.

302 was rebuilt about 1 year ago and now has new intake and a Holley 4bbl 600CFM with a mild cam. I also have an aftermarket dual exhaust, but not sure of the brand.

Wondering if it's worth to consider Headers and what would be the additional HP?

Also willing to wrap them to restrict the heat.

Thanks

 
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From my research to maximize the performance gains you need to get as much air in and then out as efficiently as possible. If you only do intake or exhaust you are only improving only half of what you need to do. For example replacing the intake you will improve the air coming in but if your exhaust has a lot of restriction the pistons have to work harder to force the gases out.

Headers improve scavenging and back pressure. Scavenging ensures that there is no destructive interference between the exhaust flowing from one cylinder to another. In-fact good scavenging causes a low pressure region to be created downstream of the exhaust port of the adjacent exhaust pipe sucking the exhaust gases on its own. This is usually accomplished by tuned header systems where all the pipes are of equal length and designed to optimize scavenging effect. Most headers that you buy are not tuned headers, an example are the Hooker Comp and Super Comp headers. The prices vary a few hundred dollars between the two.

Then other factors also come into play. A cam with a higher lift and duration on the intake to get more air/fuel into the cylinders, bigger carb to add the required amount of fuel needed and low restriction mufflers.

Sorry for this being a little long but I would say the headers would only add 10HP if nothing else was changed. Since you have changed the cam, intake, carb, and exhaust already I think that adding headers will probably add more power than the 10hp with just headers alone. Don't think that tuned headers are needed as they are intended for higher performance motors.

I am not an engine builder but I did do a lot of research before I made the changes to my motor. When I was younger I only put headers on my car and really didn't notice any difference and was disappointed. Again just my opinions.

 

mpbsr

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From my research to maximize the performance gains you need to get as much air in and then out as efficiently as possible. If you only do intake or exhaust you are only improving only half of what you need to do. For example replacing the intake you will improve the air coming in but if your exhaust has a lot of restriction the pistons have to work harder to force the gases out.

Headers improve scavenging and back pressure. Scavenging ensures that there is no destructive interference between the exhaust flowing from one cylinder to another. In-fact good scavenging causes a low pressure region to be created downstream of the exhaust port of the adjacent exhaust pipe sucking the exhaust gases on its own. This is usually accomplished by tuned header systems where all the pipes are of equal length and designed to optimize scavenging effect. Most headers that you buy are not tuned headers, an example are the Hooker Comp and Super Comp headers. The prices vary a few hundred dollars between the two.

Then other factors also come into play. A cam with a higher lift and duration on the intake to get more air/fuel into the cylinders, bigger carb to add the required amount of fuel needed and low restriction mufflers.

Sorry for this being a little long but I would say the headers would only add 10HP if nothing else was changed. Since you have changed the cam, intake, carb, and exhaust already I think that adding headers will probably add more power than the 10hp with just headers alone. Don't think that tuned headers are needed as they are intended for higher performance motors.

I am not an engine builder but I did do a lot of research before I made the changes to my motor. When I was younger I only put headers on my car and really didn't notice any difference and was disappointed. Again just my opinions.
Great info.

Thanks

 

Hemikiller

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With what you've done, absolutely. I recommend the reproduction Tri-Y headers for clearance and ease of installation. Have had them on two 302 powered cars and they never gave me a bit of trouble. They also have a slightly different sound than the standard 4-tube header.

 

Mikes73

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Longtubes headers definitely make a noticeable difference, I have had good luck using hedman longtubes as far as price and fit. I would consider a crossover pipe as well while you are there.

 

c9zx

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A WAG on HP increase is 10-15. As Mike said a balance tube, or X-pipe would also help. I would not advocate wrapping headers on a street car. Damage caused by heat induced metal fatigue and premature corrosion are known problems. High temp coating, inside and outside, is mandatory if you want the headers to last (or go with SS). Scientifically, and specifically, designed Tri-Y headers can indeed yield significant gains in mid-range torque. However, they are much more sensitive to any design or construction short comings than a 4 into 1 long tube header.

 

mpbsr

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Thanks for the info.

Funny, way back in the 70's, you'd just buy a set of headers for a cheap price and throw them on.

 

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