Headers or not?

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manyo

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Washinton Twp, MI USA
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71 Mach 1
Just had my 351 c. m code rebuilt , with upgraded cam, punched out .030. I torn between going with stock exhaust or headers. Your in put apreciated.

 
I personally think headers are an easy power adder, especially if you've modified your engine a bit. Headers significantly reduce back pressure and improve your exhaust flow. It's a no-brainer when think about spending $ modding your engine internals only to have them inhibited by a restrictive exhaust system.

A fairly good summation: http://auto.howstuffworks.com/question172.htm

 
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You need to consider two things. Headers can reduce low end torque.

Ground clearance may become an issue.

For the latter and for keeping a more stock look underneath I went with shorty headers. That will still give you the increased flow (save for a few tiny bits that you will only notice under race applications where you need the very last bit of power) but you can use a stock exhaust system behind them.

 
I have been thinking about this as well. I'm a ways off but was wondering if the shorties buy you much. Also, I'm worried about the whole system being compatible. I don't know what picking headers, pipes, and muffler from three different sources does vs. A complete tuned system. I would love to hear some comments on this.

 
I agree with all the comments. Main concern would be ground clearance especially if you have lowered the car. A good set of headers is a must especially if you want to ensure good fitment. I am partial to Hooker so that is the one I installed recently and was the first set that I put on the car back in 73. The Super Comp headers are much larger and give good performance but sit much lower to the ground. The Competition ones tuck in really good and you should not have any ground clearance issue with those. I had the Comp ones installed briefly and they sounded really good with no fitment issues with the exception of the header flange touching the tranny oil pan. I believe that this was because I installed a extra capacity oil pan that was thicker than the stock one. The exhaust collector angles in towards the tranny with this model. I got another set of Hooker Super Comp and again no fitment issues and the exhaust collector exists parallel to the drive train so no contact with the tranny oil pan. Not sure what the final ground clearance will be as I currently have the car on jack stands again. The shorty headers are also a good choice but I have no experience with them. Good luck on your decision.



I have been thinking about this as well. I'm a ways off but was wondering if the shorties buy you much. Also, I'm worried about the whole system being compatible. I don't know what picking headers, pipes, and muffler from three different sources does vs. A complete tuned system. I would love to hear some comments on this.
I have heard good reviews about the Pypes exhaust system so I decided to go with those. Not installed yet but they are sitting in the garage and the quality looks really good. I'll comment soon when I try to install them.

 
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Thanks for the input guys. I like the idea of using shortys but does not look like they are available for 351 4v Mach 1

 
You have to go too big on primary pipe diameter for the torque loss to occur. For example, 1 and 7/8 primary pipe on a Boss 302. One guess as to how I know this. Chuck

 
I am loving the Sanderson shortys. Did they swap out with factory manifolds and hook up to stock exhaust?? I hate to by ceramic and have to hack on them,

Thank you to all for your input!!

They are available

http://www.sandersonheaders.com/Sanderson-FC4-Ford-Cleveland-Header-Set-for-1969-73-Ford-Mustang.html

I'd opt for ceramic coating as it keeps some heat out of the engine compartment.

I agree with almost everything that has been said with the one exception being the loss of torque-it's a myth in my opinion and probably caused by a failure to tune engines and make appropriate jetting changes to a cars carburetor after header installation.
 
You have to go too big on primary pipe diameter for the torque loss to occur. For example, 1 and 7/8 primary pipe on a Boss 302. One guess as to how I know this. Chuck
this is true- huge primary pipes can reduce effective scavenging especially when the cam isn't matched to them.

Reasonably sized headers don't cause an engine to lose torque.

Most headers are appropriately sized these days . . . most

as to fit

I'm running hooker comps myself so I don't know. The Sanderson headers will probably require a muffler shop to make the down pipes I imagine-but that is not a big deal. They may mate to factory pipes-I'd ask Sanderson directly

 
I'll go counter to the group here. It depends on what you want... Headers make more noise and heat under the hood, end to rot out, require constant maintenance, have leaks and failed gaskets, require expensive fasteners to attempt to reduce maintenance, headers look cool. Iron manifolds are quieter, produce less under hood heat, are nearly maintenance free, cost WAY less and work well with the stock H-Pipe, unkempt manifolds look bad.

Maybe I'm way off here but it seems to me the mufflers will cause more of a restriction than the manifolds will. I'm not sure if the minor gains in performance are worth the headaches headers can cause. As with any system it's not just one component but the entire system. Headers with free flowing mufflers (loud) can be a performance benefit. Headers with quiet mufflers probably not so much. I need to make this decision all over again soon when I switch from the 351c to my 5.0 F.I. there are few good manifold options.

All this from an old racer who likes to cruise with the top down with a tame noise level. This is just MY opinion, no testing of the theory, no data, just many years of thinking and talking this stuff through.

 
As to the loss of torque: I am by far no tech guy and I have no numbers to back up the theory but I know of two Mustangs (a 71 coupe with a over bored 429 and a "Shelbyized" 66 Fastback with a 302) where you could feel the increase in low end torque after retrofitting stock manifolds.

The cars responded better to the throttle

As I said "feel"! No numbers to back up the theory though.


Oh, by the way: I will not contest or dispute what others have said above as I don't have the knowledge to do so.

Just stating a personal observation.

 
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The Cleveland exhaust manifolds actually work very well, and from information I have gathered over the years the performance gains for street vehicles will be minimal.

In reading a lot of posts about ground clearances for some brands of headers, stock may be preferred, squashed collectors will not help performance.

If you do decide to go with headers, get the ceramic headers and then wrap them to keep engine bay heat down, as well as help scavenging, and reduce rusting through.

When you install them make sure you support the collectors, so they will be as high as possible.

 
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