Thinking of going back to exhaust manifolds...

What kind of power loss should I expect going from Hookers to stock manifolds?

I think they would quiet my car down a bit, and help with the resonance issue. And not drag on everything...

Just a bunch of thoughts going through my head making me think stock manifolds may be better. I might do a little porting on them, but I doubt it.

 

I wouldn't bother with the porting. Plus, the two are significantly different, so there is also the question of if one side flows better than the other. The left side looks like a much better design to me, but you'll lose any positive effects of scavenging that long tube headers give you. I actually have been considering the same thing, more for heat control than clearance tho.

 

It would be easier to flip them over and plumb in a hair dryer...

 

You guys know my engine setup...So, what do you think my power drop would be if I went down to manifolds?

I am more concerned with torque, but most people talk HP. So, what do you think? 10, 15, 25, 50 HP decrease?

I could easily live with 10-20, but will stick with the headers if I lose more than that.

I only have 330-ish to play with as it is.

 

What about shorty headers....like the Doug Thorley that many of us have used?

 

I recently read 15-20 hp drop depending on the manifold. I am building a 5.0 with E7 heads, E303 cam and hi-po manfolds for my Mustang. I'm personally not a fan of headers on a street car. Some shorties are ok.

 

Don't take this wrong Scooper, but I really doubt the resonance issue is coming from the headers, more than likely from those POS mufflers you have, and let me guess, you have the turn downs just on the other side of the rear axle. All of the sound is being reflected from the pavement to the underside of the car..............how much sound deadening material do you have on the floor under the carpets?
IMHO if you would get a decent exhaust system you would cut the noise level by 20/30db, and not using FlowMaster junk would also make a huge difference.
As for HP loss, my guess would be around 30. Not sure if the old HiPro Style cast manifolds would fit, but they are about the best "Factory" style you can get for a SBF and you can buy them repro from a number of places.
I have had headers on almost every vehicle I've owned for the past 40 years and the only thing I can hear is the "Ticking" of the headers............as my exhaust always runs to the rear bumper even on my pickups.

 

I think you're right on most of this. IIRC Scooper has the extra-extra large exhast pipes. If he wants torque then 1-7/8' or 2-1/4" will give him torque. With fat exhaust pipes the temp is too low to flow and exhaust gasses will bottle up inside the pipe. The old HiPo manifold won't fit an early Falcon so I don't see them fitting a Maverick...I could be wrong. The 351W manifolds might be a better fit...again I could be wrong. If it was me I'd go with 2-1/4" pipe with Thrust Torbo and tail pipes past the bumper.

 

I have screwed with the mufflers, and I think the noise is from the headers.

Re-read all my posts. Yes, I have "drone-masters" on this car, but I have them on my truck, too, and it is quiet.

I think the headers is where most of my noise is coming from.

 

I had manifolds on a dual setup on a 73 and it droned more than what I nave now. One other thing to consider is the way the pipes are put together. If it heats up and gets in a bind, it is more likely to resonate.

 

Like I posted in another post. I am thinking of it like a tuning fork. I think they create sounds and it is greater at the longer straighter areas. I am thinking that maybe attaching some flat bar connecting the two pipes in a couple of areas to help dampen the resonence. If there was a piece of metal connecting the forks in a tuning fork, they wouldn't resonate near as much if at all.. Some strategicly placed hangers may also be something to consider..

 

Rthomas,

Guess I didn't realize the Scooper had sewer sized exhaust pipe on his car.
Since he is probably down 10/15hp because of using big pipe he may never notice the difference if he takes off the headers.............but probably will either way.
The only good hangers are the ones that are welded onto the pipe and isolated from the mounting point with a rubber donut or sandwitched rubber mounting. Take a look at th new factory dual exhaust sometime on the new Mustangs, Chargers.........etc.
So in a turndown system dumping behind the rear axle if you don't have at least 3 hangers per side after the header collector you will most certainly get some type of droning/resonating............etc,
If someone thinks that headers resonate/vibrate/drone................I suggest taking a look at what you have put downstream of the headers and how you have supported everything...........like those "drone masters" and if you have an X or H pipe placed in the correct place. Also, talking about Trucks....................not quite the same as a car unless you truck is a Looooooowwwwwwrider. I changed from the dreaded FlowMaster's on my 1 ton dually to some good mufflers and left the drone in the dumpster with the FlowMasters.....................IMHO

 

This is what I am sayin ... But along with tieing the tubes together with some flat bar along the long straights..

 

All else being the same I swapped from Flow Masters to regular turbo mufflers on my 455 powered GTO and the drone went away. I'll not run the FM's again but mostly due to the overpopulation of them on the street.

 

So Blugene.........are you talking about the headers and tying them together?
If so, it's not a really great idea, remember........the headers expand and contract and all the strength should be at the flange where it attaches to the exhaust port and the header/collector.
The only headers I have ever seen that were tied together are Zoooooomy's..............and the reason is vibration on those 8000hp motors.
If you have to tie the individual pipes together with some type of brace then they are not designed correctly.................IMHO

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