360 header gains?

[Zach1234]

360 bored .030 over, eq magnum heads slightly ported, edelbrock rpm airgap slightly ported, 10.7:1 compression .
Cam: 109 lsa
Duration @.050 239 242
Lift .562 .559
Currently have hooker headers 1 5/8 primary 3.0 collector.
Currently makes 440 hp 490ftlbs

Exhaust is 2.5. To rear diff exhaust is pretty good. Over the axle not so much. It is crushed bent. Some spots are crushed to 2 1/8. Instead of redoing it I am thinking of putting an x pipe in so each cylinder can take advantage of both pipes. Any estimate on how much the x pipe would gain? Read x pipes gain between 7-12 hp

Also thinking of getting 1 5/8 - 1 7/8 tti step headers any advantage of this over the hooker headers?

 

[a-bodyguy]

thats a 1ks bucks for not much gain 25 hp
1k bucks is a nice dual stage shot of spray 200 hp
shift@5500 with spray instead of of 6300 6500 live longer much faster

 

[33IMP]

My educated opinion only:
The expense of replacing your hookers with tti will not be justified. Maybe ten hp, so $100 each
The expense of an x-pipe will not be worthwhile. An H-pipe will accomplish 90% of any gain you would get from an x, be much cheaper and easier. You can keep the exhaust you have.
Engine masters did a test of crush bent pipes compared to same shape mandrel bent. They found zero hp loss from crush bent pipes.

 

[AJ/FormS]

My combo is very similar to yours except one size smaller cam, and my car has full-length 3" duals
When I installed my GearVendor overdrive unit, I had to cut the H out of there for room. Afterwards, rightaway I noticed a very significant loss of low-rpm torque. I tried every trick I could think of to get it back but no way.
My combo has a 4 speed, so what it took was a swap from the 2.66low trans to the one with the 3.09 low. By the math, that is a difference of 16%.
Now, I can't say the loss was 16%, only that the new low-gear felt a bunch closer to what I had before the loss of the H.
Obviously, if you have an automatic with a 3000 or more stall, this means nothing to your combo.

I agree with others.
Plus if it makes you feel better, by the time the exhaust gets to the tailpipes, it is a whole bunch cooler than it was at the head. So the gasses have condensed and now physically occupy less space, so the tailpipes can be significantly smaller than the headpipes.
A 3-pass muffler will suck a lotta heat out of the exhaust.
I wouldn't change a thing in your combo, unless your carb is sucking hot under-hood air. Fresh air, on mine, made a very noticible change in driveability
The reasons I have 3"full-length duals on my 360, is twofold;
1) they sound absolutely fantastic at WOT on the way to a 7200rpm shift. and
2) I was hoping that, because of the increased radiating area of the system, it would run cooler, which would help to ease back-pressure, which would allow a cam with a smaller overlap period, which would help fuel-economy, without sacrificing power.

 

[Mattax]

Any estimate on how much the x pipe would gain? Read x pipes gain between 7-12 hp

Also thinking of getting 1 5/8 - 1 7/8 tti step headers any advantage of this over the hooker headers?

The X-pipe may or may not help. There's diffent flavors and diameters. Depending on where in the exhaust it is located it may help at certain rpms, and it might help share or may just be a disruption in the flow.
Off the top of my head, I know the placement for an H pipe using pipemax usually works out to roughly 20" after the end of primaries.
I would not worry about 2 1/8" tailpipe after the muffler if that is the only damage. If its a sharp turn right at the muffler or crushed right there, then get it redone.
Got two things going on.
One the exhaust is cooling off as it progresses through the system. Mufflers abosrb a fair amount of energy themselves (turns into heat). With the drop in exhaust density a smaller diameter is fine.
Second, at low rpm the smaller tailpipes will keep velocity up. The better the velocity, the less atmosmopheric pressure can effect the exhaust pulses.

The step headers might help with reversion at low rpm, and they might help in the upper rpms but no guarentees.
You could run the numbers in pipemax for a ballpark estimate.

 

[340six]

There was an Engine Masters episode that Dyno runs of crush vs mandrel was no diff.
In your power level on street car good flowing cast manifolds are fine.
What Pypes says of their test show that the X Pipes give more Lower End Torque and H gives more Top.
But am betting that in street level HP and TQ apps does not matter.
I think the main thing is the X will change the sound and have diff sound than the H.
Some guys dislike (hate) the X Sound over the Sound of H pipe.
I grabbed the X as the H was out of stock. As things would have it I still never put the new stuff in use.

 

[RustyRatRod]

360 bored .030 over, eq magnum heads slightly ported, edelbrock rpm airgap slightly ported, 10.7:1 compression .
Cam: 109 lsa
Duration @.050 239 242
Lift .562 .559
Currently have hooker headers 1 5/8 primary 3.0 collector.
Currently makes 440 hp 490ftlbs

Exhaust is 2.5. To rear diff exhaust is pretty good. Over the axle not so much. It is crushed bent. Some spots are crushed to 2 1/8. Instead of redoing it I am thinking of putting an x pipe in so each cylinder can take advantage of both pipes. Any estimate on how much the x pipe would gain? Read x pipes gain between 7-12 hp

Also thinking of getting 1 5/8 - 1 7/8 tti step headers any advantage of this over the hooker headers?

You MIGHT see something on a dyno. Might not. Certainly not enough to even feel in the seat of the pants. If you're just looking to dump a grand, just send it to me.

 

[273]

360 bored .030 over, eq magnum heads slightly ported, edelbrock rpm airgap slightly ported, 10.7:1 compression .
Cam: 109 lsa
Duration @.050 239 242
Lift .562 .559
Currently have hooker headers 1 5/8 primary 3.0 collector.
Currently makes 440 hp 490ftlbs

Exhaust is 2.5. To rear diff exhaust is pretty good. Over the axle not so much. It is crushed bent. Some spots are crushed to 2 1/8. Instead of redoing it I am thinking of putting an x pipe in so each cylinder can take advantage of both pipes. Any estimate on how much the x pipe would gain? Read x pipes gain between 7-12 hp

Also thinking of getting 1 5/8 - 1 7/8 tti step headers any advantage of this over the hooker headers?

At this level dollars per gain of hp generally goes up and harder to get big # increases.
490 lbs-ft is it a 3.58" stroke? If so that's pretty impressive

 

[Oldmanmopar]

Mufflers make a big difference . I ran Bullit style with an H pipe here it is shifting at 8000. mid 10's. Sounded much better in the car.

 

[Mattax]

A BIG factor in sizing the tubing is the rpm of the power band.
and the rest of the combo makes a difference too
If one is setup for 1/4 mile racing like oldmanmopar just illustrated, then the rpm through the lights is going to be at or near the end of the rpm of max power.
If one has a car set up with street gearing, then through the lights is often far below that rpm.

 

[Oldmanmopar]

The engine was a High RPM built 686 lift solid roller. gears were 456 . If you listen the car ran most of the quarter in Low and second. with 456's. The car had no torque without the mufflers, Top rings were shot so compression was low. Car was heavy,

 

[MopaR&D]

I'm guessing you have the exhaust necking down from 3" to 2.5" right after the collectors? Try this... run 3" pipe off the collectors at least 2 feet back THEN have it go down to 2.5".

Having the diameter change right off the collectors kills the mid-range scavenging effect of the secondary portion of the headers. From where the primaries meet at the front of the collector it needs to be consistent diameter at least a few feet back.

This is also the main reason why running open headers with no collector extensions loses power, same effect.

 

[Mattax]

I'm guessing you have the exhaust necking down from 3" to 2.5" right after the collectors? Try this... run 3" pipe off the collectors at least 2 feet back THEN have it go down to 2.5".

Having the diameter change right off the collectors kills the mid-range scavenging effect of the secondary portion of the headers. From where the primaries meet at the front of the collector it needs to be consistent diameter at least a few feet back.

This is also the main reason why running open headers with no collector extensions loses power, same effect.

That same 18 to 22" from the end of the primary to the H-pipe can be used for collector length. Its a disruption in flow so from the harmonics same length.

 

[MopaR&D]

That same 18 to 22" from the end of the primary to the H-pipe can be used for collector length. Its a disruption in flow so from the harmonics same length.

Agreed. I'm just making the point that for it to work to its best effect the pipe diameter has to stay the same for that full 18-22" length of the collector. It's also possible to gain a little more bottom-end by making them even longer than 22".

When I get around to putting Doug's headers in my Duster in place of the Hedman shorties I'm going to redo the exhaust so it's 3" off the collectors all the way back to maybe 4-6" ahead of the mufflers and then have it go down to 2.5". I want to leave some length of 2.5" pipe ahead of the mufflers in case I decide to put in an H-pipe. I have an X-pipe now and I'm tired of the sound, too similar to modern muscle cars. I want that THUMP THUMP THUMP not just a BrrRrrrRrr if that makes sense lol

 

[crackedback]

Any claims that one set up is better than another, X, H, no crossover is ALL combo dependent.

What works on one build may not work as well on a different set up when it comes to exhaust.

 

[rumblefish360]

The X-pipe may or may not help. There's diffent flavors and diameters. Depending on where in the exhaust it is located it may help at certain rpms, and it might help share or may just be a disruption in the flow.
Off the top of my head, I know the placement for an H pipe using pipemax usually works out to roughly 20" after the end of primaries.
I would not worry about 2 1/8" tailpipe after the muffler if that is the only damage. If its a sharp turn right at the muffler or crushed right there, then get it redone.
Got two things going on.
One the exhaust is cooling off as it progresses through the system. Mufflers abosrb a fair amount of energy themselves (turns into heat). With the drop in exhaust density a smaller diameter is fine.
Second, at low rpm the smaller tailpipes will keep velocity up. The better the velocity, the less atmosmopheric pressure can effect the exhaust pulses.

The step headers might help with reversion at low rpm, and they might help in the upper rpms but no guarentees.
You could run the numbers in pipemax for a ballpark estimate.

I'm guessing you have the exhaust necking down from 3" to 2.5" right after the collectors? Try this... run 3" pipe off the collectors at least 2 feet back THEN have it go down to 2.5".

Having the diameter change right off the collectors kills the mid-range scavenging effect of the secondary portion of the headers. From where the primaries meet at the front of the collector it needs to be consistent diameter at least a few feet back.

This is also the main reason why running open headers with no collector extensions loses power, same effect.

Any claims that one set up is better than another, X, H, no crossover is ALL combo dependent.

What works on one build may not work as well on a different set up when it comes to exhaust.

Top replies!!!!!

I’ll add…… the header ends at the collector which should have an extension of the same size on the end to increase low end torque. It may or may not have an effect on top end HP. It is a very much so a combination dependent thing. While experimenting at the drag strip will cheaply tell you what’s working, the expensive dyno will show you very quickly what’s best.

Once the length is known for the collector extension, a torque cancellation box is recommended and then into the rest of the exhaust piping. I myself would not go down in size but it is possible there will be little to zero effect, again, very much so,
Combo dependent!