Should I build some new headers?

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F-BIRD'88
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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 11:27 am

Instead of a round tube side pipe what about a oval shaped outer side pipe with the three internal perforated pipes set side by side within that oval side pipe. Wider but more ground clearance.
Better configuration for the wrap material to absorb the sound. The longer the side pipe the deeper the tone should be. Get the exit end of the side pipes Behind your ears.
Ultimately a under the car full dual exhaust system with turbo mufflers and exhaust exit at the back bumper is just better.
that's quite the Machine. You are quite the fabricator guy.... right on.

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 11:56 am

Re: the Oval shaped side pipe with 3 internal perfed pipes.
3 2" internal perforated pipes within a oval outer pipe has the same flow area as a 3.46" (3 1/2") round pipe does.
The oval shaped outer pipe with the 3 internal pipes might be 6.5" x 2.5"

or the three 2" pipes in a round pipe might be 5" round or so.

3 1-3/4" internal pipes is the same flow area as a 3" pipe which is plenty big
Allows a 5.75" X 2.25" oval side pipe or a 3.50" to 3.75" outer diameter round side pipe.
The smaller 1-3/4" x3 inner perforated tubes will be quieter. 3" of effective pipe flow is plenty.

Someone smart will tell you whats the best internal muffler material for this.
I'd make the side pipe as long as possible, exiting right at the rear tire

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 12:28 pm

See the radius at the red arrow... I'd repeat it a the green arrows on the door.
i'd put a smaller corner radius on the hinge corner of the door too.
I'd make the side pipes extend back as much as possible yellow arrow.
This would hid the gap between the rear tire and the rocker too.

I 'd consider shortening the length of the bottom of the door skin too..Say 1" shorter and with corner radii.
It will clear the side pipe better and look better too.
A better appearance. it is not too late to do these with the body still not painted.
Cool car.
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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 1:10 pm

This the kind of custom built street car where you can be creative.
Consider adding a Dual 4bbl carb adapter and 2x600 or 2x750 Edelbrock AFB carbs to that single 4 bbl Air gap
dual plane intake.
On that car it would look really smooth with the 2x4's on a adapter. It will add about 2.25" to 2.5" to the carb height. A suitable fabricated 2x4 carb scoop will finish the look... With the XR mechanical street roller cam change and the 2x4 carb induction you will see the smooth, progressive EXTENDED powerband and rpm capability.
The Edelbrock dual quad carb linkage setup allows smooth PROGRESSIVE carb throttle action.

Optional on the inside of this dual car adapter you can add a internal removable plenum divder plate.
This divider plate isolates the right and left sides within so that the 2x4 carbs see a strong signal from the dual plane Air Gap intake manifold. This plenum divider keeps the carb(s) signal strong for crisp responsive driving and throttle response yet the 2x4 carbs really howl on the throttle with a big (and extended) top end. You can make this divider plate extend into the air gap intake manifold plenum to fully divide the 2 planes in the plenum. On a dual plane manifold that has 2x4 carbs you don't need a open plenum.
A full divided plenum is what makes the throttle response in the critical street driving rpm range Very crisp, sharpe and responsive.

The engine will hang in there on the top end MUCH BETTER.
You will love the dual quads on that motor. If you can tig weld you can make your own custom 2x4 carb adapter...Or you can buy it from BDS blowers. SAME SAME.
You'll have the STREET ROD hi perf BBC motor you wanted.
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Re: Should I build some new headers?

Post by GRTfast » Mon Oct 23, 2017 1:45 pm

Those are all great ideas. I really like the idea of multiple small perforated pipes in a single side pipe muffler. Three in a triangular arrangement could be really neat and effective.

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 2:09 pm

I have a variation on that theme that is 2x 1-3/4" pipes + a 1- 1/2" pipe arranged within a D shaped outer pipe.
say 4" by 3" D shaped side Pipe. The internal effective pipe size of the 3 pipes is 2.90". Plenty big .

The flat side of the D pipe goes against the car body. The D shape profile is made with a half of a 3" round pipe welded to a C shaped half . 4" tall. Do you have a sheet metal brake.

This shape allows close mounting and more effective room for the stuffing maternal and a smaller profile.
Yet 2.90" effective pipe diameter. The odd pipe size will help avoid internal resonance noise.

1-3/4" and 1- 1/2" exhaust pipe is pretty common stuff.. The transition cone will have the be hand formed.
Somebody smart will tell you how big to drill all the perf holes in the 3 pipes.
the outer D pipe could be 3.75" x 3" or 4" x 3"....

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 2:52 pm

Cover the ( D shaped profile) side pipe with a Aluminum slotted (could be louvered slots) side pipe heat shield.
Make the heat shield ( leg protector) 2 layer ply with a small air gap between the 2 plies and between the shield and the side pipe. The shield must not touch the side pipe. Mount the shield to the car body so it "cages" the side pipe and is removable for cleaning and servicing the side pipe muffler.
The 2 ply slotted heat Shield with air gaps will be MUCH COOLER than the hot side pipe.
Avoids burned pants and skin. Gives it a real finished look too.

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 3:13 pm

Just looking I'd drop the back of the transmission a hair lower. Just spacer the transmission cross memeber down a bit more. This will tilt the engine back in the chassis and make the carb pad more level and the headers/side pipe will drop down a hair too . More pipe clearance at the (open) doors bottom.
you can re-correct the drive shaft U joint angles (180 degrees inclusive) by raising the car ride height a hair at the back axle. So the 2 drive shaft U joints are in phase. The engine is a bit too level in the chassis. The oil pan and the transmission pan and the carburetor (s) will function better.

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Re: Should I build some new headers?

Post by GRTfast » Mon Oct 23, 2017 3:38 pm

Man, thanks for all the ideas and info. You are right about the flatness of the engine. I could be dropped a little in the rear for sure. I love the D pipe idea too. Hand forming the transition cone is not an issue, I have a slip roll, shrinker stretcher, and an English wheel. All good food for thought. I really appreciate it.

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Re: Should I build some new headers?

Post by F-BIRD'88 » Mon Oct 23, 2017 4:46 pm

Another thingy that you can employ to tame the exhaust is to put one of those round case high performance hi flow mini catalytic converters in the side pipe or right in the header collector.
These big 3.5" in out round cats have a noticable effect on the exhaust sound yet add minimum restriction or power loss. It goes between the collector and the 3 perfed pipes.
Carsound ( Magnaflow Mufflers) has them. Works in combo with the muffler.
They also burn off unburned hydro carbons in the exhaust so they do create HEAT.
The heat is only excessive if the carb (s) are not setup correctly. When the cars are right the cats function as designed. They want a 14.7:1 afr at cruise to work. Over rich cruise jetting is to be avoided.
A effective sound modfiier/reducer with minimum restriction. Many many small flow tubes in a big honeycomb.
You'll be doing your part for the environment too. As long as the carb jetting is not all out of wack there is no down side to using these in your side pipes to tame the sound.

The comp CB XR274R-10 cam (K11-770-8) is a better choice with these in the exhaust.
You really need to ditch that "rabbit cam"...

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Re: Should I build some new headers?

Post by GRTfast » Mon Oct 23, 2017 5:31 pm

"rabbit cam"..."thumpr".. I get it!!! :lol:

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