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Header diameter size?

Propwash

Propwash

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Hey fella's,

Trying to dial in the appropriate header diameter for the wife's Dart

340 (punched 40 out), 10.5:1 Comp, Zero Deck, .040 Gasket
Closed Chamber 63CC Edelbrock Performer RPM Heads (Ported), Howards double valve springs-Open seat pressure 353@ 1.1
Howards Cams Solid flat tappet 254/260 [email protected], 550/555 Lift 108LSA
Edelbrock Dual Plane Air Gap intake (port matched), 1" Phenolic Spacer
Quickfuel 750SS MecSec
Rear 3.73's, 28" tall tire
4 speed
Guessing rest of exhaust will be 2.5" H-Pipe
Street/strip with primary street application

Just looking for the best diameter for scavenging/breathing. I know going too wide or going too narrow can make quite a difference, so just trying to get advice on what may be the best DIA.

Thanks for your time.
 
Normally, small block header tubes are 1 5/8" dia, but in this case, I would think 1 3/4" would be appropriate.
 
On similar builds I have used the Hooker Super Comp headers at 1-3/4.
I have not tried them against the tti headers which are of course, stepped and may have a good advantage on the street.

I normally run 360's and a 4spd.
 
Diameter is not the only consideration. Tube length as well as collector size affect the exhaust scavenging, rpm for peak hp, rpm for peak torque, etc. . Get those specs from any headers you're considering, and match the closest to your combination & intended use.
 
A rule of thumb is 1/8" larger than the exhaust valve head diameter to deal with the boundary layer inside the tube. The 108 LSA cam will make this an upper mid range to high RPM screamer so assuming the 1.6" valve the 1.75" primary pipe should be a good fit. Even if the valve is slightly over stock the 1.75" pipe won't kill you.
 
WileERobby said:
Diameter is not the only consideration. Tube length as well as collector size affect the exhaust scavenging, rpm for peak hp, rpm for peak torque, etc. . Get those specs from any headers you're considering, and match the closest to your combination & intended use.
Click to expand...

Meep-Meep said:
A rule of thumb is 1/8" larger than the exhaust valve head diameter to deal with the boundary layer inside the tube. The 108 LSA cam will make this an upper mid range to high RPM screamer so assuming the 1.6" valve the 1.75" primary pipe should be a good fit. Even if the valve is slightly over stock the 1.75" pipe won't kill you.
Click to expand...

Thank's Gent's! Appreciate it. I got a killer buy on an older set of 1 3/4 A-body Headers off Craigslist several months back...$30! Just needed a little bit of welding around a couple flanges, sand blast and a ceramic dip. I was hoping to use them. Sure beats spending $300-700.

You're right Meep....The Eddy heads just incorporate the universally popular small block 2.02/1.6 valves


One more question for you guys, and off subject a tad. I wanted to go dual plane with the intake for response & moving the torque peak RPM a bit lower & possible gain. Would it be wiser to go the single plane route being the powerband on the cam, or can I try and find a happy medium with a taller riser under the carb (if that will even dynamically make any kind of real diffrence)? I plan on going with the AAR six pack hood for this car, so should gain the extra headroom.
 
Stick with the rpm for now. Considering your gears and tire size, it'll be what you'll want and like on the street. I currently have a Comp .525 solid cam that is slightly shorter in duration. Also running a 4spd $ 4.10's in my 360 Cuda.

I'll shory be making a change to a 6pack and AAR hood. As well as heads and cam.
 
In my experience running the 108 LSA cams the single plane works pretty well. But perhaps these days with the free flowing dual planes you might be OK with an air gap or something. The tighter the LSA the higher the peak torque but it happens at a higher RPM. If you want better low end and overall drivability put in a 112 - 114 LSA cam.
 
Hey thanks Gent's! Again, I appreciate it. Sounds like I'll go ahead and go with the D/P. If I can score a used/cheap single plane off craigslist or something, I'll pick that up too. If possible, I'd like to swap them around when I take this engine to dyno, just to see what happens. Gotta say, a dyno's probably some the best money spent when it comes to grabbing more HP/TQ. Obviously the tuning qualities are huge. Spent 8 hours, 10 pulls, learned a lot and had a blast when my 512 was at dyno.

Anyways, thanks again guys. You guys here always steer me in the right direction with your experience/expertise. You've help make my Mopars definitely have quite the edge, compared to someone just "lone-wolfing" a build.
 
Prop....I'd go with either 1 5/8 but not larger than 1 7/8"...IMHO. Oh, BTW, you steer us in the right direction as well. You have been a big help with my car but more importantly, with my friends 69, like yours
 
rrTor-Red said:
Prop....I'd go with either 1 5/8 but not larger than 1 7/8"...IMHO. Oh, BTW, you steer us in the right direction as well. You have been a big help with my car but more importantly, with my friends 69, like yours
Click to expand...

Thank you sir! I appreciate it!
 
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