• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Header Primary Tube Size?

robinsonwr

Well-Known Member
Local time
1:42 PM
Joined
Feb 21, 2011
Messages
467
Reaction score
62
Location
Carriere, ms
I'm currently building 512" 440 with the following specs: CH4B Dual Plane, CNC Stealth heads, 11:1 compression, mid 500 lift hydraulic roller(XR286HR Comp Cam). My question is since this will be primarily a street car would an inch and seven/eight primary tube alright for this build or do I need to step up to a two inch primary?
 
I don't understand building a big engine with good heads and then choking it with a CH4B intake......if you're going to use that intake, then yeah...the 1 7/8" will be fine.
 
I would go with the larger tubes on a big motor like that. Lots of air being pumped out.
 
check out these specs..this might be useful
 

Attachments

  • exh.jpg
    exh.jpg
    22.2 KB · Views: 653
  • eh2.jpg
    eh2.jpg
    21.3 KB · Views: 647
A good rule of thumb is about 1/8" larger than the exhaust valve because the effective diameter of the pipe is smaller as some of the flowing gas sticks to the wall of the pipe. This is called the boundary layer. If you have 1.81" valves than a 2" primary should do nicely.
 
What's the CH4B going to do to the flow going in? If you can't get the air and fuel in, then there's not much of a need to have large tube exhaust imo. But go with the large tubes in case you see the CH4B isn't a good choice.....
 
Cranky,
My first choice was a set of hi-po manifolds. The reason for the CH4B is because it resembles a factory intake when painted turquise. I am still looking for a Weiand Action + because it was supposed to a service replacement intake for the cast iron RB manifold. The headers will help from killing to much power and still look fairly stock under the hood.
 
The CH4B isn't terrible. Dick Landy ran 11's with one in a 69 Charger back in 69. I personally saw a difference of .4 secs and 4 MPH between a DP4B and a Torker on my 383, with the Torker being the quicker/faster of the two. I will say that was not a fair manifold test as I ran a 750 Holley on the Torker and a factory 440 AVS on the DP4B. My goal was not to test intakes but the complete induction system from a "race" set up vs. a smog passing "legal" set up. A better dual plane is the Eddy RPM but it doesn't look stock.

My current 440 is running the factory iron intake with 2" primary headers and I'm running low 13's on street tires and 3.55's @ 109 MPH. I think the key is to not over cam the somewhat restrictive dual plane. I'm running the MoPar .455" / 272 cam with 10.1:1 CR.

If you decide you don't want your CH4B I'll buy it! PM me.
 
You have to be careful not to go too big on primary tube size because you have to keep the velosity of the ex. pulse up. If it dies in the tube air will tend to stack and actually kill the flow. That is why I was wondering what your port size was. Also a good way to find out what you need is to run your numbers through the Pipemax software it is a good starting point, and is what we start with when building for a new combo
 
It's not so much the 1 7/8 primaries as it is the small 3" collector on 1 7/8 headers. Cut off the 3" collectors and weld on some 3.5" pieces and you're good to go.
 
I use to kind of think the bigger the better on header tubes to an extent, it's not completely true, at all... With several engines 479ci 493ci 511ci tested on a dyno heads were Eddy RPM small chamber Ported w/2.14"int & 1.81"ext, the 32" long 1-7/8" w/3" collectors & a 20" extension 1-7/8" diameter primary tube out performed the 34" long 2" w/3-1/2" with 20" extensions, across the board HP/TQ, until I went to the Max Wedge Stage VI CNC ported w/2.25"int & 1.81"ext & Eddy Victor Max Wedge port configuration then then the 35" long, tuned tubes w/2" "step headers" w/3-1/2" collectors & 18" extensions performed better than the 34" long, tuned tubes w/1-7/8" "step headers" w/3" collectors & 18" extensions... I would have never believed it! if I hadn't seen it for myself! I'm not going to go thru all the numbers, but it was a decent change between the two styles & diameters of tuned & non tuned tubes & collector sizes & styles... You can't just say this 1 tube size fits all, or is what is needed, until you see what the effect is with the correct diameter tube size, style & length open or thru full exhaust or just a extension can make the world of difference especially in TQ #'s... The earlier statement about volume of air & the least amount of reversion dead heading exhaust gases & being maintained thru out the tubes is the main reasoning for the smaller diameter tubes & the stepped tuned tube working better than just throwing on large diameter tubes willy nilly.... J M H O ...
 
Budnicks you are right on. Now I'll toss out another thing to think about. Try some of your tube combonations and primary lengths with different sizes of merge collectors. And you also touched on the other key part of this which is the stepped primary tube. I have more but will let you all chew on that for a while.:)
 
Guys,

this is a good discussion for someone seeking max power and torque numbers, but the application referenced above is for a car that is primarily street driven, which based on the stout engine Robinson is using, not many street tires are going to handle well any way.

Since headers are (nowadays) a big investment, I'd recommend going with the 2" primary to give you a platform that can support future upgrades - like larger flowing heads, induction, carbs, etc, however, if finances are a concern - I'd run whichever one fit my budget. I've ran them both over the years, and the 1 7/8 primary did seem to pull (a little) harder on the bottom, but then the 2" pipes pulled great through the mid and higher rpm range.

From a purely street (driven) perspective, I doubt you could feel the difference, as both will run just fine - especially with 500 cubes on tap. Also, MeepMeep is correct; the typical line of thought is 1/8" larger than your exhaust valve, which means either will work just fine.

Anybody out there remember, just a few years back, that we used to have the same conversation about whether or not to run a 1 7/8 or 2" primary with....our 440's ? With 500 + cu. in. being the norm nowadays, you'd think the discussion would center on 2" primaries or larger ?

Again, just my personal experience. Good discussion guys.

Southernman
 
i noticed a BIG difference going from my Hooker Super Comps (2" primary into 3 &1/2" collector) to the Hooker Comp 1 & 7/8"---better low end & mid range for the Comp's --lost my top end...but my Super Comps---they were just awesome all around--low-mid & top----but,.i am comparing this with my 498-with a 8.71 & dual 1150 HP dominators.....so actually my opinion would be,.ditch the CH4B.. bolt a Edelbrock RPM on (love the Thermoquads) & go with the 1 & 7/8" headers.. its a street machine remember.....i built a guys 1968 Polara (2-door) 383 magnum used 9.8:1 compression pistons-M.P. 484/284* cam--906 heads ported & bowl work with 2.14 & 1.81 valves 2,200 stall--3.91 gear,.2 &1/2" exhaust clear to the rear bumper--(used Hooker Aero chamber mufflers also)--its a big car,.but it gets up and boogies & runs side by side with these 5.slows around town...so thats my personal experience---sorry soo long a story--but figured its useful info..as headers are now a friggin fortune investment anymore...good luck
 
P.S.---i had not such good results using the CH4B---it was like ,.felt no different power wise compared to a factory 4bbl. intake other than it was aluminum...i really am impressed with the RPM intake (dual plane)---off idle to 6,800 rpm it pulled hard...just my opinion though-- others here with way more knowledge than me may chime in & see if i have put ya on the correct train of thought....
 
Budnicks you are right on. Now I'll toss out another thing to think about. Try some of your tube combonations and primary lengths with different sizes of merge collectors. And you also touched on the other key part of this which is the stepped primary tube. I have more but will let you all chew on that for a while.:)

I would agree 100% even if it's a street car with street tires you want to get the best for your dollar spent "every freaken dimes worth of power" & especially torque with these heavy B-Body cars... I did touch on the extension subject some it really makes a big difference with open headers or cut outs, also there is the placement of the X or H pipe on full exhaust is equally important, especially to get everything out of your street car combo, most will just throw them in willy nilly not were they will actually help, They need to be installed were the heat level drops off in the pipe to keep the exhaust pulses from causing reversion in your pipes & killing HP/TQ, the effect is it will actually help draw or create a vacuum or at least low pressure area in the exhaust somewhat pulling gases out of the tubes.... I didn't comment on the mas multitude of collector types including try y's & blended styles or even 1's with reversion cones & extended lengths, it seems nobody wants to listen to what really works they just go with the old school Wives Tales theory on performance from an earlier era that bigger is always better, it really isn't better 99% of the time, unless maybe it's a full on all out race car, well you know I guess that's just my opinion... Good luck to all...
 
If the main concern is cost for only street driven then by all means I would go with 1 7/8. less problems melting things, fit better, spark plugs and wires, and so on. With that said, if you are planning fo the future, you should think about spending a little more up front insted of just setteling for good enough. I have often wondered why people spend tons of money on the motor and put a $200 header on it.

Best of luck with your project, and remember it will never be finished:)
 
1-7/8 Hookers fit good on my R/T. R/B with power steering and power brakes. I think the smaller header will help build more torque down low. I went with the 1-7/8 because I need all the torque I can get. 3900 pound B-Body and 3.23's....

Michael
 
Auto Transport Service
Back
Top