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Yes,, here at least they measure the outside diameter,,, but of course the engine sees the inside diameter.... and usually the wall thickness is around 1/16'' so the engine sees pipes that are 1'8'' smaller and I always count the inside diameter when calcing for pipes although it is "wrong" lol
 

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Discussion Starter #3
Yes,, here at least they measure the outside diameter,,, but of course the engine sees the inside diameter.... and usually the wall thickness is around 1/16'' so the engine sees pipes that are 1'8'' smaller and I always count the inside diameter when calcing for pipes although it is "wrong" lol
So now im wondering, would a 2-3/8" header be better for my 555 or 2-1/4"???
 

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So now im wondering, would a 2-3/8" header be better for my 555 or 2-1/4"???
You can debate one size over the other and IMO as long as they are not to small. With all the testing I have done with headers, 90% comes down to the collector and more specifically the choke size...

Nick
 

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I ran 1 and 7/8 stepped to 2” stepped to 2 and 1/8th with every engine I ran the last 23 years, with a choke down, then 3 and 1/2” collector, merged. And all ran well. And I truly don’t know shit about headers. It just sounded good to me.
 

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I ran 1 and 7/8 stepped to 2” stepped to 2 and 1/8th with every engine I ran the last 23 years, with a choke down, then 3 and 1/2” collector, merged. And all ran well. And I truly don’t know shit about headers. It just sounded good to me.
All on engines under 300” from 23 degree, to the Dart/Buick.
 

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Discussion Starter #7
You can debate one size over the other and IMO as long as they are not to small. With all the testing I have done with headers, 90% comes down to the collector and more specifically the choke size...

Nick
Its a pulling truck application. Its wide open all the time. According to the port dimensions, the 2-1/4" should work. Collector size will be 4". The headers are schoenfeld fender well exit, formerly Stahl.
 

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Not sure I would build exactly that but I have done quite a few strong pulling truck sets and they dont always stay at the top of the RPM....the header plays a key role in a few different places..... one, when the wheel speed needs to get at its peak and also when the box hits the the back of the truck, it will need to be able to recover.... quite a few things go into a pulling truck header for sure... not just one size and choke size...
 

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Discussion Starter #10
If you are making around 950 to 1000hp at around 7200 rpm something like 2.375x32 4.500x16.5 will work. If you are 1050 to 1100 at 7800 then go 2-3/8x8, 2-1/2x19, 5x13.5, this will get you close.
It made 936;@ 6500
 

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I roughed it into pipemax and this is what it output.

--- Single Primary Pipe Specs --- for 554.429 CID from 4500 to 7000 RPM
Diameter= 2.045 to 2.170 Length= 29.2 to 31.8 inches long
--- 2-Step Primary Pipe Specs ---
1st Dia. inches= 2.045 Length= 14.6 to 15.9
2nd Dia. inches= 2.170 Length= 14.6 to 15.9
--- 3-Step Primary Pipe Specs ---
1st Dia. inches= 2.045 Length= 14.6 to 15.9
2nd Dia. inches= 2.170 Length= 7.3 to 7.9
3rd Dia. inches= 2.295 Length= 7.3 to 7.9

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3.717 to 3.967 Tuned Lengths= 16.7 best and also 8.4 or 33.5


Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness


Here's pipemax's customer dyno thread, you can check out some the builds there that might help you make a choice.

 

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Can you work "backwards" with Pipe Max to come up with cam specs ?

Specific size engine, RPM range, target HP, head flow information, intake and headers to be used and get a range of cam specs from it ?
 

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I haven't ever seen A BB port that was bigger than 2.25" tube. Step every ten inches and run to about 28-30 inches long for that RPM. So two steps, 2.25-2.375-2.50. 3.5" collector is enough.:)
If a 2 1/8 is bigger than the port, would you start with that?
 
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