Header question for a 950 hp bbc

[gnicholson]

I'm trying to build some headers for a 532 70chevelle. Going with 2.125 2.25 2.375 step headers . Optimum pri length is 25.5 inches. My problem is 29 to 30 in is about as short as I can package in this thing unless I built some kind of fenderwell header. I know fitment in a stock vehicle is a huge compromise. I'm just trying to figure out if there is a better way to go about this. I'm between 28and 31 on the left side. I know the general consensus is primary length isn't as important as a collector dimensions and the diameter of the primaries. Just thought I'd get some opinions

[hoffman900]

RPM is going to dictate length.

Out of curiosity, where did you get the diameters from? World of Outlaw Sprint cars are making that power from 410ci with stepped headers starting at 1 7/8”.

[gnicholson]

The dimensions are from burns stainless but this is pretty std recommendation. This engine was down 30 hp with my old 2.125 headers compared to the 2.25 to 2.375 dyno headers with a 4.5 collector. More interested in how other guys have been able to get short primaries in these cars

[englertracing]

Run some at 28 and some at 31....

[englertracing]

RPM is going to dictate length.

Out of curiosity, where did you get the diameters from? World of Outlaw Sprint cars are making that power from 410ci with stepped headers starting at 1 7/8”.

Some even run a couple inches of 1.750" first

[maxracesoftware]

RPM is going to dictate length.

Out of curiosity, where did you get the diameters from? World of Outlaw Sprint cars are making that power from 410ci with stepped headers starting at 1 7/8”.

Some even run a couple inches of 1.750" first

you cannot make a true or fair comparison of a relatively lower Compression Ratio
BBC 532cid with 950 HP running on Race Gasoline
-to-
a 410 SBC 16:1 , maybe even up to 18:1 CompRatio in some Combos,
running on Methanol

the 410cid 16:1 Methanol injected Sprint Engine
will require a overall smaller Tube and Collector diameters
and also require overall shorter Tube and Collector lengths .


Header Tube and Collector Specs "Trends"

Exhaust Gas Temperature ( EGT )
has a huge overall effect on the entire Exhaust System !
EGT sets up the Speed of Sound FPS + temperature gradient thru the entire Exhaust System !

Compression Ratio effects
Low Compression Ratios : ( High EGT's )
= Larger Tube + Collectors , and Longer Tubes + Collector lengths

High Compression Ratios : ( Low EGT's )
= Smaller Tube + Collectors , and Shorter Tubes + Collector lengths


Fuel Effects
Gasoline -vs- Methanol
Gasoline will have higher EGT temps than Methanol
so that Gasoline Engine will have slightly larger Tube + Collector diameters
and slightly longer Tubes + Collector lengths -vs- Methanol Fuel


EGT Effects
Low EGT's :
= Smaller Tube + Collectors , and Shorter Tubes + Collector lengths

High EGT's :
= Larger Tube + Collectors , and Longer Tubes + Collector lengths


other Effects are :
Header / Exhaust System Coatings, Tube Material, Wraps, Tube thickness