exhaust diameter and length requirements
 

there's been a few threads asking about exhaust collectors etc. i have a pipemax program that is pretty accurate for predicting exhaust requirements. what i propose is a list of a few of the popular engine requirements so everyone can have an idea of what they need. engines should probably be in the 10 or 11-1 comp range and representative of something that can run on pump gas.

how about a 347, 408, 427w, 427or 428fe, and one of them monster motors made out of the 428 block.

info needed

bore size, crankshaft stroke, rod length, peak hp rpm, comp ratio

intake data: valve head diameter, valve lift, dur. @ .050, degreed centerline, lca

exhaust data: valve head dia., valve lift, dur. @ .050.

there is an input for exhaust port centerline from face of the exhaust valve to mating surface of the exhaust flange, i'll use 3.2 unless somebody has this number, so length requirements of the primaries will be approx.

Is this just for headers build data or entire exhaust system? I'll take a chance it's for complete exhaust system as I have to figure out how to fit undercar exhaust and tailpipes on my ERA. I don't need to be trying to fit any larger dia. pipes under there than I have to.

bore size (4.145), crankshaft stroke (4.25), rod length (6.70), peak hp rpm (around 5300 to 5500 - very flat), comp ratio (9.0)

intake data : valve head diameter(2.09), valve lift (.563), dur. @ .050 (231), degreed centerline (108 intake cernter line), lca (lobe separation - 112)

exhaust data: valve head dia. (1.65), valve lift (.575), dur. @ .050. (236)

Thanks

Dan

--- Single Primary Pipe Specs --- for 458.795 CID from 3400 to 5900 RPM
Diameter= 1.742 to 1.867 Length= 36.1 to 39.1 inches long
--- 2-Step Primary Pipe Specs ---
1st Dia. inches= 1.742 Length= 18.1 to 19.6
2nd Dia. inches= 1.867 Length= 18.1 to 19.6
--- 3-Step Primary Pipe Specs ---
1st Dia. inches= 1.742 Length= 18.1 to 19.6
2nd Dia. inches= 1.867 Length= 9.0 to 9.8
3rd Dia. inches= 1.992 Length= 9.0 to 9.8

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3.197 to 3.447 Tuned Lengths= 20.8 best and also 10.4 or 41.5

--- Header Collector Specs (Megaphone or Diffuser Cone Shape) ---
Diameter= 2.697 taper to 3.697 Megaphone/Diffuser Length= 20.8 inches

Best HP/TQ Tuned Collector Lengths= 20.8 , 41.5 , 83.0 , 166.1 inches long

Worst HP/TQ Loss Collector Lengths= 31.1 , 62.3 , 124.5 , 249.1 inches long

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

---- Primary Pipe's Harmonics ----
1st Harmonic = 157.1 inches long ... typically never used
2nd Harmonic = 59.9 inches long ... longest recommended
3rd Harmonic = 36.1 inches long ... highly recommended , best Torque Curve
4th Harmonic = 25.3 inches long ... shortest recommended
5th Harmonic = 19.2 inches long ... typically never used
6th Harmonic = 15.2 inches long ... typically never used
7th Harmonic = 12.5 inches long ... typically never used
8th Harmonic = 10.4 inches long ... typically never used

---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----
1st Harmonic = 166.1 inches long ... longest with Mufflers and TailPipes
2nd Harmonic = 83.0 inches long ... longest recommended with Mufflers
3rd Harmonic = 41.5 inches long ... more bottom-end Torque
4th Harmonic = 20.8 inches long ... highly recommended , best Torque Curve
5th Harmonic = 10.4 inches long ... reduced Torque , more top-end HP sometimes
6th Harmonic = 5.2 inches long ... reduced Torque , not recommended

from what i understand, order of importance if i remember right:

1) collector length
2) collector dia.
3) primary dia.
4) primary length

also, ends of exhaust should be square cut (90*), not tapered, scavenging i'm guessing.

Thanks - I'll have to compare that to the headers ERA provided.

Dan