headers and intake box
Discussion
Chris yes at full chat it makes noise like a 1990 leman's car. if you look closely we left a flange on the end of the tail pipe to mount a super trapp. fortunately for me the tracks that I visit Willow Springs and Auto Club Speedway or in the future Button Willow do not impose noise limits. As far as street use goes the system is reasonable as long as your not in it to win it. Lee
looking at the photos again, initially i was thinking 180 degree headers.. but this is a 8 into one then megga phone pipe afterwards.
i wonder if having 2 x 4into 1 pipes then 1 exit pipe with megga phone will produce the same sound.. the only thing that worries me is these header pipes look tiny and the gasses wont get out quick enough and produce too much heat in the pipe for my application
do you know what size headers were used and primary lengths?
i wonder if having 2 x 4into 1 pipes then 1 exit pipe with megga phone will produce the same sound.. the only thing that worries me is these header pipes look tiny and the gasses wont get out quick enough and produce too much heat in the pipe for my application
do you know what size headers were used and primary lengths?
The primary pipes are 1.75 transitioned to 1.875 at 18 inches from the port. The reason the primaries look small is the size of the tail pipe. The muffler has a 4.5 inch I.D. Air flow through a pipe is geometric a single 4.5 inch pipe will easily outflow a 2 x 2.5 inch system. restriction in this system is not an issue. Lee
V8Dom said:
looking at the photos again, initially i was thinking 180 degree headers.. but this is a 8 into one then megga phone pipe afterwards.
i wonder if having 2 x 4into 1 pipes then 1 exit pipe with megga phone will produce the same sound.. the only thing that worries me is these header pipes look tiny and the gasses wont get out quick enough and produce too much heat in the pipe for my application
do you know what size headers were used and primary lengths?
Dom I think it's the 8-1 collector that is creating the unique sound.i wonder if having 2 x 4into 1 pipes then 1 exit pipe with megga phone will produce the same sound.. the only thing that worries me is these header pipes look tiny and the gasses wont get out quick enough and produce too much heat in the pipe for my application
do you know what size headers were used and primary lengths?
1 3/4 inch headers should flow a fair old bit of exhaust. I guess you could always size them larger if needed. But then you would need to tune the lengths to get the pulses right at the collector. This is rpm dependent also so you could move the sweepsot of the system around a little. Well that's from my understanding anyway .
chuntington101 said:
Dom I think it's the 8-1 collector that is creating the unique sound.
1 3/4 inch headers should flow a fair old bit of exhaust. I guess you could always size them larger if needed. But then you would need to tune the lengths to get the pulses right at the collector. This is rpm dependent also so you could move the sweepsot of the system around a little. Well that's from my understanding anyway .
+11 3/4 inch headers should flow a fair old bit of exhaust. I guess you could always size them larger if needed. But then you would need to tune the lengths to get the pulses right at the collector. This is rpm dependent also so you could move the sweepsot of the system around a little. Well that's from my understanding anyway .
Also bigger is not always better. Having too larger diameter primary's can stall the exhaust flow,
whereas small can accelerate flow, its a tricky art getting zorsts spot on but if done correctly, flowed and matched ports etc. Can pay dividends in terms of optimum power/torque spread.
Chris: Timing on a 8 into 1 is independent of length. The timing is set by clocking the pipes in firing order. Each pulse in order is preceded by the tube next to it. The issue of diameter of the tubes was discussed with the builder Greg Holman who has built headers since the 1970s for everything from Indy to Nascar. His input was for the street where a lot more is involved then just wide open throttle these tubes for this motor would be going backwards in overall performance if sized larger. This is a 383 cu inch L.S. 565 HP at the crank. So a ls 7 at 427 cu inches might use bigger tubes.The only caveat on this header set up is the configuration of the engine dictates that the primaries are a little longer than what you would do in a perfect world. Lee
but what's the difference between system 180 degrees and 8 in 1 ???
180 degrees seems sounds more like F1.
but it is very much more complex to build in the gtr.
and that performance difference there?
modes of dispensing?
hp?
hp at equal rpm ???
I have a 4 ,4 into an 1 empty container (empty muffler) and with 2 outputs final
sorry for the bad english
180 degrees seems sounds more like F1.
but it is very much more complex to build in the gtr.
and that performance difference there?
modes of dispensing?
hp?
hp at equal rpm ???
I have a 4 ,4 into an 1 empty container (empty muffler) and with 2 outputs final
sorry for the bad english
Stefano: Certainly if I had a 180 header system on the car I would not change it to a 8 into 1, not enough difference to justify the change. But starting from scratch I like the 8 into 1 better than the 180s, because of the idle quality. I had a Pantera with 180s on it and it never sounded good until you hit about 3000 rpm from there up all was well. As far as power goes if you look at page 2 on this subject 8 posts down I speak about that a bit. As far as your English goes its a hell of a lot better than my Italian, I for one always get the idea of what your saying on your posts. Lee
italian linguage...
Many thanks to Lee, you're very kind.
sometimes someone does not answer me why I write bad English,,, I think.
Also I was thinking of doing a job like yours, because now my gtr is disassembled to rebuild some parts and and change them.
I was thinking to add to my L98 a volumetric, add stabilizer bars and an exhaust as do your (easier I believe) or 180 degrees
now my job (4,4 in 1 muffler empty ):https://www.youtube.com/watch?v=Nik0nCk8bVA
however many compliments for your good work and for your great sound!
F.C. said:
chuntington101 said:
Dom I think it's the 8-1 collector that is creating the unique sound.
1 3/4 inch headers should flow a fair old bit of exhaust. I guess you could always size them larger if needed. But then you would need to tune the lengths to get the pulses right at the collector. This is rpm dependent also so you could move the sweepsot of the system around a little. Well that's from my understanding anyway .
+11 3/4 inch headers should flow a fair old bit of exhaust. I guess you could always size them larger if needed. But then you would need to tune the lengths to get the pulses right at the collector. This is rpm dependent also so you could move the sweepsot of the system around a little. Well that's from my understanding anyway .
Also bigger is not always better. Having too larger diameter primary's can stall the exhaust flow,
whereas small can accelerate flow, its a tricky art getting zorsts spot on but if done correctly, flowed and matched ports etc. Can pay dividends in terms of optimum power/torque spread.
if after the 8 into 1 i presume we need the min 18 inch pipe off the header, but if we then split into 2 tail pipes i presume noise would be the same?
V8Dom said:
so who can we ask about primary lengths... i have sbc with special exhaust system. however the 4 in1 collector is removable and all 4 pipes sit square next to each other and are ready to turn 90 degrees towards the dizzy before 90 again into a 8 into 1 collector. its the lenth im worried about. i presume the 8 into 1 doesnt mater which pipe enters where like a bunfle of snakes does matter?
if after the 8 into 1 i presume we need the min 18 inch pipe off the header, but if we then split into 2 tail pipes i presume noise would be the same?
Dom,if after the 8 into 1 i presume we need the min 18 inch pipe off the header, but if we then split into 2 tail pipes i presume noise would be the same?
Too much is made of equal length headers on dual plane or non flat-plane V8's like ours.
We have essentially what is two v 4's bolted together and they do not have even exhaust pulses along each bank like you would on a flat plane V8.
A flat plane crank (Ferrari etal) is essentially two straight fours bolted together, and we know that primaries on a straight four are more sensitive to primary length.
Seriously primaries of two to three feet in length (in increments of three inches) will make hardly any difference to the sort of engines we have and equally up to 9" variation in individual pipe length again will make not a lot of difference other than enabling smoother flow on some of the pipes.
Sure if you are spending on £100K engine tech then that is a little different!
Hi guys: To Tony and the entry above his. Yes it does matter somewhat how the tubes enter the collector they should be in firing order as the go around the collector. This is a fine point but if your going to do it, this is the way its done. As to equal length headers I completely disagree with Tony there is horsepower to be had, not a great deal but why leave it on the shop floor for the lack of a little effort. Even perhaps more importantly is sound, the extreme example of this is the Subaru STI that I used to own, great car but the stock unequal length headers are what causes the off beat almost sounds like its running on 3 cylinders NOISE that comes out of the back of a Subie I changed mine to an equal length headers and it transformed the car. The sound was more like a Porsche much more even and it made about 2% more h.p. and torque. iF you get the lenghts just wrong on the L.S. motor you can wind up with a very unpleasant sound at cruise that you will not like at all Lee
ROWDYRENAULT said:
Hi guys: To Tony and the entry above his. Yes it does matter somewhat how the tubes enter the collector they should be in firing order as the go around the collector. This is a fine point but if your going to do it, this is the way its done. As to equal length headers I completely disagree with Tony there is horsepower to be had, not a great deal but why leave it on the shop floor for the lack of a little effort. Even perhaps more importantly is sound, the extreme example of this is the Subaru STI that I used to own, great car but the stock unequal length headers are what causes the off beat almost sounds like its running on 3 cylinders NOISE that comes out of the back of a Subie I changed mine to an equal length headers and it transformed the car. The sound was more like a Porsche much more even and it made about 2% more h.p. and torque. iF you get the lenghts just wrong on the L.S. motor you can wind up with a very unpleasant sound at cruise that you will not like at all Lee
To be fair I was thinking of power rather than sound when I replied to Dom.Your 2% could come from practically anywhere in the new system build.
With our motors there is documented evidence that secondary dia and length can have a bigger influence on the power and torque distribution than primary.
Exhaust pulses are spaced 90, 180, 270, 180, 90 and so on.
The two cylinders discharging only 90 degrees apart are seen by the collector as one larger cylinder which is where the "chevy" dual plane sound comes from.
The collector acts as if it were on a 3-cylinder engine having different sized cylinders turning at fewer rpm, it stands to reason that due to this un-even discharge that primary length of the headers is nowhere near as sensitive as it would be on a flat plane engine with evenly spaced discharge pulses.
All of this is a matter of record.
I do not know where your matter of record comes from but just to make sure I looked up results that other folks have documented on the internet on back to back pulls with the same engine, equal and unequal length headers and I will tell you that the 2% I quoted is conservative. I will also say that collector length and diameter has an impact on power. As far as the rest of your response all L.S motors have a firing order of 18726543 and this causes a space or void in the exhaust flow when the 2-6 and 3-1 cylinders fire. This causes the uneven sound of these v8s by running all of the cylinders into one collector and timing the collector so that each cylinder pulse is preceded by a pulse right next to it you get a steady stream of exhaust gas and a accompanying higher pitch more even sound, thus generating a better scavenging effect at all RPMS As I have stated before, on my engine this flattened the torque and horse power curves on both the bottom and top end of the rev range thus making the car easier to drive due to a reduction in the torque spike it had previously at 4200 RPM. lEE
im really interested in doing this
my engine is a still a 383 sbc
so am i right i read somewhere there is a bit of flex in primary length due to pulse length
also my limiting factor on my engine is my mufflers are bolted to my collectors so there is no secondard legth and im zapping hp
dom
my engine is a still a 383 sbc
so am i right i read somewhere there is a bit of flex in primary length due to pulse length
also my limiting factor on my engine is my mufflers are bolted to my collectors so there is no secondard legth and im zapping hp
dom
V8Dom said:
im really interested in doing this
my engine is a still a 383 sbc
so am i right i read somewhere there is a bit of flex in primary length due to pulse length
also my limiting factor on my engine is my mufflers are bolted to my collectors so there is no secondard legth and im zapping hp
dom
Correct, pulse length is not even due to the two cylinders that fire at 90° apart.my engine is a still a 383 sbc
so am i right i read somewhere there is a bit of flex in primary length due to pulse length
also my limiting factor on my engine is my mufflers are bolted to my collectors so there is no secondard legth and im zapping hp
dom
Experimenting with collector length should result in a better spread of power,
generally speaking short collectors 10"or< favour the high rpm range (8,000rpm ish). longer >10-20" favour the low to mid rpm range (4000rpm ish).
You could do worse than look up David Vizard's "How to Build Max Performance Chevy Small Blocks on a Budget"
He can explain far better than I why equal length primary's are not a big deal on a dual plane V8.
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