I want to know if anyone has done this before OR if its impossible. Please help me and guide me.

Thank you

 

It is possible but the lengths of the portions that have to cross over under trans will be 20" longer than other primaries. What you end up with is 4 primaries near similar length and another 4 verrry long.

If you are doing this for sound, it will not have the 180 deg sound.

This is what i did on my ls1 4th gen. I did a 4 into 2 into 1 but paired the cylinders differently so they would be in 180 deg firing orders at the final collector.
I did 1.75" into 2" then 2 into 2.5" at the final collector
I had v band flanges at the two 2" first y section. This way i could easily install everything.

It sounded different than normal ls1 longtube setups but did not have the flat plane crank sound i wanted to hear. Most told me it sounded bad haha


Maybe the 4-2-1 design wasnt helping the sound but the unequal lengths never times the pulses right at the collector to generate the rapid 180 deg firing pattern.