Custom duals to y pipe

[toolmanmike]

What I have noticed right off the bat, car revs up higher faster, car is running lean and pops, need to enriched the mixture with better metering rods,Too soon to tell about mileage and power. Cost 120 to have the pipes made, 60 for y pipe 200 for the manifolds less than 400.00 for the whole set up. Sure beats paying almost 400 shipped for the front casting only.

Looks good.

 

[WV64Signet]

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[Jim Kueneman]

Still debating on where to connect the Y pipe at, Before or after my torque shaft Z bar, Pishta i found that article from Pete Hagenbush recommending to run the two pipes from the split manifolds 6 to 8 feet before connecting them to a Y pipe. Probably will try that out so how it works out for me keep you guys posted

Where do you want the peak power point? I wanted peak torque at normal driving RPM so right behind the transmission cross member puts it just under 2500 RPM. That is where I merged my Dutras. I used 1.75” pipes to the Y then 2.25”. If you go to big before the Y you loose the velocity and the scavenging effect of doing all this.

 

[Duggie]

Where do you want the peak power point? I wanted peak torque at normal driving RPM so right behind the transmission cross member puts it just under 2500 RPM. That is where I merged my Dutras. I used 1.75” pipes to the Y then 2.25”. If you go to big before the Y you loose the velocity and the scavenging effect of doing all this.

Hey Jim. My tube headers are 1 3/4" and end at the power steering head and above the Z bar. I think it was @high.rev.trev that said he would paint a latex stripe down the 2" exhaust (from the header collector) and put either the Y or the two in / one out muffler where the latex paint stopped looking burnt. I don't recall if peak torque vs RPM was part of the comment. How did you determine your pipe size and optimal torque/RPM?

 

[Jim Kueneman]

Hey Jim. My tube headers are 1 3/4" and end at the power steering head and above the Z bar. I think it was @high.rev.trev that said he would paint a latex stripe down the 2" exhaust (from the header collector) and put either the Y or the two in / one out muffler where the latex paint stopped looking burnt. I don't recall if peak torque vs RPM was part of the comment. How did you determine your pipe size and optimal torque/RPM?

Through Vizards equations. Went back and looked at my spreadsheet. Actually aiming for 3400 RPM give you 1.4" (this is assuming single tube headers from each cylinder so you have to extrapolate a bit). The distance to put the Y is a function of the cam exhaust BBDC as well. My cam was about 70 degrees so my length came out to about 34" collector length. If you think about what exhaust scavenging is these parameters make sense. You are trying to time an exhaust pulse travel down one tube, pass the Y which put a suction pulse on the other tube in the Y and travel back up the pipe and hit the valve at the correct point in its opening cycle and this only occurs perfectly at one RPM for a one set of lengths and cam timing.

 

[Duggie]

Through Vizards equations. Went back and looked at my spreadsheet. Actually aiming for 3400 RPM give you 1.4" (this is assuming single tube headers from each cylinder so you have to extrapolate a bit). The distance to put the Y is a function of the cam exhaust BBDC as well. My cam was about 70 degrees so my length came out to about 34" collector length. If you think about what exhaust scavenging is these parameters make sense. You are trying to time an exhaust pulse travel down one tube, pass the Y which put a suction pulse on the other tube in the Y and travel back up the pipe and hit the valve at the correct point in its opening cycle and this only occurs perfectly at one RPM for a one set of lengths and cam timing.

I found this reference to Vizard. Looks like I need to sharpen a pencil.