so i have a question. i am getting ready to build a manifold that will most likely be similar to artechs design. i have a choice between two flanges that are mostly the same other than weld el size. one is 1.25 and the other is 1.5

any preference or opinion from those who have experience?

 

go with the thicker flanges

 

1.25 works very well for log manifold. El's and Tee's need only a little material removed for it all to fit in the cylinder port spacing. I built mine El, Tee, Tee, El.

Also, 1.5 usually needs to be flattened into the oval shape of the ports. There are flanges available for the 1.25 that transition perfectly from the Oval to the 1.25 diameter.

EDIT: Oh, you're not making a log. 1.25 still makes sense to me.

 

1.25 supposedly spools faster. Its a pain to make 2 1.25" els fit over a t3 flange though. Lots of swearing and hammering. Any more than 2 meeting at the flange would be better.

I'm assuming hes talking about a flange that transitions to the right size. It makes it way easier to fit and weld your bits.

 

They make the flanges that transition to oval in both 1.25 and 1.5

 

I am using a t2 flange so the fit there is fine. I am mainly curious about this spool thing and how significant it actually is.

 

Probably not much at all.

1.5 will flow more at the top end.

 

Go 1.5" and get your head flange from prl motorsports.

 

I'd stick with 1.25 unless you're shooting for something like 450hp. I think thats the number I settled on when I did the math when I built my first EFR manifold.

 

1.25 spools better and I think will make more power unless you somehow manage some magical porting on the head oversized valves and mega lift cams shooting for north of 450hp. Having the exhaust gas slow down in large diameter tubes after leaving the head then speed back up as it necks down to the to the nozzle of the turbine will cost hp over keeping the velocity more constant.

400 hp here with 1.25" sch 40 longish equal length weld el manifold.

 

so my goal is 300whp but i do want to keep the torque lowish for drivetrain longevity. 300/260 i think would be nice.

This is on a VVT motor and i plan to rev to 7500. part of the reason i was originally leaning to 1.5, so that it could build good top end power.

i am probably overthinking it and it wont matter much either way

 

at 300 HP you will be happier with 1.25"

 

I'm in the same boat, I've decided to drop my crazy double helix design and go with a log. How do you guys attach the flange to the log though? Do you find a pipe with the right perimeter and crush it into a T25 shape?

 

You buy this head flange and 1.5" schedule 40 weld welds fit on perfectly. Well you buy that flange if 1.8, they also have the 1.6 flange if you need that.

 

He's asking about the turbo flange.

 

Well then I have an answer for that also. Here is the flange to use for T2. Here is the flange for t3. Or just shoot me a pm.