Which headers with PMO ITBs

[shahram]

hmmm, i am planing to use a set ot PMO EFI ITBs on a 993 3.6 that we are rebuilding.
What size of headers and which kind of headers would you guys recommend to use with that combination?
Thanks

[DW SD]

I might wait for Bill Verburg to chime in, but suspect 1 7/8" primaries will be the recommendation.

Doug

[shahram]

Thanks doug,
I also was thinking to get a 1 7/8" but PMO recommends to use 1 5/8 or less with EFI ITBs. I don't know why. I guess the stock heat exchangers are 42 mm or something around 1 5/8".

[Steve@Rennsport]

What cams are you using????

Header diameters depend on operating RPM range as much as displacement.

[shahram]

Hi Steve, for now I leave it with stock cams. The car is used 80% street and 20% track or DE...
what do you think?

[Steve@Rennsport]

Originally Posted by shahram

Hi Steve, for now I leave it with stock cams. The car is used 80% street and 20% track or DE...
what do you think?

Thanks for that key piece of the "puzzle".

JMHO, but based on a lot of dyno work, 1 3/4" & 1 7/8" headers are FAR too big for a 3.6 with stock cams and simply kill the low end power without a payback near redline (6750 RPM). Those big headers are fine for engines operated to 7500 RPM and beyond.

1 5/8" headers, properly made and with the right muffler, will make a lot of power in the operating range of stock or RS cams.

When or if you decide to change cams (and a lot of other internal modifications), sell the smaller header for the bigger ones that are appropriate for the engine's configuration.

[shahram]

Thanks Steve for great adivse. I have to contact you soon anyway to figure out the best way for the ignition and engine management system.

[Steve@Rennsport]

Originally Posted by shahram

Thanks Steve for great adivse. I have to contact you soon anyway to figure out the best way for the ignition and engine management system.

I have headers, too,....