header tube dia/ hp-tq on lx9

[grnrdragon]

at what point will n/a lx9 need 1.75in header tubing to get more out of it?or is 1.75 to big for lower rmp scavenging to benefit? I don't want to kill bottum end tq because I still want it as dd also. any input will help.

[Superdave]

Probably north of 400 HP. 1 5/8" primaries are fine for most builds.

[grnrdragon]

so should one step their headers if they have good porting. if i remember the ports measured 1.65625in. x 1.40625in. don't want a choke point at the flange. and im not sure if stepping it is the answer ether. Really doubting myself lately and don't want to order the wrong flange.

[Superdave]

Who ported them?

Do you have any pictures of a D port header flange sitting on the head?


Mine are opened up to the 3400 gaskets and with the D port header flanges i had no overlap issues. I did de-burr the edges just in case though.

[grnrdragon]

work was done out of shop in southern Oregon couple years back. sorry no working camera. so do the 3400 gaskets have larger opening then the 3500? because on my stock metal gaskets the gasket is smaller then the port is now. I guess that I could put 7 deg. bevel on it. from what i can read it's just over a 1/32 all around. bigger then the gasket.

[Superdave]

The 3500 manifold gaskets are huge, i really hope they didn't port them out that far. Pictures are really going to be the only way we'll be able to help out in this case. If they really did go that big you'll need to modify some flanges and step the tubes back down to 1 5/8"


These are very old pictures but here is an original 3500 gasket sitting on a 3500 head after opening up the ports to the 3400 gasket size. Is your gasket the same part number as the one in the picture?



Here is a 3400 header flange on that same head;

[grnrdragon]

same part number on the gasket. holly crap they screwed up my heads. from the looks of your pics my ports must be paper thin. dam it to hell

[Superdave]

did they give you flow numbers?

[grnrdragon]

I don't recall what I got from them. It's been 3 years and now 500 miles away. Was looking into twice the output from stock with n/a.

[grnrdragon]

still looking for my formulas to post. but if I remember right. doesn't 1.75 tubing have 17% more flow over 1.625in. tubing. and so if you calculated your header length out to xxxx rmp then with 1.625 tubing. isn't it close to 10 inches shorter with the 1.75in tubing? or is it more of a bust because you would have to be well over a 100% volumetric efficiency in order for the principle to work?

[pocket-rocket]

Personally I would user the size Dave recommended. He has experience with headers on a 3500 and I would be too worried about losing velocity and scavaging from using the larger pipe.

Sent from my HTC One X using Tapatalk 2

[3400-95-Modified]

I'm actually looking to try a set of 1.5" primaries on my setup to see if I get some more low end torque from them, without hurting the top end power of course.

[grnrdragon]

anyone consider doing like the jap motors have. where they have short tubing with a expansion chamber and have the cat within a foot from the heads?

[pocket-rocket]

Most of the guys on the Ranger Station (Ford Ranger forums) believe if you have a hollowed cat on a vehicle the cat will act as an expansion chamber and cause reversion bad enough to blow head gaskets. Expansion chambers are awesome on 2 strokes, but I'm not sure I would want to risk a daily for that sort of experiment. Most modern cars have a cat within a foot of the head. It's part of the tougher emissions thing on mainly OBD 2 cars.

[grnrdragon]

hope this doesn't post twice. stupid computer crashed. so how much clearance does the exhaust gasket need around the port so it wont burn out? or will a metal gasket be fine if it's right to the edge of the port?