Header design help required

[amichie]

I have ordered set of Supra NA headers for my 7MGE Cressida and I know I will need to replace the rear section. The basic design is the 6-2-1 and the whole thing comes apart in the middle section where there are only 2 pipes. I plan to have a new section made that includes the 2 pipe section, the Y pipe and then all the way to the Cat.

Question is how long should I make the 2 pipe section before it rejoins in a Y section?

I want to tune it for a torque peak around 3500rpm.

This is what they look like.

[ed]

the two pipe section should be about as long as the primary pipes, or a multiple therof

cheers
ed

[amichie]

the two pipe section should be about as long as the primary pipes, or a multiple therof

cheers
ed

Thanks Ed

Do you know of any online calcs or anything like that?

[ed]

nope

http://www.v-eight.com/tech_forum/viewtopic.php?t=53

[uncivilised]

Are these the obx headers usually advertised on ebay us? Hope they dont foul the steering shaft. If i stay with my 7M for a bit i might do this as well.

[amichie]

Are these the obx headers usually advertised on ebay us? Hope they dont foul the steering shaft. If i stay with my 7M for a bit i might do this as well.

Yes they are. I will let you know how well they fit.

[1jzracing]

the critical length is the total from the valve to the last collector, so for torque in the lower range like you want go for about 35 to 36 inches. remember this is from the VALVE not the head face right past the midle collector to the start of the Y you are adding

by comparison an engine with peak power at 8000 the length would be about 31 to 32 inches

[IN 05 NT]

hey andrew,

didnt you get some liverpool headers?

have you got a link to these obx suckers?

cheers, blake

[amichie]

hey andrew,

didnt you get some liverpool headers?

have you got a link to these obx suckers?

cheers, blake

I had a second hand set of hurricane headers and sold them to slowcressy on the cressida forum. He has since fitted them up and seems to be happy.

I wanted mandrel bent stainless headers and these appear to fit the bill.


BTW I may need your help in fitting them up.


Here is the link. Ask for Alex and he charged me $120 US for shipping. Our dollar is so high ATM I couldn't rseist. I also had some Paypal credit to use.

http://cgi.ebay.com/ebaymotors/OBX-R...spagenameZWD2V

[ed]

the critical length is the total from the valve to the last collector,

disagree... first collector. thats where your primary wave boundary is coming from

[amichie]

Headers arrived today. On first inspection they look good.

I will post up some pics shortly.

[big wad]

old speedway trick . cut the 2 into 1 collector off , fit the pipes to the engine , warm the engine up and run it up to a constant 3000rpm untill the pipes warm up then with a spraycan squirt a line of paint down the secondary,s and where the paint stops burning off , put your collector there. i,m sure i,ll get a bagging for this but if it was good enough for the likes of dave bennett ,phil irving, the crumps etc theres got to be something in it. cheers bigwad

[Ben Wilson]

You'd want to hold the engine at the revs you want to tune the extractors to..

[ed]

old speedway trick . cut the 2 into 1 collector off , fit the pipes to the engine , warm the engine up and run it up to a constant 3000rpm untill the pipes warm up then with a spraycan squirt a line of paint down the secondary,s and where the paint stops burning off , put your collector there. i,m sure i,ll get a bagging for this but if it was good enough for the likes of dave bennett ,phil irving, the crumps etc theres got to be something in it. cheers bigwad

thats called a harmonic antinode

and ben is correct

+rep... i like the idea