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2.9 headers on a 4.0?


greasemonkey6886

greasemonkey6886

Well-Known Member
U.S. Military - Veteran
Joined
May 13, 2010
Messages
278
City
Sulphur Springs, Tx.
Vehicle Year
88,89,07
Transmission
Manual
Ok does anybody know if the flange on a set of 2.9 headers is the same as for the 4.0. Reason I ask is that I have a pair of 2.9 headers and I am in the process of doing a 4.0 swap on my BII. Not really worried about the rest of the headers just the flange that bolts to the head, i can bend up and weld new primary tubes that will work if need be. they look to be really close to the same spacing and bolt pattern from what I can see. And yes I am cheap! I don't have the money to spend on new 4.0 headers, trying to get by with what I have.
 
IIRC I read in a post somewhere that copycat confirmed that the 2.9 and 4.0 had the same bolt pattern. I'd also like to know if if it works because I've read that the 2.9 came with factory tubular headers and I'd also like to cut and weld to make some cheap ass headers that would work for me.

Richard
 
I was told that 2.8 headeras may be able to bolt to a 4.0. If this is correct, then they all interchange. But the 2.8 has two of the exhaust ports next to eachother and dont know if the other have the samething (time to go research on this).
 
As far as the 2.8 goes I know for a fact that they are very different than the 2.9 and 4.0 heads. The 2.8 has the front two exhaust ports on the drivers side and rear two on the pass. siamesed(sp?) together. The 2.9 and 4.0 are evenly spaced.
 
2.9 and 4.0 patterns are the same.
 
Most excellent news there!!!!! I will let you guys know how they turn out. To make things more interesting they are actually 2.9 4x2 headers and are going on a 4.0 in a 4x4 hence the comment about cutting and fabbing my own primaries. The pass side from what I understand is the same for both apps but the drivers side is a shorty style on the 4x4. I will say that after looking at the wifes 4.0 BII last night with the header in my hand it looked as though it would clear everything just fine. We will see.
 
While the bolt pattern may be the same for the exhaust manifolds the 4.0 ports are larger.

Also a 4.0 has a higher block deck than a 2.9 to accomodate it's longer stroke

To the Y-pipe that connects the header will be around 1.5" too narrow.


On the factory manifolds both engines use the same Y-pipe because
the 4.0 cast manifolds hug the block more.

AD
 
^^^ thanks for the info. Did ford make a tubular header for either engine that you know of?

Richard
 
No, but Borla did, I have a set of Borlas that I pulled off my 1993 engine last fall

The collector was cracked on the driver side header and rather than deal with an exhaust
leak all winter I swapped manifolds and stock Y-pipe back on.

I'll be putting them back on as soon as I find someone willing to weld 409 stainless steel

AD
 
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