Coyote Gen4 header bolt pattern adapter

[topherchrisb]

Hey Everyone... asking for a little help to make sure I'm doing this correctly. I have the Gen3 headers with the cats in them. I couldn't get to ordering an engine before the Gen3's were really hard to find. I now have a Gen4 on hand and originally planned on buying a new header flange to convert the system to using the new left side bolt pattern natively. Forte parts has started making an adapter plate that goes over the old flange and matches it up to the new pattern. I just got the adapter in the mail today but I'm having trouble figuring out if I'm doing something wrong or maybe the adapter is wonky. Maybe some more experienced eyes can point something out to me?

First thing is... this is the header I should be using for the left side correct? The O2 hookup should be on top and the pipes should route forward and slightly up before conforming to the collector pattern. I'm not sure it matters either way due to the bolt pattern being symmetrical but I'm checking all the boxes. If so I've circled in red all the bolt holes I'd not be using when mounted. The problem lies in the two locator pins on the bottom adapter on the second set of holes from either side. I painted them with a red paint pen. I need those spots to be open to pass the bolts through from what I'm seeing. I would think locator pins should be on the centers for the bottom and one out from the centers on the top if you were to add them. Am I bonkers? It's not really a hard fix... grind off the pins and drill holes for the pass through.

https://thefactoryfiveforum.com/attachment.php?attachmentid=207689&d=1734562142

Here I marked the two bolts that the interference occurs.

https://thefactoryfiveforum.com/attachment.php?attachmentid=207690&d=1734562212

Also looking at the adapter this way shows I'll be giving up half of the original mounting locations. That seems a little rough but I imagine there isn't much pressure build up making this not hard to seal. I'd probably rather have the flange changed out... but I've already been waiting two weeks for one to show up. Christmas logistics!!! Had three other postponements this week already.

I also see mentioning of people opting to replace the studs for bolts. I did get a header bolt kit from FFR but I imagine I probably want to get a little longer set to make up for the extra room the adapter plate adds.

[gbranham]

It's this type of trailblazing that makes me glad I pivoted from Coyote to Windsor when the Gen3 inventory dried up. I don't think I have the gumption to deal with the inevitable issues that come up when being one of the first with a new platform. That looks like a nice piece Forte fabbed up, though, and I'm sure he'll get you in a good place soon. Looking forward to reading about your journey with the Gen4.

Greg

[topherchrisb]

Just for fun I did try the orientation for which the bracket does work and this is what I got. I think this is more of a traditional orientation of the header when mounting into a mustang right? It puts the end of the collector below the oil pan even.

https://thefactoryfiveforum.com/attachment.php?attachmentid=207712&d=1734577010

[rich grsc]

The header is on the wrong side?

[topherchrisb]

The header is on the wrong side?

Yeah I'm having a hard time finding clear photos of the FFR cat headers installed to verify my orientation assumptions. I'm 95% sure the O2 sensors are supposed to be on top. And either header in that orientation results in the same bolt pattern that doesn't work with the bracket. I'll compose an email to Forte today and see if he gets back to me. I'll likely just mod them myself to get moving forward.

[rich grsc]

The headers sweep forward, not to the rear.

[topherchrisb]

Just an update on how this progressed. I'll update my build thread in the next day or two but I know there are a couple that are looking at this header situation in particular right now. I was able to take the brackets and modify them to work. I pretty much stuck to the plan... drilled out the two locator pins and wallowed out some of the holes as we know everyone says the coyote left hand header is a really tight fit. I also shaved a little extra on the spacers where they were interfering with the welds. I coated everything with some high temp silicone paint and with some patience, cussing, and contortions I was able to get everything together. It's hard to believe how tight the fit is until you have to do it. One of the most challenging fitments I can remember from my time on this earth. I'll definitely have some finger prints burn into the paint. It was impossible to do with gloves on. I needed every nerve to feel where I was sticking bolts in blindly.

Before mod:
https://thefactoryfiveforum.com/attachment.php?attachmentid=207928&d=1734916319

After mod:
https://thefactoryfiveforum.com/attachment.php?attachmentid=207933&d=1734916362

And it's all together:
https://thefactoryfiveforum.com/attachment.php?attachmentid=207944&d=1734916460

[460.465USMC]

This is good news. Glad you got them to fit. Thanks for posting.

Yep, tight fit is an understatement for the left side header in the Roadster. I should have just a little more space in my Coupe. I haven't tried fitment yet of the Forte adapters with my F5 headers. He told me he designed them specifically for the F5 headers, so hoping no mod is needed. I'll find out soon enough.