Exhaust manifold studs keep or remove

[kcorn]

Need some advice from members who have "been there done that". The coyote engine I am using for my roadster build came out of a 2016 low mileage F150. I have pulled the cast iron exhaust manifolds which mount to the heads with studs that are 1 1/2" long. My inital inclination was to unscrew these studs as I will be using the F5 stainless 4 into 4 headers which are bolted to the heads when a crate engine is being used in the build. However before I take that step I would appreciate any guidance that those " who have gone before me" can provide. In reading the various build threads it seem that the header attachment in frame is a major "pita". I wonder is there room to get the headers into position with the exhaust studs left on the heads? Would installing nuts on the studs be any easier than getting bolts into place and tight? Any other recommendations ?

[edwardb]

I think most remove the studs and use bolts into the head to hold the exhaust headers. That's mainly what I did on my #8674 build. But I did find it was slightly easier for 3-4 of the hardest to reach ones on the driver's side to leave the studs and use nuts there. I don't remember exactly which ones they were, but it's pretty obvious when you look at the location of the bolts and the footbox where you're going to have some difficulty. Bottom line, the passenger side is no big deal. Once the engine is in place, all eight on that side are relatively accessible. The driver's side is more difficult, as I already mentioned. One thing I tried, which seemed to help a little, is I attached the driver's side header before the engine was completely lowered into place. It has to be down pretty low in order to get the header under the 3/4-inch chassis tube that is above the header. But that inch or two of height before it drops all the way down gives a little more access. I also found if I removed the driver's side engine mount while it was hanging there, I could reach the header bolts a little more easily. Then replaced the motor mount (which needs to be a little loose anyway to drop into the chassis mounts) and dropped the engine into place with the driver's side header completely installed. Now if I have to get it back out... Well I'll cross that bridge if necessary. Just under 1800 miles driving the first season, and all is well.

[grluisi150]

I removed all studs and went with stage 8 fasteners. The driver side access is a pain and I didn't want to worry about retightening the header bolts in the future.

[FFinisher]

Take the studs out, You will not get the header on the drivers side with them installed. Just use the FFR provided bolts and gaskets and you will be good to go. Its actually not as bad as you might think.

[2bking]

I'll have to disagree with "take the studs out" on this one as I'm a fan of keep the studs. The studs being imbedded into the aluminum with Loctite remain stationary while torqueing the nuts and will provide a stronger connection. Several installation and removal cycles of bolts into the aluminum, especially where the bolts don't have enough thread engagement to develop full strength of the bolt/aluminum interface, wear/damage the threads and can lead to thread failure requiring a thread repair procedure such as helical coil inserts or other types. Trust Ford and their testing for knowing what's best, they wouldn't put studs in the heads if bolts would provide the same results and don't fall prey to the advertising of after market hardware. The studs also make it much easier to install the headers because the studs are the alignment pins. But the studs are too long and will need to be shortened which a cut off wheel on a Dremel tool will make short work. I did a test fit of the headers with the nuts and cut off the protruding stud length. There are still issues getting the headers install as Paul points out especially on the drivers side.

[edwardb]

I'll have to disagree with "take the studs out" on this one as I'm a fan of keep the studs. The studs being imbedded into the aluminum with Loctite remain stationary while torqueing the nuts and will provide a stronger connection. Several installation and removal cycles of bolts into the aluminum, especially where the bolts don't have enough thread engagement to develop full strength of the bolt/aluminum interface, wear/damage the threads and can lead to thread failure requiring a thread repair procedure such as helical coil inserts or other types. Trust Ford and their testing for knowing what's best, they wouldn't put studs in the heads if bolts would provide the same results and don't fall prey to the advertising of after market hardware. The studs also make it much easier to install the headers because the studs are the alignment pins. But the studs are too long and will need to be shortened which a cut off wheel on a Dremel tool will make short work. I did a test fit of the headers with the nuts and cut off the protruding stud length. There are still issues getting the headers install as Paul points out especially on the drivers side.

All good points. They could certainly be left in and used as you recommend. I agree that Ford engineering has very specific reasons for using the studs. I'm sure for technical reasons, but also I suspect for manufacturability. They work pretty hard to make that stuff as easy and repeatable as possible. If you do choose to use the studs, agree they need to be cut off to clear, especially in the close drivers side area. Also agree having them in place helps with aligning the header while installing.

I did choose to replace most of them, as I described earlier. But I was very careful to use cap head bolts of the proper length to use as much of the threads in the head as possible. I've used the Stage 8's and Percy's split lock bolts in the past. But the stock offerings weren't the ideal lengths IMO. I used hardened Allen head bolts from McMaster (96144A261), header gaskets from RemFlex, and high temp silicone on the bolts to (hopefully) keep them from loosening. After one driving season, looked everything over very carefully and all looks perfect. As long as nothing leaks, and the Coyote lasts as long as it's supposed to, I don't expect to be removing anything soon if at all.

Another of the many choices while doing these builds.

[kcorn]

2bking After cutting the studs did you taper the end of the stud to help with starting nuts?

[AC Bill]

I used the Percy split locks as the bolt heads were very small, and I could still thread them in, and tighten them up, without the headers interfering. It could be a real challenge with regular sized nuts with the header interference. Tightening the nuts is the another challenge. IE; Getting a regular wrench, or socket over them.
The bonus of using a Remflex gasket, is you don't need to use a lot of torque on the Percy bolts to still get a good seal. The gasket isn't meant to be compressed completely. Because of that you can use a small wrench. I used a mini closed end, ratchet wrench. The Percy locking screws ensures the bolts won't back out, from heating/cooling and vibration.

[2bking]

2bking After cutting the studs did you taper the end of the stud to help with starting nuts?

If you use a cut-off wheel to shorten the studs which will leave the remaining threads undistorted, the nuts are easily started. I also used a ratchet end wrench to tighten many of the hard to reach nuts. My crate engine came with both exhaust manifolds attached so I had both the nuts and Ford gaskets for reuse. My experience is with the 4:1:4 stainless headers; the shorty ones may be different.

[Dave Howard]

My Coyote is the same vintage as 2bking. 2012 for the purists. The build started off using the FFR shot headers and J pipes. After the first start, and seeing the new 4x1x4 Stainless Headers, I switched to these instead. The engine stayed bolted in place. Off with the shorties. Out came the studs as recommended by the FFR instructions and the Stainless Headers slid in and bolted up with the bolts recommended by FFR. No special bolts. No modification. The bolts where easier to get at on the Stainless headers than on the shorties. Yeah, a couple of bolts on the drivers side are more difficult to get at but no big deal. A box end took care of that and I said screw the torque spec on those ones. I check every year and there's been no movement. As for thread wear, I think it's a no brainer that putting a couple thousand babied miles a year on your Coyote and it's a safe bet the engine will never need to come out of the car. EVER!

So, to the original question, I followed the FFR instructions. Remove the studs.