ACE Header/Overpipe, and STI Engine Mounts: Looking for Tips

[Ultramaroon]

+1 on getting replacement sensors up front. I don't know about subsequent years but the early ones were way over-torqued, at least the couple that I've removed. Threads were mangled.


Might be better to just leave the originals with the factory header in case you need to go back to stock.

[H1C]

Lots of good tips already in this thread -- I'll throw in a couple:


That one hard-to-reach header nut (on the driver's side I believe it was) -- you can get a ratchet or torque wrench on it with a 6" extension, u-joint and 14 mm crow's foot.


I found that the header-to-engine nuts vibrate loose over time, even after torque-ing them a second time after a few days' driving after initial installation. I installed Nord-lock locking washers and haven't had the problem since.


https://www.amazon.com/gp/product/B007VAW3AC


When I reinstalled OEM front LCAs and tie-rod ends to get legal for STX, I used the M12 sized Nord-locks instead of the cotter pins for the castle nuts. They've held up great there too.

[Stang70Fastback]

Originally Posted by 86TOYO2k17

I did sti mount and ace header. Both 02 sensors are in header and will need swapping over. Although like supertom mentioned at 70k miles and salty winters you might as well get fresh new 02s.

Yeah, new O2 sensors is pretty much what I was thinking. Can someone confirm for me if these are the correct part numbers? I never even realized they were different until just now.

https://parts.theautobarnsubaru.com/...2641AA640.html

https://parts.theautobarnsubaru.com/...2690AB000.html

Originally Posted by 86TOYO2k17

Header / overpipe is pretty straight forward although easier and more wiggle room with engine slightly lifted. So perfect time to do mounts. Only thing I did (not sure if necessary but I took off the intake box before jacking engine up to do mounts). Was able to jack engine up enough to get mounts out no problem.

Stock mounts are really soft engine rocks a lot even new. So definitely a good idea to swap. STI mounts are perfect for a DD I didn’t notice any NVH at all.

I hear people say they jack their engine from the oil pan with a block of wood, but the ACE instructions linked to further below say to only jack the engine on the cast aluminum sections. Any advice here?

Originally Posted by 86TOYO2k17

Also don’t forget to hammer down the skid plate there is a “bubble” on the plate right under header. It looks like a good 1/4” clearance but under load when engine rocks it will rub and you will hear it.

I'll keep an eye out for that, thanks!

Originally Posted by Doozer

Official ACE installation guide

Thank you! I couldn't find that anywhere on the CSG site (maybe I'm blind) so I wasn't sure if it would come with any or what. This makes me feel a lot better.

Originally Posted by Ultramaroon

+1 on getting replacement sensors up front. I don't know about subsequent years but the early ones were way over-torqued, at least the couple that I've removed. Threads were mangled.


Might be better to just leave the originals with the factory header in case you need to go back to stock.

Yeah, pretty much my thoughts as well. Can you confirm if the part numbers I posted above are correct?

Originally Posted by H1C

I found that the header-to-engine nuts vibrate loose over time, even after torque-ing them a second time after a few days' driving after initial installation. I installed Nord-lock locking washers and haven't had the problem since.


https://www.amazon.com/gp/product/B007VAW3AC


When I reinstalled OEM front LCAs and tie-rod ends to get legal for STX, I used the M12 sized Nord-locks instead of the cotter pins for the castle nuts. They've held up great there too.

Hmm. This is interesting. I may pick those up as well and use them on the install. Makes sense to me! Thanks for the link!

[cjd]

Originally Posted by Doozer

Official ACE installation guide

But no instructions on installing the studs in the header so they don't fall out... If that's even possible. Wish I'd been sent this when I asked if there were instruction s even though it doesn't have this bit, which is what I needed...

[e_lunatic]

Originally Posted by Stang70Fastback

I hear people say they jack their engine from the oil pan with a block of wood, but the ACE instructions linked to further below say to only jack the engine on the cast aluminum sections. Any advice here?

yes it can be done but I wouldn't recommend doing that. I have only ever done that to take pressure off the mounts, I wouldn't do that to lift it up enough to swap the mounts, it would put a lot of pressure on the pan and if it were to roll off the wood while you were swapping the mounts you'd be up shit's creek.

Help's that I always have access to a nice shop and engine hoists though lol

[Fred E]

For the engine mounts, I would suggest:

• remove the header
• unbolt the engine mounts from the frame on both sides
• use a floor jack and a piece of wood to lift one side of the engine from the block
• replace the engine mount on that side
• repeat for the other side

This would also overlap with the overpipe installation as you should move the overpipe into position while you're replacing the mounts on the passenger side. I would feel very uneasy about trying to jack the whole engine up to replace the both mounts at the same time because you would essentially be balancing the entire engine on one small jack point. In my opinion, it's much safer to do one side at a time and doing it that way should alleviate some of your concerns.

As you've already alluded to, the hardest and most time-consuming part of this installation is going to be breaking the old salted nuts (lol) off. Some angled/joint sockets might help there as well. Also, loosely thread on all of the nuts for every connection and get everything loosely connected together before torquing them all down. Be sure to get back under there after a few heat cycles to check the torque on the nuts.

We've had our cars for about the same amount of time and I'm glad to see you finally starting on power mods. I'll probably hit you up for some switches soon!

[Stang70Fastback]

Originally Posted by Fred E

For the engine mounts, I would suggest:

• remove the header
• unbolt the engine mounts from the frame on both sides
• use a floor jack and a piece of wood to lift one side of the engine from the block
• replace the engine mount on that side
• repeat for the other side

This would also overlap with the overpipe installation as you should move the overpipe into position while you're replacing the mounts on the passenger side. I would feel very uneasy about trying to jack the whole engine up to replace the both mounts at the same time because you would essentially be balancing the entire engine on one small jack point. In my opinion, it's much safer to do one side at a time and doing it that way should alleviate some of your concerns.

That makes a lot of sense, actually. I suppose there is no reason to jack the entire engine up at once. I guess I just don't have enough understanding of the entire engine assembly to know how you can or can't move it in the engine bay. Twisting it seemed like not a good idea, but I suppose an inch or two won't hurt (no idea how much clearance is needed to remove the mounts.) I'm just terrified of over-stretching some harness/hose somewhere, or damaging the transmission mounts or something in the process.

My previous car to this was a 16 year old Outback with 286,000 miles... and while it was in relatively good shape, it was easy to break old, brittle bushings/hoses/things while working on it because they were so old - so that's probably part of where my apprehension comes from.

[Fred E]

Originally Posted by Stang70Fastback

That makes a lot of sense, actually. I suppose there is no reason to jack the entire engine up at once. I guess I just don't have enough understanding of the entire engine assembly to know how you can or can't move it in the engine bay. Twisting it seemed like not a good idea, but I suppose an inch or two won't hurt (no idea how much clearance is needed to remove the mounts.) I'm just terrified of over-stretching some harness/hose somewhere, or damaging the transmission mounts or something in the process.

My previous car to this was a 16 year old Outback with 286,000 miles... and while it was in relatively good shape, it was easy to break old, brittle bushings/hoses/things while working on it because they were so old - so that's probably part of where my apprehension comes from.

That is an understandable concern, but I'd like to think that the quality of hoses/bushings/etc have improved since the days of your Outback, but that could be wishful thinking.. However, many shops and other people have swapped engine mounts without the complete removal of the engine. There is definitely enough leeway in the harnesses and hoses to lift each side of the engine just enough to swap the mount out. It would only be about an inch or two to wiggle the mounts in and out.

[Ultramaroon]

Originally Posted by Stang70Fastback

Can you confirm if the part numbers I posted above are correct?

Those are correct. The A/F sensor is a wide-band oxygen sensor. The old O2 sensors can only tell the ecu if the mixture is rich or lean. The A/F sensor tells the ECU how rich or lean.

Originally Posted by Fred E

old salted nuts

Boooo...

[gtengr]

When you go to tighten the exhaust, get everything loosely into position (just a little bit loose, leave about 1/8" of play at each nut/bolt) and torque fasteners starting at the mid-pipe and working your way forward. The nuts at the cylinder heads should be the last ones torqued.

When you're finished installing the mounts and headers, leave it on jack stands with the under panels off and let the car run about 15 minutes, then let it cool off for a bit. Repeat a time or two then recheck all nuts and bolts.

If you're looking for some "while you're in there" parts, consider the sti trans mount and steering bolts/bushings.

[Stang70Fastback]

Originally Posted by gtengr

When you go to tighten the exhaust, get everything loosely into position (just a little bit loose, leave about 1/8" of play at each nut/bolt) and torque fasteners starting at the mid-pipe and working your way forward. The nuts at the cylinder heads should be the last ones torqued.

When you're finished installing the mounts and headers, leave it on jack stands with the under panels off and let the car run about 15 minutes, then let it cool off for a bit. Repeat a time or two then recheck all nuts and bolts.

I have to do that datalogging stuff for my Delicious tune anyway, which IIRC starts with 15 minutes of idling, so I can use that as my "heat cycling/vibration" step before re-torquing everything and reinstalling the shields. The lockwashers suggested earlier also seem like a great idea, so I'll probably use those as well.

Originally Posted by gtengr

If you're looking for some "while you're in there" parts, consider the sti trans mount and steering bolts/bushings.

Yeah, I considered doing the trans mounts and some other things, but the cost is already running away from me with the STI mounts, and new O2 sensors, and whatnot, so I'm going to leave well enough alone for now!

I appreciate all the feedback! I'm feeling a bit more confident about this install. It's all going to come down to how rusty the existing bolts are. If it comes down to needing an angle grinder and stuff, then I'll probably just call it quits and visit a local shop. Fingers crossed it doesn't come to that!

[SuperTom]

If your are able to have the car jacked up in advance with the skid plate removed and soak the bolts with PB blaster 24 hours beforehand. And have a cheap torch from home depot (I use the yellow bottle of propane not sure the exact names) ready. You will be amazed how 10 secs of torch on a bolt will make it so easy.

[Stang70Fastback]

Originally Posted by SuperTom

If your are able to have the car jacked up in advance with the skid plate removed and soak the bolts with PB blaster 24 hours beforehand. And have a cheap torch from home depot (I use the yellow bottle of propane not sure the exact names) ready. You will be amazed how 10 secs of torch on a bolt will make it so easy.

That yellow-bottled Benzomatic Butane thing from Home Depot is exactly what we got a few weeks back. We were trying to break my friend's coilover bolts loose, but his other idiot friend had torqued them to 6 trillion ft-lb with an impact, so even the torch did nothing.

And yes, I plan on jacking the car up the night before, removing the heat shields, and soaking everything in PB blaster. Also, anyone think it's worth running the car briefly day-of, just to warm up the exhaust a bit (not burning hot obviously) or will that just expand the studs too and not really be worth the effort?

[CSG Mike]

tl;dr version

- take off metal under pan
- take off paper pan
- unbolt passenger side engine mount
- remove stock header
- lift engine gently
- remove overpipe
- put ace over pipe where stock overpipe was, but do not tighten down
- drop engine back down and torque engine mount
- put on ace header
- torque header to engine
- bolt ace merge overpipe to header
- bolt ace merge overpipe to front pie
- check torque
- flash tune
- revise tune
- check torque on all hardware after a few heat cycles. Re-check until a subsequent recheck yields no additional torque being needed.

O2 sensors left out to do at your convenience.