Helicoil exhaust header bolts on a loyale?

[Milemaker13]

Is it a good idea to helicoil the thread on one of my header bolts? I got under to check out my exhaust leak, found a loose stud. Its stripped out.

Any tips or hints? What size is this exhaust stud?

[azsubaru]

Is it a good idea to helicoil the thread on one of my header bolts? I got under to check out my exhaust leak, found a loose stud. Its stripped out.

Any tips or hints? What size is this exhaust stud?

 

My 91 Loyale exhaust has been helicoiled for about a year on one head, and it's working fine. The size was 10M X 1.25

 

It was pretty easy, but I was cautioned not to drill too deep.

[idosubaru]

yes, i've done it a dozen times. you can attempt to chase the threads, clean them up and use longer studs to see if that helps, but usually it doesnt on the exhaust studs. probably best and save time to just assume they're shot.

 

the job is actually fairly straight forward for a helicoil job. access and room isn't a problem. the most annoying part of the deal is removing and replacing the exhaust manifold. on the ones i've done the holes in the exhaust flange are too small for the drill bit and insert, so the headers have to come off. other than that, drill, tap and insert. probably one of the easier helicoil jobs to do on a soob.

 

if i remember correctly the hole will be actually deeper than just one insert. but you can get away with using just one or make the attempt of trying to insert two on top of each other. i've done both and had no problems either way. just figured i'd mention it in case you notice the inserts aren't as long as the studs/original holes.

 

have eye protection handy, you'll be lying on your back with metal (possibly hot) shavings falling on your face.

[Milemaker13]

It is 1.25 pitch? 1 and 1.25 look pretty close. Thanks for that. Where did you get you coils?

[idosubaru]

it's definitely 1.25 pitch.

[Milemaker13]

On the coil length... If I order them from McMaster(like Granger) I can get 10mm, 15mm or 20 mm long... Which would you choose? The stud under the nut measures *about* 15 mm. Can I get the coils and tools from the auto stores?

[idosubaru]

you posted at the exact same time i did, check out the pointers i posted above.

[idosubaru]

the 15mm should be fine. they can be trimmed as needed, though that can be annoying sometimes. yes they are available locally. call and ask first, but they should have them in stock.

[Milemaker13]

Thanks GG!

[idosubaru]

forgot to add, the holes are almost always a little deeper than the bolts or studs used in them. so if the helicoil is the same...or even if it's a tad longer than the stud you shouldn't have a problem getting it to go all the way in and sit flush with the exhaust outlets. 15mm all the way. i don't ever remember having different length helicoils to choose from, i'll keep that in mind next time i buy some for sure.

[benebob]

Another option is to go get threaded rebar in the I wanna say 3/8 inch course pitch size but I don't think that's right (regardless it'll be just slightly larger than the standard Subie exhaust stud. Then you get a threader and some grease and go to town. Don't even need to drill the hole out it'll just go right into the stud hole just fine. I've never had one that I redid like this come out.

[Milemaker13]

Yeah, my buddy suggested that. 3/8 or 7/16 standard stud should tap right in. I am going to look into that at work tomarrow, then just use a bolt for now. I assume the gasket is toasted, so I'll eventually be replacing that as well.

[torxxx]

7/16 is what we used IIRC when I stripped out my exhaust studs. I have also ran a bolt from the top of the rear strut assembly (17mm head on the bolt, 12x1.25) into the hole when i didnt have a tap..

[benebob]

Yeah 7/16th is probably it. Nice and cheap at a Home improvement center. For $3 you'll get enough threaded pipe to do 'em all.

[Gloyale]

Yeah 7/16th is probably it. Nice and cheap at a Home improvement center. For $3 you'll get enough threaded pipe to do 'em all.

 

I don't like threading untreated mild steel into an Alloy engine. Weak, and bad for corrosion. What do you got against using actual 7/16 exhaust studs? They do make them. And I bet you could get em for $3 bucks as well. No hacksawing. And good ones have some measure of corrosion protection.

[ZRX Doug]

Yeah, SAE studs work fine. As a bonus, you can get 'em along with nuts in a GM manifold repair kit at most any parts store for under five bucks, in those little blister packs sold as "HELP!" products. Get the studs that are supposed to go on the end of a General Motors manifold, where the exhaust pipe bolts up. These look stupid-long for our application, but they work great and are intended to be used for exhaust purposes.

As a further bonus, the Helicoil kit is MUCH cheaper in the SAE version than it is as a metric kit. Don't try to do this without drilling for the correct tap size first, you'll crack the head trying to force an oversize tap into the little hole. Once everything is Helicoiled and ready to be screwed back together, use some LocTite red on the stud where it goes into the head..but keep the Loctite away from the nuts!

[benebob]

I don't like threading untreated mild steel into an Alloy engine. Weak, and bad for corrosion. What do you got against using actual 7/16 exhaust studs? They do make them. And I bet you could get em for $3 bucks as well. No hacksawing. And good ones have some measure of corrosion protection.

 

I've never had one rust under there. In fact I find 'em perfectly easy to service. To each his own but honestly its a 15 year old car. I'd be more concerned with rot elsewhere then a exhaust stud.

[benebob]

Yeah, SAE studs work fine. As a bonus, you can get 'em along with nuts in a GM manifold repair kit at most any parts store for under five bucks, in those little blister packs sold as "HELP!" products. Get the studs that are supposed to go on the end of a General Motors manifold, where the exhaust pipe bolts up. These look stupid-long for our application, but they work great and are intended to be used for exhaust purposes.

As a further bonus, the Helicoil kit is MUCH cheaper in the SAE version than it is as a metric kit. Don't try to do this without drilling for the correct tap size first, you'll crack the head trying to force an oversize tap into the little hole. Once everything is Helicoiled and ready to be screwed back together, use some LocTite red on the stud where it goes into the head..but keep the Loctite away from the nuts!

 

You don't need a helicoil with the fix I suggested. Don't even need a drill. Just a tap that'll regrind the hole to the SAE size and some wheel bearing grease to help it turn nice. Will be as strong as a factory stud was if done right.

[ZRX Doug]

Ahh..see when I did mine, two of 'em were so stripped that the SAE studs were undersized. Helicoil was the only option..besides, it's preferable to have a nice steel insert in any threaded aluminum part IMHO.

If'n you can make it work, more power to ya, but I really like the peace of mind that comes with over-engineering, lol.

[benebob]

Ahh..see when I did mine, two of 'em were so stripped that the SAE studs were undersized. Helicoil was the only option..besides, it's preferable to have a nice steel insert in any threaded aluminum part IMHO.

If'n you can make it work, more power to ya, but I really like the peace of mind that comes with over-engineering, lol.

 

Personally I'd trust it more than a helicoil.

[ZRX Doug]

You're recommending using threaded rod (something like Grade 3, if it's graded at all) and ya think a non-Helicoiled hole is stronger than one with an insert?

Okey doke..but please don't work on my car, ever..mmkay?

 

BTW, taps are designed to thread holes which are drilled to the correct size..they are NOT intended to be used as reamers. Forcing an oversize tap into an undersize hole is sorta like stuffing a size 12 foot into a size 10 shoe..only aluminum doesn't stretch like shoe leather, ya know?

Broken taps are a pain to extract, and broken alloy castings are a pain to weld. Again, if it works for you, so be it..but recommending incorrect methods to a mechanical noobie is sorta asking for disaster, IMHO.

[benebob]

Wouldn't touch you're car with that kind of additude there buddy.

 

His inexperience is why I said do the threading rather than a helicoil. 1. Its easier. As strong as factory, FYI there I explained that you do not need to force the tap in at all the hole is virtually identical to the what the tap needs. 2. I got this advice from my Subaru cert. mechanic about 14 or so years ago and have done it ever since to virtually every used subie I've bought never to have one come out or an issue to speak of. That has been working on Subarus since the ORIGINAL DL. Are you a cert. Subaru mechanic? Didn't think so. 3. As I said, to each his own but reality is if you have 4 strong studs in there a helicoil is overkill. 4. If he screws up a helicoil then its a heck of a lot more trouble to fix. 5. I recommended no incorrect methods, simply an easier solution to his problem then you instead of pounding my fists on my cheast to prove my penis is bigger then yours. Then again, I'd trust someone with 11 posts over someone that has been here forever, HELPS out when he can and knows enough to put an stock engined SVX into the low 14s with an auto tranny to boot!

 

You're recommending using threaded rod (something like Grade 3, if it's graded at all) and ya think a non-Helicoiled hole is stronger than one with an insert?

Okey doke..but please don't work on my car, ever..mmkay?

 

BTW, taps are designed to thread holes which are drilled to the correct size..they are NOT intended to be used as reamers. Forcing an oversize tap into an undersize hole is sorta like stuffing a size 12 foot into a size 10 shoe..only aluminum doesn't stretch like shoe leather, ya know?

Broken taps are a pain to extract, and broken alloy castings are a pain to weld. Again, if it works for you, so be it..but recommending incorrect methods to a mechanical noobie is sorta asking for disaster, IMHO.

[Gloyale]

Simply tapping the stripped factrory stud hole works fine. Lots of cutting oil(or WD) and go very slow and easy, backing out the tap ever so often to clear the chips. I can attest to having done this many times with no trouble on many soobs. NotHelicoiling it now also leaves the option for it later, should another teardown/rebuild may see that hole strip again. (seems like they always do!) Helicoils are tricky. And if you don't already have the set, are expensive. (relative to studs and a tap)

 

If you just have one stud that popped loose causing an exhaust leak, tapping and stud can be done to a single stud, leaving exhaust in place, without distrubing the other 3 bolts. Which would likely lead to having to "fix" 3 more holes than you wanted to do this weekend:)

[Milemaker13]

Yeah, what Gloyale said!

So, I fixed it. Here is what I did... I checked out the drill size for 7/16. My stripped 10mm hole (.40) was just about perfect size for a fine thread 7/16, but a little large for the coarse thread 7/16. I only had fine thread (7/16-20) tap and bolt anyway. I used a ratchet and socket and WD40 and went nice and easy. It worked out perfectly. Did not have to remove exhaust flange to repair, still have helicoil option later. Very easy, fast (emergency) fix.

Thanks to all who helped me here... Thanks Dan.

[ZRX Doug]

No attitude, I just don't like hack jobs regardless of the worth of the vehicle..I prefer to do it right the first time and forget about it, ya know?

BTW, I've been an ASE certified mechanic off & on since the days when they were known as NIASE, 'bout 26 years now. Worked in Toyota, GMC, Mercury, and Kawasaki/Yamaha/Honda shops. Nowadays I wrench out of my garage for spare cash and work with electronic banking equipment for my "real" job. You don't need to be a Subie mechanic to know how to work with tapped alloys..that's basic knowledge, not something that's specific to any particular make. I have no problem with doing the occasional band-aid fix on my own vehicles..but I'd never treat someone else's ride with anything but kid gloves, and this work ethic spills over to advice given.

 

I don't wanna start a fight with the resident gurus. I'm glad that the shortcut works for you guys.

 

Peace.