rdweninger Posted February 29, 2012 Share Posted February 29, 2012 Hello all, '85 GL Wagon, 1.8 liter, carb. I have an exhaust bolt that has vibrated out twice now... in 19 years (with locktite). So I think I need to drill out and heli-coil the threads. Does anyone know the drill size, tap size, thread size, hole depth for the exhaust bolts? I have a line on some heli-coils (maybe not that brand). And I have drill bits and metric taps. So I don't want to buy a kit. One other thing, why is there one stud and one bolt on the exhaust? Is this for ease of installation? Has anyone just installed with 2 bolts? Quote Link to comment Share on other sites More sharing options...
tractor pole Posted February 29, 2012 Share Posted February 29, 2012 (edited) the thread size is a M10x1.25 the Heli-Coil kit requires a 13/32 drill bit and uses their special tap size the part number on the tap is 575-10. I just bought a kit a couple months ago and it was $65 from NAPA. I should say that this was for my EA82, I believe that they are the same thread size/pitch. I can't remember if they were ea81 or ea82 in 1985. hth Ben Edited February 29, 2012 by tractor pole add info Quote Link to comment Share on other sites More sharing options...
rdweninger Posted February 29, 2012 Author Share Posted February 29, 2012 thanks for the reply. So it sounds like the tap is something special... not just a straight forward metric tap? Did the kit say what the 'size' of the heli-coil is? Did you install 2 bolts or did you stick with the one stud? Quote Link to comment Share on other sites More sharing options...
tractor pole Posted February 29, 2012 Share Posted February 29, 2012 thanks for the reply. So it sounds like the tap is something special... not just a straight forward metric tap?Did the kit say what the 'size' of the heli-coil is? Did you install 2 bolts or did you stick with the one stud? not just a straight forward metric tap, it is an oversized diameter with the same thread pitch.you might be able to source one in a 'very fine' thread pitch but I don't know what diameter would work. so the kit size is M10x1.25. I replaced all 4 of the studs (2 each side) Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 29, 2012 Share Posted February 29, 2012 You can't use a regular tap to install a heli-coil. You have to use a special heli-coil tap that's correctly oversized for the insert. I've looked into this in the past and they do not correspond to any commonly availible sizes. The stock exhaust stud size is M10 x 1.25. The "Screw Thread Insert" (STI) Tap for this size heli-coil is called an "M10 x 1.25 STI Tap". They run about $25 on their own. Here's the complete kit with inserts: http://www.threadtoolsupply.com/M10x125-professional-helical-insert-repair-kit.html You don't have to heli-coil them if you don't want to buy a kit though. Just oversize them to 7/16" x 14 with a plug tap and bottoming tap. Then use 7/16" x 14 all-thread to make new studs. Loctite really won't help with exhaust studs much since the temps can easily exceed what even the red (271) thread locker will withstand. GD Quote Link to comment Share on other sites More sharing options...
rdweninger Posted February 29, 2012 Author Share Posted February 29, 2012 Hello there GD. I read a previous thread where you said 7/16 x 20. I guess that's a fine thread. Is the 14 better? I think I'll go with drilling them out and tapping for 7/16. I've got a friend who works for Cascade Nut & Bolt... he can get me some deals on stainless hardware. How deep are the existing holes or the insert coil lengths? My brother thinks I should go with Keenserts. Uses standard drill bit and tap. You can see them at http://www.newmantools.com/kee.htm Off topic... my '85 Negro decided to kill all it's electrical equipment. The alt. went out, the disty went out, and starter. I replaced the alt. with a spare I've been packing around for 10 years. The disty is being rebuilt at Philbins. And I found the starter contacts here in Tillamook for $1.98 / pair. I filed down the copper plunger ring and all is well. Quote Link to comment Share on other sites More sharing options...
desertsubaru Posted February 29, 2012 Share Posted February 29, 2012 Why do you need the bottoming tap? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 29, 2012 Share Posted February 29, 2012 Hello there GD. I read a previous thread where you said 7/16 x 20. I guess that's a fine thread. Is the 14 better?I think I'll go with drilling them out and tapping for 7/16. I've got a friend who works for Cascade Nut & Bolt... he can get me some deals on stainless hardware. Beware of stainless on stainless - if you use stainless studs then don't use stainless nuts. Use zinc coated. Stainless paired with stainless will easily gall the threads and they will never come apart. 7/16 x 14 or 7/16 x 20 will both work fine. The 20 is a finer thread and typically with aluminium a coarser thread works better. How deep are the existing holes or the insert coil lengths? My brother thinks I should go with Keenserts. Uses standard drill bit and tap. You can see them at www.newmantools.com/kee.htm Existing holes are 3/4" deep or so. The general rule with aluminium is 2x the diameter of the thread for proper engagement. Well - the problem I see with those inserts is they use much larger taps than a heli-coil. The M14 x 1.5 tap is still about $15 with shipping from Amazon. I see no appreciable difference in price nor any compelling reason to use them over a standard heli-coil. You are still going to buy their inserts and installation tool as well as a tap from another supplier.... you might save $10 in the process. I would rather have the whole kit in one box from one supplier. Being aluminium the tap is not really a wear item if you are careful with it. I have used a lot of heli-coils in my career. I've never had one fail or back out on me. Off topic... my '85 Negro decided to kill all it's electrical equipment. The alt. went out, the disty went out, and starter. I replaced the alt. with a spare I've been packing around for 10 years. The disty is being rebuilt at Philbins. And I found the starter contacts here in Tillamook for $1.98 / pair. I filed down the copper plunger ring and all is well. Nice! It all worked out well I see. GD Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 29, 2012 Share Posted February 29, 2012 Why do you need the bottoming tap? Get those last few threads for extra strength. Aluminium should have 2x the diameter for thread engagment. It's just added insurance and it's the *right* way to do it. You don't *have* to - but if it fails won't you feel silly? GD Quote Link to comment Share on other sites More sharing options...
BendSuby Posted March 8, 2012 Share Posted March 8, 2012 I have the same problem with one vibrating out, and having trouble with an exhaust leak. 7/16 by 20 or by 14 correct? What do you mean by 2x? Also, did subaru have a gasket between manifold and block from the factory? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 8, 2012 Share Posted March 8, 2012 Yes - get your exhaust gaskets from the dealer. 2x means that aluminium should have a thread engagement that is twice the diameter of the threads. Steel = 1x Cast iron, brass, and bronze = 1.5x Aluminium, zinc, and plastics = 2x GD 1 Quote Link to comment Share on other sites More sharing options...
BendSuby Posted March 8, 2012 Share Posted March 8, 2012 Sweet! Thanks! Quote Link to comment Share on other sites More sharing options...
ivans imports Posted March 8, 2012 Share Posted March 8, 2012 do so many 10/1.25 hili coils the parts guys cant keep them in stock part of my headgasket jobs i heli coil them all i have found that a tap on size bigger fits i use a 11/1.25 tap for 10/1.25 hili coil make shure you buy the kitt with meatal insert tool the plastic ones are crapy i end up hili coiling alot of head bolts to mostly 2.5 d s and ea 81 /ea82 they are 11/1.25 insert also put a bitt of antisize on the coil when you install will save greif sometimes there a bitt tight to put in Quote Link to comment Share on other sites More sharing options...
rdweninger Posted March 8, 2012 Author Share Posted March 8, 2012 So, I'm pulling the motor in another '85 EA82 and will be doing a reseal from the HG's up. I want to be prepared for head bolts stripping out. Anyone know the thread size for head bolts? And what length of heli-coil goes in there? Quote Link to comment Share on other sites More sharing options...
naru Posted March 8, 2012 Share Posted March 8, 2012 do so many 10/1.25 hili coils the parts guys cant keep them in stock part of my headgasket jobs i heli coil them all i have found that a tap on size bigger fits i use a 11/1.25 tap for 10/1.25 hili coil make shure you buy the kitt with meatal insert tool the plastic ones are crapy i end up hili coiling alot of head bolts to mostly 2.5 d s and ea 81 /ea82 they are 11/1.25 insert also put a bitt of antisize on the coil when you install will save greif sometimes there a bitt tight to put in I make a metal insertion tool by grinding the end of a bolt when the kit only comes w/a plastic one.Good tip on the taps.Certainly lowers the price. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 8, 2012 Share Posted March 8, 2012 So, I'm pulling the motor in another '85 EA82 and will be doing a reseal from the HG's up. I want to be prepared for head bolts stripping out. Anyone know the thread size for head bolts? And what length of heli-coil goes in there? I can sell you the other half of the one's I bought for your GL-10's block. Have to buy them in quantities of 50 and you only need 18 per block so I have plenty leftover. They are M11 x 1.25 x 33mm inserts. GD Quote Link to comment Share on other sites More sharing options...
rdweninger Posted March 8, 2012 Author Share Posted March 8, 2012 thank you for the offer GD. However, I'm using Keen-serts. I've already got the drill, tap and insertion tool the size I'm using for the exhaust studs. I just need to know the threads for the head bolts. Which now I know is M10 x 1.25 Which is the same as the exhaust bolts. Only difference is the depth of the Keen-sert (read length). I'll use something between 20 & 30 mm. Depending on what they offer. I just want to be prepared... beings I'm a long way from town and I'm planning on getting this done in one weekend. (Hopefully). Still gathering parts! Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 9, 2012 Share Posted March 9, 2012 No the head bolts are NOT the same as the exhaust studs. The head bolts are M11 x 1.25. One millimeter larger. With aluminium you want as much thread engagement as you can get for the head bolts which is why I use 33mm inserts. The threaded section of the holes is 37mm deep. I would not use the Keen-serts as they have those tiny locking tabs that have to be driven down - those could cause issues with the head gaskets not to mention the driver tool that seats them could create a divot around the hole. With any insert you are enlarging the hole but it would be best to keep the amount of the enlargement to a minimum. Which the heli-coil's do. And besides all that the Keen-serts aren't availible in the required size so you can't use them regardless of desire GD Quote Link to comment Share on other sites More sharing options...
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