Royston W Posted August 3, 2022 Report Share Posted August 3, 2022 Exhaust manifold GT6 mk3 is missing some fixings ! anyone know what they are please, bolts or studs, and size too would be good. thanks in advance if you can advise. cheers Royston Link to comment Share on other sites More sharing options...
johny Posted August 3, 2022 Report Share Posted August 3, 2022 How strange - I hope there not snapped off in there or the thread stripped😮 Link to comment Share on other sites More sharing options...
Royston W Posted August 3, 2022 Author Report Share Posted August 3, 2022 I've poked a wire down the hole and I think they are just missing ! Link to comment Share on other sites More sharing options...
Royston W Posted August 3, 2022 Author Report Share Posted August 3, 2022 I presume all bolts on the Triumph are UNF thread ? Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 3, 2022 Report Share Posted August 3, 2022 I'm trying to remember if those are just rollpins or dowels not bolts. I think they might be? Link to comment Share on other sites More sharing options...
Royston W Posted August 3, 2022 Author Report Share Posted August 3, 2022 Sorry , but while I'm attempting to understand Bolt dimensions, could I also ask about spanner sizes too, does a 9/16" spanner relate to a 9/16" bolt ? The bolts on the end of the exhaust manifold are definitely undone with a 9/16" spanner , and their thread seems to be UNF, Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 3, 2022 Report Share Posted August 3, 2022 these exhaust fixings are studs and nuts being 3/8unf x24 on your Mk2 6cyl ( 9/16AF spanner ) as for spanner sizes 1/2 af is the width across the hex flats and would be 5/16 x 24 UNF 9/16AF is for a 3/8 x 24 unf nut/bolt MkII 2 Litre Cylinder Head : Canley Classics MkII 2 Litre Manifolds : Canley Classics Link to comment Share on other sites More sharing options...
Josef Posted August 3, 2022 Report Share Posted August 3, 2022 13 minutes ago, Royston W said: Sorry , but while I'm attempting to understand Bolt dimensions, could I also ask about spanner sizes too, does a 9/16" spanner relate to a 9/16" bolt ? The bolts on the end of the exhaust manifold are definitely undone with a 9/16" spanner , and their thread seems to be UNF, UNF spanner sizes are given as AF. This means ‘across flats’ - the distance between parallel faces of a nut/bolt. The thread size is the diameter of the actual threaded part of the bolt. Normally a given thread size corresponds to a given spanner size. But there are exceptions (seatbelt bolts usually have larger than ‘normal’ heads relative to their thread for example) Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 3, 2022 Report Share Posted August 3, 2022 17 minutes ago, Royston W said: Sorry , but while I'm attempting to understand Bolt dimensions, could I also ask about spanner sizes too, does a 9/16" spanner relate to a 9/16" bolt ? The bolts on the end of the exhaust manifold are definitely undone with a 9/16" spanner , and their thread seems to be UNF, See which size of spanner fits the bolt shank, not the head. That's the lazy man (me) method of checking the required size. A 1/2 inch spanner might fit the hex head but the actual hole required is 5/16, and so on, so I'll fit the bolt into a smaller spanner and if it touches the sides of the 5/16, or a 3/8 or 1/4 then that's the size I need. Link to comment Share on other sites More sharing options...
NonMember Posted August 3, 2022 Report Share Posted August 3, 2022 56 minutes ago, Josef said: Normally a given thread size corresponds to a given spanner size. But there are exceptions There's a particular oddball with the 7/16"UNF which is specified to have 5/8" AF bolt heads but 11/16" AF nuts, IIRC. Link to comment Share on other sites More sharing options...
Josef Posted August 3, 2022 Report Share Posted August 3, 2022 9 minutes ago, NonMember said: There's a particular oddball with the 7/16"UNF which is specified to have 5/8" AF bolt heads but 11/16" AF nuts, IIRC. The one I was thinking of was 7/16” UNF. I’ve got ex seatbelt fitting kit bolts with larger heads than the non-seatbelt specified ones I bought. Recently fitted a vice to my metalwork bench with a mix of these so it was stuck in my head. Link to comment Share on other sites More sharing options...
Stratton Jimmer Posted August 3, 2022 Report Share Posted August 3, 2022 This might be useful to you Royston W: Link to comment Share on other sites More sharing options...
Royston W Posted August 3, 2022 Author Report Share Posted August 3, 2022 thank you for all the info. Seems like I will have to remove inlet and exhaust manifolds in order to gain access to the stud holes. Just to complicate matters I searched all the spares that came with car , including a large box of nut and bolts of assorted sizes and threads ( certainly not all from this car) and found 3/8" stud with UNC one end and UNC the other so if this is a missing stud ,the holes in the head might actually be UNC. Life is never simple. Thanks again Royston Link to comment Share on other sites More sharing options...
johny Posted August 3, 2022 Report Share Posted August 3, 2022 Certainly something strange seems to have happened to leave out those fixings - the exhaust gasket wont last very long before leaking. Can you take that bolt out on the far RH end of the exhaust manifold or find a suitable length 3/8 UNF bolt and try it in the empty holes to verify what the thread is and if its any good? Link to comment Share on other sites More sharing options...
Steve P Posted August 3, 2022 Report Share Posted August 3, 2022 I see the end one is a bolt,that`s what i have on mine.All UNF. Steve Link to comment Share on other sites More sharing options...
johny Posted August 3, 2022 Report Share Posted August 3, 2022 Yes theyve got changed over the years but would have been studs originally to facilitate installing the gasket and then sliding on the whole manifold assembly. I would expect UNF in cast iron and then the courser UNC thread used in softer metals or where theres risk of cross threading... Link to comment Share on other sites More sharing options...
Royston W Posted August 3, 2022 Author Report Share Posted August 3, 2022 unfortunately there is no access to " the holes" without taking off carbs and inlet manifold, just ordering new studs and gaskets from Rimmer bros and have begun the tedious task of removing carbs ( fitted with heat shields that restrict access to their bolts too) Oh the fun of it, just unbolting stuff , taking it off, putting it back on, 🤪 then tightening it up again, a mechanics life ! Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 3, 2022 Report Share Posted August 3, 2022 the studs are 3/8 x24unf both ends the head is tapped 3/8" x24 UNF they are not UNC you can use a setscrew iinstead of studs f you can get them in and aligned without removing the manifold you only need a length in the head of 1.5 times its diameter so thickness of flange plus around 0.6" Pete Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now