Cylinder head exhaust manifold threads threaded

1. Jonny_wilk Newbie Joined: Jan 2013 Durham Posts: 15 Flat arch saxo Forte with vtr engine/box conversio

   #1 5th March 2013, 21:54

   Fitted my 4-2-1 manifold at the weekend and one of the holes is threaded on port three will it be ok to run a tap down the threads and put a longer bolt in as it's only the first 3-4 threads that are gone.
2. user_39461 Super Moderator Joined: Nov 2009 Cambridge(ish), UK. Posts: 10581 BMW 5x M50d.

   #2 6th March 2013, 08:37

   Quote:

   Originally Posted by Jonny_wilk Fitted my 4-2-1 manifold at the weekend and one of the holes is threaded on port three will it be ok to run a tap down the threads and put a longer bolt in as it's only the first 3-4 threads that are gone.

   I wouldn't run a longer bolt but you could maybe go up a size. You risk drilling into an oilway in the head if you run a longer bolt. The thing to do would be to see how deep the factory hole is - measure it with a coat hanger or something - then run the longest bolt you can into that hole - might give you an extra 5mm or something doing it that way.
3. axsaxoman Saxperience Forum Bum Joined: Jan 2003 Scotland Posts: 3380

   #3 6th March 2013, 09:21

   that will teach you for trying to refit the studs with the nuts still on them .
   very common --you must fit studs to head , if they come out with the nuts still on them .
   
   cure is to fit a helicoil or better still a "time sert "
   this replaces the thread with a steel insert back to correct size going up to 10mm size will make it hard if not impossible to fit manifold nut
   golden rule any bolt must threade in to a depth of at least 1.5 times the diameter of the bolt --so that means its an 8mm bolt it needs to be in 12mm
4. yr51ocw Frequent Poster Joined: Oct 2005 Posts: 751

   #4 6th March 2013, 19:22

   When I design a part I aim for minimum 2D thread engagement when aluminium is the parent material. 1.5D minimum for steel
5. Jonny_wilk Newbie Joined: Jan 2013 Durham Posts: 15 Flat arch saxo Forte with vtr engine/box conversio

   #5 6th March 2013, 21:23

   Thanks for the help people the one that's threaded is the only stud that came out and it was already blowing from there before I removed the old one and when it came out there was sum coils of thread around the stud. But I need the car to get to work so had to put the manifold on and just leave the stud out until I sort it so it didn't do any more damage to the threads.
   
   I'll measure how deep the hole is tomorrow so I know what length to go for.