Using bolts 8.8 with heads cut off for engine studs

Discussion in 'General Questions' started by crackers, Sep 9, 2009.

  1. crackers

    crackers Member

    I thought upgrading my engine mount carb and exhaust studs to 8.8 was a good idea since I couldn't find any metric allrod close but I've read since I've done this that the 8.8 bolts can snap because there too hard and brittle. Plus they would be really hard to get out with an easy-out because of there hardness. Is this true, do I need to remove them and replace with grade 5 hardware? :confused:

  2. Al.Fisherman

    Al.Fisherman Active Member

    I'm going with 8.8 in the jugs and 5 on the exhaust/intake. There are a number of places that have all thread, but I've only found it in grade 5. Where are you located? I have another engine coming in (should be here Friday) first thing I'm going to do is pull the jug and drill and tap (twice a many threads for holding) exhaust studs and upgrade to a grade 5. I made a jig to do this out of a 2 x 6. You can drill the exhaust stud holes and tap all the way through to the head bolts...just remember if a need to remove the jug is needed the exhaust studs need to be backed off. Grade 5 for intake (no drill and tap) as there is not the strain on them as the exhaust studs.

    By the way...I thought about and tried to cut threads on a #8 Grade 8.8 bolt with the head removed......Good luck.
    Last edited: Sep 9, 2009
  3. crackers

    crackers Member

    I've read on several post on this site and other's that say to upgrade all the hardware with grade 5 or better, so I thought grade 8.8 would be above and beyond any problems that could arise from vibrations produced by my 47cc engine. I don't understand your answer Al whats the good luck for? They haven't snaped yet. I need to know if you think these bolts will fail or not. I would'nt think a 8.8 bolt would just snap, that's the reason for upgrading! Your using 8.8 for head bolts wright? Do you think or have you heard of these bolts snaping because there to hard and brittle? Makes no since to me what would be the point in anybody using them for any reason!
  4. Al.Fisherman

    Al.Fisherman Active Member

    As far as using 8mm (8.8) bolts, cuting the heads off and threading them....Good luck. I don't think they will turn out the way you think they will. As far as the 6mm ...all thread rod will work fine.

    I cut the heads off of a couple 8mm, grade 8.8 and I won't use them (I can post a picture...they were lopsided...both of them)....I'm going to purchase (2) sets from Sick Bikes. $10.00 a set plus ship. Need a set for my sons motor and my motor, but won't know the size until it comes in Friday. At the moment I have grade 8.8 cut down bolts, but can't use locktite with a bolt in these engines. So Good Luck was in reference to threading 8mm grade 8.8's
  5. crackers

    crackers Member

    Thank's Al
    I cut the heads off the bolts and have had them installed in my engine now for about a month and there doing fine. I did find some 6mm 1.0 pitch allrod grade 5 so I'm going to have to pull my engine and replace all of them. I was hoping I wouldn't have to but better to be safe than sorry. I Googled 8.8 bolts and did find that they do become brittle as they get harder.
  6. crackers

    crackers Member

    Now I see what you thought I was trying to do, the bolts I installed were 6mm 8.8 grade, I got them at ACE Hardware.
  7. Al.Fisherman

    Al.Fisherman Active Member

    Did you install them as bolts or cut heads off and thread as studs? If as bolts I wouldn't use lock tite
  8. crackers

    crackers Member

    I cut the heads off and installed them as studs what Iam afraid of is them snaping from all the vibration ( the very reason I put them in the first place because there harder and stronger) but now I find out there also brittle. If they do snap off I might not be able to drill and easy-out them out of the block! Thats my main qustion do you think the 8.8 studs will snap off or do you think they will out live the engine.
  9. Silvaire

    Silvaire Member

    A grade 8.8 metric bolt is nothing magic. Grade 8.8 bolts are about the equivalent of an SAE grade 5 bolt. Both have essentially the same yield and ultimate strength.

    Here is a link to a simple chart showing both metric and SAE bolt head markings and rated strengths:

    A metric grade 12.9 bolt though, now THAT'S hard!
  10. Luka

    Luka Member

    Go to any 'quality' auto parts store.

    You can find studs there, of pretty much any length/size/thread... Which are made for such purposes as exhaust manifolds, intake manifolds, heads, carburetors, etc...

    Get the black ones, and you will never have a problem.
  11. crackers

    crackers Member

    Thanks Silvaire that chart explanes it for me. I think I'll stick with the 8.8 mm studs I've already installed in my engine, I've used an easy-out on grade 5 bolts without any problems and I didn't want to pull the engine to change all studs to a lower grade.
    Luka I live in Calif and they will laugh out loud at you if you ask them for a 6mm 1.0 pitch stud especialy a harden one, I know this from experance.
  12. Pablo

    Pablo Motored Bikes Sponsor

    Really all you need for these bikes is quality Grade 5 (8.8) hardware. If you are snapping or stripping Grade 5, you are an animal in search of a calibrated torque wrench.
  13. crackers

    crackers Member

    Thanks Silvaire after seeing your chart I think I will leave the 8.8 studs I made out of the bolts in my engine. I've had to use an easy-out on grade five bolts before and there were no problems drilling for the easy out.
  14. crackers

    crackers Member

    Speaking of torque wrenchs can somebody show me a pic of one small enough to work on these bikes. When tighting my carb, motor mounts and exhaust bolts all I can get on them is the open end of a 10mm combo wrench because theres no room even for the box end. All I've been doing is to tighting them down untill the lock washer is closed and then giving them about extra 1/4 turn. I wish I had a torque wrench that small, I can't even picture what it must look like. Seeing how theres no room for a socket on these bolts it must be some type of a combation wrench? I've looked on habor freights site and saw nothing, can anybody tell me who sells them?
  15. Al.Fisherman

    Al.Fisherman Active Member

    I use a 3/8 drive (inch # torque wrench....1 foot # = 12 inch #) for the cylinder studs, carburetor and the right exhaust stud. On the left exhaust stud I use a 10mm 1/4 drive socket, a short (6") extension, a 3/8" to 1/4" reducer. PLENTY of room to spare. Aslo I replace the studs with grade 5, use lock tite and locking nuts.

    He has more in stock....well worth the money. I have a 1/2 drive also but not good for these engines.... 12 foot #'s not as easy as 144 inch #'s and larger is very hard to use...too many reducers and extensions.

    Attached Files:

    Last edited: Sep 12, 2009
  16. crackers

    crackers Member

    Thanks Al I'm going to order one today. My clearance problems with getting a scoket on a nut is when I'm installing the exhaust pipe, carb, and rear mounting nuts. There to close to the welds and the round part of the clamp for a scoket to fit on, Ive had to file on these area's just to get clearance enough for a lockwasher to fit flat. Are you having these problems? MY intake and exhaust manifold has welded bead all around there pipe's. The picture of your intake manifold shows no welded bead like mine has, were you able to grind it flat or is it aftermarket?
  17. Al.Fisherman

    Al.Fisherman Active Member

    That is a brand new engine I'm doing all the prep work before I install it. If a washer won't lay flat onto the exhaust flange I'll rework it so it will. The socket that you see is a 1/4" deep thin wall socket...hapens to be a Crafstman....any GOOD brand will have the thin wall. I doubt that a 3/8" drive socket will produce the results you want. To see what I do prior to starting my engine...check this out. I may go overboard but I have plenty of time and this is not needed for transportation.
    By the way, the intake manifold was manufactured as you see it.