Using bolts 8.8 with heads cut off for engine studs

crackers

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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:
 
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.
 
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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!
 
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
 
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.
 
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.
 
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.
 
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:

http://www.k-tbolt.com/bolt_chart.html

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