Crankshaft Bolt Problem- See Pic
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,583
Likes: 5
From: Richardson Tx.
Crankshaft Bolt Problem- See Pic
I messed up the threads inside the crankshaft hole that you see on the top. The old bolt will not even start in the thread. Can this be re-tapped or am I in trouble? 
http://www.photohost.org/gallery/upl...8/100_0414.JPG
http://www.photohost.org/gallery/upl...8/100_0414.JPG
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
The picture is a little out of focus. If just the first thread or two is messed up you can probably run a tap in and clean the threads. If you have messed up about 1/2 of the htreads it might be a little more problem. Try a tap and see how it cleans up.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
I did the same thing but did it about 1/4 of the in, I used a thread chaser and bought a longer bolt.
BTW I did it by trying to install my balancer with the stock balancer bolt
, I now always use a balancer install tool.
BTW I did it by trying to install my balancer with the stock balancer bolt
, I now always use a balancer install tool.
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Race Director
Joined: Mar 2001
Posts: 11,322
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From: Living in the Hartland
Originally Posted by 79vetter
Is a thread chaser the same thing as a tap?
I also need to change the bolt that goes in there. Is that a dealer part or somethng that I can get at the hardware store?
I also need to change the bolt that goes in there. Is that a dealer part or somethng that I can get at the hardware store?
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
That looks like a main saddle bolt in the pic.
If so, they are specially hardened, specially shanked bolts. The threads are also usually "rolled". Rolled threads are stronger due to cold working. Typically, rolled threads are 20% stronger than cut threads. I, personally, would not use a hardware store variety bolt in there. The damaged bolt might clean up with a die.
If so, they are specially hardened, specially shanked bolts. The threads are also usually "rolled". Rolled threads are stronger due to cold working. Typically, rolled threads are 20% stronger than cut threads. I, personally, would not use a hardware store variety bolt in there. The damaged bolt might clean up with a die.
Last edited by Tom454; Sep 9, 2005 at 09:50 AM.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
From ARP's site:
"Far superior to any other main bolt kit offered for use in competition engines. ARP® main bolts are designed to meet the exacting standards and demands of professional engine builders. Forged from 8740 chrome moly, all bolts feature generous under-head radius and rolled threads for the utmost reliability. The threads are rolled after heat-treating, which makes them about 1000% longer fatigue life than most main bolts, which are threaded prior to heat-treating. Available in the popular High Performance Series, which, at a nominal rating of 170,000 psi, is a premium replacement for OEM fasteners, or the 190,000 psi nominal rated Pro Series, application-specific main bolts with reduced wrenching head and are designed for use in competition applications.
Parallel-ground, hardened washers are included with each kit. "
Even factory main bolts are parallel ground.... which a hardware store grade 8 bolt will not be. The unthreaded shank will also be the wrong length for proper torque/stretch attainment, and they will not be 170,000 psi rated.
Reduce your chances of failure, get the correct bolt. IMOP
"Far superior to any other main bolt kit offered for use in competition engines. ARP® main bolts are designed to meet the exacting standards and demands of professional engine builders. Forged from 8740 chrome moly, all bolts feature generous under-head radius and rolled threads for the utmost reliability. The threads are rolled after heat-treating, which makes them about 1000% longer fatigue life than most main bolts, which are threaded prior to heat-treating. Available in the popular High Performance Series, which, at a nominal rating of 170,000 psi, is a premium replacement for OEM fasteners, or the 190,000 psi nominal rated Pro Series, application-specific main bolts with reduced wrenching head and are designed for use in competition applications.
Parallel-ground, hardened washers are included with each kit. "
Even factory main bolts are parallel ground.... which a hardware store grade 8 bolt will not be. The unthreaded shank will also be the wrong length for proper torque/stretch attainment, and they will not be 170,000 psi rated.
Reduce your chances of failure, get the correct bolt. IMOP
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Originally Posted by Fevre
Tom he stated 'I messed up the threads inside the crankshaft hole' since none of the main bolts go inside the crank so I am pretty sure he means the balancer bolt hole threads.
Thanks for correcting me... my bad.
The pic is so large on my computer that I only saw the main saddle bolt.
Never mind.
har har
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,583
Likes: 5
From: Richardson Tx.
Well, I re-tapped the hole in the crankshaft and put the bolt in the new hole. It goes in fine but when it is all the way in the bolt head looks very slightly crooked. Is this a no-no to leave it this way ?
Safety Car
Joined: Feb 2002
Posts: 4,286
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From: Guam
Did you cut new threads? Was their any shavings coming out as you worked the tap in? I seriously doubt that you could easily cut new threads in that kind of steel and make it very crooked. Anyways, the bolt is only used as a retainer to keep the balancer from sliding off. It has a keyway and the end of the crank is tapered. So if the bolt is tight and puts pressure on the harmonic balancer to keep it on, then it should be okay.
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
When you are screwing around with new bolts, you might consider the ARP bolt with the square opening in the head. Makes it a lot easier to rotate the engine - just stick a 1/2" square extension in there and turn. No worries about rounding a bolt head.