fixing a crooked hole in a engine block need ideas

[buildmyown]

I screwed up was putting one of my snowmobiles back together with a new top end. Broke one of the cylinder bolts off in the block on the final round of torquing them down. No idea how or why they are only torqued to 45ftlbs. I drilled it and went for an easy out but it would not budge so i just kept drilling it out bigger and bigger i thought i was drilling it straight but with the motor mounted on an angle i was not. With the weather changing i said screw it and pulled the motor out and brought it inside.

Option one make a jig to hold the motor level and square in my drill press and use one of the other holes to index off off and drill over size and time sert it.

Option 2 split the case and give it to a friend of mine that works in a machine shop and let him do it in the bridgeport,

Option 3 if i can find a long enough drill bit in the right size i could use the cylinder as drill guide.

 

[joecon]

Use the head as a jig by putting a drill bushing in the bolt hole and than drilling
though it and retapping it.

 

[FOCUS.FREAK]

Would it be possible to Timesert it? I had to timesert the bottom of my case on my yz125. previous person helicoiled it and the thread fell out.

 

[shawnspeed]

What about using your drill press & a block of wood, along with a base gasket for reference, and make your self a drill guide that you don't need a long bit for???Then place it over the 3 other studs & use your hand drill as needed.....I would also mark your bit so you don't go too deep...Shawn

 

[buildmyown]

What about using your drill press & a block of wood, along with a base gasket for reference, and make your self a drill guide that you don't need a long bit for???Then place it over the 3 other studs & use your hand drill as needed.....I would also mark your bit so you don't go too deep...Shawn

Oh man i think you just nailed it thank you. Wish i thought of that before it would have saved a lot time and aggravation.

 

[NHBandit]

Hard to tell but it looks like you may be at the point where you can use a small hammer & punch to remove what's left of the old bolt by collapsing it into the hole and pulling it out. Then use the cylinder to center the hole & drill it our for a timesert.

 

[gorilla]

A twist drill will follow the existing hole, you might get away with a drill and a jig with a bushing, Best way is to get it on a milling machine open the hole up with an end mill to make it round and then install the insert of choice.

 

[buildmyown]

Hard to tell but it looks like you may be at the point where you can use a small hammer & punch to remove what's left of the old bolt by collapsing it into the hole and pulling it out. Then use the cylinder to center the hole & drill it our for a timesert.

I was able to get the rest of the old bolt with a pick and and punch. The real problem now is the hole needs to be 90 degrees to the deck and my first attempt has the hole going at like a 5-10 degree angle.

A twist drill will follow the existing hole, you might get away with a drill and a jig with a bushing, Best way is to get it on a milling machine open the hole up with an end mill to make it round and then install the insert of choice.

I have a feeling its going to do exactly that so my plan now is to use the wood jig/drill guide to get me centered up and i can drill over size thread the hole insert a bolt with some permanent loc tite and cut it off flush with the deck. Make another jig with the right size hole and drill into that bolt and tread it for the right size cylinder bolt. clear as mud right.

 

[gorilla]

Wood is the worst choice you could make for a drill jig. The drill bit will cut it away like butter. You need a material hard enough and thick enough to keep the drill perpendicular to the surface. You don't really need a drill jig for the first drilling operation because you are going to glue your insert in and then grind it parallel to the surface. I've done exactly what your trying to do many times with good results, your on the right track. Good luck!

 

[shawnspeed]

I forgot to mention hardwood...or a chunk of aluminum would also work...good luck Shawn

 

[Deadhead]

i vote option 2

that needs an endmill on a brideport before you ruin it

 

[garboui]

+1 on the machining of a new hole. you already have someone to do it the proper (least risk) way for you so you might as well. it will be worth the case of beer

 

[Lurker]

i vote option 2

that needs an endmill on a brideport before you ruin it

Another vote for Option 2.

 

[zkling]

A twist drill will follow the existing hole, you might get away with a drill and a jig with a bushing, Best way is to get it on a milling machine open the hole up with an end mill to make it round and then install the insert of choice.

That is how I would repair it, plunge down with a short 4 flute. The hardest and most time consuming part is going to be getting it jigged up properly.

 

[tdkkart]

Bridgeport, sink an end mill in to get a clean hole and then repair it. One fix is to drill/tap to a convenient size, make a brass or aluminum threaded plug to screw in the new hole then go back and drill/tap to the original size.

AND when you're all done, double check those torque specs, 45ft/lbs is 540 in/lbs seems REALLY high for what appear to be 10mm bolts in aluminum. There's no way you should have twisted a stud off on reassembly.

 

[ilovevocs]

Another vote for pulling it out and getting it on the mill. Not allot of work and its the correct path.

 

[shoot summ]

If you don't fix it correctly it will always have issues and can cause more damage. Split the cases and do it right....

 

[brucer]

as a toolmaker, I would suggest taking it to a machinist..

That way you dont screw it up


I think it might be able to be setup without splitting the cases.. A guy with a bridgeport mill could shim it flat, clamp it down firmly, but not get stupid with it, tilt the head of the mill and plunge mill it with carbide, then drill and tap it...

The biggest thing is getting it back on correct location.. make sure you take the cylinder with you so the guy can measure the cylinder..

 

[iajonesy]

as a toolmaker, I would suggest taking it to a machinist..

That way you dont screw it up


I think it might be able to be setup without splitting the cases.. A guy with a bridgeport mill could shim it flat, clamp it down firmly, but not get stupid with it, tilt the head of the mill and plunge mill it with carbide, then drill and tap it...

The biggest thing is getting it back on correct location.. make sure you take the cylinder with you so the guy can measure the cylinder..

This is the best way to do it,by far.

Mike

 

[buildmyown]

Bridgeport, sink an end mill in to get a clean hole and then repair it. One fix is to drill/tap to a convenient size, make a brass or aluminum threaded plug to screw in the new hole then go back and drill/tap to the original size.

AND when you're all done, double check those torque specs, 45ft/lbs is 540 in/lbs seems REALLY high for what appear to be 10mm bolts in aluminum. There's no way you should have twisted a stud off on reassembly.

Close enough they are 8mm and i fat fingered that it should have been 25ft/lbs still no idea why the bolt broke.

I think im just going to split the case this weekend will give me a chance to throw some new crank seals in it and inspect the crack. Its not that bad of a job done them before just one of those if i dont have to type of things./

I should have just pulled the motor in the first place to get the bolt out. I was working in an awkward position in my trailer. For the extra 30mins it would have taken me to pull the motor out and do it on the bench its going to cost me a lot more time.

 

[tdkkart]

Close enough they are 8mm and i fat fingered that it should have been 25ft/lbs still no idea why the bolt broke.

Even that seems high(300in/lbs, the single cylinder stuff I'm used to is 8mm, spec'd at 200in/lbs aluminum and we don't even go that high, usually 160, because as they get older the aluminum tends to soften. Seen A LOT of them pull out, never seen a broken stud though.
Double check, are the bolts all the same length??

 

[buildmyown]

Even that seems high(300in/lbs, the single cylinder stuff I'm used to is 8mm, spec'd at 200in/lbs aluminum and we don't even go that high, usually 160, because as they get older the aluminum tends to soften. Seen A LOT of them pull out, never seen a broken stud though.
Double check, are the bolts all the same length??

Yes they are what im thinking is a piece of dried hard loc tite fell down in the hole and was compressing and caused the bolt to bottom out till it had no where to go and gave a false reading. I dont really know just a theory. I did just double check my book and for the bolts that hold the jugs to the block it is 25 and for the bolts that hold the head to the jugs its 22.

 

[buildmyown]

Case is split he is going to pick it up tomorrow

 

[spv]

Would it be possible to Timesert it? I had to timesert the bottom of my case on my yz125. previous person helicoiled it and the thread fell out.

I vote for this. I would however mill a straight hole with a slot drill, and then put a "big-sert" time-sert in as the hole is likely going to be rather over sized. Time-serts are amazing, and have a really nice snug fit thread.