repair of bolt threads on block or weld repair

[MACDABS]

I have used HELI coils on cast iron blocks several times , you have to drill and install them perfect or they will be nothing but trouble! But they work and have saved me from pulling engines or removing cylnder heads . I have also welded many stripped starter mounts on Big Block chevys with iron rod. This is the best fix. If you can not tackle the job find someone it is your best bet.
Drill the old out weld in the new.

 

[bamatoolmaker]

72 are you trying to drill the broken bolts with a hand drill?You can rent a magnetic based drill and it will make it much easier.I too would drill and tap 1 size larger.

 

[AGRIMAN]

I have faced this situation many times and call tell you that there no "one way" to remove broken bolts. Many times (if your lucky) and there is a 1/4 inch or so sticking out you can weld a nut to it and turn it out, but it's not 100%.

Here's my opinion on removing broke bolts, which is based off countless extractions

Use a sharp center punch to center a starting point for your bit. Start with a small bit first, no larger than the punch mark. It's much easier to stay on center and make the first cut with a small bit. Use a good cobalt bit and you may want to buy a few extra if you have very many grade 8 bolts to drill. (Unless you can sharpen them)

Keep stepping up in size until you have at least 3/4 of the bolt drilled out. It you have a set of extractors give them a try but Don't break it! If it don't move stop. If possible put some heat to it. If that don't work then drill it a little bigger.

Usually a bolt will give up and come out by this time, but we all know that's not always the case. One of the best tools I found and what I usually end up using in someway is a die grinder, especially if I get get off center while drilling. A die grinder with a good bit is hard to beat. If you have one or can get one I would advise you to try it. Be sure to get a good (straight not tapered) bit which also has a cutting tooth on the tip, it will cut a hole like a drill bit. I have also used it to grind away material until the treads start to show, then use a good tap to remove the rest, but you have to be careful. If you break a tap then you really only have to options. Cut it out which a torch or bust it out with a punch and it's not fun. I have a tap extractor set but it's only about 30% effective at best.

If you have clearance and can drill to the next size larger bolt that's fine, but DON'T be scared to use a Heli-core. I have used hundreds and they are just as strong if not stronger than the original threads. I've used them in exhaust bolts, engine blocks, wheel bolts, transmissions housings and countless other locations. I have also used them in several engines to replace worn head bolt threads both diesel and gas. Three of the cylinder head studs in my racing engine have Heli-cores and I personally know of at least four 130 and 160 hp JD tractors that are currently being held together with Heli-cores (A problem very similar to yours)

When properly installed (which is not hard) they will hold. Out of the hundreds I've personally used I have never had one to fail.

 

[Soundguy]

Hmm.. I've seen the 'staked' inserts you guys linked to.. my only concern is this sentence at the end of the 2nd paragraph on their main page describing them, and their uses, and materials they can be used in:

(except cast iron or sintered materials).

Soundguy

 

[ctjstr]

I really like Timeserts
++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread repair , stripped sparkplug's, Ford sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts, Ford spark plug repair, Blownout spark plugs, fulltorque, blownoutsparkplugs.
We use them quite a bit with good success. The
real key for any of these methods, drill/tap, Keenserts etc
is getting the hole drilled nice and strait and tapping it strait.
If you don't get that part right, it doesn't matter what you
use.

I've always thought of the keyserts, or keenserts as being
most useful on aluminum

 

[bjcsc]

Hmm.. I've seen the 'staked' inserts you guys linked to.. my only concern is this sentence at the end of the 2nd paragraph on their main page describing them, and their uses, and materials they can be used in:
Soundguy

Yeah, I missed that. I've used them in steel and aluminum but didn't think about the cast iron requirement

 

[toy]

I have a tractor which has a subframe assembly which bolts to the front of the lower portion of the engine block. The front axle, FEL, bonnet, and a few other pieces mount to this subframe.

The bolts holding the subframe onto the block have all sheared or wallowed out. Drilling and extracting is not going well, so I'm looking for suggestions. The depth of the existing 'wallowed' out holes is approximately 1". Three of six holes per side, are sheared, which doesn't leave a lot to work with.

#1 I could helicoil the existing holes-can they take enough torque to provide the lost strength if I can't drill out the other 3 holes?

#2 welding on the block: could I arc weld using a cast iron stick? If so, I would open up the existing holes through the subframe and weld the subframe onto the block. My guess, IF it's allowable, I could only do one shot at a time, then let it cool for a considerable amount of time so as not to heat up the block too much (of which oil pan is nearby). The other concern is will the weld hold through out the years?

If anyone has some ideas, please share

Have you tried drilling them out with left hand drill bits. They drill in reverse on your drill, and as they drill they are putting force on the broke bolt and a lot of times they will pull the bolt as they drill.

 

[laurencen]

be carefull welding around grade 8 bolts, they harden up making it impossible to drill, good quality left hand drill bits usually do the trick

 

[Eagleview]

Another trick i have done in the same type of situation is to use any other existing bolt holes anywhere in close proximity . All you need to do is fabricate a bridging bracket to weld/bolt to the subframe . Have a good look around the area , horizontal or vertical holes , it does not matter its easy to weld on a tab to the frame to utilize another hole . Do not weld to the cast housing It will look shody and will not work as it will crack even if you use stainless rods not to mention not being able to remove it later for repairs . Weather you use stainless thread inserts ,tap new threads or utilize other holes or all of the above make sure you grind all surfaces flat again as the holes will be flared . If you dont it will be loose again in hours .

 

[jimmysisson]

I second Iron Horse with the no welding. Cast and steel two different animals and will handle stress differently. You'd probably damage the cast once you started to load it again. The bolts and the steel are your leeway - cast is brittle.
Jim