Installing a Heli-Coil on a 2.5 Hi-perf Block...Best way to Drill Out Old Hole...Help

[G-Train]

I need to install a Heli-Coil in a 2.5 Block.
I have done this with a hand held drill several times before, and had success, with no guide.
I have since become more cautious, and would like any advice on how to drill it with a portable guide of some sort (what type of guide?).
I don't want to strip the bock down and take to a machinist, if I don't have to.

Any good advice is appreciated.

Thanks
Greg

[Motv18]

If I have time I step up the tap set and screw it in.

Ive also gone with a step bit to make a guide hole.

Theirs a special bit available that has a sheath that keeps the bit square.

As as long as you have lube and a good tip on the bit it should go straight

[skeeter91]

If you want a guide for drilling it square, drill a clearance hole in a 3/4" piece of aluminum. Line it up over the hole to drill. Hold it with one hand, drill with the other. Depending on where you are drilling, you could also make the guide block large enough to pick up another threaded hole and use it to hold it down.

[Jay Smith]

JMO Might look at the Time Sert thread repair method I’ve been very successful with them for years they are an insert and no need to “stack” to get full length of thread repair needed , if your repairing head bolt thread damage they make an insert that’s 1”.200” long perfect for head bolt thread repair , the kits aren’t cheap but neither are blocks ....

Good luck if you need part numbers for your repair call me ,
Jay @ JSRE

[G-Train]

Thinking about it, why couldn't I use an old head as a Guide?
This is a head bolt on a 2.5 Drag. I have some old 260 heads that the pattern is the same.

Jay, what is the part # for the Time Sert?

Thanks you guys for giving me ideas

Greg

[Chaz]

If you want a guide for drilling it square, drill a clearance hole in a 3/4" piece of aluminum. Line it up over the hole to drill. Hold it with one hand, drill with the other. Depending on where you are drilling, you could also make the guide block large enough to pick up another threaded hole and use it to hold it down.

If you don't have access to a mill and a 30* fixture to level the deck. Then the above is your best bet for getting the pilot hole straight.
If you go the Time-cert method, you might want to stick with the stainless inserts which only go up to 1.000" ( more than enough thread @ three times bolt diam. )
Or if you do put a mild steel 1.200" insert in the hole, make sure it's waxed shut if you ever send the block in to be replated.
Heli-coil makes a straight one-piece insert's in both 1.000" and 1.250" long .375 x 16 in stainless that wouldn't be affected by the acid bath @ the platers. Just thinking ahead ...

[Jay Smith]

Greg , pictures and information ( parts numbers and phone number ) sent !

Good luck ,
Jay @ JSRE

[G-Train]

Thanks Jay...Good Stuff

[LakeFever]

If the bolt is steel and the block aluminum I weld nuts on top of flush broke bolts all the time with 100% success so far ( auto heads ) but if its broke down the hole a bit and theres some threads avail? I center drill out a threaded bolt 1/8" or so on the drill press and thread that into the hole to use as a pilot guide then hand drill and its perfectly centered so you dont drill askew. Once you have your center you can carefully hand drill the rest or use an extractor

[FUJIMO]

while on the subject, does anyone stud they're blocks, for the heads, like we used to do with Champ race blocks, a million years ago? or is that a no-no these days?

[G-Train]

Fujimo...This is a Stud that pulled out. I tightened to the wrong spec and pulled the threads in this one hole. I try to always use Studs, I know others like the bolts.

[FUJIMO]

gotcha

[Jay Smith]

JMO , I’ve NEVER use studs in heads ever ... Just built a drag motor that was studded put the set in the trash can , motor had 3/8” coarse all thread ( junk ) , bought and installed new set of the proper bolts from WSM done deal ...

Disclaimer :
BTW All I respond to on any post is simply my opinion and what’s successfully worked for me and my customers for the 25 years I’ve been building and racing these engines , some may agree some disagree you’ll not hurt my feelings at all ..




God bless,
Jay @ JSRE

[flabum1017]

Thinking about it, why couldn't I use an old head as a Guide?


Greg

That would work fine, drill the head the size you need on a drill press. Drill the hole in the block, put the old head back on the drill press and tap it with the insert tap, put it bac on the block and you can tap the block square too.

[LakeFever]

I thought there was a bolt stuck in it I was in a rush and didnt read. Use varsol for cutting fluid on aluminum and it comes out very nice with no burrs or galls. A guide tube of some sort is ideal and whenever I need a tool that I dont have I tend to make a tool that does the job. A small piece of plate with two head bolt holes drilled you can bolt down flush 1/4" thick or whatever you have, you could even use plywood if you like. Then a drilled guide billet or pipe plotted out directly over the hole and welded or fastened to the base plate will keep the bit true. Hope some of this helps