Helicoil kit for Inlet Manifold

[73stagman]

Sorry to be argumentative but if you use a 5/16 drill to tap a 5/16 UNC hole your tap will fall in the hole. (The 5/16 is the major diameter of the thread the UNC is the thread form.)
If you are using helicoils or any other brand of kit ONLY USE THE TAP AND DRILL THAT COMES WITH THE KIT. (An imperial kit will use an imperial drill bit. There will be a "nearly the same" metric equivalent but when you are trying to recover threads in old aluminium castings and drilling the holes by hand you need to be very accurate with drill sizes.
Always tap with lubricant. Always turn the tap 1/4 to half a turn max at a time and back it right off to clear the swarf from the threads. You can do it quicker, use different taps and rills but you will risk damaging the thread for the helicoil or the coil will bind and twist when you are installing it.

We use helicoils and their equivalent to reinforce threads not just to repair them every day. We also use "locking" inserts that remove the requirement for spring washers

We found the biggest difference in the brands is not the coil insert but the insertion tooling that comes with the kits.

Just to be clear I know people are talking about "Thread repairs" and that a 5/16 thread "REPAIR" can be tapped when the hole is predrilled with a 5/16 drill but my point is to use the drill bit that comes with the kit. Those of us who have been doing this stuff since our school days can bend the rules and learn our own ways but the people who doing this stuff for the first time should be encouraged to use the kits as they are designed and delivered.

[73stagman]

There is another point... Always remember that when you are drilling and tapping into the cylinder heads you are drilling and tapping into irreplaceable parts. (Not strictly true I know but you cant ring the Brothers up on Monday morning and order a new one!).
So take your time.
Drill and tap and insert each hole as you go
Dont be tempted to drill them all then tap them all then insert all the coils. If you make a mess of one you will most likely have done the same in all of them.

By the way there is another better thread repair using full thread inserts rather than wound wire. They are called full thread inserts (for example "wurth" insets) but a kit of five with the drill and tap kit will set you back around £200 plus the chancellors bit and some charge for the postie! If you destroy a thread completely they can be repaired like this. I believe there has been some who have had their machinists do the repairs that way.

[Bassy]

So to summarise. I need to take my time, do one at a time, mark drill depth, and cut with plenty of lube 1/2 turn forward then 1/4 turn back. From what I have gathered its a case of go slow and steady using the bit that comes with the kit.

I will follow that advice thankyou very much. And can I add that the advice given to someone who has just joined the forum is refreshing and much appreciated, seeing as I have not really given anything back yet.

thanks to you all

Andy

[73stagman]

So to summarise. I need to take my time, do one at a time, mark drill depth, and cut with plenty of lube 1/2 turn forward then 1/4 turn back. From what I have gathered its a case of go slow and steady using the bit that comes with the kit.

I will follow that advice thankyou very much. And can I add that the advice given to someone who has just joined the forum is refreshing and much appreciated, seeing as I have not really given anything back yet.

thanks to you all

Andy

You are welcome Andy. That's what we are all here for. I'm sure you will do OK its not so difficult.

[jleyton]

As Neil says, you're welcome and it makes it all worthwhile for us when we get a thank you.

Don't completely forget my suggestion that, if the holes are in poor condition (ie opened out) then you may be able to tap the hole without drilling which would remove some of the worries.

Good luck and come back on here to let us know how you got on.

Cheers

Julian

[dasadrew]

So to summarise. I need to take my time, do one at a time, mark drill depth, and cut with plenty of lube 1/2 turn forward then 1/4 turn back. From what I have gathered its a case of go slow and steady using the bit that comes with the kit. ....

Andy

.... and keep on checking that you're drilling or tapping at 90° to the surface. A small cubed object will help you check this - like a Duplo or Lego brick or two. An old matchbox would even do.

[v8ken]

Just my twopenneth worth,
All of the above,but,,, on my helicoil kit it said that you needn't drill aluminium before tapping for the helicoil.
I haven't done an inlet manifold hole,but have done various holes around the head,steering pump mounts+spark plug holes and have not used a drill .This was fortunate as it would have been really awkward to use a drill.All the holes have tapped quite tightly and inserts fitted .
Regards Ken.

[Mike Stevens]

If you do have to drill (and I did with the manifold fixings), it's not too bad as when you're drilling out the old threads it's easy going. When you reach the bottom of the old hole, the drilling gets harder, giving you another indication that you've gone far enough. Marking the drill (insulation tape is good) gives an additional safety feature!

If you're doing it with the heads on the block, don't forget to tape up the inlet ports! You don't want any swarf in there.

Cheers,
Mike.