Engine casing question r.e. tapping new welding

[alanscottj]

A long time ago a thread went on a 200 casing - it was one of the 4 cylinder stud holes. So, I helicoiled it and it lasted ages until yesterday when I was changing the cylinder head. As I was torquing up the nut the helicoil started to unscrew out of the casing! Anyhoo, I retapped it and replaced the helicoil, with fingers crossed I tightened it up and the bugger went again

Anyway, I have access to a fantastic ali welder who does stuff for me for a very reasonable price, I should have gone to him originally but hey ho! So, I'm dropping it off tomorrow for him to do his stuff. I have just got off the phone with him and he was asking me if I want him to drill and tap the hole for me. He asked if originally do they have an insert as he said it would be good practice when working with ally to put an insert in there due to the metal being relatively soft. So, my question is, do they originally have an insert or not - I can't tell by looking at the other cylinder stud holes so thought I'd ask on here. Or, does he just drill and tap it for me???

Many thanks in advance.

[fluff34567]

No inserts on any of the holes in my casing

[alanscottj]

No inserts on any of the holes in my casing

I didn't think there were - just wanted to confirm it. He does weld on aeroplanes though, so maybe he isn't used to the fineries of the Indian Lambretta casing

I'll just get him to drill and tap them.

[fluff34567]

My guy is also an NAA welder... ask him what it means

[alanscottj]

My guy is also an NAA welder... ask him what it means

I will

What is the specific tap size to use for tapping cylinder studs? Does it have to be a certain pitch?

Thanks

[fluff34567]

Take an old stud with you just to be sure.

[Knowledge]

The stud is a standard M8 (8mm diameter and 1.25mm pitch).

I would take the cylinder head and/or barrel with you, so he can drill through and be certain of getting the hole in the correct location.

[alanscottj]

The stud is a standard M8 (8mm diameter and 1.25mm pitch).

I would take the cylinder head and/or barrel with you, so he can drill through and be certain of getting the hole in the correct location.

I was just going to take the barrel with me but will take the head as per your suggestion - I have an old head that he can use to drill through (don't want to scratch my new CNC head )