Which thread types can be used together

[geneticmateri]

Hi, I am looking to adapt a car intake manifold.
There are 4 injector holes (untapped) that measure a touch over 18.5mm.
I plan to tap these holes and fit some reducing nipples to them.
I have a 7/8" BSW tap bit and some M20x2.5 ISO tap bits.

I need some help on the following;
Will the 7/8" bsw be too large for this hole?
if not, what other threads would work with the 7/8 bsw?

If I use the M20x2.5 bit instead, what other male threads would work with it?

The reason I'm asking this is because these are the only bits I have but I am struggling to find nipples or reducers that fit with either the 7/8" bsw or the M20x2.5 bit.

Thanks

Dan

 

[Navin A S]

The 7/8" BSW tap bit is too large for the hole and would likely damage the hole. I would suggest using an M14x1.25 tap bit as this should fit the hole size. As for reducers, you could use reducers with M14x1.5 or M14x2 threads.