Plenum Bolt sizes

[Ballistic Banana]

Anyone know what size bolts/tread type of these bolts on a V8 Griffith

I need to use another threaded hole on the Engine block, it takes the same threaded bolt as the plenum ones..
I have tried numerous other bolts I have kicking about which are mainly Metric ones and cant find one that fits.
Could they be imperial???

TIA

BB

[topsparks]

From memory they are unc thread.Let me know what length you need as I have a load in my shed

[2 sheds]

The plenum bolts are M8 , the trumpet base bolts are 5/16 UNC.
Tim

[Ballistic Banana]

Cheers Tim,You made me realise that I had tried the spare Trumpet base bolt I have.

So its a 5/16 UNC

Thanks

BB