Air inhection thread sizes

badger · Post by **badger** » Wed Dec 30, 2015 11:27 am

Folks, got an urgent issue....

I have a friend who has a pair of heads with the threaded ports for the pulsair air injection pipes just above the exhaust ports, but the thread size seems a larger diameter than other heads I have previously seen with this arrangement. I don't have the heads in front of me to check, but it would appear to be a similar size to a spark plug thread - can anyone confirm this please, or tell me the exact thread size?
Thanks in advance.

Darkspeed · Post by **Darkspeed** » Wed Dec 30, 2015 3:07 pm

Likely to be a pipe thread 1/4 BSP / NPT or some such. - Taking a guess I would say 1/8 NPT considering the boss size and the US origin

badger · Post by **badger** » Wed Dec 30, 2015 4:51 pm

Yeah, that's the smaller, more "normal" boss size. This is the larger size thread, appears to be around 16mm, possibly a metric fine?

ged · Post by **ged** » Wed Dec 30, 2015 8:10 pm

Any good to you?

https://www.famousfour.co.uk/new_parts/ ... part=14243

badger · Post by **badger** » Wed Dec 30, 2015 10:59 pm

Cheers ged, that's the smaller size blanks, used on the pulsair systems that have 4 pipes per side. The ones I'm needing are an oddball - the system used on late model V8 defenders that only had 3 pipes connected per side. Apparently, they sussed out that due to the firing order and pulses, this was more efficient, but they changed the thread size at the same time!

Darkspeed · Post by **Darkspeed** » Thu Dec 31, 2015 10:40 am

There are bits an pieces on the net about the Pulsair system and the very oddball thread size - There is a post on here from JRV8 say that they had the plugs in stock.