Threads for airbox bracket

[Stian_P 1 1 Cars]

Hi. Does anyone know the thread size on the exhaust manifold for the airbox bracket? M6 bolts drop straight in, M8 is to big. Could it be m7? I foolishly threw away the bolts I removed due to beeing very rusty. 

[PhilNW 44]

http://www.miamistu.co.uk/pug/GB/205N/1/14G50A.HTM

 

Says M6 but sounds like it has been replaced by an M7

Edited June 10, 2022 by PhilNW

[Stian_P 1 1 Cars]

Cheers Phil. I guess the threads have corroded away then, I barely got the bolts out using a lot of heat. Maybe I should try to drill and tap to M8

[PhilNW 44]

Bigger is better, and use stainless steel bolts 

[Tom Fenton 1,542]

I have come across manifolds with both M6 and M7

 

Yours sound like M7.

[Richie-Van-GTi 72 2 Cars]

Mine has m7

[Stian_P 1 1 Cars]

Thanks guys. I'll see if I can find some M7 bolts somewhere, and hopefully the threads are ok. If not, I guess its drill and tap time. 

[welshpug 1,661]

Not listed anywhere for 205, however  the 309 does have both M6 and M7 hex head capscrews listed, 12mm long and an 8x18- 1.4mm thick toothed spring washer  (not the typical split spring washer)

 

 

Would not rate your chances of cutting a new thread in these manifolds, make sure its a bottom tap not a 1st or taper tap if you want to clean the existing threads.

 

[Stian_P 1 1 Cars]

Maybe cast iron is a bit hard for tapping? I have also been thinking about JB welding studs in the excisting holes, but have yet to find something that can withstand the heat. I have a mig welder, but worried the manifold will crack if I weld studs in the holes. 

[SRDT 182]

Cheap taps are good for soft materials or for cleaning threads.

The last thing you want is a tap that isn't up to the task and yet just hard enough to be a pain to remove when broken inside.

[Gohn 68]

ALARM !

Don't retap to M8 unless absolutely necessary, it could cause a whole bunch of other problems you currently dont have

 

its the legendary 205 M7 bolt, usually 1.0 thread pitch

takes repairing corroded bolts in awkward locations to another level of difficulty and stress

 

you've done well to get your bolts out intact,

chekc your bin, are the bolts still in there ?

probably M7x1.0 x ? length

 

either way heed mei and SRDT's warnings about retapping to M8, not recommended

 

and don't spare the anti-sieze once you've sourced some replacement M7 bolts

 

[Stian_P 1 1 Cars]

Thanks for the advice guys, I wont try to retap then. I have ordered a couple of M7 bolts, they were not easy to find. I'll report back when I get them. 

[SRDT 182]

M7x1.0 is a bit too big to properly retap at M8x1.25 anyway, it's better to use a fine thread like M8x1.0.

Another option is to go with helicoils.

[Stian_P 1 1 Cars]

The M7 bolts I got today fits. Thanks for all the help guys