gearbox the block bolts...
Turbo Mini Forums

right i am in the process of putting my new engine together and i have sat the short engine on the gearbox and have gone to fix it together and i am having real troubles with the right size bolts!.
I have found a size that fits the block threads but it will not go through the gearbox casing holes and i have tried the bolt on another box and its the same.So is there another fixxing method or strange size bolt?

your help would be much appreciated

cheers pete

Sounds like the block has been drilled/tapped the next size up (7/16 from 3/8 or something)
Can you carefully drill the gearbox to suit? Without filling it with filings lol.

guess this would make sense as the block had loads of machine work done to it before i bought it.

First thing I would say is you should really put the box on the block (ie, have it all upside down) to see what is really happening.

Second thing.... are the dowels in - to make sure the holes line up ???

And when you say trouble with the right size bolts.... is it that they don't go in, or they fall out.... or thread mismatch ???

Edited by Rod S on 19th Apr, 2009.

Schrödinger's cat - so which one am I ???

I thought bigger was ALWAYS better? Ha!

Had my birth coincided with the pre-cambrian era, I would be familiar with imperial jargon.

if you have a mini you should be familiar with it lol

As Tom said they are normally 1/4" UNF but some people including myself take them out to 5/16" UNF (I have a piler drill & a full set of taps so it cost me nothing) however if they have been drilled out there's no guarantee that they are 5/16" UNF, I've also heard of them being taken out to M8 although I don't like mixing metric & imperial.

Edited by Rob H on 19th Apr, 2009.

Rob is right, you need to check what size thread they are, M8 is also not a million miles away from 5/16" UNF.

right turns out the block was re taped to m8 but i believe it was morspeed that did the work so no supprise there!so i have just re drilled the gearbox to suit and all is good i hope...

Schrödinger's cat - so which one am I ???

Every engine I build is done this way,

Short motor in engine upside down,

fit all gaskets, Gasket seal'nt and half moon seal to block fit big O ring to gearbox invert gearbox fit to motor and bolt away in comfort so much better IMHO.