Problem on Mugello Head nuts

[Strummer10]

Hi All, We have just been working on a Muggy 225 tonight. Had to rub the head of the barrel down to get to a squish of 1.45 but noticed we had a problem tightening up the 3 hexagonal bolts. It seems to me the threads are not long enough ??

Has anyone had this problem and knows the resolution, I would say the threads need to be another 10 mms longer, maybe even 15mm's as they were turning and not tightening up. The actual bolts are 57.4 mms long, of which 22.8 mms is the thread


Any ideas please ?

[Strummer10]

was wondering whether there are different length hexagon nuts maybe between the 186 and 225 kits which might explain ?

[rosscla]

Do you mean bolts or nuts?

[Strummer10]

Hi, its the 3 additional Hexagonal bolts that go in after the 4 main cylinder nuts are done up.

[rosscla]

Measure the depth of the holes in the head from gasket face to where the bolt should tighten down on to. That will tell you if they're actually long enough to reach the holes in the barrel. 57mm sounds like it ought to be enough to get through the head.

Also check that the bolts actually fit into the holes in the barrel.

[Strummer10]

Hi Ross.......thanks for response, we checked the bolt hole depths last night with a piece of solder down the thread hole and marked it where the 'hexagon' nut would theoretically start to pull tight onto the cylinder head, to get the 'effective stud length'. Then we compared it to the length of bolts and found that the thread down the cylinder was between 10 and 15 mm's deeper than the bolt we were using. It seems the bolt thread is not pulling in enough to allow for any tightening.

I have suggested we just buy some threaded bar and cut correct lengths / use washers and nuts but I was just wondering whether inadvertently there's a difference between the 186 and 225 kits and maybe we have the wrong hexagon bolts for it....?

[Strummer10]

Problem resolved.............use studs, nuts and washers to get down into the thread !!

[corrado]

Problem resolved.............use studs, nuts and washers to get down into the thread !!

That's what they're supposed to come with, not bolts. Suspect they've been changed at some stage.

[Strummer10]

thanks Corrado, must confess I've built 2 mates lammies in the last year with 186 muggy kits and they both had the bolts, but no issues, so maybe the 225 barrel wasn't machined down enough on the threads, which is minor problem for us......just a case of waiting for the studs to arrive.

We are informed to use the longer sized inlet manifold studs (as used for the 30mm carb manifold) and nuts and washers. Only question being, you would normally screw in studs before the cylinder head is fitted to ensure they are properly seated , but I suspect trying to get the cylinder head over 7 studs now might be problematic. However, I guess if we grind out grooves into the end of the studs we can use a screwdriver to 'wind them down' .

Would you agree with the above OR is there a better way..............

Incidentally the piston circlips.....is there a preferred position they should go in (ie; the opening to the circlip turned inside the groove so the opening in the circlip is at say 9 O'clock ) or does it not really matter ?

[rosscla]

Generally its preferred to fit the circlips with the open end in the direction of motion, so either 12 or 6 o'clock.