RB20 fitment issues.

[Adam_Winstone]

That's all I'm trying to do here, identify a possible cause for your issue and help you to resolve it. Surely that is the whole point of these forums?

Adam

[10 inch Terror]

That's all I'm trying to do here, identify a possible cause for your issue and help you to resolve it. Surely that is the whole point of these forums?

Adam

I have to be honest, I do rate MB for both their products and customer service. I think both are the best out there, which is why I spend my money with them. You didn't name their product as being the problem and they did jump in with both feet, but with the amount of sniping they receive on forums, I can't really blame them. I'm not saying you are one of those snipers and your advice is always spot on and impartial. I'll be back in due course and let you all know the outcome. Thanks again Pete.

[Adam_Winstone]

I couldn't agree more. I myself use and appreciate MB's products, service and ability. I regularly point people (locally and on forums) MB's way for general parts, in-house MB parts (manifolds, etc.), rebores, tuning, head reprofiling, stainless, BGM parts... and the list goes on.

However, if the MB studs are a bigger diameter than the factory studs then they are adding to the fitment issues that people often experience when assembling motors. My comments on this thread have never been directed against MB, nor any dealer, just to (quite rightly IMO) identify a common problem that many are faced with to some extent. Some assemblies will have ZERO issue when using 'fat' studs, others will have real problems. What cannot be avoided is that using fat studs greatly increases your chance of having alignment problems. Some combinations of casings and kits may well still have issue even with the standard 7.20mm shaft studs! In which case, send it back to the dealer and demand a kit that fits a standard casing.

If you design a kit then you design it for a standard casing, using standard studs. If someone then decides to fit non-standard 'oversize' studs, it is more than a little unfair to blame the kit manufacturer for not allowing for these aftermarket studs that someone else has introduced at a later stage.

I'm not mud-slinging and genuinely do rate MB's work and products but that doesn't mean that I should keep quiet when I know that there is an issue that may be a contributing factor to the thread starter's problem that he is asking for help with. I didn't even mention MB and the 'fat' studs were mild steel studs supplied by another party! This isn't about MB, AF, Tino, Innocenti, Serveta or anyone by name, it is about the increase of cylinder stud diameter reducing assembly clearance and resulting in alignment troubles (and in some cases damage) on some motors... the bigger the stud = the more likely you are to have issue.

Cheers for now,

Adam

[Spanish Fly]

According to ISO, DIN & ANSI standards the clearance hole for M8 should be:
8.4 (close fit)
9.0 (normal fit)
10.0 (loose fit)

What size are the holes in an RB cylinder?

SF

[10 inch Terror]

According to ISO, DIN & ANSI standards the clearance hole for M8 should be:
8.4 (close fit)
9.0 (normal fit)
10.0 (loose fit)

What size are the holes in an RB cylinder?

SF

According to my accurate vernier gauge the top holes are 8.24mm and the bottom ones 9mm. Why they are different diameters I don't know.

[Spanish Fly]

[/quote]
According to my accurate vernier gauge the top holes are 8.24mm and the bottom ones 9mm. Why they are different diameters I don't know.[/quote]

No chance with with full fat 8mm studs then.
There is just not enough clearance to allow for the unavoidable manufacturing errors in the case and cylinder.
The standards I referred to earlier have evolved to cater for reasonble and workable manufacturing errors. +/- 0.25mm positional accuracy on holes in this type of assembly would be typical. If the tolerances work against you then 0.24mm clearance and a mallet is not going to get you out a fix without bending or flexing something.

Maybe A/F's apparent disregard for engineering standards is an attempt to locate the cylinder head more centrally?

The waisted (SIL?) studs may well provide the required clearance. Finger crossed.

SF

[lockman69]

Interesting thread, went a bit wobbly in the middle but very informative, thanks for your input Adam.

[10 inch Terror]

[/quote] maybe A/F's apparent disregard for engineering standards is an attempt to locate the cylinder head more centrally [/quote]
Exactly what I was thinking...

[drunkmunkey6969]

According to my accurate vernier gauge the top holes are 8.24mm and the bottom ones 9mm. Why they are different diameters I don't know.

Maybe A/F's apparent disregard for engineering standards is an attempt to locate the cylinder head more centrally?

SF

I'd hazard a guess the its more likely due to the fact that the Boyesen feeders popped through the top stud holes on early cylinders.....so they reduced the size of the hole to reduce the chances of this happening again.

[Adam_Winstone]

^... good shout!