Technical Rocker/Valve Cover Stud Bolt Length

[Pete145]

Hi everyone,

This is closely linked to my recent alloy rocker/valve cover thread, but the subject seems to warrant a new thread I think.

I tried to install the new, aluminium rocker cover/valve cover today, as all of the bits had finally arrived.

I needed to fettle the corners a little (removing some material from the aluminium cover's corners, as the new cover was fouling own the engine shrouds/covers), and the breather hose is now too small to stretch across to the nozzle (which doesn't sit at an angle like it does on the standard tin rocker/valve cover).

However, there is a more serious issue. Specifically the new rocker/valve cover is taller than the tin version, I measured the height (albeit crudely) and was pretty sure than there would be enough length and thread on the stud bolts to fit the new cover..... I was wrong!

When I present the cover to the gasket, add the sealing washers and the standard washers, the stud bolts do not have enough height to take the nyloc nuts (I need 10-15mm more).

Does anyone know the standard length of the stud bolts, and where I might be able to source longer ones?

To thicken the plot a little, I know that both of the threads stripped in the modified cylinder head during the car's first drive under my ownership (some three years ago now). This issue was fixed by helicoiling the threads.

This makes me a little nervous about messing around with the stud bolts too much, should I be nervous and get this looked at properly, or will the helicloiled threads be rock solid?

 

[the hobbler]

Hi Peter;
I have sorted out a couple of studs for you, complete with shallow nyloc nuts---give me a ring at home--(01244-683824)

 

[Pete145]

Quick update on this, the 'standard' length of these studs (designed for the tin rocker cover/valve cover) is indeed 9.9cm.

There are, apparently, longer studs that are available specifically to accommodate the taller alloy covers (the very issue that I'm experiencing). They're 115mm in length.

I've made a few email enquiries and, as luck would have it, Franco at ricambio.co.uk has some on order from Italy and should have them in stock in the next few weeks.

Looks like my shiny new Abarth Valve Cover will have to remain an expensive paper weight for a few weeks!

 

[Toshi 975]

I have heard of tulips from Amsterdam but studs from Italy is a new one on me
If your local garage or engineers cannot make you two suitable studs then they are not much cop.
I am glad that you have pointed this problem out as I will be fitting my rocker cover quite soon. I looked on ebay and you can get 10 high tensile M8 x 120mm hex head bolts for £6. All you need to do is cut off the bolts to length and thread them to the desired length with an M8 die.

 

[Pete145]

I have heard of tulips from Amsterdam but studs from Italy is a new one on me
If your local garage or engineers cannot make you two suitable studs then they are not much cop.

A local engineering company has agreed to make some to spec if I need them, from high tensile steel (10.9). Not cheap, so before I order those I've managed to source these:

http://www.pedparts.co.uk/product/4098/cylinder-stud-bolt-m8x125--vespa-t5

This is a little bit creative, but my research uncovered that vintage Vespas use a cylinder head stud that's M8 and 125mm in length (perfect). I don't think there's any reason why they won't do the trick, as long as I makes sure that the short thread (that sits in the cylinder head) isn't too long.

As you suggest, I can easily trim them to length.