9 replies to this topic

[TEM]

Stock 998 MK3. The exhaust/intake manifold is secured in with some studs and nuts and they are difficult for to work on. What is the size and length of a regular bolt that can be used in place of these?

[Big_Adam]

You want to use a bolt instead of a stud?

Sounds like a bad idea but the thread in the head is 5/16 UNF thread.

[lrostoke]

Somebody on here mentioned doing this a while back, it didn't sound a bad idea actually I can see the benefits. bolts can be removed completely meaning you don't need to struggle to get the manifold over the studs.

I'd guess cap heads would make them easier to get at as well

[TEM]

You want to use a bolt instead of a stud?

Sounds like a bad idea but the thread in the head is 5/16 UNF thread.

I stick my socket in there and it's tight fit. Sometimes only the nut comes loose and sometimes the stud with the nut if I'm lucky. If the nut comes out only, I have to take a lot of time getting the stud out or the block won't come out. Isn't it a lot easier to just use a bolt? What is the downside in using a bolt? Also, what is the length I need?

[jaydee]

Ask cooperman on here, by the way its a GREAT idea if you're using an lcb manifold.

[bmcecosse]

It's a good idea for the outer pair - 1" long is fine. But it's better/easier to keep studs on the others - and use brass nuts of course! The 'long' brass nuts sold for the purpose (and originally used on Spridgets) are ideal.

[TEM]

Thanks for the replies! I'll go for the outer ones for now then. Stage 1 kit (headers and all) will go in eventually when I have my list of other things worked out!

[Cooperman]

On an 850-type manifold which has the integral inlet/exhaust manifold, ity's easy to use studs. However, on all Cooper and Cooper 'S' with alloy inlet manifolds and tubular exhausts I always use 5/16" UNF hex head screws x 1.25" long. With this arrangement, it is possible to change the head gasket without undoing the bottom exhaust clamp on the tubular (3-into 1 or LCB) manifold. Also, the inlet manifold, complete with carbs, can be removed and hung upside down from the screen header rail by a bungey (yes, the oil fron the carbs runs out onto the piece of towelling you use to protect the screen), without disconnecting throttle or chjoke cables, you just undo the fuel line.
This way, you can change the head gasket easily. I've done this for over 45 years and it's the best option IMHO.
I've never tried socket head screws, although that should work fine as well.
One other tip, if you file the inlet manifold so that the semi-holes for the studs/bolts, become slots you can lift the inlet manifold out without fully removing the bolts, just slide the manifold, complete with carb, back after undoing the bolts a few turns. I use locating dowels on my 1310 cc 'S' as the inlet tracts/manifold ports are enlarged and I don;t use the location rings. For dowels, the split roll-pins from the remote gear linkage, cut down in length to suit are fine.

[mini_matt_106]

i think the studs have a courser thread the end they go into the head so would these not be harder to tighten? easy way would be to weld the nut to the stud then the stud would work as a bolt

[bmcecosse]

No - they don't. Mis-information again i'm afraid. You're not Calver - are you ??

Edited by bmcecosse, 15 August 2009 - 05:09 PM.