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MG Midget and Sprite Technical - Manifold Bolts - Access

Glad I don't have to do it too often, but I forget the last time when I come to undo the manifold bolts again. Lucky if I can turn them 1 flat at a time with an open ended 1/2" spanner. can't get a ratchet or ring spanner in there.

Anyone come up with a better method?
Tim Carter

I assume you mean A series?

With the original twin su manifold(s) I used a very slim profile ring spanner. But yep, it's still a slow pain.

Also easier if you take the carbs off, but by the time you've done that you could have slowly undone the manifold nuts anyway.

It's massively easier if you have a single hif inlet manifold and 3 branch.

anamnesis

What nuts do you have? The deep brass ones make this task easier if you are going to be doing it a lot.

e.g. from Rimmers, https://rimmerbros.com/Item--i-51K1177
AdrianR

Again, assuming A-series, I use a combination spanner, which has an almost flat ring spanner at one end. It also helps if the studs are in good condition, as once the nuts have been loosened, they can be turned with the fingers.

The nuts don’t have to be removed completely. Once the manifold can be pulled far enough away from the head to clear the location rings, it can be lifted vertically.
Dave O'Neill 2

ARP's finest readily fastened and unfastened with a 3/8 spanner without losing any skin off your knuckles. Since they are also stainless steel it's neat if you have a friend machine you up some thick washers in stainless to go with them.
Daniel

As others have said, find a slim spanner. Having a selection of spanners helps and even cutting the length a cheapy one with a hacksaw can be useful. Long brass nuts, particularly for the centre studs, part number 51K1177 are available from a range of suppliers e.g.

https://www.somerfordmini.co.uk/nut-brass-516-unf-manifold-to-head-extra-long

https://www.minispares.com/51k1177-long-brass-manifold-nut

https://rimmerbros.com/Item--i-51K1177--SelectedCurrency-1?utm_content=mediabuy&gad_source=1&gad_campaignid=17518277177&gbraid=0AAAAAD500i8UgF9kJeSAEjNraqj0Mg4dp&gclid=Cj0KCQjwsNnCBhDRARIsAEzia4Ba6nE349aaMwv7EJPmSXFJWtRgHVfPLdNZUJVuL6QMJwoJDp6WruYaAkabEALw_wcB

Cheers
Mike
M Wood

Thanks for all the suggestions. Looks like I may need to sacrifice a 1/2" combination spanner and take the grinder to it to slim it down.
Tim Carter

I must admit I thought the long brass nuts Mike mentioned were standard. They're on Triumph manifold studs as well. They're supposed to be less inclined to slacken off from repeated heating and cooling cycles, plus they don't readily seize to the studs by corrosion.
They're not too hard to get at on Triumph engines but it's been so long since I touched an A series that I can't remember what the access is like.
Would a 1/4" drive half-inch socket on a wobble bar get at them okay for example?
IDK, You chaps will know better than me.
Greybeard

I always understood that the idea of the brass nuts is that as the steel studs heat up, expand and elongate, the brass would expand more and extend axially to maintain the clamping pressure onto the manifold gasket.
GuyW

My understanding too Guy, as I mentioned in very different words. You expressed it more clearly than I.
AFAIK the extra length of the nuts is partly at least to compensate for the material being softer than steel so the length provides additional thread engagement to spread the torque load.
But I still don't know how much harder they are to access than those on the 1500 manifold.
That would be interesting if someone can educate me. I've forgotten.

ETA: Daniel's mention of 3/8" AF nuts by ARP is interesting. I only just saw it. Thanks D.
Greybeard

As I recall, the 1500 has 2 manifold nuts very awkward to get at? Thiugh that could have been something different alltogether!
I have never found the A series ones particularly awkward though as others have said, it does help to have an appropriate spanner which may involve a little work to make a 'special'. I have a cut in half spanner though I cannot always find it when needed.
I find it easier to start the nuts by reaching under the manifold and working by feel. Once slackened off slightly, brass nuts will usually just spin off with your fingers.
GuyW

This thread was discussed between 20/06/2025 and 23/06/2025

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