Intake Manifold Nut Install

[dennisv]

I started to install the nuts to secure our intake manifold to the heads. The nuts got tight pretty quick, before they were completely engaged on the stud. I backed off for fear of loosening a stud from the head. I measure the studs at about 22.5 exposed length. The parts catalog lists 25. Even then, it seems the stacked items (not including height of 2 paper gaskets) should allow full engagement.

Questions:

1. Did I simply not apply enough force (i.e. lock nut and / or aluminum washer require a lot of torque?
2. Do the different manifolds have different base heights?
3. How the heck are you supposed to measure torque on these nuts given the lack of access? Best I can tell, these are meant to be torqued to ~14 ft. lbs.

Notes:

• 1970 914-6 (same as 1969 911T) engine
• Shroud openings have been ground to allow full seat of gasket and manifold on the heads
• Have 901-108-321 1R manifold without threads for vacuum ports. Technically not original for our car, but since we're not planning to use the emission control system didn't see the harm.

[Magyar Kiwi]

Hi
1/ At the cylinder head stud it looks like you have a deformed head lock nut, this is not what the factory originally fitted. I recommend not using these nuts.
The original factory nut, 999 084 601 02 had a different locking mechanism and was 12mm across the flats. I recommend using these nuts. See more here: https://forums.pelicanparts.com/911-engine-rebuilding-forum/603688-intake-manifold-nuts-nla-now-what.html
2/ No comment.
3/ You may have to use calibrated hand to torque or crows foot adaptor or thin socket.
Hope this helps.
Cheers
PS Parts Katalog here:
https://assets-v2.porsche.com/nz/-/media/Project/PCOM/SharedSite/PorscheClassic/Original-Parts-Catalogue/PDF-EN-WW/KAT070_E_914_76_KATALOG

[dennisv]

Originally Posted by Magyar Kiwi

Hi
1/ At the cylinder head stud it looks like you have a deformed head lock nut, this is not what the factory originally fitted. I recommend not using it.
The original factory nut, 999 084 601 02 had a different locking mechanism and was 12mm across the flats. I recommend using this nut. See more here: https://forums.pelicanparts.com/911-engine-rebuilding-forum/603688-intake-manifold-nuts-nla-now-what.html
2/ I suspect that for the length of studs fitted to your heads you should only use one gasket.
(Two gaskets sandwiching insulators requires longer studs to be fitted to the heads.)
3/ You may have to use calibrated hand to torque or crows foot adaptor.
Hope this helps.

1/ The nut you see in the photo is 999-084-601-0C, ordered from Delaware Porsche who indicates this supersedes 999-084-601-02. It is a non-nyloc 12mm ATF locking nut. My understanding is the deformation is what makes it lock.

2/ Single gasket would buy a bit of room. I used two since that's what the parts catalog indicated and came in the gasket kit.

[TimT]

Get rid of those prevailing torque lock nuts...


I don't know why all of a sudden people feel the need to use them, another poster used them on the chain boxes and effed up the threads on some fasteners..

These particular nuts work by damaging the threads.....Also you have to adjust the torque values when using them...i.e. if it takes 4 ft/lbs to just rotate the nut, you have to add 4# to the spec value

Toss those nuts in a round file..

Use plain nuts and wave washers.

[dennisv]

Originally Posted by TimT

Get rid of those prevailing torque lock nuts...


I don't know why all of a sudden people feel the need to use them

I can't speak to the others. I bought them because it's the part number listed in the catalog. Same for the aluminum washers. At least for the 914-6. If they'e not needed, it would probably solve this immediate problem. I don't know if it would cause another.

Regular nuts and spring washer are what's specified for the carb to the manifold.

[TimT]

Those nuts work by distorting the threads..

Top stud not to bad.. bottom stud trashed..

[OsoMoore]

Originally Posted by TimT

Get rid of those prevailing torque lock nuts...


I don't know why all of a sudden people feel the need to use them, another poster used them on the chain boxes and effed up the threads on some fasteners..

These particular nuts work by damaging the threads.....Also you have to adjust the torque values when using them...i.e. if it takes 4 ft/lbs to just rotate the nut, you have to add 4# to the spec value

Toss those nuts in a round file..

Use plain nuts and wave washers.

I'll never get those hours back. It was awful!

I put my headers on with Nylok nuts like 5 years ago, and they looked fine when removed for this rebuild earlier this summer. The ones on before than (from around 2001) were also Nyloks. One inner one wandered off over the years, but no leaks.
Dug up an old photo from 2013!

[Flat6pac]

The 12 mm flats on 8mm use JIS NUTS FOR 8 mm. You can get them through the heat boxes too instead of cap nuts. 1/4 inch drive 12 mm socket. Snap on 12mm works others may need grinding.
On the intakes, the factory used split 12 mm, not the brass exhaust but steel 12mm.
Bruce

[Magyar Kiwi]

Hi
"1/ The nut you see in the photo is 999-084-601-0C, ordered from Delaware Porsche who indicates this supersedes 999-084-601-02. It is a non-nyloc 12mm ATF locking nut. My understanding is the deformation is what makes it lock."

Unfortunately supersessions recommended by Porsche don't always work that well in some situations.

You need the aluminum washers on the magnesium manifold because the "as cast" upper surface of the manifold is not always perpendicular to the stud.
The aluminum washers take up any misalignment as the crush.

Good advice from Tim T:
"Get rid of those prevailing torque lock nuts..."

Cheers