Intake Manifold Nut Install
 

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.

http://forums.pelicanparts.com/uploa...1761324708.jpg

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

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.

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 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.

Those nuts work by distorting the threads..

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

http://forums.pelicanparts.com/uploa...1761056321.jpg

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!



http://forums.pelicanparts.com/uploa...1761339875.jpg

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

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 they crush.

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

Cheers

Per the suggestions here, I got rid of the thick aluminum washers and metal lock nuts. Here is the install with wavy spring washers and regular M8 12 ATF nuts. I couldn't find a Porsche torque spec, so I used the low end number I've found in forums at 15 ft. lbs. They seem secure, but I still would have expected to have a bit of thread exposed above the nut as an indication of full engagement.

http://forums.pelicanparts.com/uploa...1763731475.jpg

I wonder where F1 would be if they eliminated the Jet nut?
For intake flange applications we always use flanged/prevailing torque Jet nuts.
8mm thread with a 10mm wrench gives unparalleled socket access.
Most professional mechanics understand that thread lube is used for proper installation.

http://forums.pelicanparts.com/uploa...1763732197.jpghttp://forums.pelicanparts.com/uploa...1763739002.JPG
http://forums.pelicanparts.com/uploa...1763739002.JPG

Those aren’t going to hold.

Agreed
Given the choice of base spacer and gaskets it really looks like new/longer studs are required.

Thanks for the suggestion and photos Henry. I will see if I can find these. There are a lot of different flanged nuts. Are you using lock and / or serrated? Best I can tell you're using something like these: Smooth Flange Nut JIS B1190

Obviously, I'm not a professional. ;)

I didn't make a conscious choice regarding the size of the flange or gaskets, other than to buy the factory part numbers. Are there alternatives in different thickness?
901-108-131-00: Intermediate Flange Gasket - Intake manifold
901-108-391-04: Gasket - Intake manifold

I am still curious if different manifolds have different base thickness.

Not to answer for Jim but the phenolic base spacer can be used with a sealant without any gaskets. I like to use Dirko Grey HT between the head base spacer and Curil T2 between the spacer and carburetor or MFI throttle body. We tend to see less warping rom over-tightening with this method. Prevailing torque nuts stay in place with minimal clamping force.

Bell Metric has nuts and studs.

studs) https://belmetric.com/m8-even-thread-stud-class-8-8-steel/?sku=S8X38EYLW

nuts) https://belmetric.com/conical-lock-flange-nut-smooth-class-10-steel-din-6927/?

simply a preference.

nuts) https://belmetric.com/conical-lock-flange-nut-smooth-class-10-steel-10mm-wrench-special/?sku=NTLH8X10YLW

Thanks again for sharing your knowledge Henry.

Someone had posted earlier concern about the distorted shape lock nuts (not nylock) chewing up the stud threads. I take it you have not seen that.

A gorilla can break a steel ball bearing with a rubber hammer. Try not to be that gorilla

Whenever you work with a nut that uses a steel on steel mechanical locking system (prevailing torque), thread lube is always recommended. We make our own in house.
It adds an extra step but provides the best results


http://forums.pelicanparts.com/uploa...1763751603.JPG

.

Those reduced hex jet nuts are fantastic for intakes on 911s... especially some of the aftermarket manifolds.. We built an engine with MODE manifolds.. where in places full hex would never work..

Also I imagine in the F1 world, the prevailing torque nuts were installed following correct procedures.... i.e. determining the prevailing torque, adding that to the design torque, resulting in the correct design tension in the fastener..

Those top locking nuts are great if you're wanting to distort the threads on a stud..

Jet nuts... the nut deforms... not ruining a stud...


http://forums.pelicanparts.com/uploa...1763770752.jpg

Low quality studs with high quality nuts is the issue, not thread locking design. As I've said more than once, assembly lube will prevent most thread damage. We also support the nuts with hardened AN washers.
We build every die cast aluminum case using the factory nuts you disparage so vehemently.

http://forums.pelicanparts.com/uploa...1763829917.JPG