Question about intake flange Mounting.

[kimdrummel]

Hello!

I have just started with these engines and i have discovered something that boggles my mind.

I just bought a Mangoletsi DCOE intake manifold for my L31 stroker, which is the very first L-series engine i have owned.
And just now i saw that there are only holes for mounting the intake manifold on the upper side of the manifold. I was puzzled by this and had to go and test mount it on the engine, thinking that maybe i have to drill my own holes in the manifold in case different heads have different location of the lower mounting screws, but i was further thrown into thought when i saw that the head didn't have any mounting holes for the lower part of the manifold as well.

 

The first thing to come to mind when seeing this is that it's not gonna be sufficient for properly sealing the intake to the head. Especially if running high boost? At least this is the feeling i get. It feels like i want to drill out some holes in the head and tap them with 8mm thread so that i can properly mount the lower part of the intake to the head.

If someone could explain this to me, i would feel much better. Because right now it feels really wierd..

[dexter72]

The intake and exhaust manifolds use washers between the two, to hold them tight against the cylinder head. If you look up pictures of the intake and exhaust manifolds mounted on the head, you should be able to see that.

[NewZed]

Those washers are actually called "yokes" and they have a certain shape that distributes the clamping force.  Some call them thick washers, but thick washers would probably not work correctly.  Studs and nuts, or bolts, are used to clamp the yoke to the flanges on the intake and exhaust manifolds.  Each yoke clamps two manifolds.  The holes are evident between the runners.

 

This won't help much with visualizing but you can get the part numbers.  Part #28 is the yoke.

 

http://www.carpartsmanual.com/datsunS30/DatsunZIndex/Engine280Z/ManifoldEgr/FromAug76/tabid/1606/Default.aspx

[kimdrummel]

Oh, so that's how it works. Found some here too: http://www.rhdjapan.com/kameari-l-type-in-ex-manifold-yoke-washer.html

Looks like something similar to the washers that's mounted on the exhaust manifold on a CA18DET, which i have some experience with.

Though i can't help thinking what was going through their minds when they designed it like this? I can't see any reason why this would be better than a regular M8 being screwed into the head?
Oh well, i'm satified. As long as it will give a tight fit that will be sufficient to seal the flanges against the head i don't see any problems. Might even be easier to mount.

Thank you for the information!