Inlet manifold tech

[Dr S]

I’m bumbling along fitting my shorrock. After a post from @fanfarinman suggesting I make a manifold I’m giving it some credence. I’ve got a cut down cast manifold but for the life of me I can’t see how anyone fits this with a cooper freeflow. The bottom of the centre plenum is in the same place as the centre exhaust.

My thinking is two angled straight pipes from the head to the inlet. Steel plate either end and mig it up.

However looking at the manifolds I have they seem very ‘log’ shaped with an inlet port and then two exit ports on a common plenum. I assume this is by design? I note the manifold steel inlet is a pair of curved pipes?

What’s the science here?

[Dr S]

Loads of good stuff on this in TBASE. Cheers again mister viz.

Some rough and ready measurement suggests the below is about 200mm wide (that’s 0.8 / 4.5 * 35mm)

8E933ECA-55A0-449C-A416-20BEF4BB38EE.jpeg

That’s around the space between the ports there or thereabouts.

Combined with some pigeon shit mig and some 8mm flat plate I reckon I can have a crack at making the below.

[Dr S]

DDD14FC2-EFE1-401C-B1DA-C2863F2A2477.jpeg

[cheesebadger]

Interesting topic...

I too have a shorrock that I plan to fit, but I am prioritising getting the wheels back on my project at the moment.
The inlet manifold is the one area I am missing too. My plan was to do exactly as you have already tried, sacrificing an cast manifold, but you have obviously found some issues with this...

I think I have an original reece/fish carb single inlet manifold, that might work.

Although I think your suggestion of making one yourself can't be that difficult. I guess the challenge would be jigging it properly, although there are a few obvious options here...
1) Build a jig around the cast manifold.
2) Dry fit the shorrock and mounting kit to the engine, and use that as a jig.

Please share any progress, interested to see how you get on...

Cheers, Rich

[Dr S]

Hey mister cheese burger. Have a squiz at my build thread for further shorrock shots... PM me your email address if you want to join me and Andy H on this journey. We are both mid install and emails are pinging back and forth.

[cheesebadger]

Thanks for the heads up. I'll have a look.
I have dropped you a PM. Cheers

[mk1]

I have done Shorrock installs using thwe correct Shorrock manifold as well as standard 850 inlets & aftermarket alloy ones. Although making your own manifold is not "that" difficult, I would ask "why bother?" when there are so many cheap well made inlets available. modifying an existing manifold to gain the extra clearance is many times easier & more accurate than making your own.

[Dr S]

Hi Mark,

I think I’m coming to the conclusion that the freeflow exhaust is the problem. In order to clear the centre branch it needs a lot of material taken out.

Did you use an lcb? Or an original cooper manifold? They seem to hug the block much more?

Naivety and a lack of machining experience is probably to blame here but I’m not seeing how the cast manifold clears until well until it has a hole in it?

[Dr S]

Modded to clear a freeflow ...

FCA27B9C-A69D-4DAA-A768-C59A95DFBB1D.jpeg

[mk1]

When I have done those, I have brazed a patch on & also done a bit of judicious hammering on teh centre pipe to get everything fitting nicely.

[Dr S]

Ok! That makes more sense

[Nick W]

I found it best to leave some meat on the 850 cast manifold, and reshape the centre pipe.
Couple of images here

[Dr S]

Cheers guys, I’d been chasing the idea that it was a ‘clean’ fit, not an interference fit. I could be running next weekend