Hi noahwins, there's a chance that this manifold has been surgically modified. I've recently finished modding my G63B carby manifold by deleting the external exhaust gas gallery form the port under #3 inlet runner to the side of the manifold plenum (mine still has part of the EGR valve mount attached). It looks like this one has gone a step further and had the breaches into the plenum filled and welded (it's possible...) This is what mine is looking like now -
Interesting...I see yours has that one thermo switch hanging off it, too. Can you post some more pics of what you did to clean it up? Maybe before and after if you have them?
No problemo I have done a few mods to this manifold - everything from dressing the inlet runner walls and radiusing the trailing edges from the plenum ports to oversizing the coolant gallery from the base into the thermostat housing. I also discovered the cover plate welded into the base of the coolant basin had been eaten through by corrosion (I'd put money on this being one of the reasons this engine went into catastrophic fail mode) Before -
No problemo I'll throw some links up to my photobucket account so you can see what it looked like before modding it and most of the stages I went through to get it up to the image I posted earlier.
If you've gone through the links you'll notice that the exhaust gas gallery on the inlet manifold is actually a pre-formed aluminium tube that is inserted into the casting mould before being poured. I used a thin cutting wheel on a grinder and made a series of parallel cuts and peeled the gallery wall away from the manifold. Yeah, it's a lot of work and you're going to remove fair amount of metal. The final finish is all sanding discs, die grinders, files and hand finishing with wet and dry paper.
I made a series of parallel cuts into the exhaust gas gallery with a thin cut off wheel on an angle grinder, then proceeded to peel sections off the manifold (there is a lot of work involved in removing the gallery and it took some thought in order to avoid breaching anywhere that would reduce the manifold into scrap metal) . The exhaust gallery itself is an alloy tube that was inserted into the manifold mould prior to casting. This is what my manifold looked like before modification -
Here are a few steps I went through to remove the gallery -
Interesting. What did you do to the EGR holes in the plenum?
I was thinking about cutting out the bridge bit between the two barrels for the carb because it doesn't seem to do anything.
I haven't gone the extra step of cutting through the gallery return into the side of the manifold as, after having a good look at it, it breaches the plenum in 2 places (obvious one is the entrance of the gallery into the plenum as it's gotta go somewhere - but it also has a sizeable cavity under it that turns out to be one corner of the plenum chamber) I've had to compromise with attempting a complete deletion of the EGR gallery by leaving this section intact and I'll be making a small block off plate to seal it up. This is the section of the gallery I'm left with -
I forgot to answer the question about the 'bridged' section between the primary and secondary ports into the plenum. Don't mess with it. If you're planning a carby upgrade and you're not going to reverse it, you can get away with removing it. But if you're keeping it standard or want to try out an upgrade, don't cut through it. It supports the middle of the butterfly throttle plate in the base of the carby and without it, you run the risk of it distorting when the engine heats up. The end result will be vacuum leaks and coolant leaks, not awesome
I have seen people on here cut out the center of the manifold and match the opening with the weber adaptor. there is a ring on the primary side that is supposed to help with emissions, but it is not really needed. I plan to cut it out of Geronimo's manifold when I do the 2.0 head swap with the Mikuni Muscle cam. I have extra manifolds I can mod - may even bypass the coolant floor heater to help cool the intake. That mod requires the bottom of the manifold to be cut off, and the coolant passage plugged or rerouted under the whole manifold with a pipe like the heater return line on the right side of the block.
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With all this work performed is this an experiment? Looks like your doing a good job on this project. What would be great is an MRI of the initial intake and bring it into a digital 3D image and do all the cutting through the system. It must tedious to cut and hope to not breach into the manifold. Though a weld could repair it. Very interesting thread for sure.
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I saw that sleeve for the primary, too, Pennyman, only looks like it's there to increase velocity a bit (maybe?). Easier to cut everything out and port it. Those EGR outlets screwing up the flow in the plenum could be filled with a TIG.
The other bit of potential turbulence I saw was the outlet from either the PVC or breather (can't remember) going to the #4 intake (IIRC). Easy enough to fill that with a TIG, too, I guess.
The design of the coolant passage around the thermostat is odd to me. There's that strange passage that goes from the thermostat housing and nosedives back behind #2 intake, but it goes nowhere. And there's that very small passage that half loops from #2 to #3. I don't know what that's for.
Good thing you made a point of the plenum ports assisting velocity/decreasing turbulence noahwins, as it does help. I've performed a fair bit of work on this inlet manifold partly due to my obsessive hatred of the EGR garbage - the rest is as a result of the generally poor quality of the casting, a corroded out base plate in the coolant chamber (), a blocked coolant gallery (if you've wondered where that coolant gallery that ramps down over #2 inlet runner goes, it feeds into the coolant basin under the plenum chamber) and my observation of how restricted that gallery actually is (once I'd chipped out the debris with a needle file the passage is barely big enough to poke a colour pencil through - I took to it with a hefty HSS drill and opened her right up ) I'm not 100% sure of the side effects of completely killing off the coolant basin would have but it might cause issues with coolant passing from the rear of the head to the front - plus if I do go down the Weber adapter path, part of the coolant flow that would normally enter the base of the factory carby will be blocked off so I figured I wasn't going to lose anything by improving coolant flow back into the thermostat housing. I've done my best to remove deflections inside the inlet runners but due to the castings' porousity it'll be impossible to get them looking flawless (plus the seams of the casting plugs leave a pretty ragged line that was going to require the removal of more metal than I was prepared to take out...) . This is what it ended up like after cleaning up the walls of the runners -
Good thing I have a junk manifold with a snapped off bolt AND snapped off bolt extractor bit in the thermostat housing to experiment on. I agree on the casting, it's spotty at best. But those runners on yours look fantastically smooth. Well done.
Is there a precise diagram somewhere of all of the water plumbing? Like exactly which route it's supposed to take? I saw one in a service manual but it was very generic, basically said it comes from the raditor, to the heater, to the intake and head, to the thermostat, back to the radiator.
Thanks guys for the positive feedback. This is my first attempt at a full house reflow of a stock manifold and head (I'll get to the cylinder head phase later - omg this !@#$ing head ) I've only done a basic port align and manifold tidy up before on a 4G32B head with a stock carby I tricked up. With some luck and a heap of knuckle busting I hope to get the G63B running strong and smooth
You don't like the head?
Can admin kill off my double post and the post with links only? It was glitching on me when I attempted to post my initial comment and refused to play ball (either than or my noobness got in the way...) Thanks