Manifold Fitment Questions
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
Manifold Fitment Questions
I have an 84 Engine (at least I think it is). I am about to install a modded nikki and want to install an older intake manifold. The manifold I want to use is an old "non emission" 70's era intake. A lot of old road racers claim it is the best flowing stock manifold.
There is this small rectangular shaped hole in the center housing. This hole looks like it goes inside the engine somehow. The old style mani does dot have a provision for this hole. The 1984 Mani gasket has the provision.
Older manifolds do not have this hole.
What do I do with this hole? Which gasket should I use?
Please advise!!!
BTW:
1st pic (old style manifold)
2nd pic (back of old style manifold)
3rd pic (1984 manifold)
4th pic (My engine)
5th pic (gasket)
There is this small rectangular shaped hole in the center housing. This hole looks like it goes inside the engine somehow. The old style mani does dot have a provision for this hole. The 1984 Mani gasket has the provision.
Older manifolds do not have this hole.
What do I do with this hole? Which gasket should I use?
Please advise!!!
BTW:
1st pic (old style manifold)
2nd pic (back of old style manifold)
3rd pic (1984 manifold)
4th pic (My engine)
5th pic (gasket)
I'm no expert on these engines..... yet, but If I had to take a guess (please correct me if I'm wrong) a port for the smog pump? But Just a guess. I haven't had a chance to remove my manifold or smog pump just yet. Soon.....
I want some more info on this pre emmisions manifold.
It doesn't look like the older manifold would cover the hole by eyeballing the gap. I'm at a loss on a solution for that
I want some more info on this pre emmisions manifold.
It doesn't look like the older manifold would cover the hole by eyeballing the gap. I'm at a loss on a solution for that
Ok so maybe if the old manifold wont cover it, you could bolt a flat piece of metal to the manifold and use the gasket to cut the shape of the newer manifold. build it up thick with some jb weld to the right shape. the piece of metal shold keep the jb weld flush use plastic wrap to keep it from adhearing to the metal. grind a smooth shape if you want it to look nice. and then paint it so it doesn't look like jb weld.
I couldn't say if this would work or not but I'm just trying to give you some Ideas. use my idea at your own risk. and make sure its strait to block off before you do it
That intake looks to have some potential btw.
I couldn't say if this would work or not but I'm just trying to give you some Ideas. use my idea at your own risk. and make sure its strait to block off before you do it
That intake looks to have some potential btw.
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
I'm no expert on these engines..... yet, but If I had to take a guess (please correct me if I'm wrong) a port for the smog pump? But Just a guess. I haven't had a chance to remove my manifold or smog pump just yet. Soon.....
I want some more info on this pre emmisions manifold.
It doesn't look like the older manifold would cover the hole by eyeballing the gap. I'm at a loss on a solution for that
I want some more info on this pre emmisions manifold.
It doesn't look like the older manifold would cover the hole by eyeballing the gap. I'm at a loss on a solution for that
I think on this 84 engine I will use the 84 intake. The previous owner did a nice job of eliminating the shutter valve. I will clean up the manifold and smooth out some of the bends, port the center ports to match my engine and call it a day.
I will use the older intake on my 1980 RX-7. I know it will fit the 80 engine.
Still makes me wonder, what exactly is the hole for and what would I do if I really ended up using the older manifold.
Trending Topics
Joined: Feb 2006
Posts: 3,162
Likes: 1
From: London, Ontario, Canada
Sorry I meant to chime in earlier. That manifold is absolute garbage, you would be better off gluing some straws to your intake ports. I'll take it off your hands for ya. Don't need to be wasting your time with junk like that. $100US. Final offer.
that rectangle is tied to the exhaust. exhaust gases introduced back into the intake charge reduces combustion temps, allowing for a leaner mixture. racing beat sells blocking nozzles to replace those in the exhaust to block that passage. or u could find someone that can weld aluminum and add a piece to the intake.
Joined: May 2002
Posts: 5,972
Likes: 37
From: Ottawa, Soviet Canuckistan
that rectangle is tied to the exhaust. exhaust gases introduced back into the intake charge reduces combustion temps, allowing for a leaner mixture. racing beat sells blocking nozzles to replace those in the exhaust to block that passage. or u could find someone that can weld aluminum and add a piece to the intake.
IIRC That port doesn't actually go anywhere once it's inside the intake manifold. It doesn't mix exhaust gas into the intake charge, it just gives the exhaust gas a place to be. Why would you want exhaust gas in the back of your intake manifold just sitting there you might ask? The answer is to reduce the engine warm-up time.
Engines do very poorly for emissions until they reach operating temperature. As such, if you want to do better on emissions tests, you want to build a car whose warm-up cycle is as short as possible. The purpose of this passage is actually to heat the intake manifold up using the exhaust so that the intake charge is *warmer* , which would reduce the amount of time it takes for the car to get to operating temperature.
The same principle applies to the heatshield around the stock exhaust mani, which has a hose that goes up and connects to the snorkel on the stock airbox. Its job is to take air from around the exhaust manifold (which we all know gets really hot - hot enough to catch a rubber hose on fire, take my word for it) and feed it into the intake until the car is at operating temp, at which point the little "flapper" in the snorkel closes that hole so that air intake comes from the end of the snorkel instead of that tube going down to the exhaust manifold.
Again, the same principle goes for the coolant passageways in the stock manifold (which you can use frost plugs to cap, making it MUCH easier to swap manifolds)
In short, if you can block off the passages that lead the exhaust gas up the iron to that port, you can use the older manifold and you'll be better off for it because you'll have a cooler (and thus denser) intake charge by a little bit... But that's trickier than frost plugs.
Jon
Last edited by vipernicus42; Apr 11, 2009 at 09:59 AM.
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
Close... but that's not an EGR port if that's what you're thinking.
IIRC That port doesn't actually go anywhere once it's inside the intake manifold. It doesn't mix exhaust gas into the intake charge, it just gives the exhaust gas a place to be. Why would you want exhaust gas in the back of your intake manifold just sitting there you might ask? The answer is to reduce the engine warm-up time.
Engines do very poorly for emissions until they reach operating temperature. As such, if you want to do better on emissions tests, you want to build a car whose warm-up cycle is as short as possible. The purpose of this passage is actually to heat the intake manifold up using the exhaust so that the intake charge is *warmer* , which would reduce the amount of time it takes for the car to get to operating temperature.
The same principle applies to the heatshield around the stock exhaust mani, which has a hose that goes up and connects to the snorkel on the stock airbox. Its job is to take air from around the exhaust manifold (which we all know gets really hot - hot enough to catch a rubber hose on fire, take my word for it) and feed it into the intake until the car is at operating temp, at which point the little "flapper" in the snorkel closes that hole so that air intake comes from the end of the snorkel instead of that tube going down to the exhaust manifold.
Again, the same principle goes for the coolant passageways in the stock manifold (which you can use frost plugs to cap, making it MUCH easier to swap manifolds)
In short, if you can block off the passages that lead the exhaust gas up the iron to that port, you can use the older manifold and you'll be better off for it because you'll have a cooler (and thus denser) intake charge by a little bit... But that's trickier than frost plugs.
Jon
IIRC That port doesn't actually go anywhere once it's inside the intake manifold. It doesn't mix exhaust gas into the intake charge, it just gives the exhaust gas a place to be. Why would you want exhaust gas in the back of your intake manifold just sitting there you might ask? The answer is to reduce the engine warm-up time.
Engines do very poorly for emissions until they reach operating temperature. As such, if you want to do better on emissions tests, you want to build a car whose warm-up cycle is as short as possible. The purpose of this passage is actually to heat the intake manifold up using the exhaust so that the intake charge is *warmer* , which would reduce the amount of time it takes for the car to get to operating temperature.
The same principle applies to the heatshield around the stock exhaust mani, which has a hose that goes up and connects to the snorkel on the stock airbox. Its job is to take air from around the exhaust manifold (which we all know gets really hot - hot enough to catch a rubber hose on fire, take my word for it) and feed it into the intake until the car is at operating temp, at which point the little "flapper" in the snorkel closes that hole so that air intake comes from the end of the snorkel instead of that tube going down to the exhaust manifold.
Again, the same principle goes for the coolant passageways in the stock manifold (which you can use frost plugs to cap, making it MUCH easier to swap manifolds)
In short, if you can block off the passages that lead the exhaust gas up the iron to that port, you can use the older manifold and you'll be better off for it because you'll have a cooler (and thus denser) intake charge by a little bit... But that's trickier than frost plugs.
Jon
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
har har har.....I went through hoops to get that manifold!! NAH....I'll just keep the piece of junk!!
Joined: Mar 2001
Posts: 31,857
Likes: 3,243
From: https://www2.mazda.com/en/100th/
Close... but that's not an EGR port if that's what you're thinking.
IIRC That port doesn't actually go anywhere once it's inside the intake manifold. It doesn't mix exhaust gas into the intake charge, it just gives the exhaust gas a place to be. Why would you want exhaust gas in the back of your intake manifold just sitting there you might ask? The answer is to reduce the engine warm-up time.
Engines do very poorly for emissions until they reach operating temperature. As such, if you want to do better on emissions tests, you want to build a car whose warm-up cycle is as short as possible. The purpose of this passage is actually to heat the intake manifold up using the exhaust so that the intake charge is *warmer* , which would reduce the amount of time it takes for the car to get to operating temperature.
The same principle applies to the heatshield around the stock exhaust mani, which has a hose that goes up and connects to the snorkel on the stock airbox. Its job is to take air from around the exhaust manifold (which we all know gets really hot - hot enough to catch a rubber hose on fire, take my word for it) and feed it into the intake until the car is at operating temp, at which point the little "flapper" in the snorkel closes that hole so that air intake comes from the end of the snorkel instead of that tube going down to the exhaust manifold.
Again, the same principle goes for the coolant passageways in the stock manifold (which you can use frost plugs to cap, making it MUCH easier to swap manifolds)
In short, if you can block off the passages that lead the exhaust gas up the iron to that port, you can use the older manifold and you'll be better off for it because you'll have a cooler (and thus denser) intake charge by a little bit... But that's trickier than frost plugs.
Jon
IIRC That port doesn't actually go anywhere once it's inside the intake manifold. It doesn't mix exhaust gas into the intake charge, it just gives the exhaust gas a place to be. Why would you want exhaust gas in the back of your intake manifold just sitting there you might ask? The answer is to reduce the engine warm-up time.
Engines do very poorly for emissions until they reach operating temperature. As such, if you want to do better on emissions tests, you want to build a car whose warm-up cycle is as short as possible. The purpose of this passage is actually to heat the intake manifold up using the exhaust so that the intake charge is *warmer* , which would reduce the amount of time it takes for the car to get to operating temperature.
The same principle applies to the heatshield around the stock exhaust mani, which has a hose that goes up and connects to the snorkel on the stock airbox. Its job is to take air from around the exhaust manifold (which we all know gets really hot - hot enough to catch a rubber hose on fire, take my word for it) and feed it into the intake until the car is at operating temp, at which point the little "flapper" in the snorkel closes that hole so that air intake comes from the end of the snorkel instead of that tube going down to the exhaust manifold.
Again, the same principle goes for the coolant passageways in the stock manifold (which you can use frost plugs to cap, making it MUCH easier to swap manifolds)
In short, if you can block off the passages that lead the exhaust gas up the iron to that port, you can use the older manifold and you'll be better off for it because you'll have a cooler (and thus denser) intake charge by a little bit... But that's trickier than frost plugs.
Jon
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
that is totally wrong! RTFM! http://www.jimrothe.com/mazda/84_tra...raining_4a.pdf
ANyhoo... I got to thinking earlier today (before drinking) that how in the world could it have anything to do with getting exhaust. This is the center housing....has NOTHING to do with exhaust. The exhaust comes out of the rotor housings.
When I pulled the intake off, there was no exhaust residue. Maybe just some oily residue. Not exhaust.
Come on folks......somebody really knows what this hole is for!!
Joined: Mar 2001
Posts: 31,857
Likes: 3,243
From: https://www2.mazda.com/en/100th/
OK, I have read through the manual you sent...still don't fully understand what the rectangle is for....Maybe I have had a little to drink today.
ANyhoo... I got to thinking earlier today (before drinking) that how in the world could it have anything to do with getting exhaust. This is the center housing....has NOTHING to do with exhaust. The exhaust comes out of the rotor housings.
When I pulled the intake off, there was no exhaust residue. Maybe just some oily residue. Not exhaust.
Come on folks......somebody really knows what this hole is for!!
ANyhoo... I got to thinking earlier today (before drinking) that how in the world could it have anything to do with getting exhaust. This is the center housing....has NOTHING to do with exhaust. The exhaust comes out of the rotor housings.
When I pulled the intake off, there was no exhaust residue. Maybe just some oily residue. Not exhaust.
Come on folks......somebody really knows what this hole is for!!
not much crap in there, because most of the flow is fresh air going INTO the exhaust, its not supposed to go the other way
blow some air into it, see where it goes...
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif
That hole is a passage for air pump air to be fed into the exhaust ports. If you leave it uncovered, you will have exhaust leaking from it. If you want to use the early manifold, the easiest thing to do is plug the rectangular hole or weld a small aluminum block to the bottom of the manifold to cover the port.
Here's a picture of one that I did with an aluminum block welded to the intake. If you do it this way, just make sure to use the gasket with the rectangular hole in it and all is good.
Thread Starter
Joined: Jul 2008
Posts: 1,671
Likes: 9
From: Chino Calif