Rotary intake manifold advice

Hey guys,

Well last summer I was getting a faint hint of coolant smell from my 74 REPU. I didn't think much of it at first, but then it was getting a bit low on coolant every couple of weeks. I wasn't getting any white smoke, but I was afraid of what I may find. So I dragged my feet for a while, and put it away for the winter. Well the other day I decided while in the garage that I would put my cooling system pressure tester on the radiator. I topped off the coolant and pumped up the system to 13psi. Ran some errands, and came back about an hour later to 12psi, but no visible leak. Well I pumped it up some more, and went back out a few hours later to find a small puddle, but not smoking gun in my quick look over of the engine. Went out there this afternoon, and jacked the truck up to find the leak. What I found was a pretty good puddle on the top of the intake manifold where it meets the engine.

I made a pretty good mess with the coolant after I started removing the intake manifold without draining the radiator first. Dumb move I know, and I'm no rookie so I should have known better. Well here is what I found.

I bought the truck with this "newly rebuilt ported" engine in it. I always knew it was a bit of a frankenmotor with one RX-7 GSL-SE housing(front), and another unknown housing(rear). It appears the leak was more from the rear unknown rotor o-ring coolant passage, but I truly don't know for sure at this point. Replacement of that is easy enough with a new o-ring, but what should I do with the front coolant passage? Goober it up with silicone or whatever is in there now, or some sort of alternative? It is different than the rear as it doesn't have the recess for the o-ring like the rear. This is a 4-port by the way, but not the factory 4-port.

By the way the ports feel really large in this motor!! Which would explain the power this thing has.

GSL-SE rotor housings should not have coolant passages in them at all. So if you have one, someone put the hole there. (I assume you mean rotor housing since you say it's a 4 port, A GSL-SE "front housing" would make it a 6 port)

Basically, it appears that you're the subject to a mild case of well-intentioned buffoonery. I believe in manifold heat for a street driven carb application, and it appears that this was the only way to do it since '74-78 rotor housings are really hard to find. So I can't really fault the guy if he did drill a hole for coolant. So, new gasket, new O-ring for the rear, Right Stuff silicone for the front. It will NOT leak.

You're right the gsl-se shouldn't have coolant passages, but I really have no idea what these housings are from. The front rotor housing has a plugged oil injection hole in it but not the rear rotor housing. The engine is a 4-port. Runs great too. Strange that the rotor housings are different. I wonder if the port timing is the same?

Chris

So to be clear Chris, is the engine a 13B carbed or EFI originally, all carbed 13Bs were true 4 ports. I am confused by the 4 port but not a factory 4 port comment.

Factory 4-port REPU engines were different than this engine. This is a 4-port, but a Frankenstein 4-port.

Still trying to figure out what these housings are from? They are not factory REPU housings I know that much for sure. Anyone know what they could be from. Could be one is an S4 housing, but I thought they moved the water seals from the housings to the plates at some point. My guess is the irons are 12A in origin, but the housings are odd to say the least. The front has an oil injection hole that has been sealed, but the rear doesn't.

So just some silicone for the front coolant port, and be done with it? It seems to have worked for the last 10 plus years that I have owned it, and was on there before I got it.

4 port side housings are all the same year for year. A '74 13B had the same ones as a '74 12A.

If a rotor housing has an oil injection port, it IS from a GSL-SE. Only EFI cars had oil injection ports in the rotor housings and, as you note, starting with the FC the coolant seals moved.

It is perfectly clear to me that that truck is no good for you at all- in fact, it may even be dangerous.

Let me know when I can come and take if off of your hands.

For your own good, of course.

So I am finally getting around to repairing this. I know it has been neglected way too long. I just got some of the Right Stuff to apply to the front rotor housing coolant passage. My question is should I just apply a little of this stuff because it is just going to squish around anyway, or should I go crazy with it? Also do I apply it to the housing face/coolant passage, the manifold, or both? Should I add some to the rear housing o-ring or just leave it dry?

Thanks,

Chris

Before smearing goopy crap all over the place, I'd pop over Bruce's tomorrow and go through some of his VW engine gasket sets. The oil cooler seals are various OD sizes, have a "T" cross section, and might work perfectly for the passage without the indent for the "O" ring. There are also some with an "L" cross section. You could easily trim or shave one down to work for you. Worth a check, better than Right Stuff or whatever else comes in a tube and never really works, or use it along with the goopy stuff.

http://www.airheadparts.com/vintage-vw-parts/vanagon-engine-gaskets-oil-seals/seal-oil-cooler-late-style-021117151-a

Right Stuff never doesn't work.

I have lifted an engine by the intake manifold (bolts removed) after Right Stuff-ing the China walls and a thin smear around the coolant passages in the gasket.

I used the Right Stuff, and I have the whole cooling system together without any coolant(see other thread). Upon further review the housing without the means for the o-ring has a hole, bit not all teh way through the housing, so I am even more confused by it. I am still thinking GSL-SE housing, but I am unsure if they have even this setup.I pressurized the system without coolant, and have had it pumped up since around 9am, and it is still at 13 psi, so I think the system is solid. I think I may pull the transmission out tomorrow to figure out why the clutch was slipping last summer.

Chris

Mazdax605 wrote: Upon further review the housing without the means for the o-ring has a hole, bit not all teh way through the housing, so I am even more confused by it.

That's normal, then. Mazda only machined the hole and the recess for the O-ring if the intake manifold needed it. GSL-SE didn't need it so the housing was left as-cast/rough-machined in that area. I always kinda wondered if the coolant passage there was used to locate the housing at some step in the manufacturing process, since otherwise why bother to machine the recess?

If you use a stock carb intake then you still need to seal it from coolant since the coolant will flow to there through the intake manifold. If you are using an intake that doesn't get coolant (99% of aftermarket intakes) then you only have to seal the other one.

Stock intake with with passages for coolant. I guess it just goes in through the rear housing, and just dead ends there. Not sure how that works with a lack of flow, but it has been fine for the past 10+ years so I guess it is fine.

Chris

Transmission and clutch out as of ten minutes ago. Clutch is really toasted. Needs a new one in a bad way, but thankfully the flywheels looks fine in my opinion. Now I need to determine which size the clutch is. The flywheel says GSL-SE on it in paint pen, so I am thinking 225mm, but I have to measure it. Transmission came out no problem even by myself. I guess it pays that I have done this job on my RX-7's about 300 times, so I am getting good at it. This one was a bit different with the two piece drive shaft, but the rest of the job was pretty similar.

If the flywheel is flat then it is 215mm. If the pressure plate bolts into stands and the friction area is recessed then it is 225mm.

Or you can look at Mazdatrix's flywheel page, get an inspection mirror and look for the casting number, and erase all doubt.

But it's probably a 225.

Definitely a 225mm clutch, and flywheel. I measured it, and I was pretty sure anyway just by the fact that the pressure plate bolted onto stands.