Bought my '79 a couple years back from an Ex-Girlfriend, engine was worn, but still pretty healthy. Engine blew about 3 months later. Bought an '81 model with a good engine to swap in (Had a couple surprises like a lightened flywheel attached..BONUS!!) bought a header while the engine(s) were out, also removed the rat's nest. After 2 years of unreliable people, the engine was FINALLY back in. Here's where I messed up. Installed the '79 running gear (intake manifold and carb) and then had the header installed. Muffler shop took a week to get it done, went to pick it up, and it won't idle at all, if you keep it running, the front rotor begins to make the header pipe glow cherry red. Figured my carb dried out from sitting. Had it rebuilt, and now the inlet bolt is spraying fuel like crazy. Threw on my brother's carb from his '82, same issue. Found out later that you need an FB manifold to cover the EGR port. Is there anyway I can keep the SA manifold? The old style flows much better. nd if not, can I get rid of the stupid flap in the FB manifold?? Have a header, no presilencer, and 2 glasspacks, which are pretty much burned out, and I'd like to have a nice little flameshow from the exhaust, and I don't think the FB manifold with the fuel cutoff flap will help that too much..

Thanks,
Giuseppe Giulianni, FIAT collector haha

 

The glowing header pipe was possibly not carb related, but ignition related. Check for good spark, leading and trailing. I had the same problem but with dual weber carbs and kept thinking it was the carbs. I kept tuning them and took them apart several times before asking trochoid for help. He told me to check the ignition and lo and behold I had a bad ignitor. Luckily I have a few extra hanging around and it ran fantastic after I re-tuned the carbs. Did you use the '81 distributor or the '79? The '79 is points, but the '81 is not so it could be the problem.

 

I retained the points, used my old dizzy. Lined up the scribe marks on the shaft so they were right under eachother, and brought the engine to top dead center before I dropped it in... That is the correct method, right?? The points are new, and the plugs are new... I think I have spark, it'll start with starting fluid/fuel down the carb, but won't keep running. You say it was the ignitor that was plaguing your '79? Interesting.. I will definately check on that.. Thank you. I'm LITERALLY about to just give up on this thing..ha

 

Mine wasn't a '79, but it was the ignitor. I also had a problem with a rebuild a few years ago and did have the dizzy in 180 degrees off, but it sounds like you got it in right. Just use the old screwdriver in the sparkplug wire trick while cranking to see if there is spark, or use a timing light and check timing also.

 

I just got done testing that, I got spark... It reacts to fuel, I'm pretty sure it's doing this because the EGR port isn't blocked, and it's bleeding tons of air directly into the engine... At least, I HOPE that's what it is.. Thanks for your input, btw

 

well that egr port only pumps out exhaust, so technically it should run ok with it open, but again you do have an exhaust leak.

 

Get a timing light so that you know for *sure* that the spark is dead-on then start checking for vac leaks. Glowing header often means you're running lean which is something a vac leak would cause.

I had that issue a few times and you learn to be an expert at tracking down all possible sources of vac leaks. The EGR won't be causing this issue but it's also not a good thing. You really need to get an FB manifold. Flow isn't any better with the 79 manifolds, the runner on the FB with the butterfly is proportionally larger so that flow is the same between the two primaries. So it's best to just JB Weld the butterfly shaft so it stays open otherwise you will have different flow between your primries.

That said, the sources of vac leaks starting at the engine are:
- Engine-to-manifold gasket
- AAB #2 tube hookup spot
- Air tube to cat from back of mani
- ACV block-off plate
- Manifold-to-spacer
- Ports on spacer
- Spacer-to-carb
- And any spots on the carb that have vacuum hoses going to them

20mm frost plugs are a great idea to block those coolant holes between the engine and manifold. It makes it easier and cleaner to install/remove the manifold.

PM me your email and I'll send you a PDF that shows how to prep the FB manifold for vac-leak-free use without a rat's nest.

Good Luck, and don't give up.

Jon

 

Basically if you set the timing, get an FB manifold, prep it per my tutorial and try your friend's known-good carb you're almost guaranteed to find it there somewhere. Then if it runs fine with his carb, try yours again and hopefor the best If it's your carb (or even if it's not, really) I'd get a Sterling.

 

You can weld aluminum on the bottom of the SA manifold to block off the SA port. Be sure to block sand or belt sand the manifold face afterwards as it will warp from the heat.

ALSO, either manifold you use stuff some aluminum foil down that egr port on the intermediate plate and top it off with some high temp silicone. So hot exhaust won't be directly heating the manifold there. It can cause warpage.

Don't give up indeed!

 

Yeah the engine will run with a nice loud exhaust leak, but it'll run!

 

If you're willing to take some constructive criticism, firstly, it is an ACV port, not EGR. Only the 1980 CA model used EGR in US-spec 1st gens. Secondly it is best to fill in the port instead of modifying the manifold. I've never had a manifold warp from ACV heat. Ever. Sounds like welding aluminum to an SA manifold is what warped it. lol

Here is what to do to get a leak proof blocked ACV port. Clean the port out really well first, using a dremel with a small stone or similar, down to bare metal. Then use a little brake cleaner and clean off any residual oil and carbon residue. Don't use a lot. You only need to wet a rag with brake cleaner (terry cloth towel or an old clean sock works better) and wipe it around in there. Don't spray into the ACV port (kaboom! on startup maybe). Then knead up about half a stick of quicksteel or similar strong putty (jb weld?) and work it into the hole. I've found no need for aluminum foil. Heck I wouldn't know how deep to stuff it in there, nor would I like the thought of a some day loosening up wad of aluminumn foil moving around in there. The quicksteel holds itself in really well as it cures. Trim the excess off with a razor blade edge before it hardens. It really is the best way to us an SA manifold on any '74-'75 or '81-'85 12A. Same applies for a couple models of Hitachi manifolds which lacked ACV port coverage.

Using quick steel keeps the manifold cooler since zero exhaust will be in contact with it. The next step is adding a brass freeze plug to each coolant port but only AFTER you've blocked the ACV port. NEVER add freeze plugs with an open ACV port; this applies more to FB manifolds which had an active ACV port where the coolant flowing through was meant to keep the manifold from getting too hot. A cooler manifold is better for power.

I feel I'm the lone voice on this subject. Let's talk about this more until it is common knowledge!

 

Hmm... I've always thought (and read) that coolant going through the manifold was to help heat it up to operating temp sooner to help with emissions. Though I guess the exhaust in the ACV port would do that, come to think of it.

I've been running freeze plugs in the coolant passages on my '84 with an un-blocked ACV port for two or three years now and haven't seen any ill effects in terms of warpage, leakage or related issues. I guess I might be losing some power to the heat though, I didn't think about that. I'll make sure that I take care of that in my next engine build, though I don't think it's detrimental enough to say "NEVER" do it, or for me to go through the hassle of blocking the port between now and the next engine build...

Jon

 

Racing Beat has something to say about this subject. "the hot exhaust can back-flow up the intake manifold and heat it, creating an undesirable situation."

Ask yourself which you'd prefer. An intake manifold heated by exhaust heat or heated by coolant? Which gets hotter? Exhaust, typically. Now you see how having coolant flowing through keeps the manifold cooler, but once the ACV is blocked you can also block the coolant. I call this the cool manifold mod. Jon, you may have unknowingly allowed your manifold to be way hotter than if you'd left the coolant ports open. Food for thought, eh?

This goes for everyone else. If you've blocked your coolant ports but don't know whether your ACV port is still active, pull your manifold and check. I mean what's the point of adding coolant plugs in the first place, right? Wasn't its secondary purpose to allow easy manifold removal without loosing coolant? So pull off that manifod and have a looksee. Then fill the ACV port in with something (as described above) and go for a test drive. A cooler manifold yeilds more power. Isn't that what we're after doing all these mods anyway?

Oh, uh get a new intake gasket and two new o-rings on hand before you do this. Some seepage from the freeze plugs can occour if they're not in 100% perfect. Better to contain it within the manifold than let it soften the gasket paper.

 

Yeah the primary reason I put the freeze plugs in was ease of removal of the manifold. The car's 600km away with the engine out at the moment, so I'll try to remember to fix it before we reassemble. You have a very good point with the ACV port, mine is most definitely open, allowing exhaust to heat my manifold, definitely not a desirable situation.

I should probably fabricate a heat shield between the headers and carb, too. I never did get around to that. Though there's much less heat pooling there since the swap from the stock exhaust manifold to the RB Headers.

When I drop the new engine in I'll be heat-wrapping the new manifold and adding a heat shield, as well as blocking off the ACV port. That should hopefully help.

Which is yet another reason that it's amazing that I'm putting 105rwhp down on a stock 12a that's running 6.9km/cm2 compression all around, has over 230,000km on it, and has an open ACV port! It's not a lot of hp, but it's more at the rear wheels than the car had at the flywheel from the factory, and on borderline compression that isn't bad! Stock ignition system and timing to boot!

Jon

 

I've never owned an SA manifold let alone one welded up. A shop put one on my car and we went over the options on how to fix it. Went with a FB manifold.

Quicksteel is rated for only 500*F and a rotary gets up to 1400*F on a regular basis and 1700*F after a long full throttle run on the freeway.. I've tried JB Weld
for exhaust patching and it lasts for minutes. Dries out, becomes brittle, cracks and disintegrates into a powder. I don't want that stuff getting into my engine. So I'll stick to aluminum foil. It doesn't rattle around if you pack it in there tight, and exhaust pressure pushes it up to the manifold port where it shapes into a plug.

Manifolds warp, I've put a straight edge on a low mileage IDA manifold and it was warped. If I evenly, gradually tighten down the manifold bolts & nuts to factory torque specs, then how does the manifold flange warp? Could it be 1700*F of exhaust gasses?

Nice thing about coolant in the intake manifold, it prevents manifold icing.

I'm suprised no one here mentioned this. Now, if you want a Nikki manifold that flows well from the factory and doesn't have a shutter valve, find an Rx-3 manifold. Has very little smog crap on it too and Racing Beat made an ACV block off plate for it too. I had that setup and loved it.

 

Actually i just removed the shutter valve all together, just be careful because those screws are very soft (bad engineering on their part), and i plugged the two holes with aluminum pressed in plugs. For those who i know would ask, i hand made them on a lathe, to a +.0025 press fit, added a little silocone and pressed them in. No butterfly blocking my port at all :-)

 

I put freeze plugs in my rebuilt engine so that I would not have to deal with a water seal going out in the future. I wanted to keep the carb, intake and exhaust all stock. So what your saying is that I should not do this because it will cause other issues (.i.e. unwanted heat). How hard is it to pull the freeze plugs out now? I'm just so paranoid of this engine's water seals out out like that last engine in this car.

 

Is a possible coolant leak due to aged o-rings your only motivation? Those are really easy to change and usually last 20 years.

By blocking off the coolant ports, you've changed the way the manifold is heated up so by definition you are no longer keeping it fully stock. You must remove the freeze plugs in order to get back to stock. Sorry you were misguided by others' information presented here on this subject.

Do you have to run stock intake and exhaust? Emissions in your area?

It would be better to upgrade intake and exhaust, which you already know. Half the fun of these rotaries is how much more performance they have lurking just under the surface. That's a fresh rebuild, ins't it? Treat it right by letting it breath cool air.

If I were you and already had the coolant ports blocked, I'd finish the job by sealing off the ACV port. Then upgrade various things going into and out of the engine to extract more performance. A stock exhaust manifold with a free flowing 2" system has some performance. You already know a stripped Nikki makes things easier to work on.

 

How hard is it to pull the freeze plugs out? They're soft brass, right? Or maybe steel?

If you have a slide hammer, like a dent puller, it can be used. You know the drill, drill a hole, thread the screw tip in, start jerking it off until it comes out.

 

I'd second the "fix the ACV port rather than pull the freeze plugs".

But for myself I don't think it's enough of a problem for me to do something about until the next time I've got the manifold off anyway. In the meantime I have to find something that'll stand up to the rotary exhaust heat because DriveFast7 had a good point about QuickSteel. I've seen what our exhaust heat does to JBWeld and that's rated for quite a lot of heat! There must be something we can use for that... I'm not too big on the aluminum foil idea. I don't know that it will really stop that much heat from getting through...

Edit: I just found someone online saying he used it to patch the hole from "a doodad (a sensor of some sort, I guess) which had rusted and fallen out of my car's catalytic converter" and that it held up to the heat unlike other epoxies he'd tried. Though both him and the manufacturer state that it's only good up to 260C which wouldn't nearly be enough under normal circumstances for our exhaust.

http://everything2.com/title/QuickSteel

Jon

 

I had another thought...

The air that comes up the ACV port and gets into the manifold hits a dead end. It has nowhere to go to get out (as long as your ACV is removed and you've installed block-off plates). So once that cavity is filled up to the same pressure as your exhaust, there's no easy way for new exhaust to get up in there. The air that's there dissipates its heat into the manifold, then sits there, unable to leave back down the ACV port because of the constant pressure.

Keep in mind, I am not very well versed in airflow dynamics. I know how air flows in relation to all sorts of carb-related questions, but I could be completely wrong in this case... But I figured that in much the same way that air flowing through a hot radiator cools it off, or hot air flowing through exhaust pipes heats them up, it's the continuous supply of air at that temperature which gives the heat somewhere to go (something called "Enthalpy" that I vaguely remember from Chemistry involving the difference in temperature between two things). Air not really flowing *through* the manifold might not have enough heat to melt QuickSteel, for example.

I'm thinking someone should give the QuickSteel thing a try and see if it holds up to the heat.

Jon