Just got done talking with Todd over at Wolf Creek Racing. I ordered a few main fuel and air jets to have when I get it running so I can tune it. Gonna try to start it up with the new plugs today and see how it idles and determine if I need smaller pilot jets.

I told him how the Mikuni likes to bog down at low RPM and he said it could be either a lean or rich problem and I needed the proper equipment to determine what the issue was. Gonna do some more research but I think this is basically solved by checking the plugs after letting the car idle a bit. Maybe I should get some type of monitor? Not sure what that would be though.

 

Google is neat.

So I need to install a wideband O2 sensor. Shouldn't be too hard, I can cut and weld.

Anyone recommend me a good brand?

I was looking at this one: MTX-L Wideband O2 Digital Air/fuel Ratio Gauge

I called Todd back and told him to also order me two smaller pilot jets. He said they step down by 2.5 so that would be 60 and 57.5, he said he didn't have the 60's but he had the 57.5 and 55's so I've got that coming as well.

 

Heyooo, got her running. She doesn't idle below 1300 or so though. I got to start her up with some good sunlight, boy is it running rich. White smoke coming out the exhaust, not heavy, but visible in the sun. That plus a strong smell of fuel.

Gotta wait till the new jets come in to play arouund with it. I have been reading reviews of the wideband I posted above and a lot of people use them with great success apparently.

 

Even with the recommended jets being apparently on the rich side, I don't think they are so large as to cause a flooding problem, I think that was the float level. Now my question is why can't I get the car to idle? It runs fine at 1400 or so RPM and up but dies as soon as I dip the throttle to idle speeds.

Everything I read points back to a vacuum leak and solutions to that are on the order of dry ice and water or a fog machine and letting the vapors get sucked into the intake and see if anything blows it out.

Should I have used silicone or something to help the intake manifold gasket I cut seal? All the other gaskets on the carb have been replaced recently and are in good condition.

All the ports have been capped with brand new vacuum caps and I have the dist advance hooked up.

 

Yeah vacuum leak could be the cause of the high idle.. don't put silicone on gaskets basically the same as double gasketing. You can sometimes put a light coating on intake gaskets to reuse..I would replace all the intake gaskets and make sure you have no open ports sucking in air. Btw don't make the gaskets buy um from Mazda..I know they're kind of expensive but you won't have to worry about the quality. Also don't clean any gasket surfaces with any rotary tool..try to do it with gasket scrapers. If you absolutely cant get um off soak them in carb cleaner that should take any gasket residue off. Or use Kerosene.

 

I meant a light coating of grease like wheel bearing grease.

 

I made a gasket because there are ports that aren't used on the Mikuni intake (coolant ports and ACV port). Also the holes on the Mikuni intake are slightly larger than on the stock Nikki intake so I made the gasket to the size of the Mikuni intake manifold holes rather than modifying a Nikki gasket.

I used a dremel with a wire brush attachment (doesn't alter the surface) and went lightly over where the old gasket material was, then cleaned it all with carb cleaner. All the mating surfaces were smooth and I checked for any defects before using the new gasket.

 

Here is why I made my own gasket. The one on top matches the Mikuni intake perfectly, the one on bottom is one from Mazda I believe.







These are the only ports I vacuum capped. the only other port open is on top and I connected it to the vacuum advance on the distributor.

There is a small screw hole that looks like it accesses the innards of the carb, I plugged it but it changed nothing so I have to guess it wasn't leaking.

 

I've been over this thing front and back about 5 times now. How do I check for a vacuum leak to rule it out?

I've read methods of propane, fog machines, and dry ice. What's the safest and most effective?

 

Use a can of Brake Cleaner man. Have the car running with someone watching the tach and spray brake clean over the intake in the areas you think it might be leaking. If its leaking vacuum it'll suck the Brake clean in and make the rpms rise. Dont douse it in brake clean though slowly go over the areas you think it might be leaking. Don't worry it wont just catch fire it needs a good ignition source. Definitely safer than propane or ether. Safest way would be to use a smoke machine but you probably don't have access to one and they're definitely not cheap.

 

Would carb cleaner work? The kind in the can, not the paint jug.

Also, I think I can get some dry ice to make CO2 vapor, just not sure how to apply that method. Spread the vapor around and see if it gets sucked in at points it shouldn't be? If that's so it shouldn't be hard to fill a mason jar with a little water and dry ice then have a small port in the top with a tube to direct it.

 

Weber 48 ida

 

Buy me one, I'll put it on as soon as it gets here.

 

You're planning on spending 300.00+ for a wideband, which is a good idea, but you want to skimp on the carb. I don't get it? Sell the Nikki and Mikuni and buy a used 48 IDA.

 

Just because you think Weber IDAs are the best doesn't mean everyone else does..sure they're the most tunable but Webers are the most expensive carbs. I would take a Holley over an expensive Weber any day.

 

$200+, the kit I am looking at now is $199 and it's got good reviews over the internet. And I can swap it to another car whenever if need be.

 

Just ordered a MTX-L Wideband O2 Digital Air/fuel Ratio Gauge. Talked to my cousin that works where I work. He said spray can ether is a good solution and won't affect anything whereas brake cleaner might. He said carburetor cleaner would work but ether would be more noticeable.

I also asked him about this:


The hissing sound when the engine shuts off. This was with the nikki, but it does the same with the mikuni. Sound comes from around the brake booster area. He said it's not normal, but I have read forum posts on here saying it is.

 

There are two 84-85 cars here with the hiss after shutdown. It might be normal. I hope it is.

 

Just spent 15-20 minutes going over every inch of the car with starting fluid. I can't detect a vacuum leak anywhere.

 

New jets came in today. Wideband will be here Friday.

Went and picked up a compression test kit as well.

 

pull the a hose off the booster and see if the booster holds vacuum, if it doesn't its bad...

 

In dummy terms please.

Pull the "a" hose, or "pull a hose" and see if it holds vacuum (what's the test for that?).

 

the brake booster has one vacuum line, remove that line from the booster, and apply vacuum to the booster, if the booster does not hold vacuum, then it is bad.

sometimes a bad booster will make weird noises

 

Sounds like it would require a vacuum pump.

 

Hrmm... Could I just remove the hose from the hard line to the intake manifold (the one that comes from the brake booster) and cap the port on the intake? That way I am not so much testing the booster but ruling out that as the cause of not idling.

Also, can I perform a compression test without the intake manifold and carb installed since you don't need fuel and just air?

I was planning on taking the carb back off and completely taking it down, ordering a seal kit and rebuilding it. A master rebuild kit is only $75 and includes pilot needles/seats and accel pump diaphragms as well as gaskets.