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1984 720 z24 Weber Carb exhaust manifold


Rbdinamico

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Just swapped for a 32/36 Weber carb on my 1984 720 z24. Having issues with the exhaust manifold heating up and smoking, so I'm guessing I made a mistake on the install. My first rebuild so I'm learning as I go. I didn't do a full egr delete, and I just capped (not removed) the air injection pipes...not sure if that's why. I'll get some pics up soon.

 

Appreciate the help, pictures especially. 

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The air injection pipes were capped at the exhaust manifold??? If so you probably handled the manifold with oily dirty hands. This will burn off in 10 min of running. Did you have the valve cover off? same thing oil dripped down on it.

 

REBUILD????? Definitely oily hands pulling it off and putting it on. Never seen an engine rebuilt yet that didn't have a manifold smoke for 15 minutes after starting.

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Here's a pic 

I'm getting plugs for the 2 pipes going into the manifold.

 

Thanks datzenmike. I used gloves but I'm sure oil or grease could have gotten on. I'll let it run for awhile and see if it burns off.

 

I'm still concerned I may have missed (or mixed up) something on the carburetor install. I haven't seen any threads that show (with pics) exactly how to remove all of the vacuum lines and remove/cap the air injection pipes and all egr equipment. The truck fires up and runs but doesn't accelerate correctly when I hit the gas. 

 

Like I said, I'm a noob. Done a lot of work already thanks to this forum, just trying to get this issue worked out and get this beast to the woods.

 

I'll post a link to a video soon with a look at the weber install to make sure it's done correctly.

 

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ACtC-3faDObf6wGNMY5Zxhb8mlCLjQb1ofiAhGGK

 

 

The exhaust is a series of pressure waves with a vacuum pulse between each one. This is piped to the stock air filter that has one way reed valves that stop the pressure wave but allow the vacuum pulses to draw filtered air down in little packets and into the exhaust manifold. The added air had oxygen that the catalytic converter uses to burn off any unburnt hydrocarbons. It's benign in operation.

 

Carburetor install won't cause the exhaust manifold to smoke.

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The EGR only affects running if it isn't maintained properly. It's only on on above idle and not a full throttle... in between it tweaks the cylinder temperatures by introducing som inert exhaust that does nothing but take up space. The power is reduced very very slightly but you'll never notice it because you would just step down on the gas pedal slightly more to get what you want. If needing full power for acceleration or passing the EGR is turned off. 

 

If the valve isn't cleaned every 50K it may collect deposits on it preventing it closing. The engine won't idle well with any EGR so a poor idle is a result. If the pipe from the exhaust manifold corrodes and leak outside air can get in. Exhaust has no free oxygen and is inert. If outside air gets in the mixture will go lean and affect power.

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Good stuff, thank you.

 

So for more power would you recommend a full EGR delete? Or would it not be significant enough to notice?

 

And for the current lack of acceleration, could it possibly be a vacuum line leak/misplacement from the carburetor upgrade? 

 

Thanks again for the help.

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When the throttle is floored the ported vacuum signal that turns the EGR on disappears... there is no EGR and you make full power. Removing the EGR will have no effect. At part throttle there is some EGR but any 'loss' is simply countered by stepping farther down on the gas. It would be like getting used to having extra slack in the throttle cable but again at full throttle you still get full power.

 

Lack of acceleration can only be detected if it was working and then suddenly isn't there. If you are new to the Z24 I have to say it's not a performance engine to begin with. So was it better with the old carburetor? and now is lacking???

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Hey guys, I have the same 84 720 and I'm thinking of doing the Weber swap but I'm concerned with plugging all the vac lines as it was my understanding that some are for high altitude. I live @5000' in Colorado. I've already swapped the engine with a lower mileage z24, replaced the idle control selonoid and replaced 95% of the vacuum lines, plugs-wires, cap-rotor. Tightened the head bolts like you suggested datzenmike, and I can't get a smooth idle to save my life. It has good days and bad days. When is cold out doesn't like to idle steady, when it's warm out seems fine. The selonoid had an extra wire that I grounded and that helped but I lost my electric choke. This is why I'm asking about a Weber swap. I can't get the stock Hitachi dialed in. I had some "help" come look at it and all he did was drill out the factory air/fuel plug and played with that. I've checked the timing and it seems to be on the mark.It definitely won't pass emissions now but I have 5 yr plates so I have time to figure it out. As of now, I have 2 stock carbs that are somewhat different around the base mount. Any feedback would be tremendously helpful as I'm stuck. The truck runs. I drive it almost everyday but some days have to keep the gas lightly depressed when coming to a stop.

 

pictures are always worth a thousand words.

All the vac lines are in the appropriate places.

thanks

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We recently had a guy in Colorado who's 720 was running too rich. We moved down in jet sizes 109 to 103 or something and this fixed it. My 710 is from Nevada average elevation 5,000 feet and I'm at sea level. Had a 99 primary and I put in a 112. WAY better performance and better mileage.

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19 hours ago, NC85ST said:

What was the problem to begin with, that made you decide to change the carburetor? Has the truck ever run right since you’ve owned it?

 

The previous owner had it jacked up and parked on a public street, not running and was issued a warning by the city. I bought it for next to nothing under the condition the I got it running before he got fined. It ran with the old carb, but idled high and had a host of other problems.

 

@SatoRich I'm in CO also, at 6300ft.

 

@datzenmike Thanks for the info (I hope you get paid for that kind of knowledge man). With the new carb the engine starts up better, idles correctly, and sounds much better (for my vanity). It wasn't accelerating as well as previously, but I went through and adjusted all vacuum lines and plugs, and made sure the gas wasn't getting pinched to the carb and now it's doing great.

 

All-in-all the Weber seems to be doing well. We'll really see once I take it up the mountain...

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OK one thing ALL 720 owners who have a Z24 engine need to do is onec a year re-torque all the head bolts. The Z24 is very prone to blowing head gaskets at 100k mile intervals. Somehow the grip on the head gasket relaxes and they blow. At your earliest convenience...

 

Engine cold from over night

Loosen just one bolt and tighten to 60 foot pounds with a torque wrench.

Move on to the next bolt and do the same.

You can do in any order you like.

Do this every year.

 

This maximizes and evens the clamping force on the gasket. Some owners doing this have reported some bolts are loose to begin with so tightening is a good thing.

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19 hours ago, datzenmike said:

Does it still have the stock ATC (air temp control)? This pipes air warmed by the hot exhaust manifold into the air filter snorkel. With it working the engine only sees 90-100 degree warm air. 

Is this the large tube coming from the e.man shroud? if so, then no. engine that i swapped the bolts holding the shroud were rusted so i couldn't put the shroud on.

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Yes. Hold in place with stove pipe wire but get it on somehow. I made one years ago for my L20B 620 out of a Folgers coffee can and heater duct hose. It's unbelievably damp where I am and when it get below 37F the carb will frost up all over the venturi and it won't run.

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