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In wrestling the tranny out of the car this corroded pipe leading to the cat cracked. Is this something that I can fix later and still drive the car for a few miles. Or will it be really loud or destroy the cat? Need to get it off the lift and drive it home, and hopefully actually get to drive it for fun a couple of times before taking it apart again.
You might get some backfires when you let up the gas pedal but otherwise okay. Minimize that on warmup by feathering the choke and once warmed up "relax" the pedal rather than suddenly pulling off the gas.
Edit, also that's not a very high temperature part of the system, and you can get away with a segment of silicon tubing like this. Just clean up the pipes to get to a more structurally sound point and you can in fill with that. Here's a new cat that comes with that tubing and my old '83 cat for comparison.
Anyone know of a source of flexible metal tubing with a hose clamp style fitting on each end? Tried high temperature silicon tubing to fix the broken pipe.... but just noticed after a few drives I have melted a hole through the tube. Could default to some braided hose and a couple of off the shelf hose clamps, but wonder if there is something more... dedicated?
Hmmm, that's interesting. That tube shouldn't get hot enough to melt, it is for adding fresh air to the cat from the air control valve and air pump. I wonder if there might be something going on that 's overheating your exhaust...others here will be able to comment, but I think a super rich idle or a clogged cat will cause overheat problems in the exhaust. @Maxwedge has an image of his bright red glowing header as his avatar. I bet he could tell you about the cause of that.
Maybe the little check valve on tube is faulty? It's up near the air pump and is connected the rubber hose.
I will dig into that check valve as symptoms do match hot exhaust flowing out of cat and in to air pipe. The silicone tube was melted from the inside and was charred inside but not outside.
Any quick instructions on inspecting that check valve?
Maybe wrong material? Tubing I used was from McMasters. ‘High Temp Silicone’ for temps up to 450 degrees F. Should be enough for air from the air pump, but if your theory is correct and gasses are flowing the other way..... out of the cat and into the air pipe... then my guess is those temps are much higher.
Always something isn’t there!
Okay, now I'm going to check the inside of the tubing on mine!
My 84 workshop manual says to break the connection at the rubber hose, run the engine to 1500 rpm and see if you get exhaust coming back up through the pipe.
And here's the tubing that came with my cat, "Original Monster Stacks"
Ahhh.... so if I am extrapolating correctly the check valve is a one way valve that is fully closed both directions below 1500rpm and open in the direction from pump to car above 1500rpm ‘cause at that point the pump is producing enough pressure to overcome the valve. And what I am feeling for with my finger over the end of the pipe is exhaust pressure as gasses should not be flowing that way. Most times if I can understand something I can fix it. Will take a look tomorrow and report back.
Cut a steel pipe in half like a C , then weld around it , **** you can even add some high temp epoxy and clamps if you can't weld and it should reduce the leak like 95% if it bothers you so much. The exhaust on these cars is all BS smog . I have driven hundreds of miles with my exhaust seperated from my down pipe with the only side effect being the loss of power at high rpm's . If you backfire your carb is not tuned properly. All backfire went bye bye when I tuned my carb , thank you to a certain member here who helped me all the way from germany .
Also all those flexable exhaust parts that are factory are NLA and very hard to find .
Yup, just ordered some stainless tube from McMaster, slightly larger diameter than broken pipe. Have an idea for attaching using slots in the end, hose clamps and high temp epoxy. One day I will learn to weld. But not this day.
Cut a steel pipe in half like a C , then weld around it , **** you can even add some high temp epoxy and clamps if you can't weld and it should reduce the leak like 95% if it bothers you so much. The exhaust on these cars is all BS smog . I have driven hundreds of miles with my exhaust seperated from my down pipe with the only side effect being the loss of power at high rpm's . If you backfire your carb is not tuned properly. All backfire went bye bye when I tuned my carb , thank you to a certain member here who helped me all the way from germany .
Also all those flexable exhaust parts that are factory are NLA and very hard to find .
I'd love to get your experience on tuning your Nikki but I don't want to thread jack (but I guess I do!). When I'm choked on startup, I'll get backfires. Push in the choke, no backfires even if it's not warmed up. Did you write thread on it at all?
I'd love to get your experience on tuning your Nikki but I don't want to thread jack (but I guess I do!). When I'm choked on startup, I'll get backfires. Push in the choke, no backfires even if it's not warmed up. Did you write thread on it at all?
How cold is it when you use the choke ? I have been starting the car then pulling the choke at all temps for 1-2 mins just to avoid the car shutting down . When it is under 60 deg the car " burps " but doesn't back fire.
Anyways I have a 79 with both the screws . What you want to do is adjust both screws all the way in and then back out a certain amount of turns ( I will get back with you on the exact amount), hen turn your car on. It should run relativley well but this is just a base line, if not you probably have a air leak .Once done, then back the big bolt all the way out until your car is chasing , engine will run really rough , turn it back until the engine stops chasing but not super smooth , then adjust the small screw back and forward until your engine sounds smooth. From here you have to drive it to see if you have any gaps in power, if you do adjust the air one to give you more air by a quarter turn and repeat until you are satisfied. My only downside was the car was a bit rough at idle before it warms up on the first start up. Once it warms up it's super smooth. .I'l see if I still have my PM's . For a nikki without the two screws I dunno.
P.S. Mark your bolts with a line at 12'o clock and you can preety much revert back to your old settings by counting how many turns to closing you did.
No worries. Kinda curious to see if there is a write up on the carb tube too... I am almost there but still keeping idle at 1200 as too scared to go below.
Get car to optimal temp.
Ok to tune your carb the steps are simple.
Adjust the big screw to the right until your engine idles at 700 RPM.
Once the engine is at 700 rpm , adjust the small screw to the right until your car starts to chase and run rough , from here turn the screw back out 1/4th. Then adjust to the left until your car is smooth.
The steps i gave you guys before is just to reset a carb that has been messed with and no longer holds idle.
How cold is it when you use the choke ? I have been starting the car then pulling the choke at all temps for 1-2 mins just to avoid the car shutting down . When it is under 60 deg the car " burps " but doesn't back fire.
Anyways I have a 79 with both the screws . What you want to do is adjust both screws all the way in and then back out a certain amount of turns ( I will get back with you on the exact amount), hen turn your car on. It should run relativley well but this is just a base line, if not you probably have a air leak .Once done, then back the big bolt all the way out until your car is chasing , engine will run really rough , turn it back until the engine stops chasing but not super smooth , then adjust the small screw back and forward until your engine sounds smooth. From here you have to drive it to see if you have any gaps in power, if you do adjust the air one to give you more air by a quarter turn and repeat until you are satisfied. My only downside was the car was a bit rough at idle before it warms up on the first start up. Once it warms up it's super smooth. .I'l see if I still have my PM's . For a nikki without the two screws I dunno.
P.S. Mark your bolts with a line at 12'o clock and you can preety much revert back to your old settings by counting how many turns to closing you did.
Thanks! It's usually cold start with the ambient temps >= 50°F. It happens even when it's 90° though. I've got both air and idle speed screws on my 83 Nikki.
I'll give this a go. I did adjust the mix and idle speed back in the day, but that was before I replaced the restrictive factory pebble catalyst with the one in the pictures above. So maybe with the freer flowing exhaust I'm too rich and the choke really gets it popping.
04-09-22, 09:19 AM
