stripped down 12a, red hot cat
09-02-20, 09:37 PM
#1
stripped down 12a, red hot cat
Hi all, I have a 1985 gsl, and when trying to adjust the idle and mix I noticed smoke coming from the engine bay. Engine temp was normal, so I cut off the engine to start looking for the culprit. Nothing under the hood or around the carb was on fire, hot, smoldering, melted, nothing. Smoke is still coming from the engine bay but I notice it's coming from under the car. I take a look under there and the tube coming from the cat to the back of the intake manifold is glowing red hot! It was only glowing in the cat and the beginning of the tube (coming directly out of cat), but it was enough to think I was on fire...
Now, this car had most of the rats nest stuff disconnected, missing or wasn't functional when I bought it. So I took it out completely. Everything related to emissions is gone ( I think completely ). And with the emissions delete, I stripped down and rebuilt the carb following Carl, Sterling, GlazedHam, and Jeff20b's posts/threads. The rebuild kit was from AtkinsRotary. I also blocked off the omp and lines at the carb.
Premixed 8 gallons (100:1 1oz per gallon) and added 2 extra ounces for what was in the tank (car was on E, so I guessed about 2 gallons was in there).
Last night I slap the carb on, pour a little gas into the primaries and it starts right up and even idled right away, (idle was high, 2-2300rpm in park and neutral). The fuel in the sight glass was dead nuts in the middle, and my idle and mix were set to the settings I found in the FSM ( idle 6 1/2 turns out from seated and mix 3 1/2 turns out from seated) Couldn't get the idle down by adjusting the idle screw at all so I figured I would get some carb cleaner and spray for vac leaks the next day.
Today, I start the car, let the temp rise, and started spraying around the carb looking for vac leaks. Then my smoke dilemma starts happening.
So not only can I not find my vac leak (or other issue) to get the idle and mix dialed. But now I can't run the car without it smoking and getting the cat really hot (red hot).
Anyone else have issues like these? Especially when running a stripped setup! I read something about delayed timing causing hot exhausts but I am not sure if this applies. I will have to wait til tomorrow to get my timing light and check timing.
But in short, emissions delete, stripped nikki, stock exhaust. Idles too high, and won't adjust lower than 2000rpm. When running for 10 minutes (once at temp) cat starts to glow and smoke.
any suggestions or thread links are a great help. I am used to piston engines so my trouble shooting isn't on point with the rotary (at least i think)
Now, this car had most of the rats nest stuff disconnected, missing or wasn't functional when I bought it. So I took it out completely. Everything related to emissions is gone ( I think completely ). And with the emissions delete, I stripped down and rebuilt the carb following Carl, Sterling, GlazedHam, and Jeff20b's posts/threads. The rebuild kit was from AtkinsRotary. I also blocked off the omp and lines at the carb.
Premixed 8 gallons (100:1 1oz per gallon) and added 2 extra ounces for what was in the tank (car was on E, so I guessed about 2 gallons was in there).
Last night I slap the carb on, pour a little gas into the primaries and it starts right up and even idled right away, (idle was high, 2-2300rpm in park and neutral). The fuel in the sight glass was dead nuts in the middle, and my idle and mix were set to the settings I found in the FSM ( idle 6 1/2 turns out from seated and mix 3 1/2 turns out from seated) Couldn't get the idle down by adjusting the idle screw at all so I figured I would get some carb cleaner and spray for vac leaks the next day.
Today, I start the car, let the temp rise, and started spraying around the carb looking for vac leaks. Then my smoke dilemma starts happening.
So not only can I not find my vac leak (or other issue) to get the idle and mix dialed. But now I can't run the car without it smoking and getting the cat really hot (red hot).
Anyone else have issues like these? Especially when running a stripped setup! I read something about delayed timing causing hot exhausts but I am not sure if this applies. I will have to wait til tomorrow to get my timing light and check timing.
But in short, emissions delete, stripped nikki, stock exhaust. Idles too high, and won't adjust lower than 2000rpm. When running for 10 minutes (once at temp) cat starts to glow and smoke.
any suggestions or thread links are a great help. I am used to piston engines so my trouble shooting isn't on point with the rotary (at least i think)
09-02-20, 10:51 PM
#2
3D Printed
Edit: Read through the whole shebang before coming to conclusions. I went a little all over the place and I'm too tired to make it more logical, my apologies.
Sounds pretty likely that you have a vac leak, but you already mentioned that. Vac leaks mean lean, and lean means a hotter exhaust (although you've probably already put that together). Lean mixtures are also more likely to roast a cat, or the cat could potentially be clogged which can cause overheating due to excessive back-pressure.
It's entirely possible that during the stripping process something got missed, or a vacuum cap is cracked/broken (beware of cheap vacuum caps). Could also be that the carb just needs a little resettling on the intake/phenolic spacer - did you use new gaskets on the phenolic spacer, if so that's another likely culprit. A couple pictures would be really helpful, particularly since things have been modified.
I've had good luck with using an unlit propane torch for vacuum leak hunting. I've never heard of using carb cleaner, although I guess it may be flammable enough...? Ether or propane would be a better bet.
Another thing to check is the adjustment of your throttle cable. I've done it myself; made it a little too tight and the car won't quite reach idle. However if all the butterflies are fully closed, then yeah, definitely a leak somewhere.
Like you mentioned, check timing, it's a good thing to have a basis on.
Around 2k is where the main circuit comes online. There could potentially be something amiss with the idle circuit, but don't look too far into that yet. Many simpler things to investigate first.
Does the engine run smoothly at this high idle? Is there any stuttering, shaking, or notable misfiring occurring?
Have there been any modifications to the carb other than the stripping? Jet changes, shaved parts, etc. Did the car run before the changes or is this the first start up in your ownership? Any history on the car?
Sorry for all the questions, just trying to establish a baseline. Pardon the jumbled mess as well.
Sounds pretty likely that you have a vac leak, but you already mentioned that. Vac leaks mean lean, and lean means a hotter exhaust (although you've probably already put that together). Lean mixtures are also more likely to roast a cat, or the cat could potentially be clogged which can cause overheating due to excessive back-pressure.
It's entirely possible that during the stripping process something got missed, or a vacuum cap is cracked/broken (beware of cheap vacuum caps). Could also be that the carb just needs a little resettling on the intake/phenolic spacer - did you use new gaskets on the phenolic spacer, if so that's another likely culprit. A couple pictures would be really helpful, particularly since things have been modified.
I've had good luck with using an unlit propane torch for vacuum leak hunting. I've never heard of using carb cleaner, although I guess it may be flammable enough...? Ether or propane would be a better bet.
Another thing to check is the adjustment of your throttle cable. I've done it myself; made it a little too tight and the car won't quite reach idle. However if all the butterflies are fully closed, then yeah, definitely a leak somewhere.
Like you mentioned, check timing, it's a good thing to have a basis on.
Around 2k is where the main circuit comes online. There could potentially be something amiss with the idle circuit, but don't look too far into that yet. Many simpler things to investigate first.
Does the engine run smoothly at this high idle? Is there any stuttering, shaking, or notable misfiring occurring?
Have there been any modifications to the carb other than the stripping? Jet changes, shaved parts, etc. Did the car run before the changes or is this the first start up in your ownership? Any history on the car?
Sorry for all the questions, just trying to establish a baseline. Pardon the jumbled mess as well.
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LEGALIZECHEY (09-02-20)
09-03-20, 10:27 AM
#4
Edit: Read through the whole shebang before coming to conclusions. I went a little all over the place and I'm too tired to make it more logical, my apologies.
Sounds pretty likely that you have a vac leak, but you already mentioned that. Vac leaks mean lean, and lean means a hotter exhaust (although you've probably already put that together). Lean mixtures are also more likely to roast a cat, or the cat could potentially be clogged which can cause overheating due to excessive back-pressure.
It's entirely possible that during the stripping process something got missed, or a vacuum cap is cracked/broken (beware of cheap vacuum caps). Could also be that the carb just needs a little resettling on the intake/phenolic spacer - did you use new gaskets on the phenolic spacer, if so that's another likely culprit. A couple pictures would be really helpful, particularly since things have been modified.
I've had good luck with using an unlit propane torch for vacuum leak hunting. I've never heard of using carb cleaner, although I guess it may be flammable enough...? Ether or propane would be a better bet.
Another thing to check is the adjustment of your throttle cable. I've done it myself; made it a little too tight and the car won't quite reach idle. However if all the butterflies are fully closed, then yeah, definitely a leak somewhere.
Like you mentioned, check timing, it's a good thing to have a basis on.
Around 2k is where the main circuit comes online. There could potentially be something amiss with the idle circuit, but don't look too far into that yet. Many simpler things to investigate first.
Does the engine run smoothly at this high idle? Is there any stuttering, shaking, or notable misfiring occurring?
Have there been any modifications to the carb other than the stripping? Jet changes, shaved parts, etc. Did the car run before the changes or is this the first start up in your ownership? Any history on the car?
Sorry for all the questions, just trying to establish a baseline. Pardon the jumbled mess as well.
Sounds pretty likely that you have a vac leak, but you already mentioned that. Vac leaks mean lean, and lean means a hotter exhaust (although you've probably already put that together). Lean mixtures are also more likely to roast a cat, or the cat could potentially be clogged which can cause overheating due to excessive back-pressure.
It's entirely possible that during the stripping process something got missed, or a vacuum cap is cracked/broken (beware of cheap vacuum caps). Could also be that the carb just needs a little resettling on the intake/phenolic spacer - did you use new gaskets on the phenolic spacer, if so that's another likely culprit. A couple pictures would be really helpful, particularly since things have been modified.
I've had good luck with using an unlit propane torch for vacuum leak hunting. I've never heard of using carb cleaner, although I guess it may be flammable enough...? Ether or propane would be a better bet.
Another thing to check is the adjustment of your throttle cable. I've done it myself; made it a little too tight and the car won't quite reach idle. However if all the butterflies are fully closed, then yeah, definitely a leak somewhere.
Like you mentioned, check timing, it's a good thing to have a basis on.
Around 2k is where the main circuit comes online. There could potentially be something amiss with the idle circuit, but don't look too far into that yet. Many simpler things to investigate first.
Does the engine run smoothly at this high idle? Is there any stuttering, shaking, or notable misfiring occurring?
Have there been any modifications to the carb other than the stripping? Jet changes, shaved parts, etc. Did the car run before the changes or is this the first start up in your ownership? Any history on the car?
Sorry for all the questions, just trying to establish a baseline. Pardon the jumbled mess as well.
A little background on the car. Car ran when I bought it, not well though. It's an automatic (not for long) and if you didn't put it into neutral coming to a stop it would stutter and die.. Too much gas while accelerating, it would rev up and die. You would have to rev it up putting it back into drive and skirt off so it wouldn't die also. Owner said he pulled the original carb, bought a spare to clean and try out (which is how I bought it, with the spare installed). But I realized after I removed the spare carb on the car, that he had a "manual" carb? The jetting was different/bigger and that was all I noticed, everything else looked the same.
Ok time for answering questions,
Yes I used new gaskets on the phenolic spacer (both sides, recommended by atkins if the original gasket is gone)
and I must've been tired cause I was using brake cleaner for the vac check not carb clean.
Adjusting the throttle cable too tight, do you mean too tight to where it opens the butterflies? I just gave the cable no slack when adjusting (but not crazy tight). It did not appear that it was opening the primaries. I will double check this too...
Engine seems to be running smooth, it's a little noisy with the air filter off. I would describe it as chattery noise... but revs up and down smoothly
I will post some pictures of the carb when I get back to the car later today. But the carb is otherwise stock. Everything was blocked off with a plate or NEW vac plugs. But there was NO modifications to the body, airhorn, jets or venturi's
09-03-20, 02:11 PM
#5
Could you have possibly put the gasket in backwards between the main body and the throttle body? I recently had that issue and there was a vacuum leak and idle was high. It will also keep the secondaries from opening. Installing the gasket properly solved that problem although it exposed other problems related to my enlarged primaries.
Just a thought.
Carl
Just a thought.
Carl
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LEGALIZECHEY (09-03-20)
09-03-20, 02:23 PM
#6
This was a small-ish vac leak on my carb with RB header installed. Keep looking till you find the leak.
*Did you make/use paper gaskets on all the block-off plates?
*Double and triple check all your vac lines and connections, caps, etc.
*Double check your vac line routing.
*I thought the rule of thumb for the vac / phenolic plate was NOT to use paper gaskets. From the factory it has reusable, rubber gaskets permanently attached to both sides. Had mine off and on several times and didn't leak.
*Check for leaks where the throttle/butterfly shafts stick out of the carb body. Thats where mine was leaking (see pic above).
I have no experience with clogged CAT but if it was okay before removing carb, and now showing classic vac-leak symptoms, Id keep looking for a leak.
Last edited by Maxwedge; 09-03-20 at 02:26 PM.
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LEGALIZECHEY (09-03-20)
09-03-20, 02:43 PM
#7
Could you have possibly put the gasket in backwards between the main body and the throttle body? I recently had that issue and there was a vacuum leak and idle was high. It will also keep the secondaries from opening. Installing the gasket properly solved that problem although it exposed other problems related to my enlarged primaries.
Just a thought.
Carl
Just a thought.
Carl
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09-03-20, 02:53 PM
#8
This was a small-ish vac leak on my carb with RB header installed. Keep looking till you find the leak.
*Did you make/use paper gaskets on all the block-off plates?
*Double and triple check all your vac lines and connections, caps, etc.
*Double check your vac line routing.
*I thought the rule of thumb for the vac / phenolic plate was NOT to use paper gaskets. From the factory it has reusable, rubber gaskets permanently attached to both sides. Had mine off and on several times and didn't leak.
*Check for leaks where the throttle/butterfly shafts stick out of the carb body. Thats where mine was leaking (see pic above).
I have no experience with clogged CAT but if it was okay before removing carb, and now showing classic vac-leak symptoms, Id keep looking for a leak.
The only vacuum line left is for the distributor and is going into the second nipple from the front on the phenolic spacer.
I called atkins about the gaskets on the phenolic spacer. And they told me to use their paper ones, if the original phenolic gasket was missing, which it was on both sides. I found one today in the box of parts the seller gave me, still has the gasket material on both sides. I should probably swap that out too huh?
As for the cat being clogged (possibly), I should have mentioned I am waiting on my pacesetter header to arrive, so a full exhaust is in the near future also!
09-03-20, 04:03 PM
#9
When I asked about paper gaskets on the block off plates, I should have just said "gaskets". I didn't mean to suggest paper was better than cork. Just SOME kind of gasket. Sounds like you're good.
I would swap out the degraded phenolic spacer for the good one. If the soft rubber "gasket" surfaces are good that would be preferred. *All you old-timers out there please chime in... this is just my understanding and limited experience.
When I put my new (to me) carb on I got the same symptoms: Red hot exhaust, wouldn't idle below 2000, etc.. everyone told me vac leak, but I just couldn't find it. Looked over and over and over...... sprayed all gaskets and plates, just couldn't find it. Some regulars suggested the out-of-timing thing but I hadn't touched the timing.
Then I started spraying the carb itself, and the idle started surging. Seems my "ultra low mile" used carb was actually ultra-high mile and the throttle shafts (butterfly rods) had ovalled out their holes. Put some of my kid's clay on them and BAM car idled perfectly at about 800rpm.
I will bet you someone else's money its just a vac leak. Keep looking.
I would swap out the degraded phenolic spacer for the good one. If the soft rubber "gasket" surfaces are good that would be preferred. *All you old-timers out there please chime in... this is just my understanding and limited experience.
When I put my new (to me) carb on I got the same symptoms: Red hot exhaust, wouldn't idle below 2000, etc.. everyone told me vac leak, but I just couldn't find it. Looked over and over and over...... sprayed all gaskets and plates, just couldn't find it. Some regulars suggested the out-of-timing thing but I hadn't touched the timing.
Then I started spraying the carb itself, and the idle started surging. Seems my "ultra low mile" used carb was actually ultra-high mile and the throttle shafts (butterfly rods) had ovalled out their holes. Put some of my kid's clay on them and BAM car idled perfectly at about 800rpm.
I will bet you someone else's money its just a vac leak. Keep looking.
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LEGALIZECHEY (09-03-20)
09-03-20, 08:59 PM
#10
3D Printed
Just a quick reply regarding the phenolic spacer gaskets (I'll read through more thoroughly later).
The best thing to do is avoid using any phenolic spacer gaskets included in the rebuild kits. The factory gaskets are a sort of layered rubber thing (not exactly sure what) that are bonded to the phenolic spacer. Only if they are in poor condition should there be an attempt to use the rebuild kit supplied gaskets in substitution of the factory ones (although I have never needed to do this across a number of carbs and phenolic spacers). The factory gaskets will feel relatively hard, but that's normal. As long as they aren't torn up or falling off they should be a-okay.
The best thing to do is avoid using any phenolic spacer gaskets included in the rebuild kits. The factory gaskets are a sort of layered rubber thing (not exactly sure what) that are bonded to the phenolic spacer. Only if they are in poor condition should there be an attempt to use the rebuild kit supplied gaskets in substitution of the factory ones (although I have never needed to do this across a number of carbs and phenolic spacers). The factory gaskets will feel relatively hard, but that's normal. As long as they aren't torn up or falling off they should be a-okay.
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LEGALIZECHEY (09-03-20)
09-06-20, 02:37 PM
#12
Not bumping my own threads, just a progress post. Apparently one of my plug wires decided to kaput when I went to started it after the I swapped the spacer out. The metal contact in the plug boot ripped out, so I am waiting for my plugs and wires to come in before dialing everything else in....
09-16-20, 05:04 PM
#14
Oooh! That brings back bad memories. Over 20 years ago I caught my engine compartment on fire because the hose that is normally connected there came loose. I had an oil leak that provided the fuel for the fire, but that vacuum leak is what prompted the fire. Fortunately I was stopped at a construction zone with the flagger standing right in front of me. He saw it and got his fire extinguisher. No harm no foul, although the fire prompted me to get the leak fixed.
Carl
Carl
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LEGALIZECHEY (09-16-20)
09-20-20, 07:51 PM
#15
I've gotten my idle down to 1000! and that is exciting! There was a little leak at the manifold and at the spacer as well as the one I posted above, I realized both phenolic spacers I have, still have the original gasket intact so I did not switch those. But now I have a new curiosity and was wondering if the 750/850 idle in the book is realistic once you strip all the emissions stuff?? Can anyone with their emissions equipment removed confirm if the idle will be affected or not?
09-20-20, 11:22 PM
#16
3D Printed
My Nikki is about as stripped/modified as they get (including stripped smog equipment) and I can idle at ~450 rpm if I so desire. Of course it doesn't have great drivability with that idle, but it's possible.
A carb that's stock - sans the smog equipment - should be no different. An idle of 800 rpm should be easily attainable on carb without any leaks. I haven't read through all your recent updates but if you've checked all the easy stuff, try seeing how far closed the throttle plates are sitting (this will be easiest with the carb off the car). There should be little to no gap, but this is most important on the secondaries (since the primaries are open a hair at idle anyway). Could also be some worn throttle shafts, so check those for play as well or spray some ether in that area while the car is running. Of course make sure all your vac caps are good too.
A carb that's stock - sans the smog equipment - should be no different. An idle of 800 rpm should be easily attainable on carb without any leaks. I haven't read through all your recent updates but if you've checked all the easy stuff, try seeing how far closed the throttle plates are sitting (this will be easiest with the carb off the car). There should be little to no gap, but this is most important on the secondaries (since the primaries are open a hair at idle anyway). Could also be some worn throttle shafts, so check those for play as well or spray some ether in that area while the car is running. Of course make sure all your vac caps are good too.
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LEGALIZECHEY (09-20-20)
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