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  #1  
Old 09-09-2018, 06:05 PM
Cookingguy Cookingguy is offline
230 Tornado
 
Join Date: Aug 07, 2018
Location: CA
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Big vac leak and won't stay running

I have a 79 Cherokee with the 360. So the crank bearing went to crap so I had another 360 that was built 4 years ago for my cj5 project. It has sat in the cj for 4 years never had the money to finish it. So I swapped the cj 360 into my Cherokee. After lots of headache I finally get to fire the engine for the first time ever. Now I have a massive vac leak and won't stay running. The carb is not new it was off the old block and was running fine. I'm trying to upload a video but I'm not able
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  #2  
Old 09-09-2018, 08:43 PM
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babywag babywag is offline
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cracked carb spacer is a common source if original 2bbl setup.
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Old 09-09-2018, 08:49 PM
Cookingguy Cookingguy is offline
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have a 4 bbl intake but I'm running a Mr gasket adapter to run a 2 bbl carb. So no stock spacer. I'm thinking maybe my intake manifold gasket
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Old 09-09-2018, 08:58 PM
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babywag babywag is offline
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I ran one of those adapters for smog testing.
Sure it isn’t source?

If cam is fresh/new fix it quick and get that cam broken in correctly.
Engines that don’t run right are cam killers.
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Old 09-09-2018, 09:07 PM
Cookingguy Cookingguy is offline
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It is a brand new cam. How would I be able to tell if it was the adapter? Also how can I check the intake gasket? The engine bhas been sitting for 4 years so maybe the intake gasket went to
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  #6  
Old 09-10-2018, 09:23 AM
440sixpack 440sixpack is offline
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The valley pan gasket is metal and unlikely to fail.


Double check all your vacuum ports including the one on the back of the carb if you have one.
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  #7  
Old 09-10-2018, 09:46 AM
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babywag babywag is offline
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Quote:
Originally Posted by 440sixpack
The valley pan gasket is metal and unlikely to fail.

Some folks unknowingly use standard gaskets vs. the metal valley pan.
If this is the case I'd r&r the intake and install the metal valley pan.
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  #8  
Old 09-10-2018, 11:19 AM
Cookingguy Cookingguy is offline
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Join Date: Aug 07, 2018
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Just ordered a new motocraft 4 bbl carb and I have my parts guy getting me a new intake gasket. The state of California won't like my 4 bbl carb but don't have to worry about that for two years
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  #9  
Old 09-12-2018, 01:59 PM
gpcl16 gpcl16 is offline
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Join Date: Apr 02, 2016
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If you can borrow a smoke machine that's an excellent way to detect vacuum leaks without running the engine. How do you know it's a vacuum leak and not some other problem? Could be ignition timing (engines can start with severely retarded ignition timing but they will be very low on power and not hold an idle. Could also be something mechanical.

Stock intake or aftermarket? My OEM 2 barrel intake has a trapezoid shaped plate on the bottom with a gasket that could be a vacuum leak. It's underneath the sheet metal windage tray. Not sure if 4 barrel intakes have the same thing. If that's your vacuum leak it will be hard to find and you would need to pull the intake anyways to fix it.

P.S. Heaviest F-ing intake of all-time. Good luck if you have to remove it. Don't try to pick it up from the oil fill tube, I've had one pull out while I was carrying it and fall on my shin.
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  #10  
Old 09-12-2018, 02:42 PM
Cookingguy Cookingguy is offline
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I think it's a vacuum leak by the sound it's making. It sounds like it's trying to suck the world into my engine could timing cause that
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  #11  
Old 09-12-2018, 04:45 PM
440sixpack 440sixpack is offline
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No. but timing could make it run like crap. or not at all.
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  #12  
Old 09-12-2018, 05:35 PM
gpcl16 gpcl16 is offline
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You can disconnect and plug all vacuum ports on the carb and manifold and run it. If you still have a vacuum leak then you've got an intake vacuum leak or other problem. Still recommend the smoke machine so you can find it without running though since your engine isn't broken in yet. The old carb spray trick or a propane bottle will make finding vacuum leaks easy if you need to run it
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  #13  
Old 09-12-2018, 06:07 PM
Cookingguy Cookingguy is offline
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I am really not wanting to run it any more than it has already been run which was not long. I have a new carb on the way. I was thinking of trying a home made smoke machine to check for leaks.
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  #14  
Old 09-13-2018, 10:12 PM
yossarian19 yossarian19 is offline
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Location: Grass Valley, CA
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It's a dummy mistake that I made, so I'll pass along the tip, but some of the threaded bosses on the intake are not in fact threaded bosses but NPT ports for emissions stuff you may not have hooked up.
I stripped my emissions stuff off when I went EFI and for the longest time I couldn't figure out why my idle vacuum seemed low and I had to add tons of fuel across the map from the "should work" calculated tables.
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  #15  
Old 09-14-2018, 06:20 AM
Cookingguy Cookingguy is offline
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Join Date: Aug 07, 2018
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I have my all my smoke stuff hooked up according to the diagram on my jeep. I thought the same thing as you are saying checked it all out and it all seems fine. But worth a double check
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