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general discussion => ALL mechanical and technical related questions => Topic started by: emptyhead on April 20, 2017, 06:56:48 PM
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Back ground on the engine was built by a reputable engine builder. Was rebuilt about three years ago and finally at a point where I can run it. Its running rough no matter what I do play with the distributor. Checked and double checked the timing and plug wire till I was sick of it. When I pull either 1 2 or 3 cylinder plug it wants to die but when I pull 4 5 and 6 pretty much nothing happens whether I pull one of them or all three. Getting spark to alll 6 cylinders I checked with spark tester. All cylinders are at between 118 and 120 psi. At this point don't know which direction to go. Anyone have some suggestions it would be great. Thanks.
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Sounds like a irritating situation you have! How strong is your spark? compression is good, so if the spark is strong that means you are not getting fuel into the cylinders. I'd check the lifters first and then look for an obstruction in the intake. Best of luck!
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are the plug wires going to the correct cylinders?
some unlikely things
carbon tracks in the cap or on the rotor
loose distributer shaft
bad spark plugs
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Switched plugs around the different cylinders still the same. Checked continuity on all wires and good. Triple checked wire timing. Even tried swithing around wires from 4 5 and 6. Engine ran the asame no matter what. Tried both the old distributor and a nos in the box one and still the same. Running out of options. Thanks guys
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If the compression is good it's usually fuel or spark. You know you're getting spark. When you pulled the plugs, they should be soaking wet with gas and you should have a heavy gas smell at the exhaust. If not, it may be the lifters like Steve said.
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I'm wondering about lifters too since 1-3 is the same lifter block. I think they have to be preloaded with oil to charge them before they are assembled.
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Correction: I agree with Monkeypirate's assessment of the lifters!
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Just curious, was the oil filter filled with oil prior to starting and did you do prime the motor before starting it?
Gary
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I'll pulled off the head yet again and all my valves are rising and falling as they should. Pulled the intake a exhaust manifold off just to make sure non of the ports are blocked. Have any of you guys ever had to time the valves. It mentioned something about it in the Tom but couldn't find it. Thanks so far.
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I would try using the infrared thermometer to check the temp on each exhaust tube at the block, if one is low in temp. that will be the bad cyl. Back in the old days we used water, if a lot of steam, that was the good cyl.
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Did you run a vacuum check? About all that's left is valve timing. I would check it with a degree wheel and dial indicator, not just by the marks (sometimes they're not too accurate and can cause you to chase your tail - ask me how I know). At this point, I'd sure start with that. If it's off enough, none of the rest of it matters. Keep us posted and good luck.
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I hate to be an obvious fella, but is the fuel filter partly plugged? If you only get alittle fuel into the carb and its gasping for air that could make it run rough to. If you know the engine is timed correctly and you have spark, then its fuel related issue. Carb might not be opening right or something. Its a long shot but one you can cross off your list if all checks out.
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Did you happen to check to see if the intake going to the front cylinders are plugged? This happened to Don with Zelda. The front three cylinders were partially plugged due to something getting sucked down the carb.
Steve A.
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That's why I pulled off the manifolds to make certain intake and exhaust ports where open. Will put everything back together and go through the carb today and tomorrow and see what happens. Maybe it's a fuel issue. 4 5 and 6 are feed from the right side of the carb. Maybe something is going on there. Thanks for all the help so far guys will keep you posted.
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I don't believe that the intake I'd divided like some manifolds are. I did think of that though. How is your Camera? It could be warned bad on some front lobes. How about timing gears, they might be off one tooth. Are you running with the air cleaner hooked up? That might be plugged up.
Steve A.
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have you tried backing out the idle mixture screw on that side of the carb?
and instead of pulling the carb just shoot some starter fluid down the carb and if it smooths out for a sec and then you have a fuel problem.
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have you tried backing out the idle mixture screw on that side of the carb?
and instead of pulling the carb just shoot some starter fluid down the carb and if it smooths out for a sec and then you have a fuel problem.
I concur.
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Got around to buttoning things up again and ran a compression test while the engine was running on all the cylinders and that tells a different story. 1,2and 3 between 115 and 120. 4. Is at 40 to 50 5 and 6 are between 60 and 70. So I'll put one more head gasket on otherwise crack in the head somewhere I'm not seeing crack in the block somewhere I'm not seeing. Cylinders where bored and sleeved so if cracked maybe in valve area. Hooked up a vacuum guage and low vacuum needle bouncing all over the place. Any of you guys ever play with the valves on these engines. Also checked the carb while it was running and the outboard barrel was a little weak on fuel delivery as opposed to in inside barrel. Took that apart and cleaned it but couldn't find anything wrong. Thanks guys for the input.
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You might try a differential compression test instead of static. You get the cylinder to TDC on compression stroke and typically put 80 PSI on the gauge. The second gauge will indicate how much leakage there is in the cylinder, but the bonus is that you can hear where it's leaking from and how bad. Put an ear to the exhaust pipe and if you hear air, the exhaust valve isn't sealing. Air at the carburetor, intake valve. At the breather, it's rings. It's a quick, easy way to pinpoint a problem without a bunch of trial and error. Make sure the piston is at TDC before applying the air! If it's on either side of TDC, when you put 80# on it, the piston will go down and if you have a wrench on the damper to turn the engine it can spin pretty quick and break fingers, so be careful!
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The tester he is talking about is called a "leak down tester" and is very common in the racing world. Not real expensive and are available from any high performance store-Jegs, Summit, etc.
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If you're near an airport and know an A&P mechanic you might be able to borrow one. I have lent mine to trustworthy folks. Tell them it's for a half track and you might be able to borrow the whole mechanic! You'd need a 14MM adaptor as his would have an 18MM for aircraft engines. It would be easy to make one from an old spark plug base.
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might also try checking your valve lash before you pull the head
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I agree with the valve lash idea. When I had my engine rebuilt by a professional he did not check the valve lash. One of the valves was being held slightly open and I had a miss too. Before you take too much apart again I suggest you check the valve lash on the lifters. When the valves seats were ground the valves sit lower and you loose the clearance on the lifters. Sounds to me like one set 4,5,6 might need checking. If the valve is held slightly open you could burn a valve if not corrected. I would have to check for sure but I think the clearance should be around .020 cold.
Good luck Henry
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If you could check that would be great. I can't find any info on the valve train in my books. Thanks
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Here is a copy of the page with the valve specs. It is from page 203 in manual TM9-1711. Hope this helps. The clearance was a bit more than I thought. .040-.080
Good luck
Henry
(http://i1358.photobucket.com/albums/q766/HenryVIII8/bd09d70d-5488-4ef5-a738-2988b17c2bc1_zpsgkfpumrn.jpg) (http://s1358.photobucket.com/user/HenryVIII8/media/bd09d70d-5488-4ef5-a738-2988b17c2bc1_zpsgkfpumrn.jpg.html)
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Thank you very much
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Did you figure out what the problem was??
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Check your air cleaner oil level too. Water gets in there and also causes the engine to run rough.
Also I had my little foam seal slid down into the carb!
Don G
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Remember, I am 20 miles north if you need help!!! Not that i know what I am doing! I can perform gopher duties! Ha Ha...
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A little update started playing around with the engine again. Made up a plate to block off the hole in the intake manifold where it bolts to the exhaust manifold and brazed a air fitting on it. Pressurized it and had a big air leak blowing into the intake side of the manifold so hopefully that solves a lot of my problems. Thanks all,the suggestions guys will keep you updated
(http://i292.photobucket.com/albums/mm21/davidf121/49C3DD35-E54F-4D83-985C-7DECD5BB4BF2_zpsvmjghtci.jpeg) (http://s292.photobucket.com/user/davidf121/media/49C3DD35-E54F-4D83-985C-7DECD5BB4BF2_zpsvmjghtci.jpeg.html)
(http://i292.photobucket.com/albums/mm21/davidf121/E78F9C03-62AE-457B-A4CE-0BD87164372B_zpsed9qrsan.jpeg) (http://s292.photobucket.com/user/davidf121/media/E78F9C03-62AE-457B-A4CE-0BD87164372B_zpsed9qrsan.jpeg.html)
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For what it is worth, we were having trouble with the engine running rough in my CCKW . It was especially bad when increasing the RPM's going from second to 3rd and even worse when shifting to 4th. We tried cleaning the gas tank out, the fuel filter, rebuilding the fuel pump, rebuilding the Carb, adjusting the float level 2-3 times, checked the timing and rechecked it 2-3 times. Of course we replaced the points, condenser, and rotor. Replaced the spark plugs twice. Compression and vacuum checked and double checked. STILL couldn't find the gremlin causing it. THEN, a friend suggested getting a rebuilt Distributer and DANG it fixed the problem! She purrs like a kitten and smooth as can be. The internals of the distributor must have been plain worn out. It sure was a vexing problem that had us pulling our hair out but is sure taken care of now.
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Thanks for the reply. Have run the engine with old distributor and new out of the box stil the same thing. Ran it with different intake but still running on three cylinders. The saga continues.
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Crazy!
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not for nothing....might you have a vacuum leak somewhere that is causing it to run rough?
for what it's worth, I had that problem with my old Mopar...
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Part of the vacuum leak was from the manifold but still hunting down problems will update. Thanks guys
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I haven't read back in the post, have you tried blocking off the large vacuum line going to the brake booster? The booster itself could be a source for a big leak.
Gary
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Yeah just put a plug in the middle. The only silver lining in this whole thing is I’ve gotten to know a little more about the whole engine in general since I’ve basically taken part over half of it. Thanks guys
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Pull the heat riser out of the manifold. Supply gas to the carb via elevated bottle of gas. Get new cheap coil and attach GOOD battery directly to it. Squirt SMALL amounts of gas into carb as it’s running. Make sure there are no vacuum leaks, an open hydrovac line will make it run crappy. Wiggle spark plug wires as it is running (funnier if you have a buddy do it). one of these tests should shed light on the problem.
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Wiggle spark plug wires as it is running (funnier if you have a buddy do it).
Soon-to-be former buddy! It would be funnier though.
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Remove heat riser butterfly valve in exhaust manifold. Replace ignition coil and hook a GOOD battery straight to it. Wiggle plug wires while it is running. Plug the hydrovac hole right at the carb, they run terrible if that leaks. Gravity feed gas to the carb
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Hi
I have a couple comments after reading about this problem. I cannot remember but I thought you said this is a rebuilt engine, so here goes. You have good compression on the leak down test which means the rings and valves are sealing and holding, because this test is done with the piston at TDC and the valves closed and will show OK even if you have a collapsed lifter. But you have low compression on 4,5,6 when it is running. But the valves are all moving/lifting when you check with the head removed. Also you have the correct valve lash when you checked it (.040-.080) correct? 1,2,3 are on one lifter body and 4,5,6 are on another lifter body. Each lifter block is hydraulic and fed oil from an internal oil galley. Is it possible an oil passage supplying the lifter galley is blocked or maybe a plug was left out when the engine was reassembled and the rear bank of lifters are not getting enough oil to open the valves completely and/or at the correct time. Do you have enough oil pressure when idling?
Here is my suggestion. 1 Remove the rear lifter block and see if the gasket is damaged or missing or leaking. 2 If gasket was OK remove both the lifter blocks and see if they are both getting the same amount of oil when the engine is cranking over. If not you have a oil supply problem. 3 if they are both getting same amount of oil, switch lifter banks and see if the problem moves to the other 3 cylinders. If problem moves you have a bad lifter bank.
Is the cam timed correctly? I think so because this would affect all cylinders, not just 3. The only one thing that these 3 cylinders have in common is the rear lifter block.
I think the rear three cylinders are getting fuel and spark but they just do not have enough compression to do much.
Good luck. Please keep us posted as to what you discover.
Henry