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| TB woes http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=81673 |
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| Author: | txbiker [ Tue Mar 24, 2015 9:14 pm ] |
| Post subject: | TB woes |
I am changing out my TB and have run into a problem pinning the shafts. Any time I can pin the crank, neither camshaft will pin. I can get both camshafts to pin but then the flywheel wont pin. I am starting to think the flywheel was installed without the timing hole lined up, but there is no record of any repairs requiring the flywheel to be removed. I have spent two hours rolling the engine by hand trying to get all three to pin but no luck. The engine runs great so I know it is currently timed right. Is there any other way to lock the crank and know it is in the correct position without it being pinned? |
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| Author: | GreenDieselEngineering [ Tue Mar 24, 2015 9:17 pm ] |
| Post subject: | Re: TB woes |
There is a mark on the crank front hub that will be at the 3o'clock position when the crank is in the correct orientation. |
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| Author: | geordi [ Tue Mar 24, 2015 11:04 pm ] |
| Post subject: | Re: TB woes |
This is why the camshafts are not keyed. Pin the cams. FORGET about the crankshaft. Presumably, the engine drove itself to the timing belt job, right? So then your engine is already 'pretty close' to being in time, but the reason you cannot properly find the third pinhole is because of belt stretch OR that someone previously was in the engine and left the crank a tooth out. Get the cams pinned, they are the most important to have correct. Then unlock the cam pulleys (you have to do this to change the water pump anyway) and look at the crankshaft pulley - The bolt holes should be VERTICAL and HORIZONTAL. If they aren't, bump the crankshaft in the shorter direction to get the holes perfectly vertical. In the engines I have seen, this is usually rotating the crank counter-clockwise (backwards) just a hair, up to a half-tooth. Remember that the crankshaft spins twice as fast as the cams, so half a tooth wrong on the crankshaft is equal to a FULL tooth wrong on the cams. This is why you want the holes vertical and horizontal - that is perfectly 90ATDC. There should be a timing indentation on the hub of the crankshaft, and it should be pointing to the 3 o'clock position. Good luck! |
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| Author: | txbiker [ Tue Mar 24, 2015 11:43 pm ] |
| Post subject: | Re: TB woes |
Thanks to all that responded. I can start again in the morning with much more confidence than I had when I left the job this evening. This group is the BEST. thanks again. |
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| Author: | flman [ Wed Mar 25, 2015 8:03 am ] |
| Post subject: | Re: TB woes |
When you have the cams locked, make sure the crank mark is at 3 o'clock as Keith said, after you get the belt off you should be able to turn the crank slightly in either direction until you get the pin to go in. Just don't turn it too far or you will hit the valves. You might as well get it all back in time while you have it apart. |
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| Author: | dirtmover [ Wed Mar 25, 2015 9:00 am ] |
| Post subject: | Re: TB woes |
The crank timing hole is a bit sloppy. I ended up popping a borescope in there just to confirm I'd located it properly and was a bit surprised to find that the crank was a touch behind when I had expected the belt stretch to put it a bit ahead of the cams. |
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| Author: | Mountainman [ Wed Mar 25, 2015 1:53 pm ] |
| Post subject: | Re: TB woes |
I'm in the "crank pin is a complete waste of time" club. If you're really worried, you can line a level up against the bolt holes and make absolutely certain that they are vertical/horizontal, and this makes the 3 o'clock mark perfect at the same time. 
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| Author: | geordi [ Wed Mar 25, 2015 6:34 pm ] |
| Post subject: | Re: TB woes |
The crank pin IS a complete waste of time, the crankshaft is keyed so that the hub can only fit on it one way, making the bolt hole method accurate. The hole in the flex plate is very far away from the threads (and the threads are open to the elements, so are ALWAYS filled with trash) and this means that even if you manage to get the tapered end of the pin to center on the hole... The pin itself could still be at an angle to the threads - so the crank isn't correctly perfect. |
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| Author: | flman [ Thu Mar 26, 2015 7:32 am ] |
| Post subject: | Re: TB woes |
I like Dirtmovers idea with the scope to make sure it is center, I put in the Allen Key, and move it back and fourth until I find the center sweet spot. Considering the OPs was out of time, it does not make sense to leave it that way, when you are already doing the job? |
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