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Join Date: May 2010
Posts: 59
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tdc on exhaust stroke what would happen
What would I notice if I set the timing to tdc on the exhaust stroke
So I think That I put the belt on with tdc on the exhaust stroke. I think this because the engine rotates freely. nothing feels like it is hitting. However It will not start and when I shoot starting fluid in it ejects compression from the throttle body. Does this seem like an issue with bad timing??? Again, Thanks alot |
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05-21-2010, 10:59 PM
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meister member
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The crank rotates 2 times for each revolution of the cam.
I am not sure what work you did on the car. Did you line up the timing marks of the flywheel and the cam sprocket when installing the cam tower? Did you verify and lock down the flywheel with both timing marks on the flywheel and cam tower synchronized? Can you verify they are still synchronized? If you answer NO to any of the tope 3 questions you may have bent valves. 1 more question. What method did you use to gauge the tension of the cam and balance shaft belt? Please report back. Speedy 
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1983 944 guards red with 16" Fuchs, Host of Wisconsin area timing/ balance shaft belt tensioning party 1987 944S Purchased from Legion. Corvette LT-1 V-8 conversion with Mega Squirt II Check on progress ---> www.porschehybrids.com/gallery/speedracing944 Favorite Road = www.tailofthedragon.com 318 turns in 11 miles (11 min 20 sec best run) |
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05-22-2010, 04:03 AM
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Proprietoristicly Refined
Join Date: Jul 2001
Location: ~Carefree Highway~
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1988 924S, 85,750K ..+ 1987 924S, 154K DD (+15K est. bad odo) |
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05-22-2010, 04:18 AM
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good questions speedy
Here is what I thought I had done before installing the cam tower I found and lined up a line on top of the bell housing I then lined up the cam line and installed the cam tower. When I went to install the timing belt a friend of mine pointed out that the line that I thought was the tdc line on top of the bell housing was not the tdc mark. we rotated the crank shaft several times and found an obvious white line in the top of the bell houseing. we then (with belt off) and cam tower on, rotated the came to line up its marks and put the belt on. I at no point locked down the flywheel. but it was confirmed to be in the same place when finished. If I where to start from scratch what would I do to time the engine. I am extremely confused, I have several lines on my flywheel that could constitute a tdc line |
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05-22-2010, 05:38 AM
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All Spooled Up
Join Date: May 2009
Location: Between NE and Central PA
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Try lining up the notch in the flywheel with the notch at the very BOTTOM of the bell housing. Are the camshaft & BS shaft markings now lined up?
Yes = The engine is correctly timed. No = Rotate the crankshaft 1 full revolution & repeat the above procedure. Yes = The engine is correctly timed. No = The engine is NOT correctly timed.
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold) |
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05-22-2010, 06:02 AM
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meister member
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The problem with trying to synchronize the crank and cam with the cam tower on is you may bend valves if you have not already (depends on how far off you are). If the marks or not synched it would be best to pull the cam tower, synch the timing marks then reinstall the tower. If you now have bent valves you will have to pull the head in to have the damaged valves replaced.
Speedy
__________________
1983 944 guards red with 16" Fuchs, Host of Wisconsin area timing/ balance shaft belt tensioning party 1987 944S Purchased from Legion. Corvette LT-1 V-8 conversion with Mega Squirt II Check on progress ---> www.porschehybrids.com/gallery/speedracing944 Favorite Road = www.tailofthedragon.com 318 turns in 11 miles (11 min 20 sec best run) |
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05-22-2010, 06:22 AM
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Posts: 59
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Is it possible that I may have put the distributor cap on wrong... I am doubting it, but is it possible???
Alright... This time I am pulling my cam tower. I will submit pics of each of the three openings to confirm that I have timed it properly. Thanks guys... It almost seems like I am making this harder than it is. |
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05-22-2010, 06:39 AM
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I have also heard that I can hold my finger over the first cylinder, and feel for compression. when
I feel compression I am on the correct stroke and just use a feeler tool to determine when the first cylinder is all the way up. then just line up the camshaft marks (way easy to read) |
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05-22-2010, 06:45 AM
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All Spooled Up
Join Date: May 2009
Location: Between NE and Central PA
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The caps are notched. Some of the last posts have pointed at the error the procedure that I outlined. You don't just go and turn the crank a full turn, when the belt is not connected to the camshaft. The procedure would ONLY be valid for a non-interference engine.
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold) |
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05-22-2010, 08:16 AM
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then with the head on and the cam shaft cover on... timing the engine can not be done???
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05-22-2010, 09:33 AM
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Redline Racer
Join Date: Jan 2007
Posts: 2,444
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Well, to be safe, find 90 degrees from TDC on the crank, whichever direction is closest. Use a chopstick or a long screwdriver wrapped in duct tape through the #1 plug hole to find out. This puts all the pistons at mid stroke and out of the way. Turn the cam so the timing marks line up and then slowly roll the crank to TDC. Install the belt and double check the timing. Well, to be absolutely safe, you'd remove the cam tower, but that's a PITA and it can be re-timed without that if you do it right...I've done it before. With the belt correctly installed, you should feel a strong resistance every 90 degrees of camshaft rotation when cranking the motor by hand. If any of those are missing, at least one of your valves is probably toast.
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1987 silver 924S made it to 225k mi! Sent to the big garage in the sky |
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05-22-2010, 10:07 AM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
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i think you can get the cap on 180 degrees out of time, or the wires could be wrong, or the rotor could be loose.
are you getting any backfiring when cranking the engine?
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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05-22-2010, 10:14 AM
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lol, heck yeah I am... Everytime I use starting fluid it puffs it back out at me... I just pulled the fuel rail and checked all the injectors... good there
I also checked a plug... definitely spark I am pretty sure the plugs wires are on correctly. however can the rotor be backwards??? |
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05-22-2010, 02:34 PM
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All Spooled Up
Join Date: May 2009
Location: Between NE and Central PA
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No, that is also notched.
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold) |
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05-22-2010, 02:44 PM
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well shoot...
So I must have set the flywheel wrong. To reset it in the right possition do I do it with the cam cover (valve cover) on or off. and with the timing belt on or off? I know I have asked before but I am looking for real clarity... I dont want to cause more problems than I have |
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05-22-2010, 04:40 PM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
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how much was it off? more than 10 degrees, you have bent valves.
to answer your question, i'd pull the cam tower.
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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05-22-2010, 04:43 PM
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Well that would suck... oh well at least I have another engine sitting next to it muhahah...
I am going to post pics later this evening with all of the marks in place. just to verify everything is not where it is supposed to be. thanks for following this guys. I really appreciate it! |
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05-23-2010, 07:07 AM
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well all I have some news
The marks on the top hole of the bell housing where not the right ones... I was about one 1/6th of a turn off. I had to rotate the crank just a smidgen to the right. I am going to reset it Monday (fingers crossed) Do you guys think that I bent valves? and how would I know if I bent valves??? |
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05-23-2010, 07:09 PM
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winter-hater club member
Join Date: Oct 2003
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Quote:
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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05-23-2010, 07:14 PM
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My Fault, I was unclear
I was almost 1 inch off we barely had to turn the crank shaft to get it to line up To reset it It is suggested that I find tdc, Then make it go alittle further so that the pistons start to fall. Set the cam tower then rotate back to tdc so the pistons meat the valves? What will I experience if the valves are bent |
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05-24-2010, 05:45 AM
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