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Rebuilt engine problem

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avery

02-07-2002 12:42:55




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Just rebuilt my first engine, 841 ford. thought I did a good job, by the book I had, but have a feeling timeing is off. I replaced the timing gear and lined up the punch marks, but could someone explain to me proper way to time the two gears compared to piston location. Trying to learn this stuff, so please excuse the questions. How do I know that number one cylinder is TDC and also on compression stroke. Please detail this for me, thanks

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roamrdb

02-10-2002 09:33:58




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 Re: rebuilt engine problem in reply to avery, 02-07-2002 12:42:55  
You didnt say if you already have the engine running, if you do and you feel that the timing is off; then the most likely culprit is the ignition timing, i.e. the installation of the distributor. The relationship between the crank and cam is pretty much bulletproof providing you have the marks lined up correctly and the woodruff keys or alignment pins are properly in place. Also you might want to insure the centrifugal advance is working in the distributor and not frozen in place. Hope this helps.

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avery

02-10-2002 13:09:43




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 Re: Re: rebuilt engine problem in reply to roamrdb, 02-10-2002 09:33:58  
The distrubutor was the culprit, in wrong



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Mike

02-07-2002 16:48:37




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 Re: rebuilt engine problem in reply to avery, 02-07-2002 12:42:55  
Avery,
If you align the cam gear and crank gear as illistrated in the manual, the cam will be in time with the crank. To find TDC remove the #1 spark plug, bump the engine with the starter until you feel pressurs building in the clynder (put your finger or thumb over the spark plug hole) crank the engine by hand 'til the crank TDC mark lines up with the timing pointer, viola, TDC. Good luck
Mike

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Fighting suburbia in NC

02-07-2002 14:40:56




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 Re: rebuilt engine problem in reply to avery, 02-07-2002 12:42:55  
Don't have a service manual in front of me so I may be 180 degrees out on this (pun intended). On a 4-stroke engine the valves are both closed on the compression stroke as the piston approaches the top of the bore. Most gears are designed to align the marks opposite each other for proper timing, usually top gear mark at bottom of gear and bottom gear mark at top of gear. The trick is to realize that, in two-gear systems, the ratio of gear sizes is 2:1; the cam gear rotates once for every two rotations of the crank gear. It is possible to have the gears 180 degrees out by having the marks line up when the crank gear mark is at top but not in the proper part of the stroke cycle.

The best way to check is to start with the gears lined up and both intake and exhaust valves closed (compression stroke TDC) then start to rotate the crank. If the exhaust valve starts to open as you get into the second half of the revolution then the gears are correct. If the intake starts to open as soon as you start to turn the crank then the gears are 180 out.

Somebody correct me if I am wrong because I am sitting in front of my laptop gyrating my hands in the air in front of me trying to properly visualize the rotations. I find it much easier to degree a cam when I have it sitting in front of me than in conceptualization.

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Fighting suburbia in NC

02-08-2002 04:40:05




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 Re: Re: rebuilt engine problem in reply to Fighting suburbia in NC, 02-07-2002 14:40:56  
AFTER FURTHER INVESTIGATION: I argued this one with my brothers - the crank doesn't care where it is in the cycle - when it is at TDC it is either waiting for spark or has just finished pushing out exhaust gases and is waiting for the intake to open so it can pull in a fresh air/fuel charge. The cam is what decides what goes on next. On the low rpm of a tractor the cam timing is not as crucial as on a high-rpm race motor, which is where most "degreeing-in" work happens.

Line up the marks with the piston at TDC and you will be fine.

BTW - Our car friends refuse to be around me and my little brother while we are degreeing a cam because we tend to argue forcefully about the nuances of the matter. My older brother terms it "violent agreement".

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