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Old 11-24-2006, 02:12 PM   #1
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HELP me find Top Dead Center PLEASE!

I've got a Chevy 350 and want to install the HEI distributor.

I haven't a clue on how to get the engine to Top Dead Center. I have the driver's side valve cover off and am turning the engine over by hand (socket on harmonic balancer pulley. I see the mark on the harmonic balancer but the gauge is not on the motor. I see the two rods moving on the #1 cylinder but I cannot figure out when the cylinder is TDC. Someone please give me 1st grade instructions on this cause I haven't a clue what I am supposed to see when it is TDC..........thanks
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Old 11-24-2006, 02:40 PM   #2
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I'm guessing you don't have the plate on the timming chain cover? if not I would pull #1 plug, place a small screw driver or wood dowel in and turn the engine over slowly until you feel # 1 piston, trun crank slowly and take care not to scratch the cylinder walls, you will feel the piston come up and as you turn it over really slow you'll feel the piston stop for just a breif second, that is TDC...hope this helps...
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Old 12-19-2006, 03:09 PM   #3
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You want to make sure you are on TDC of the compression stroke. Take out the number 1 plug and have someone turn the engine while you hold your finger over the hole. When you are on the compression stroke you will feel a rush of air come out. You are now approaching TDC on the compression stroke. If your timing marks are true, then you can simply line up the tab with the 0 degree mark on the balancer. If you dont trust your marks like I didnt, then you can buy a TDC locator AKA piston stop. Jegs has them for like 8 bucks. It was definitly a worthwhile tool to have around. However the method mentioned in the above post works too. It all depends on whether or not you want perfection. Hope this helped.
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Old 12-19-2006, 04:57 PM   #4
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Rotate the crank by hand (normal direction of rotation) while watching the movement of the rocker arms on #1 cylinder. Watch the intake rocker as it opens then closes. When it closes you are on the compression stroke of #1 cylinder and TDC is approaching. Continue to rotate the crank till the timing mark on the balancer aligns with the 0 mark on the timing cover tab. Now you're ready to drop in the distributor. point the rotor at the #1 spark plug terminal on the cap and your good to go. Start it up and set the timing with a timing light.
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Old 12-20-2006, 04:01 PM   #5
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All well & good. But if I understand the original post, there's no tab marker
on the t-c cover. If so, a timing light won't be of much use. Two
suggestions: (1) look for a cheapo (chrome) bolt on tab marker from most
any decent parts store. (There's 2 varieties - 6" & 8" balancer's.) All of
the above will be consistent with how the harm. bal. mark aligns with the
tab. (2) I've seen odd-ball engines, where the tab is way up under the
water pump. In which case (1) will provide VERY erroneous timing light
results. (Yes, I actually did that.)

good luck,
kk
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Old 12-20-2006, 04:38 PM   #6
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Quote:
odd-ball engines, where the tab is way up under the
water pump
Which would include, EVERY SINGLE one installed in EVERY SINGLE one of these cars with a V8, from the factory.

A bolt-on tab is all but useless with our factory dampers. Unless you create a new mark on it; and then figure out how to read it with the PS pump in the way (which is why it ended up right beolw the WPO in the first place...).

Turn the motor by hand, and watch the push rods on the #6 cylinder. Just as the #6 exhaust is almost closed and the #6 intake is just barely open, then #1 firing will be within a couple of degrees of when those 2 are at exactly the same lift.
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Numquam ponenda est pluralitas sine necessitate.
William of Ockham, c. 1330 AD, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi

Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

The simplest explanation that fits all the facts is probably the right one.
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Old 12-20-2006, 08:42 PM   #7
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Somehow I missed the part about the timing pointer missing.

So lets assume the worst, that the timing cover is not the right one for the balancer TDC mark. So that means you have to find true TDC and remark it on the balancer. Once done properly yu'll be ignoring all the factory marks on the balancer. You have to use a "piston stop". You can make on from a piece of steel 5/16" tubing and a old spark plug. Knock the porcillen out of the spark plug body. Weld or braze the steel tubing into the spark plug body hole so it is at a slight angle in the hole. You may need to bend the end a little. so it can contact the piston. Now remove the #1 cylinder spark plug and remove the valve cover on that side. Loosen of both the intake and exjhaust rocker arms off completely. So that neither valve will open when turning the motor. install your home made piston stop with the tbe extending down towards the piston. Doesn't need to be tight, just threaded in. now rotate the crank by hand in one direction till the piston contacts the stop. Mark the balancer with some stationary reference you pick on the front of the motor (water pump) or what ever. Make a timing pointer from wire coat hanger or something stable and bolt it on to the front of the motor if you want.
near the balancer. Mark the balancer in reference to this point on th front of the motor. Rotate the crank BY HAND The other way around to the piston again hits the stop. mark the balancer. TDC on the balancer is now exactly half way between these two points on the balancer in reference to the stationary point you picked or installed on the front of the motor. Mark the new TDC point on the balancer Remove the piston stop and readjust the two valves, using the intake closeing (set ex valve) and exhaust open (set intake vlave) method.
Reinstall the spark plug . Rotate the motor around by hand while watching the intake rocker arm as above.
When it just closes your on the compression stroke again TDC is approching on your new timing marks. Rotate the motor to your new TDC and stop. Now you need to mark off 10DEG BTC and 36deg BTC to allow you to time the motor with a timing light. Wrap a length of masking tape around the balancer starting at the NEW TDC mark you made. (ignor your piston stop points you made) Mark off with pen where it meets again where wrapped arround from TDC to TDC.
remove the tape and lay it out and measure along the length from TDC to TDC (the marks you made on the tape)
divide this TDC to TDC length from the tape by 10. The result is the length from TDC to 36 deg BTDC. mark that distance on the tape) Again take the distance along the tape from TDC to TDC and now divide to by 36. That result is the distance from TDC to 10deg BTDC. Mark that result on the tape.. Reinstall the tape on the balancer lining up the TDC marks on the tape with your new found TDC point on the balancer. Make sure you get it wrapped around the right way and mark on the balancer new 10deg BTDC and 36deg BTDC distances from you new TDC point you made. Ignore the factory timing groove on the balancer as you have referenced a new sight point on the motor that is different from the factory tab. Now you have accurate timing points that will allow you to set the timing with a light.

With the crank at #1 tdc drop the distrubutor in with the rotor point to #1 wire on the cap. Fire it up and set the timing with vacuum advance disconnected. Set it at 10Deg BTDC at idle. Now rev the motor and watch the timing point advance. if it does not reach your 36BTDC point when reving the motor up, turn the distributor to adjust. Getting he totoal timing right ( 36deg BTC) at high rpm is more important than the idle timing point. if 36deg turns out ot be a bit too much (pinging under load) set it at 32 or 34 BTDC. Idle timing will be 12 to 16 deg BTDC. if the distribuotor is stock.

Last edited by F-BIRD'88; 12-20-2006 at 08:48 PM.
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Old 12-20-2006, 08:56 PM   #8
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here's a pic the tube must be strong enough to not deflect as the piston contacts it. 5/16 or 3/8 steel tubing...
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Old 12-20-2006, 09:14 PM   #9
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Just to keep you on your toes, this pic is backwards. A SBC crank turns the other direction while running. You figure it out.
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Old 12-21-2006, 10:46 PM   #10
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OK, to make it even simpler for you, you have two options.
remove number 1 plug and insert a thin rod into its place. hand turn the crank until you feel the rod come all the way out, as soon as it starts to re enter, stop, that is TDC.
Option 2 is to have a friend bump the motor after you have removed plug number 1, as soon as your finger is forced off the hole, that is top dead center as well.
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Old 12-23-2006, 12:16 AM   #11
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Quote:
Originally Posted by estone06 View Post
OK, to make it even simpler for you, you have two options.
remove number 1 plug and insert a thin rod into its place. hand turn the crank until you feel the rod come all the way out, as soon as it starts to re enter, stop, that is TDC.
Option 2 is to have a friend bump the motor after you have removed plug number 1, as soon as your finger is forced off the hole, that is top dead center as well.
Not accurate at all. You won't even get within 10deg of finding true TDC, using either of these methods.
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Old 12-25-2006, 06:04 PM   #12
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Quote:
Originally Posted by estone06 View Post
OK, to make it even simpler for you, you have two options.
remove number 1 plug and insert a thin rod into its place. hand turn the crank until you feel the rod come all the way out, as soon as it starts to re enter, stop, that is TDC.
Option 2 is to have a friend bump the motor after you have removed plug number 1, as soon as your finger is forced off the hole, that is top dead center as well.
You wont even get close to TDC by doing that. But you will however know that you are on the compression stroke. I would just buy the 8 dollar piston stop from Jegs and make it easy for yourself. It Ships in 2 days.
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Old 12-25-2006, 06:04 PM
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