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Does anyone know of a handy method to verify top dead center (TDC), aside from the balancer mark and timing tab? I have heard that on rare occasions the outer balancer ring can slip and if this happens you will chase timing issues forever. I thought I read somwhere that there is one particular valve which when it just closes, then number one is at TDC... ?
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Re: Simple Method To Verify TDC?
use a piston stop in #1 cylinder,turn the engine clockwise till the piston hits the stop,put a mark in the damper inline with the "0" mark on the timing tab. repeat this in the opposite direction and half way between the marks you put on the damper is TDC -
Re: Simple Method To Verify TDC?
That wouldn't work since the valves are either both closed at TDC on the compression stroke or both open at TDC on the exhaust stroke. You can't use the cam timing specs to indicate TDC anyway since you could have some slop in the timing chain to account for. There is only one absolute method to verify TDC in an assembled engine and that is with a piston stop that screws into the combustion chamaber (spark plug hole) and a degree wheel attached to the balancer. This isn't really very hard but there is some disassembly of the lower pulley and possibly the waterpump pulley depending on how large a wheel is used.
Besides, if you're writing about ignition timing, then what shows up on the balancer is only a baseline. You want to set your timing for your engine. The factory initial timing specs are more of a "one size fits all" and are hardly optimized for your car and the way you drive it. Once you start playing with the initial, centrifugal, and vacuum advance you'll find a lot of hidden power or driveability in your engine. This assumes you're pretty sharp at these things ;-)Comment
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Eastwood Sells A Whistle
that screws into #1 cylinder and it works pretty well for me but Clem's positive piston stop is much more accurate.
Dale.Comment
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Re: Simple Method To Verify TDC?
what these guys say is correct. i have used the method. however, there was one problem. when i turned the engine in a counter-clockwise direction, to come at TDC from the opposite direction, the crank nut simply loosened and the engine would not reverse turn for me. so, i finessed as follows: hand rotate clockwise close to TDC [stop about 10 degrees BTDC]. then stick a beveled metal rod a little into the cylinder. slowly and gently rotate until the piston jams the rod. back off a little [about two degrees]. very SLIGHTLY pull out the rod. again slowly and gently rotate the engine until the piston jams the rod. do this until the piston just passes under the rod. that will be TDC. now remember, i only did this because i was not able to use clem's method. his is superior but you have to be able to rotate the engine 360 degrees in both directions. i could not rotate it backwards more than a few degrees before the crank nut would loosen. good luck.Comment
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Re: Simple Method To Verify TDC?
if you use a piston stop with a hole in the center to let out the pressure and remove all the spark plugs i have turned them over just using the engine fan for a lever by putting pressure on the fan belt to keep it tight.Comment
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Re: Simple Method To Verify TDC?
maye i'm doing somthing wrong, but even after removing all of the plugs, i cannot use the fan to back rotate the engine. in fact, i had to use a breaker bar with a socket on it to rotate the engine when i checked for TDC.
my engine seems to run great [it has been for four years, now]. is there somthing wrong here??? am i doing somthing wrong?? i really do need a breaker bar, even with the plugs removed. it is just a standard BB [427/390].Comment
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Re: Simple Method To Verify TDC?
I seem to recall seeing a tech tip on the corvetteforum.com tech tips board for C-3s.
Good luck, JohnComment
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