Member Since: 07 Oct 2011
Location: Oslo
Posts: 62
TDC while piston #1 is going down?
Hello, rebuilding an engine with flex plate correctly installed (fits only one way). I noticed that to reach TDC on piston #1 in order to place the timing tool in the flex plate (hole with flattened sides) the piston actually is moving down and about 5 mms under the cylinder top. Crankshaft shows flattened sides for oil pump drive in correct vertical position.
I always thought that TDC meant at the top of the (compression) stroke, furthest away from the crank?
4th Aug 2024 2:09 pm
dutchviking
Member Since: 07 Oct 2011
Location: Oslo
Posts: 62
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4th Aug 2024 2:11 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10732
Timing position isn’t at tdc on these
4th Aug 2024 3:52 pm
dutchviking
Member Since: 07 Oct 2011
Location: Oslo
Posts: 62
Thanks Pete! Great and reassuring to know this.
4th Aug 2024 5:10 pm
Breg90
Member Since: 04 Feb 2017
Location: Falkirk
Posts: 360
Believe timing position is at 30 past Tdc.
Find tdc at cylinder 1, rotate 30 degrees, install flex plate with flex plate locking pin in - this sets the flex plate to the correct position.
That’s the high level summary. The ford engine manual states that u use a pin on the front left corner of the engine block, via a blanked hole, then you rotate the crank against - this gives you 30 degrees past tdc. Then fit flex plate. Watch LR time as he shows it. If you join his patreon for a month (price of a London pint) you can down load a drawing for the pin.Series one 1949 - in bits, chassis is strapped to the ceiling in my garage (beside the canoe)
LR 90 - In bits
Disco 3 - currently in bits
4th Aug 2024 5:43 pm
dutchviking
Member Since: 07 Oct 2011
Location: Oslo
Posts: 62
thanks for explaining. I have seen the lrtime videos and subscribed. Since the flexplate only fits in one position I expect it sits correct and correct timing hole has flattened sides so hoping there is no need for the extra timing pin on the side.
11th Aug 2024 1:40 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5061
Yes it's 30° ATDC with a gauge or you can use the positive stop method as described by Breg90 but it shouldn't be necessary.yµ (idµ - eAµ) ψ=mψ
11th Aug 2024 3:17 pm
dutchviking
Member Since: 07 Oct 2011
Location: Oslo
Posts: 62
For completeness: since the pistons move one full stroke per rotation of the crank, could one be 30 degs past tdc of the exhaust stroke i.e. 360 degrees off combustion stroke or doesn't that matter
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