Thread: 427 or 454

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Block number is 3963512.... 4 bolt 69-71 427 / 454
My question is without taking off a head or pan how can I tell if it is a 427 or a 454 ? Seems to me the bore is the same... different stroke ? Any clues ?

This may be a hair brained idea, but there's a slick way to find your exact TDC even if you don't have a timing pointer on the block, or if you don't trust that it's right:

1) Make an indicator from some clear plastic tubing, a jar of light oil (cooking oil, olive oil, whatever) and an old spark plug.
2) Break up an old spark plug and attach a length of clear plastic tubing to it (make it airtight). A hot glue gun can help here, or you can use silicone if you're patient.
3) Remove all the spark plugs.
4) Stick your thumb OVER the #1 cylinder spark plug hole. Rotate the engine until you feel pressure on your thumb. That's the compression stroke, and TDC is at the top of this stroke.
5) Screw the spark plug with plastic tubing attached into #1 cylinder, and insert the other end of the tube into a the jar of light oil. Continue rotating the engine. Bubbles will appear until the piston reaches the top of its travel. When it starts down on the next stroke the bubbles will stop and oil will begin traveling up the tube. Stop at a convenient point and mark the tube. At the same time mark the crank pulley and the engine body at a convenient spot.
6) Rotate the engine backwards and watch the oil recede into the jar. Continue rotating. As the piston continues past tdc and downward it will again suck oil into the tube. Rotate the engine till the oil again reaches the mark you made in Step 5. STOP! Mark the crankshaft pulley where it lines up with the mark you made previously on the engine. You should now have two marks on the crankshaft pulley. The midpoint of these two marks lined up with the mark on the engine is TDC.

How about if you make your tubing/spark plug tool as noted above, but then hook that small clear tube to a larger diameter clear container with straight sides - something like a clear glass beer bottle with the bottom cut off square and the tube hot glued to the neck, or some type of straight side graduated cylinder you can destroy. Go through step 5, continue to rotate the engine and once it stops blowing bubbles it's going to be on the downstroke, drawing oil up into the bottle/tube. Watch it carefully, and when it reaches the top mark that point on the bottle/tube. Measure the ID of your bottle/tube, figure the area in square inches. Measure the height the oil was drawn as accurately as you can, like with a digital caliper. Multiply the area x the height and you have the displacement of one cylinder x eight gives you the engine displacement. Should be close enough to see if it's 427 or 454 if you measure accurately. Just my $0.02, but it seems reasonable for what you're wanting to do.