DIY Cubic Inch Checker / Whistler

[NewbVetteGuy]

Anyone have any ideas on how someone could inexpensively, "accurately enough", and easily validate the cubic inches or at least stroke in an engine that's right in front of you without having to take a head or the oil pan off?

I'm thinking of the scenario where someone is going to look at a car that they're considering buying and the owner says it's a 383 stroker or a 421 and they don't have any good documentation to back it up.


An actual whistler is just not a thing an average guy is going to have...
Hook a leak down / compression checker hose to a balloon and spin the engine over by hand as fast as you can, then figure out the volume of air in the balloon??... I've got nothing, obviously... (I'm hoping my bad ideas trigger someone smart to come up with good ideas; lol!)


Adam

[dannobee]

A whistler is actually for checking compression ratio.

https://shop.katechengines.com/product/ ... io-tester/

What you want is what we called a "bubble checker."

https://www.speedwaymotors.com/Speedway ... l,703.html

It's just an acrylic tube with a piston in it, with an o-ring on each side of the piston. You do need to take the rocker arms off to check displacement though. And the temperature of the cylinder is taken before the check.

[emsvitil]

Not that I would do this..........

Remove spark plug

Cylinder BDC

Fill with oil

Capture oil when moving cylinder to TDC

How much oil do you have?

[BLSTIC]

Can you feed a stiff wire down the plug hole? By measuring distance from plug thread to piston top at TDC and at any other crank angle (say 90*) you can measure/calculate stroke. Not necessarily down to the millimeter, but probably close enough.

[BOOT]

Unless you can level the cylinder or make the plug hole the highest point, filling it with fluid won't be ideal. Ring seal aside.

Honestly if they can't prove it then that is a bargaining chip to lower the price or a reason to walk away.

[panic]

A probe in the plug hole will work directly (1:1 ratio) to the stroke length if the plug thread is exactly vertical (parallel to the bore axis). Angles less than 8 degrees reduce the error to 1% or less., Yes, difficult to get a level and a protractor on there.
If you have an excellent blueprint of the head, P/S allows you to draw a line through the plug thread and read the angle on the display.
If a known angle, the inserted depth will be always greater than the stroke length, forming a triangle.
To calculate stroke, multiply the inserted depth by the cosine of the angle. Viz, plug angle is 12 degrees, COS = .9781, probe depth 4.345", stroke is 4.250". Works on metric also.

[dannobee]

Or just get the numbers off the top of the piston with a borescope camera. And might as well pull the drain plug and take a peek at the crank and rods, too, just to keep them honest.

[In-Tech]

The "whisler" isn't accurate, cnange chamber profiles and see what happens. I laughed at the tech pad when my over ~15 to 1 whistels 9.5

[dannobee]

The "whisler" isn't accurate, cnange chamber profiles and see what happens. I laughed at the tech pad when my over ~15 to 1 whistels 9.5

SHUT UP! There could be some tech officials here!

If you've "worked" with one awhile, you'd know how to trick it, in both directions.