Easy CID Measurement

There are some Ford engines that look exactly alike, so determining C.I.D. in a salvage yard, or with an engine still in the car can be a chore sometimes. Certain displacement FE engines, late 60's 289-302's, 351M-400's and 429-460's are virtually impossible to tell apart from each other. Here is a quick and easy method to determine the stroke of the crankshaft that will either hint at, or tell you for certain what C.I.D. engine you are looking at.

Case in point was an FE that a buddy of mine bought. It came out of a '66 Thunderbird that the owner swore was a 428. The engine had all the original pieces in place, it was a four barrel engine, the air filter housing had a 428 decal on it, and the block had the C6ME-A casting number on it, which all books told us was a 428. I was still a bit skeptical. I was going to measure the stroke to see for myself.


The first step was to get the number one cylinder to top dead center by aligning the zero mark on the balancer with the timing mark on the engine.


A way to measure was going to be needed. I use a piece of brake line tubing, and a small scribe.


After removing the number one spark plug, the piece of tubing is inserted into the spark plug hole and is held perpendicular.


The scribe is then used to make a mark on the tubing at the height of the valve cover rail. The valve cover rail is used as a commom reference point.


Since the number one piston is at the very top of the cylinder, the number four piston will be at the very bottom of the cylinder. After inserting the same piece of tubing into the number four spark plug hole, another mark is made that corresponds with the valve cover rail.




We are now left with two marks on the tubing.


Measuring between the two marks will tell you the stroke of the crankshaft. The measurement I got was 3 1/2", which was not the 3.98" I was looking for if the engine was a 428. I was looking at a 352 or 360 C.I.D. engine.


This procedure can be used on any engine to figure out the stroke, which will give you a better idea of what you are looking at.

Here are the crankshaft strokes of a few Ford engines:
-289- 2.87"
-302-3.00"
-352 FE-3.50"
-390 FE-3.78"
-428 FE-3.98"
-351M-3.50"
-400-4.00"
-429-3.59"
-460-3.85"

Nice trick! Would you be able to get the rod/tube perpendicular on most all Ford engines, given the spark plug hole location? Obviously if the rod was not exactly perpendicular, you will get a longer measurement than the actual stroke.

Ford did a horrible job of engine I.D. for sure. It's almost impossible to tell what you have without measuring it. Lot of 428's go in the shredder because no one knows what they are, shame really.

The only concern I would have is using the balancer for TDC, often these old balancers are off, sometimes a little, sometimes a lot.

I would start with the "measuring stick" in and then turn the motor, mark it at its highest point, then continue the same direction until the lowest point.

Then you know you got the full stroke

Another trick I have seen is to lay a sharpie on the v/c rail and hold the rod against it, rotate the motor a full turn, and the length of the sharpie mark = the stroke, without any concern of where you were or are in relation to TDC

Too bad though, nothing like thinking you had a 428 and having a 352 or 360 LOL

As you can see though, an FE block casting number doesnt mean a thing

Even if you got a 3.98" measurment it still would not have told you it was a 428? It could be a 406.

3.98 could be a 410

406 was a 390 crank with a 4.13 bore and would still be 3.78

i have 2 390,s 1 a stock 390 in a 65 t-bird. and 1 in a 69 ford pickup. the 390 in the truck has a 427 crank and 30 over bore. does any one know what is the cubic inches the 390 is that has the 427 crank. im leaning towards a 406 but im not sure. and i really dont know what the rated horse power is. taks davo

Originally Posted by davo691

i have 2 390,s 1 a stock 390 in a 65 t-bird. and 1 in a 69 ford pickup. the 390 in the truck has a 427 crank and 30 over bore. does any one know what is the cubic inches the 390 is that has the 427 crank. im leaning towards a 406 but im not sure. and i really dont know what the rated horse power is. taks davo

The 390 and the 427 have the same stroke (3.78"), so you have a 390 in the truck. A 406 has a 4.130" bore with the same stroke as a 390.