How can i identify my engine? is there an obvious tell-tale that i could use?

My truck was given to me while i was out of country. I didnt hesitate on the offer because 1. Ive owned this truck once before and totalled it (ROUND 2!) and 2. it was FREE. The previous Owner didnt have a clue what he owned.

I looked up the VIN number and found out the truck originally was built with a 360 under the hood. The Owner told me it had a 390 and when i asked if it was the original he couldnt tell me. 390 or 360?

 

remove a sparkplug and measure the stroke:

3 1/2" = 360
3 3/4" (3.78 actual) = 390

Josh

 

^x2
Either that or pop off the oil pan and check the crank casting number.

 

Hmmm... 5 minutes of spark plug removal and using a long screw driver or wooden dowel to measure stroke

or...

spend all day removing an oil pan, buying $20 in gaskets and having oil drip all over you in the process...

Might as well drop the tranny and look for a half moon (360) or square notch (390) in the crankshaft flange then.

Josh

 

I just went through this same process about a month ago with a 1973 F-250 4x4. PO said 390 even though it was not a factory option. Using the spark plug method I got a measurement of just over 4 inches so I ended up pulling the pan a few days later to get the casting numbers to see if it was either a 390 or a 410. It was a 390. So the spark plug method is not exactly precise, it seems (in my case) to overestimate by about a quarter inch, but it's good enough.

When I did it though I set the engine at TDC and pulled plugs 1 and 7 and measured the difference between them, so I may have been measuring the valve pocket in one cylinder and not the other, who knows. But if you do it this way I would GUESS you would measure about 3.75 inch for a 360 and about 4 inch for a 390, with the over-measurement of about .25 inch and all.

 

I would say, in my 20+ years of dealing with this, you are the first person to ever have a problem measuring the stroke thru the sparkplug hole.

I'm not just saying, I'm just saying...

Josh

 

I would say, in my 30 years of dealing with people you are not the first person to say something pointless and asinine and you will be far from the last.

I'm not just saying, I'm just saying...

Steve

 

Let the games begin.

 

Do you always repeat what others say or just think doing so somehow makes you smart?

No one has ever had a problem measuring the stroke thru the spark plug hole, just have to be half-way intelligent about it.

Josh

 

Everyone was very helpful. I went the spark plug removal way and i will admit it wasn't quite as easy as i thought. I am a machinist and I'm use to seeing very precise measurements. Dial calipers would of been nice! I went the wooden dowel route(cut up an old fishing pOle). The measurement varied plug to plug but none that i measured were 3.750" or 3.500" but close enough to get the idea.

I learned that sometime in my ole' Lunchbox's life the owner swapped out the original 360 for the 390. maybe at some other time this was someone else's project as well