What pistons

[1976kjell]

Hi

Here is two short movies recorded inside two of the bores on my 390 from a 67 Mustang. It is recorded with a android endoscope. Not the best quality, but it give som indicators

Its interesting to identify what pistons it is, if some have knowledge and can tell what pistons it is, and maybe a bit about condition, it had been great

There is some radio noise, so I an advice is to cut the sound. Thereis some "wild" movement of the cam now and then

At 2:11 in the shortest video "030" is sharply defined

From 3:20 on the longest video, the piston design is best shown

https://goo.gl/photos/kzS3JY5ANtNcFHxQ8

https://goo.gl/photos/s9bSotVMfGQpiCeB9

[KMcCullah]

Pistons look like .030 over cast rebuilder types to me. At TDC they sit down in the bore quite a ways, like .120 or so. Similar to the one in the link below.

http://www.summitracing.com/parts/slp-w381np30/overview/make/ford

[1976kjell]

Thanks for the info. Then this engine has 395.4 displacement

[machoneman]

Hard to tell condition by only looking at the piston tops. Do a compression test (engine warm to hot, all eight plugs out, throttle wired wide open, coil wire grounded with duct tape to any cast iron) and record the results. Make sure that each reading gets 3 full turns of the crank before moving onto the next cylinder. If any look to be low, shoot some light weight oil (10W, machine oil, ATF in a pinch) into each hole and try it again. See why here: 

https://www.youtube.com/watch?v=X_tbksFYhl4

[1976kjell]

A compresion test was done some months ago. Here is the results:

Piston    Bar   

1          10,9 
2          10,4
3            9,7
4          10,4
5          10,2
6          10,0
7            9,6
8          10,1

Greatest difference is 1,3 bar. Converted it to PSI and its is 12% difference between highest and lowest compression

[machoneman]

With #1 at 158 psi and #7 at 139 psi, that's not bad.

Any plans to drive it as is or is a teardown in your plans?

[1976kjell]

Not tearing it down yet, but maybe in some years. Before summer the engine will get new lifters, pushrods, valvesprings and seals. Had a ticking sound last summer, these changes may help. A new cam was considered, but instead a degree kit was bought, trying to fint out what cam the engine has