Does any body know about a 390 motor(a 360 or 318 bored out to be a 390)

[ashtin]

I have a 1972 charger se that has a seemingly modified engine, it looks like a 360 or 318( the chargers original engine was a 318) but I don’t know if it has been transformed into a 390, does anybody know how I could find out. I don’t have a picture of the full engine but these pictures have part of it

 

[Fran Blacker]

It couldn't be bored that much. Stroked yes. You would probably need to pull a head. Measure stroke through spark plug hole don't if it could be done.

 

[ashtin]

It couldn't be bored that much. Stroked yes. You would probably need to pull a head. Measure stroke through spark plug hole don't if it could be done.

Thanks bro

 

[RemCharger]

And the old deal was to bore out a thick block 318 to a 340 piston.
I wouldn't say the chances that it has a stroker crank is likely.

 

[kiwigtx]

390 cubes, or 390 HP ??? Big difference.

 

[ashtin]

And the old deal was to bore out a thick block 318 to a 340 piston.
I wouldn't say the chances that it has a stroker crank is likely.

Ok that actually helps a lot thanks

 

[ashtin]

390 cubes, or 390 HP ??? Big difference.

390 cubic inches

 

[Kern Dog]

To get to 390 cubic inches, a 318 needs a 4 inch stroke crank and a .030 overbore. It is an excellent way to make power in an engine that looks like a simple 318.
Neutral balance, traditional motor mounts, light engine with bigger cubes that a 383!

 

[Demonic]

There was a magazine article a long while back, some shop was sonic checking 318 blocks, going .090 over and welding up custom cranks. It might have been Mullen & Co. I wish I could find it, just for reference. This was long before the days of 4" stroker kits.
Like Kern said, a 'teen with a .030" over and a 4" crank is almost common. Maybe a talk with the previous owner or some receipts could shed some light?

 

[YY1]

390/392 stroker kits for 318's ARE available, but I have only seen them for the last maybe...5 years.

 

[Brandy]

It couldn't be bored that much. Stroked yes. You would probably need to pull a head. Measure stroke through spark plug hole don't if it could be done.

Agree with Fran and Kern, pull a plug and turn it over by hand slowly to find TDC/ BDC with a piece of plastic rod sticking down onto the top of the piston. Mark each spot and then measure between the marks on your rod. 4" of stroke + pulling a head and measuring the bore hole as +0.30 equals a likely 390CI. You will need to pull the heads anyway to inspect/ rebuild that motor so just do it.

 

[toolmanmike]

I have a 1972 charger se that has a seemingly modified engine, it looks like a 360 or 318( the chargers original engine was a 318) but I don’t know if it has been transformed into a 390, does anybody know how I could find out. I don’t have a picture of the full engine but these pictures have part of it

View attachment 1326022

Seemingly modified? Why do you say that? A 4 barrel and valve covers is what I see in your last photo. The block size is cast into the side and like the fellas mentioned, you will have to disassemble and measure the rest. In general terms, a 390 is a 4" stroked 318 and a 408 is a 4" stroked 360.

 

[Dave6T4]

Mopar Performance Used to sell a 390 h.p. 360 Crate Motor. Maybe this is what it is. I think they came with finned cast aluminum Mopar Performance valve covers.

 

[RJRENTON]

Seemingly modified? Why do you say that? A 4 barrel and valve covers is what I see in your last photo. The block size is cast into the side and like the fellas mentioned, you will have to disassemble and measure the rest. In general terms, a 390 is a 4" stroked 318 and a 408 is a 4" stroked 360.

The pix of the engine with the valve cover and carb shown....the carb that's visable, appears to be a Carter THERMOQUAD. I believe they were std on certain flavors of Mopar 360 and 340 engines.....possibly police option??....likely a 360.....
BOB RENTON

 

[toolmanmike]

The pix of the engine with the valve cover and carb shown....the carb that's visable, appears to be a Carter THERMOQUAD. I believe they were std on certain flavors of Mopar 360 and 340 engines.....possibly police option??....likely a 360.....
BOB RENTON

Could be, It could be any LA. The OP said the Charger was originally a 318. It would have came with a 2 barrel. Everybody wanted a 4 barrel on their Teen. A lot can happen in 50 years.

 

[Cranky]

There are cast in numbers on the side of the block....can't remember what side but they are prominent. There's also stamped numbers on the driver side of the block just below the head gasket parting surface. They are usually faint but cleaning that area of the grime (if any) really good, they should show up. If it's already clean and still can see them, sand the paint and they will appear.

 

[ashtin]

That’s the exact response I needed thanks

To get to 390 cubic inches, a 318 needs a 4 inch stroke crank and a .030 overbore. It is an excellent way to make power in an engine that looks like a simple 318.
Neutral balance, traditional motor mounts, light engine with bigger cubes that a 383

 

[ashtin]

Ok I think I will thanks

Agree with Fran and Kern, pull a plug and turn it over by hand slowly to find TDC/ BDC with a piece of plastic rod sticking down onto the top of the piston. Mark each spot and then measure between the marks on your rod. 4" of stroke + pulling a head and measuring the bore hole as +0.30 equals a likely 390CI. You will need to pull the heads anyway to inspect/ rebuild that motor so just do it

 

[ashtin]

Mopar Performance Used to sell a 390 h.p. 360 Crate Motor. Maybe this is what it is. I think they came with finned cast aluminum Mopar Performance valve covers.

The valve covers do look different than the 360 they put in molar from the factory, it very well could be that

 

[Lefty71]

Kinda curious.... why do you think that?? Previous owner claim?? Or??