6.5 with 6.2 heads.

[D Rat]

I looked at a marine 6.5 with 6.2 heads, we can't tell if it's brand new or a very fresh rebuild, we did drop the pan and it looks very clean, we were able to start it in the crate and it burbled rite up.
What I don't know is what the benefit of 6.2 heads on a 6.5 is, any help would be appreciated.

 

[MrSchaeferPants]

No noticeable difference. Sounds like a "hey, I got this laying around, think I'll use it". Think the compression is different, higher maybe. But then again, depending on what gasket was used with assembly...

Check out the injector lines, IIRC, theres a big difference in the angles between the two heads. See if they're bent in a bad way.

 

[campfire]

I haven't done this swap, but I have heard that some 6.2 or 6.5 heads have 45* angle bolts. The 3 heads that I have inspected were 90* angle bolts. Not sure why or which heads have this difference..

Otherwise, swapping heads should raise the compression. I'm not sure how much of the difference is in head design vs. bore/stroke changes. I do know that both engines use the same gasket set...

If so, I'm not sure why the maritime engine would want higher compression, but watch your boost pressure if you choose to use it. The 6.5 (18.5:1, IIRC) can handle quite a bit more boost pressure than the 6.2 (22:1, IIRC). Higher compression should increase efficiency, though.

I do have to ask, though...why do you have maritime engines hanging around Yuma?

 

[longbedder]

I looked at a marine 6.5 with 6.2 heads, we can't tell if it's brand new or a very fresh rebuild, we did drop the pan and it looks very clean, we were able to start it in the crate and it burbled rite up.
What I don't know is what the benefit of 6.2 heads on a 6.5 is, any help would be appreciated.

The injector angles are different by 30°
between the two, but if it's already plumbed and working I'd say it's not a problem.

The 6.2l heads have bigger valves, so if you're going to run a turbo they will actually breathe better.

The 6.5l heads came with pre-combustion chamber cups (precups) designed for turbo usage, the 6.2l heads did not. You can, however, swap the cups between the two.

A J-code 6.2l head is every bit as strong as a 6.5l head (the early C-code heads are a bit weaker).

Both heads have flat combustion chambers (that is, they don't have any) - compression is controlled via the piston geometry. You should get close to the same compression between the two heads on the same bottom end (with a negligible difference due to different precup volume).

 

[campfire]

Both heads have flat combustion chambers (that is, they don't have any) - compression is controlled via the piston geometry. You should get close to the same compression between the two heads on the same bottom end (with a negligible difference due to different precup volume).

Thanks! That's the piece that I wasn't quite sure of...

 

[D Rat]

A little update, turns out that the engine is a 2000 something GEP 6500 optimizer built by A.M. General, it seems to have eaten a glow plug and damaged a piston so on with a complete rebuild.

 

[blazinzuk]

A little update, turns out that the engine is a 2000 something GEP 6500 optimizer built by A.M. General, it seems to have eaten a glow plug and damaged a piston so on with a complete rebuild.

if it's an optimizer it's the best of the breed.

Not uncommon for optimizers with a waste gated turbo to hit 450 lbs feet and close to 300 hp

Yellow k 20 has one in his blue suburban with a banks kit I believe.