Engine Compression

[rsjohnsn]

Hi all. I have a couple of questions about a 2000 7.3 liter in an F550. My first one has me a little concerned. My buddy was trying to remove his fan to replace it because the clutch is messed up. In the process of doing this the whole engine would spin over. Now what has me concerned is that it is spinning to easy. There is less compression than his 302 gas engine. The motor has 130k on it and everything checks out fine other than this. My question is, should the engine turn over this easy? Is there a compression relief valve or something of the sort to make it easier to crank the motor? Should we be concerned at all?

The second question is why does the engine tag on the valve cover only say that the horsepower rating is 235 and the same year F350 says 275HP? Remember this is a 2000 F550 Cab and chassis with a 6 speed and 488 gears.

Thanks
Scott

 

[DaveBen]

Diesels do spin over, by hand, rather easy. I too was a little concerned when I discovered this on my diesels. I don't know why specifically. It is nothing to worry about. Now as to why Ford lies, I can't answer that. Ask Ford.

Dave

 

[RoyBoy]

I wouldn't say that diesels turn over EASY, but yeah if your trying to loosen a fan clutch your going to need to hold it from turning with a wrench. The diesel has WAY more compression than any gas engine. I didn't know that diesels turned easier, why is it then that you need 2 batteries on a diesel and one on a gas (yeah I know its to run the glow plugs, but) gassers still turn over easier IMO
edit: Diesels will turn over pretty easy SLOWLY as the compression can leak past the rings at a certain rate. Gasses are the same...

 

[Zookie400]

ford isnt lying, its actually true on the valve cover. the engines for use in heavy duty apps are actually tweaked differently than the ones intended for use in pickups. now please correct me if im incorrect, because this knowledge comes second hand from someone who is currently taking a ford diesel course at uti.

i dont remember everything he said, but he said the heavy motors are slower revving, and actually have a thinner head gasket because the rods dont stretch as much as is expected in a pickup motor that is allowed to rev up higher. the injectors are different in some way, i want to say its the nozzles. and also there is programming differences as far as fuel injection goes.

i asked him if the differences were worth swapping parts into my pickup, and he said they did it to handle a much different "abuse" pattern. basically they better suited the engine for the heavier trucks. i think if you looked at a dyno chart of the two engines they would be very different as far as when the power comes in.

like i said, this is all second hand so please correct me if someone knows better. i will call my buddy and double check this tomorrow.

 

[Crumm]

The second question is why does the engine tag on the valve cover only say that the horsepower rating is 235 and the same year F350 says 275HP?

Auto vs Manual. You state that the 235hp one is a standard, I am thinking the 275hp one is a auto?

 

[rsjohnsn]

The 350 is a 6 speed as well.

Scott

 

[Crumm]

Shoots that theory down.

 

[silverado3500]

Ford did downrate early 99 up to 2001 PSDs that came with slushboxes. I was under the impression that 235hp was the automatic hp rating, while 250/275 depending on the truck was for the 6 speeds.

After 2001 they were rated the same whether auto or manual