5.7 motor problems
 

I bought a crusader sd power pack motor http://www.1800runsnew.com/NLM/powerpack-NLM.html a little over two years ago and have been having problems with reversion the hole time. I've had the manifold and risers apart many times trying to solve this problem with little success. So I broke down and bought a set of custom made stainless marine manifolds and risers. The risers were made taller and longer to help stop the reversion but I think it was too late. With new exhaust I took the boat out for a ride and something just didn't seem right. got home and the risers off and still water so I pulled a compression test and found 7 cylinders at 190 to 200 psi and #6 at 145. I did a leak down test on #6 and sounds like air leaking through the exhaust. I will test the rest of the cylinders tonight. I guess I my question is what do I do now. Sounds like I need a new set of heads. Not quite sure where to go from here.

145 is normal.

190-200 is a 10:1 - 11:1 compression engine. Which, obviously you don't have.

Probably the high comp is from reading water in the cylinders as well. As the water takes up space in the combustion chambers - the higher you comp will be.

Was there water in the cylinder when you pulled the plugs?

I'm not sure if there was water in the cylinders the plugs were dry when they were removed. I do have marvel mystery oil in them now. When I did the compression test I removed all spark plugs and pulled the fuse for the ignition and fuel pump and cranked the engine until it stopped building pressure. I believe this is the correct procedure. I'll have to do another test.

Could the injectors be firing fuel and giving me a false reading?

If the plugs were dry, no water poured out the plug hole and there's no water in the oil, then chances care you aren't having issues with water in the cylinders.

Could the injectors be firing fuel and giving me a false reading?

I'd say there's a slight possibility that fuel could give you a false reading, but since you took the fuel pump out of the equation I don't think it would make a difference. You can relieve any fuel pressure at the rail by utilizing the shader valve, then run the test again to see if there's any variances.

Might want to pull that mani back off and retest your low one. Visually inspect the exaust port and seat with valve open and closed . On merc bumping yel/red wire turnes it over with no spark fuel. I have seen sbc vortec motors with aftermarket exhaust valves lose thier heads when subject to water .
Maybe crusader employs some juicy cam specs and requires specialized exhaust water dump -controls

Today I had some time to look at the motor again. I re checked compression in some of the cylinders #6 stayed the same at around 150 the others were even higher than before in the 240 range so I stopped testing. I think I mentioned before that I put marvel mystery oIL in each cylinder so I'm guessing that's causing the high numbers although I cranked the engine over several times before testing. I also did a leak down test on all cylinders here is what I found. #1 19% leaking through exhaust and rings #2 15% rings #3 30% rings/exhaust #4 18% rings/exhaust #5 25% oil/exhaust #6 55% exhaust #7 22% exhaust/rings #8 25% rings/exhaust. Im guessing with these results the heads need to be replaced?

It might just need a valve job, but you won't know until the valves are removed.

So a little update. I tore the engine apart and brought the heads to machine shop just waiting for an update and repair. I have everything cleaned and prepped to go back together but I'm a little unsure on the assembly. basically I'm looking for the torque#s and sequence of the heads and intake, adjusting the valves and possibly retiming the engine.

Was the exhaust seat in your comprimised cylinder corroded? And did you figure out the high compression test readings ? Prob want to find out what is going on before you have a exhaust valve head detach and bee bop around inside your motor

I'm not sure why the compression was so high the first time. the second time I had put mystery oil in each cylinder so that gave me a false reading. The heads were repaired I will be picking them up today. I was told that they were pretty bad but not sure what they repaired. I just hope this solves the reversion problem I've been having.

Im thinking you would have to pour mystery oil down the neck of your compression testor while your doing your test to achieve 240 on a contemporary marine engine. If reversion cooked your exhaust valves , and those boys slapped some low shelf valves in now , your not out of the woods yet