Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

Possible overheat and low compression on 2 adjacent cylinders, sounds like head gasket. Not too big of a job. Pull all plugs and run a leakdown.

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

Head gasket between center cylinders is my guess

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

what and how do you do a leak down?

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

Some good info about compression and compression leakdown tests/testers in this thread.

http://www.offshoreonly.com/forums/s...d.php?t=106452

Dave

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

If you dont have a leakdown tester (I suspect you dont since you're asking), but do have a compression guage, do this.
Turn engine so that low psi cylinder is at TDC compression, valves must be completely closed. Use your comression guage hose to pressurize cylinder to around 50psi. Now listen to where the air is coming from.
If it's from the adjacent cylinder, you've got a bad head gasket. If from the intake/carb or exhaust, it's a bad valve. If from the breather, it's going by the rings. If from the blocks water jacket, cracked head or head gasket.
Gary

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

If your hose has a check valve in it,
You'll need to remove it.

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

I appreciate all the info guys, keep it coming , I am tearing it down now, and redid comp test and the outside had 125 on all 4 and the inside had 125 on front 112 on 2nd, 45 on 3rd, and 125 on fourth

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

I'm still guessing water intrusion. If the exhaust manifolds are original, they are due for replacement.

Dave

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

I got it tore down and it had broke a valve seat, I got that fixed and am putting it back together now

Re: lost comprsion on a cylinder or two any ideas 2000 454 mag
 

Now I have water in the oil, like full, I guess that could mean I f'ed up the intake gasket?