525 SC Head gasket Or??
06-09-2019, 01:48 PM
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525 SC Head gasket Or??
Back round... Motor is 97 model 525 SC. Started popping thru carb under acceleration (trying to get on plain).
Checked valvetrain first. Everything moving fine.
Swapped carb - same problem
Swapped distributor, coil, cap & plug wires- same problem
New plugs - same problem
new fuel pump - same problem
Then (finally) stepped back and ran compression check. #1 cyl 138 psi, #2 cyl 135 psi...... #5 & #7 cyl 0 psi. Double checked valve train and valves "appear" to be getting normal full lift. At this point I am thinking it's a head gasket blown between #5 & #7 cylinders. Can anyone think of either a way to verify this, or some thing else that would cause this, or other things i should look for while replacing the head gasket.
Checked valvetrain first. Everything moving fine.
Swapped carb - same problem
Swapped distributor, coil, cap & plug wires- same problem
New plugs - same problem
new fuel pump - same problem
Then (finally) stepped back and ran compression check. #1 cyl 138 psi, #2 cyl 135 psi...... #5 & #7 cyl 0 psi. Double checked valve train and valves "appear" to be getting normal full lift. At this point I am thinking it's a head gasket blown between #5 & #7 cylinders. Can anyone think of either a way to verify this, or some thing else that would cause this, or other things i should look for while replacing the head gasket.
06-09-2019, 02:10 PM
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How many hours?
You have an obvious no compression problem but for what its worth mine started running bad like that before I tore it down and it ended up being a bad sea water pump...the cam inside that drives the fuel pump got flat and I was losing fuel pressure...
I bring this up because hopefully you didn't have the same issue and run it lean and the no compression is actually 2 bad pistons or bad valves.
You have an obvious no compression problem but for what its worth mine started running bad like that before I tore it down and it ended up being a bad sea water pump...the cam inside that drives the fuel pump got flat and I was losing fuel pressure...
I bring this up because hopefully you didn't have the same issue and run it lean and the no compression is actually 2 bad pistons or bad valves.
Last edited by BBYSTWY; 06-09-2019 at 02:13 PM.
06-09-2019, 02:13 PM
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With the valves closed pressurize #5 and see if air come out #7 spark plug hole
06-09-2019, 03:01 PM
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06-09-2019, 03:02 PM
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How many hours?
You have an obvious no compression problem but for what its worth mine started running bad like that before I tore it down and it ended up being a bad sea water pump...the cam inside that drives the fuel pump got flat and I was losing fuel pressure...
I bring this up because hopefully you didn't have the same issue and run it lean and the no compression is actually 2 bad pistons or bad valves.
You have an obvious no compression problem but for what its worth mine started running bad like that before I tore it down and it ended up being a bad sea water pump...the cam inside that drives the fuel pump got flat and I was losing fuel pressure...
I bring this up because hopefully you didn't have the same issue and run it lean and the no compression is actually 2 bad pistons or bad valves.
06-09-2019, 03:12 PM
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Might as well do a cam swap, up the compression, add a chiller, bigger blower, swap the 454 for a 540, upgrade ignition, aluminum heads.....see how that snowballs hahahahaha
In all seriousness tho...check the deck surface and head mounting surface for degradation from the head gasket being bad. Doesn't take much to start eating away at those surfaces. Hopefully it'll be a quick head gasket change and back on the water in no time!! Good luck!!
In all seriousness tho...check the deck surface and head mounting surface for degradation from the head gasket being bad. Doesn't take much to start eating away at those surfaces. Hopefully it'll be a quick head gasket change and back on the water in no time!! Good luck!!
06-09-2019, 03:28 PM
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Might as well do a cam swap, up the compression, add a chiller, bigger blower, swap the 454 for a 540, upgrade ignition, aluminum heads.....see how that snowballs hahahahaha
In all seriousness tho...check the deck surface and head mounting surface for degradation from the head gasket being bad. Doesn't take much to start eating away at those surfaces. Hopefully it'll be a quick head gasket change and back on the water in no time!! Good luck!!
In all seriousness tho...check the deck surface and head mounting surface for degradation from the head gasket being bad. Doesn't take much to start eating away at those surfaces. Hopefully it'll be a quick head gasket change and back on the water in no time!! Good luck!!
Yeah, the heads were just done right before I bought it, so hoping maybe just an oops oversight kinda thing. Definitely gonna check it all out when I get the head off
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06-10-2019, 06:11 AM
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It does not take long to erode/cut either the block or head, usually the block because there is less material there.
Hopefully you get lucky.
Keep us posted.
