454 bogging and misfire under load

[Guitarhead]

454 bbc , the boat got over heated from broken water pump belt ..,

I changed the oil and oil filter . Had good oil pressure fired right up . But when input it in the water I tried to accelerate and it had no power , just sputtered and misfired .

I took it home checked compression , all compression is good. I have 7 psi fuel pressure. I changed the ignition coil and spark plugs . Still having same issues ….

Any ideas? It is a 1973 454 BBC engine

 

[alldodge]

all compression is good

What are the numbers?

 

[Guitarhead]

 

[Guitarhead]

Could distributor cap be bad ? Here is pic of inside

 

[Guitarhead]

Could it be head gasket?

 

[alldodge]

Cap looks ok but compression number s don't. The lowest number should be within 10% of the highest. Even if the 150 is removed and use 145, this says lowest should be no less then 130.5

Yes, I'm thinking head gasket. Most likely when the motor heats up, the pressure gets less. Check the oil again

 

[alldodge]

If you do a leak down test, you can find out if its bad valves, rings, gasket

 

[Guitarhead]

I tested it engine cold . And I left all other spark plugs in

 

[Guitarhead]

So you think I have an internal issue causing my problem ?

 

[alldodge]

Yes I think its internal. Boat ran fine before over heating. Need to test to find out. The leak down test will tell a lot

 

[alldodge]

The heat may have just warp a valve, so maybe a valve job would fix. Right now don't know so need some testing

 

[Guitarhead]

Progress pictures of tear down

 

[Guitarhead]

 

[Lou C]

Any sign of water in the oil? Water in cyls?

 

[Guitarhead]

So far everything looks good. About to take the head off

 

[Lou C]

Well that will tell the tale. You have machine shop lined up to check out the cyl heads?

 

[Scott Danforth]

Careful, that head is about 85 pounds

 

[Lou C]

PS cold compression tests are not as accurate as hot. Engine should be warmed up all plugs out and throttle & choke valve wide open.

 

[Lou C]

Yep that is a 2 man job at my age. 4.3 heads are only about 43 lbs, lots easier

 

[Guitarhead]

yeah it heavy… here is one side