jp1984

boat ran outstanding for the first 2 hours then it developed a miss. pulled the plugs and cylinder number eight has massive carbon build up. it consumed about a quart of oil also. back of boat has black suit only on the side with the bad plug. plugs were new before this ride. boat sat for 2 years before i bought it last fall this was the first trip out. im going to do a comp. test tomorrow.
not sure what my next step is... thanks in advance for any input. its a 454 bored over .030 msd ignition lightning headers holly double pumper

the deep

iTrader: (8)

Blow-by in # 8 . Could be a stuck oil control ring from sitting orrrr from there we get mo seriousaaaa . Do a leak down test and maybe shoot some WD penetrate in that plug hole and let er soak . Get some good oil in her . Let us know what you discover .

compedgemarine

I would run a leak down as it sounds more like a broken ring if it is using oil and only on one cylinder.

SB

iTrader: (1)

Yup, 2+yrs old fuel. Probably hypercracking pistons,,,wallah.

Pull that carb apart too when you rebuild the motor.

compedgemarine

I take it you are not a fan of the ultra brittle hyperutectic pistons? personally I would rather run a cast piston if it is not performance and running forged but the current trend seems to be toward hyper in most things.

SB

iTrader: (1)

Emissions.

High ring placement leaves less area for unburnt fuel / hydrocarbons to hide.

rev.ronnie

Tighter piston to wall clearances too. Less blow by because of less piston rocking.
I bored an import block once that had a piston to wall clearance spec of .000”-.0005”! I'm thinking "really? No clearance?. I finish honed to .0005" ...couldn't do zero...

jp1984

i am going to do a compression test tonight i will let you guys know

4bus

iTrader: (4)

Yup, unfortunately this doesn't leave much metal near the crown, and any detonation breaks the piston pretty easy

jp1984

i removed all the plugs and started my compression test on cyl. #2. as the engine was being rolled over it shot some water out of cyl. #6. and one of the plugs on the other side of the engine had water/milky oil on the end of it. all cylinders were between 160 and 175 psi. except for #6 had 190 to 200 psi. assuming because it had the most water in it.cylinder #8 had the nasty build up on the plug but had good compression.the oil on the dip stick seems fine, doesn't appear to be milky at all. i am going to try and pressure check the lightning headers next. any input or tips in the next step i should take are greatly appreciated. thanks again.