failed compression test

[NoKlu]

Re: failed compression test

If I bought a motor and it blew up I would not pay a dime for anything till I found out what the builders were going to do about it. If it was installed by a mech he would get it back the same day it blew up.

 

[ryendube]

Re: failed compression test

If I bought a motor and it blew up I would not pay a dime for anything till I found out what the builders were going to do about it. If it was installed by a mech he would get it back the same day it blew up.

ya but hes guilty of messing with it


advanced timing has signs of preignition /shrug

 

[NoKlu]

Re: failed compression test

I was under the impression he couldn't remove the heads with out voiding the warranty, thats why he was looking for the scope. If he can't remove the heads that means someone else did the work. Did the mech set the timing to 12 deg or did the owner?

 

[ryendube]

Re: failed compression test

I was under the impression he couldn't remove the heads with out voiding the warranty, thats why he was looking for the scope.

ya but i dont know any warnty that will not be void after messing with timing

 

[wanna-be]

Re: failed compression test

I was under the impression he couldn't remove the heads with out voiding the warranty, thats why he was looking for the scope. If he can't remove the heads that means someone else did the work. Did the mech set the timing to 12 deg or did the owner?

no need to point fingers until the cause is determined. supplier provided a mech near Dallas he trust and will charge supplier for work if its the heads. detonation...nobody will cover. im told by reliable source the gas made today does not have the protectants it did 20 years ago and reg fuel can contribute to detonation. supplier recommends i start using mid-grade.

funny thing is it doesn't run like it has two dead cylinders...not overly rough, not missing, no pinging, knocking... just doesn't have the power of a 5.7L. put new plugs in, ran in driveway, and if i didn't know the compression test i still wouldn't suspect it.

 

[NoKlu]

Re: failed compression test

If wanna-be was supplied a turn key engine, and it went pop, the repairs should not be his problem. Either the supplier or the trusted mech are liable for the repairs. Drop it off at the mech's. If adjustments to the settings were made after delivery, thats a whole new ball game. The true cause can't be determined until the heads come off and the only one trusted to do that will be the mech they recommended. Be there when he opens it up if possible. I am in the middle of an almost exact repair going on right now. No comp on first cylinder on each bank and the engine runs a little rough but not that bad in the driveway. No water in oil. Pull heads and there's water everywhere in the oil and #2 cyl is full of water. The head gasket was leaking and filled the engine with water and it hydrauliced[spel?]. New to the guy,used boat from a dealer. There were no signs in the oil until the head came off. The intake and the heads are at the machine shop to find the cause hopefully, and be repaired. All this happened on the first day of a 2 week holiday with a new boat. He is going to pay for the repairs and try to recover from the dealer. Regular gas should only give you trouble on a high compression engine.

 

[wanna-be]

Re: failed compression test

well, we tore it down and pistons were in good shape, no pitting or burns. the head gasket was ok. but the valves were tuliped. dealer says auto valves are not designed to run under heavy loads and sb ss. he's replacing valves w/ss. cause detonation...possibly timing advancing to high. dealer and engine supplier blame the gas (fall guy) but what ive read that shouldn't matter.

is there a way to check maximum advance? need special timer? is there a way to add pre-ignition sensors w/warning light? do ya'll think premium gas sb used in ski/wake boats?

 

[wanna-be]

Re: failed compression test

. Regular gas should only give you trouble on a high compression engine.

how do youi define high compression? boats run under constant load and if towing skiiers or tub than your going to have high compression, no?

 

[bruceb58]

Re: failed compression test

but the valves were tuliped. dealer says auto valves are not designed to run under heavy loads and sb ss. he's replacing valves w/ss. cause detonation...possibly timing advancing to high. dealer and engine supplier blame the gas (fall guy) but what ive read that shouldn't matter.

What does "sb ss" mean?
What does "valves w/ss" mean?

 

[bruceb58]

Re: failed compression test

how do youi define high compression? boats run under constant load and if towing skiiers or tub than your going to have high compression, no?

No.

 

[rs2k]

Re: failed compression test

You are confusing compression with engine load. Marine engines are usually under heavy load, but they do not usually have high compression. I knew someone who kept tuliping valves on his 5.0 fuel injection powered Merc. He never got it fixed though, he sold the boat. I think it has some

The only way I know to tulip a valve is to get it too hot or get something in between it and the valve seat, like rust or carbon. SS valves are not a bad idea in a marine engine. They tend to slow down the rust problem.

 

[TilliamWe]

Re: failed compression test

I explained his tulipped valves to him on Trailer Boat's website a week ago, before the motor was torn down. He knows how it happens. This happened due to ignition too far advanced and lugging his engine.
Stainless steel valves are fine and all, but unecessary, if you tune and operate the engine properly. The stock valves only tulip if you are doing something wrong, which you were.