Knocking 350....

[Showtime22]

Hey -

I had my 1980 Merc 350 (260) run low on oil until it knocked for about 30 seconds. I added oil once I heard the sound. The oil helped quiet the knock but did not solve it completely.

The motor starts and will sound normal under 1500 RMP but then knocks.

Tomorrow morning I will check compression, but whats the first bearing or part to burn up with low oil on a 350? I'm guessing rod bearings. Looks like I've killed another one.

Thanks,
Showtime22

 

[Bondo]

Re: Knocking 350....

Looks like I've killed another one.

Ayuh,.... Sounds like it....

 

[mla2ofus]

Re: Knocking 350....

Better find another 350 quick before cash for clunkers destroys them all!!!!
Mike

 

[Showtime22]

Re: Knocking 350....

Really Bond O -

23,000 posts and a three word reply.
I know you have more than that.

Maybe I'd have 23000 posts if they were all as insightful.

P.S I do know you have more than that -
Say what's a ballpark fair price to have a 350 re-manufactured...or if I should buy an already re-manufactured 350.

 

[sockos]

Re: Knocking 350....

More than likely it would be a rod bearing. Usually hear them rap good when you quickly throttle back.
I've seen quite a few spun bearings. Need a new bottom end at least.
Sorry!

 

[jtybt]

Re: Knocking 350....

I could give you a full run down on what you need to do but I think


Ayuh! You spun a rod bearing.

 

[Showtime22]

Re: Knocking 350....

What specialty tools would I need to change the bottom end bearings....besides a engine hoist and an engine holder....

 

[sockos]

Re: Knocking 350....

Any specialty tool that you would need to do the job is available for rent at Auto Zone or other auto places. A puller or two, torque wrench, and preferable someone who has seen the innards of an engine before.
If it was me I would plan on building the whole motor. Pieces of bearing are probably floating around your oil galleys.
Ballpark $750 if you do it all for a like new engine.

 

[Bifflefan]

Re: Knocking 350....

your buying the whole apple when you only need a seed.
I wish i could find people that had your kind of money id sell them things all day long.
Pull the thing out and have a competent motor guy look at it. then make a decision as to whats needed. More than likely all you will need is a crank kit. you dont even need to pull the heads.
Oil pan gasket, crank kit, 300.00 buck and your back in the game. You mat need one rod resized, but come on.....

 

[Bondo]

Re: Knocking 350....

Oil pan gasket, crank kit, 300.00 buck and your back in the game. You mat need one rod resized, but come on.....

Ayuh,... I would imagine Showtime wants a Reliable motor,....
Not a Bubblegummed motor for a Quick boat sale......

$300.00 to get Running again,..?? Come On,....

 

[Showtime22]

Re: Knocking 350....

Thanks for the insight.

I am thinking that if there is compression left - I will look into the crank kit.

It's all depressing though...If I am going to dig into the motor this much I'd hope to be adding a major HP improvement....

If compression is weak I will be looking for a re-manufactured truck 350 core in the off season.

 

[sockos]

Re: Knocking 350....

I would still disassemble the whole thing and look it over , it's out why not.
Ok if you want to save $250 take the heads apart clean and lap the valves yourself. New oil Pump .... I surely would. Timing set probably. Decent gasket set, plus incidentals.
What I am saying is that for 750 or 500 w/o new heads you could have an as new engine. I guess it's whatever you feel comfortable with.

 

[fabrimacator21]

Re: Knocking 350....

1200 for a marinized shortblock seems decent.... I know you can get some truck remanufactured longblocks for $8-900.

You might be money ahead if you buy a cheap reman 4bolt longblock and marinize it yourself.

Couldn't find the 800 dollar longblocks (was about 5 years ago when I saw it) but I did find this...

http://www.chevy350motor.com/Chevy_350_motor_marine_chv-350lmlb-4.html


1280 for a marine 350 longblock.