rough idle ,black smoke ,and blowby

[Lost]

Looking into this for friend.

he has 87 down F350 cab n chassie with 460. Carb was rebuilt . The truck idles rough ,blows black smoke and is pushing dip stick out some.

New plugs wires ETC. he did Compression test 115-125 LBS. (Closer than last crate engine I got) .

Now till the compression test I thought the ring may be bad .

Enlighten me guys. Worn rings allowing blow by when hot? Gasket issue?

Thanks ahead of time.

 

[surewhynot]

Maybe a head gasket blowing compression into an oil passage?

 

[Lost]

I wondered that .Just got email 1/2 hour ago . Get up to see this weekend.

 

[Skandocious]

Jeez thats weird... What about the valve seals?

 

[blacksnapon]

squirt some oil into the spark plug hole, then check compression. If theres a big difference, bad rings/piston. You can use the air adapter for replacing valve seals....apply air.....listen for where the air is coming out (tailpipe/oil cap/intake)

 

[Bob Ayers]

Maybe a head gasket blowing compression into an oil passage?

A blown head gasket should show up on the compression test.

 

[Psquare75]

Is the PCV hooked up properly as well as the breather cap on the other valve cover?

also, if the carb was rebuilt, who is to say it was done 'right'?

 

[surewhynot]

A blown head gasket should show up on the compression test.

Good catch Bob. I didn't think about that.

 

[Lost]

Is the PCV hooked up properly as well as the breather cap on the other valve cover?

also, if the carb was rebuilt, who is to say it was done 'right'?

yea i dont have luck with rebuilds . But never had push out dip stick .

 

[Lost]

squirt some oil into the spark plug hole, then check compression. If theres a big difference, bad rings/piston. You can use the air adapter for replacing valve seals....apply air.....listen for where the air is coming out (tailpipe/oil cap/intake)

You one smart cookie . I'll tell him.

 

[flareside_thunder]

Did he play with the mixture screws on the carb to try and lean it out?Sorry just thinkin this out from first to last......I've never seen a rebuilt carb that was exactly in tune when you got it back.....