Mid Throttle Lean Condition

[Rick Stephens]

what does your compression look like on all 4 cylinders?

Scott,

His compression numbers all look great. All 4 holes between 150 and 165. Personally I don't think his needle wag on the vac gauge is anything but valve guides on a 30 year old motor. Being on the low end of normal is more worrisome when combined with lean mid range with brand new OEM carb, new ignition, clean fuel system. I would be thinking about an intake exam only 'cause I can't think of anything else.

Rick

 

[Bondo]

I would be thinking about an intake exam only 'cause I can't think of anything else.

Seems it's been mentioned before, But,....
With the motor idlin', 'n sprayin' ether at any suspect areas of the intake, if it don't Rev up when ya hit the leak,.....
There ain't no leak,.....

As for the carb, brand new don't mean much,....

 

[Goldie627]

I rebuilt my old carb 3 times, though with the same kit, big coincidence that the old rebuilt carb and the new oem carb does the same thing.

Is it a good idea to raise the float level above spec?

 

[Goldie627]

Accidental post

 

[Scott Danforth]

Try this, plumb the fuel pump to a temporary outboard fuel tank.

As Bondo stated, new doesnt mean good for carbs

 

[Goldie627]

Try this, plumb the fuel pump to a temporary outboard fuel tank.

As Bondo stated, new doesnt mean good for carbs

I tried bypassing the gas tank with a gas jug that had fresh chevron supreme. No change.

The oem carb was definitely new, never been ran, gets two strong streams of gas from the accelerator pump, I'm not sure how it could have any blockages, unless I'm the most unlucky guy in the forum...

any other sugestions?

 

[Rick Stephens]

Seems it's been mentioned before, But,....
With the motor idlin', 'n sprayin' ether at any suspect areas of the intake, if it don't Rev up when ya hit the leak,.....
There ain't no leak,.....

As for the carb, brand new don't mean much,....

Bondo, is it possible to have an internal crack on a 3.0L manifold? Goldie has sprayed so many times looking for an external leak, he's most confident that isn't the issue. My thought was maybe an internal crack could cause this behavior and he is getting exhaust gases into the intake? Plausible, I don't know? I sure haven't ever seen or heard of that, but his engine sure acts like it has an intake leak.

 

[fishrdan]

I wouldn't put much into the wagging and slightly low vacuum, since the 3.0L engines run kind of rough anyway.

is it possible to have an internal crack on a 3.0L manifold?

Yes, I had one, middle exhaust to the water jacket.

Could be an internal manifold gasket blown, intake-exhaust, doubtful though

 

[Goldie627]

I found an external intake leak!!! :facepalm: eace:

I kept going over everything in my mind, I could barely sleep, thinking about this all day every day, I couldn't let it go. I was obsessing over this. I got up early today so I could go to the boat before work. On the way I bought 2 fresh cans of starting fluid and also remembered my flashlight. I sprayed that durn intake 1 inch at a time. Spray, wait... spray, wait... spray, wait... then finally I found it!!! arty: It was way in the back, in between the valve cover and the exhaust elbow, under the water hose!!! Kinda on the corner where it slopes downward. The only way to consistently repeat it is to really get back there and move the water hose up and over out of the way, then spray the can pointing towards the bow. Its not a big leak, but apparently its enough to cause my problem. I'm so embarrassed because I've checked that intake at least 6 different times and missed it everytime :facepalm: :faint2:

Rick, you were on the right track all along thinking intake.

Thank you Rick, Bondo, Scott, Dan and everybody who helped out, I appreciate you all.

I'm going to snatch the motor out and do all the repairs at the same time.

• test intake manifold with acetone
• install intake gasket
• install oil pan gasket
• install valve cover gasket (this time not kork)
• install rear main seal (preventive maintenance, i'll be right there anyway)

To do list:

1. paint the motor while its out and apart
2. re-gelcoat the bilge as needed, if I can't clean it the way I like it to look
3. fill all the holes in the bilge that were left from moving the doghouse shocks around
4. screw down the bilge pump while the motor is out

Any tips while I have the motor out?
Anything I should check while its apart?
Should I be concerned about the valve guides?
Should I replace the front and rear end cap gaskets on the intake manifold?

 

[Goldie627]

I solved the pulley noise. It was coming from the belt. I sprayed a dab of starting fluid on the belt and the pulley noise stopped immediately, but came right back. I remember hearing that rubbing bar soap on a belt will quiet it down, I may give that a shot...

 

[Bondo]

I remember hearing that rubbing bar soap on a belt with quiet it down, I may give that a shot...

Ayuh,.... It's Gotta be Lava hand soap, or it won't work,....

Lava hand soap has pumice grit in it,...

 

[Goldie627]

Ayuh,.... It's Gotta be Lava hand soap, or it won't work,....

Lava hand soap has pumice grit in it,...

thanks bondo, ill pick some up and give it a try, wallyworld carries it

 

[Goldie627]

When I do the intake manifold gasket, should I do the end cap gaskets at the same time?

 

[Goldie627]

I'm going fishing 2maro, weather is aroumd 40 degrees. Im going to warm the engine till its room temperature. Then will lay down some RTV over the section of the intake where i found the leak. Then when it starts to skin up ill discontect a spark plug wire and bump the motor for about 2 minutes. I don't wanna suck all my RTV through the leak. I don't think I have anything to worry about as my leak is not big at all. I think its just big enough to through off my air fuel mixture.

as for now I'm just waiting on my gaskets and debating whether or not to pull the head.

 

[Goldie627]

Yikes! I forgot to pickup that lava soap, definetly going to Wal-Mart tonight

 

[Bondo]

When I do the intake manifold gasket, should I do the end cap gaskets at the same time?

Ayuh,.... Whatever ya want,....

The end caps are holdin' back water,...
Nothin' to do with the intake side of things,...