Intake plenum gaskets

[potent rodent]

find youself an older mech that worked on real engines

 

[Grit dog]

In keeping with the original question while you get help diagnosing the actual issue(s) which sound 90% carb related, it does not sound like your intake manifold gasket(s) are the problem.
If it was leaking oil out the front or back, eating coolant or had a vacuum leak (this one is still possible and could be part of your issue although if the engine smooths out, ever, then it most likely has no vacuum leaks at the intake or other areas.

 

[Grit dog]

Sounds like @Catbox kid could have a side job here. Pretty sure Maxwellvis knows more about Chebbie motors than this persons parts replacer. Seriously.
@yellowdog5 if youre anywhere within range of Portland this guys kid can fix your minor issues.

 

[85K304SPD]

Yes, take the carburetor off of the truck before taking it apart. Take a few pictures of the linkages and get a magnet to catch the clips and screws when you take them out.

 

[Catbox]

Sounds like @Catbox kid could have a side job here. Pretty sure Maxwellvis knows more about Chebbie motors than this persons parts replacer. Seriously.
@yellowdog5 if youre anywhere within range of Porthole (Portland) this guys kid can fix your minor issues.

If hay is in the equation, I am not sure how close Faith is to us here outside of Portland.

But yeah, watch YouTube videos and have at it.
That is what the boy does and our truck seems to run like a champ.

 

[yellowdog5]

find youself an older mech that worked on real engines

Not using that mechanic, already tried another, think I have to fix it myself.

 

[yellowdog5]

Yes, take the carburetor off of the truck before taking it apart. Take a few pictures of the linkages and get a magnet to catch the clips and screws when you take them out.

Will I need a new gasket between the carburetor and the intake manifold?

 

[yellowdog5]

In keeping with the original question while you get help diagnosing the actual issue(s) which sound 90% carb related, it does not sound like your intake manifold gasket(s) are the problem.
If it was leaking oil out the front or back, eating coolant or had a vacuum leak (this one is still possible and could be part of your issue although if the engine smooths out, ever, then it most likely has no vacuum leaks at the intake or other areas.

It does smooth out at about 40mph on fairly flat ground, would this indicate probably no vacuum leaks?

 

[85K304SPD]

You may need a new gasket. A new gasket is always better, but if the one that is on there isn't torn or damaged it may work fine.

 

[mucanuc01]

It's really not the hardest job. Clean good, mark the distributor location / rotor , and clean some more. Nice lines of GOOD sealer front and back, and gently replace the intake. Calling it a plenum is trying to sound intelligent. Problem is, ours DON'T have them.

 

[mucanuc01]

And don't reuse the gaskets . Spray brake cleaner in small bursts around the area where the manifold meets the block when it's running. If it gets higher rpms, it's leaking.

 

[85K304SPD]

They are going to work on the carburetor now. Not going to change the intake gaskets. We were discussing reusing the carburetor base gasket.
Just to clarify @mucanuc01

 

[yellowdog5]

It's really not the hardest job. Clean good, mark the distributor location / rotor , and clean some more. Nice lines of GOOD sealer front and back, and gently replace the intake. Calling it a plenum is trying to sound intelligent. Problem is, ours DON'T have them.

Good sealer like Ultra black?

 

[yellowdog5]

I just want to say, many thanks for all the good advice, I think I'll be able to fix it mysef, gonna try anyway.

 

[Bextreme04]

I just want to say, many thanks for all the good advice, I think I'll be able to fix it mysef, gonna try anyway.

You will need a new base gasket for the carb. They are cheap and available at the local parts store, Fel-Pro 60249 is the correct one for a 79' 400 quadrajet. https://www.oreillyauto.com/detail/...ive-truck-1979-chevrolet-k20-pickup-4wd?pos=0

Do not use silicone, they were talking about that for the front and back of the china wall if you replace the intake manifold gaskets. I would highly recommend removing the carb to work on it. Its just four 1/2" bolts, one on each corner and a jesus clip for the throttle. You'll also need to remove vacuum and fuel lines and the 5/8" hard line in the back to the brake vacuum booster. I can usually pull mine in ~5 minutes or less, but it has had everything on and off enough times that nothing is stuck.

The biggest issue you will have is that you MUST NOT tighten the bolts down too much when you reinstall the carburetor. If the hold down bolts are cranked down it will warp the airhorn and you'll have internal air leakage.