1970 Road runner 383 intake Black biuld up (to rebuild or not rebuild)???

[Jimclo2002]

I'm deciding if to rebuild a 1970 Road runner 383 motor. The motor sat for 5 years as the owner before me states. I removed the intake and this is what I had found. (see 2 photos) Two ports are almost closed with this black build up. What would cause this?
Looking inside the engine at cam, lifters push rods. The engine looks pretty clean. No sludge. Valve covers inside are pretty much free of sludge.
Prior to pulling the plugs to see they look. I was able move the crank very little bit.
There was also a freeze plug missing and a another freeze plug port had a repair plug in it.
I pulled the spark plugs and they looked pretty good (see photo) How to proceed??

 

[Banzaiii67]

That is heat cross over for the intake, I would guess the carb is pretty junked up as well ?? One thought is the p.o. left gas in the tank, let it sit for years and and ethanol in the gas junked everything up or the intake gasket wasn't sealed very well and oil was in the bathtub tray and found the path of less resistance.

 

[bigmanjbmopar]

Yep cross over gunk, and when you say slug do you mean sludge? lol Was thinking man if I founds slugs in my motor it was from a gun fight. :tongueflap:

Looks like your disciplining that heat port with your finger lmao bad gunk bad

 

[lewtot184]

somewhat typical of a high mileage engine with a very poor tune. look like last century's spark plugs.

 

[Jimclo2002]

What is cross over gunk on the intake? Yes the engine sat years. What concerns me is the missing freeze plug

 

[bigmanjbmopar]

That's the gunk you bring over with you when you switch from chevy to mopar lmao.... heat chamber part of the manifold used to bring warm air of the exhaust looks like **** load of gunk in the chamber from years of non maintenance.

 

[mopar 3 B]

Would not even both to clean that port except to reduce weight. I block it off. Do not need extra heat in the intake.

 

[Meep-Meep]

As mentioned, not uncommon on high mileage engines to have this plugged up. These days I'd sand it flat and run the valley pan gasket without the holes. The modern fuel when used in a carb doesn't like excessive heat anyway.

But if you must clean it, one method I heard is to heat the carbon with a torch then shut it off and open just the oxygen while bring the tip right in proximity to the carbon build up. The desired result is for the O2 to react with the hot carbon to burn itself out of the passage. I never tried this myself and would exercise caution if attempting it. Possibly a big flare up that can burn your arm, etc.. The addition of an oxidizer reduces the amount of heat required to ignite the fuel (in this case carbon) so expect smoke and fire.

Here is what to expect when pouring liquid oxygen onto a BBQ and the danger possibility.
https://www.youtube.com/watch?v=UjPxDOEdsX8

Just the heat of the impact, which isn't much in the ordinary sense, is quite impressive in the presence of O2
https://www.youtube.com/watch?v=zFyqilT0ld0

 

[coloradodave]

What is cross over gunk on the intake? Yes the engine sat years. What concerns me is the missing freeze plug

Carbon build up is fairly normal for a high mileage engine. I would be concerned about the freeze plug missing and one hole having a repair plug in it. Could be that water was left in the motor and froze, popping the plugs out and maybe causing a crack somewhere. Only way to find out is to have the block tanked, inspected and magnafluxed.

 

[r/t se]

amen brother, knock it down flat and block it off with valley gasket that does not have holes in that area.

 

[monaco66coupe]

Every Mopar I have ever had has that carbon buildup. from 1960 thru 1969. small block, big block, there is no difference. The cars ran rich to warm up fast, and the side effect was the carbon buildup. It is a consequence of low voltage output, and rich settings to keep the engine running. If you block it off, find a new choke setup.

 

[rscurtis]

I wouldn't block that heat passage on a street-driven car. It will act as if the accelerating pump is not working. The easiest way to clean it is to block the outlet of the RH manifold and take the car for a short drive. When the blue smoke stops, the passage is clean. Your choke will also work better.