304 Engine rebuild? Coolant leak? Manifold Smoke

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yearntolearn

Member
Hi ALL!
I have a 1969 304. It sat for about 40 years. 28k on the vehicle. COUPLE ISSUES HERE I THINK. I got the engine running on its own fuel pump and am in the process of trying to clean the cooling system. Ive reverse cleaned it with about 20 gallons of water and then put coolant flush in the engine to help cycle it through. I am still filtering the coolant before putting it back in my rebuilt radiator but what Im afraid of is the constant smoke. I thought this would go away by now after burning off any old oil etc on the manifold but it has not. The engine sounds good and runs without hesitation (maybe a little high on idle) but no metal on metal sounds its just the smoke that is worrisome. Its not black smoke so I guess it could be a grey/blue color. Its hard to tell. My thought/Questions are these:
  • Could this be coolant getting into the engine and causing steam?
  • Can this cause severe damage if I keep running it to clean the coolant system? Coolant still coming out brown as if being burnt
  • Which part of the motor would I have to rebuild? Can that be done in the engine bay?
  • In your opinion should this motor be rebuilt entirely after sitting so long anyway? Do you know a rough cost of that in 2021?
  • I replaced the radiator hoses and installed a new 180 degree thermostat from IH parts but the coolant temperature on exit is only 145-150 degrees. (Yes I saw the "This Side Radiator" indicating which way to install it). In fact, when filling up radiator, my discharge setup will start dripping that coolant (slowly at this point) but I was under the impression that it is closed off until the thermostat opens at operating temp?
  • I will also mention that the oil has a slight gas smell to it. Carb has not been rebuilt but seems to operate well. I do need to change the mount gasket tho.
  • The hot exhaust tube going to the auto choke also broke off. And geeez I cannot get the damn plug out....Please help! Im 35 and mechanical inclined. I have a manual and do my work in sections. It just comes down to not having experience. Any thoughts help.
 
Most common thing is leaking valve cover gaskets. Search the forum and you will find great info on how to r&r the valve covers.
 
Yeah I changed those out and used copper gasket to seal them in place. I was thinking header gaskets next but was also wondering if it could be leaking by way of anything else? Are changing header gaskets are a feasible thing to do with the engine still in the bay?
 
This is what they looked like previous to changing the cover gaskets
 

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yearntolearn said:
This is what they looked like previous to changing the cover gaskets
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Where is the smoke coming from, the tail pipe or up off of the engine?

The inside of the engine is super clean, doubt there is a serious issue inside if all is quiet and smooth.

Header gaskets will make a racket if they are leaking at all. They won't cause smoking.

From these photos, the valve cover gaskets were toast and leakage can be seen above the exhaust manifolds.. Paralleling FDChappie, that will need some good driving to burn off.
 
Well its nice to hear the inside of the engine looks good! The smoke is mainly coming off the exhaust manifold on the engine but some other locations that I can't really locate as well. No smoke coming off of the valve cover itself. So you don't think its possible that the coolant could be escaping through a dry header gasket? and this is just 30 years of oil and elements that are on the exhaust? Any thoughts on the thermostat expelling coolant before 180 degrees?
 
yearntolearn said:
Well its nice to hear the inside of the engine looks good! The smoke is mainly coming off the exhaust manifold on the engine but some other locations that I can't really locate as well. No smoke coming off of the valve cover itself. So you don't think its possible that the coolant could be escaping through a dry header gasket? and this is just 30 years of oil and elements that are on the exhaust? Any thoughts on the thermostat expelling coolant before 180 degrees?
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Anything that was leaking from an exhaust manifold gasket would also be billowing from the tail pipe. There is no coolant that is retained by the exhaust manifold gaskets. The only thing inside the exhaust manifold is exhaust, not coolant.

Coolant is not expelled from the engine at 180 or the thermostat opening temperature, it begins to circulate through the radiator so that it might cool before returning to the engine..

Do you have any coolant on the ground after running?
 
Ok, so then the water pump and thermostat are operating as they should then. Thanks.

To clarify, yes I realize coolant is not retained in the exhaust manifold. What I’m meaning to ask is IF the head gasket (not exhaust manifold) is shot. Would that not provide a means for coolant to escape where it should not be and turn to vapor? There is no sign of coolant leakage on the floor, no.
 
Yes, in the case of a head gasket leak. Water entering the combustion chamber would be exhausted out the exhaust and out the tail pipe. Possible you could see it at a manifold gasket leak but much more visible out the tail pipe.
 
Got it. Ok. I’ll check plugs and see about water vapor at tail pipe and report back. Currently my coolant discharge goes into a filter/5 gal bucket and not immediately back into the radiator to avoid clogging the newly rebuilt radiator. After I filter the coolant I pour it into the radiator as the level drops. So its not an accuraste gauge of coolant loss.
 
Here are a couple pictures of what the plugs looked like. Im not sure exactly what the sludgy stuff is on the one plug but it smelt a little sweet to me.
 

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Thanks for looking into this all with me. I appreciate your time.
I have a few things to work on coming from IHparts. I’ll check back in after I’ve installed for an update of how it’s running then.
 
Currently my coolant discharge goes into a filter/5 gal bucket and not immediately back into the radiator to avoid clogging the newly rebuilt radiator.
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That's a little dicey. You can risk starving the engine leading to hot spots, particularly the rear of the heads.

Cooling systems are closed loop and the pump needs a head or pressure to pump against as well as a return from the radiator or block depending on the thermostat's position to keep adequate flow

A better method is to install a filter in a heater supply line. I've done this and it works great with little mess and the only extra coolant needed was to replace what the filter soaked up.

I used a whole house cartridge style water filter and there was enough hose from the heater to neatly place it in the engine bay out of the way of belts and just needed extra hose to connect the filter to the manifold outlet. We can call this a bypass filtration set up.

Now the concern of temperature rating of the filter housing is based on it's rated operating pressure for a house. I'm not going to be there as the radiator cap is off and 180 or 200*F water temp won't hurt the filter housing or media at no pressure. Once it's set up and the engine is running it only takes about 20 minutes of fast idle to clear up the coolant and even the rust flour is gone depending on the micron rating of the filter. If you got the big chunks out before putting the radiator in, this will take of the finer stuff. Nothing like fresh green crystal clear coolant and hopefully a good flush of the heater core as well.

Here's a picture of the style of filter I used. I can't remember if I got mine at Home Depot or Walmart but no more than $30-35 and with some barb fittings it was good to gohttps://www.homedepot.com/p/DuPont-Standard-Whole-House-Water-Filtration-System-WFPF13003B/203444288

When done, take it out and rehook up the heater hose.
 
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I would not be "filtering" coolant.

Pick up a "Flush and Fill" kit. Prestone sells 'em, as do some off-brands. Then drain the contaminated anti-freeze including what's trapped in the block, so it can be properly disposed-of, instead of going down the nearest storm drain and into your local river.

Mind you, I'm not thrilled with the supplied hose clamps. I've learned to not like unshielded "worm-gear" clamps; the rubber hose they're holding tends to extrude through the little slots over time. I suggest you find shielded clamps, or a different style of clamp--OEM spring clamps work nicely.

Install the inlet tee in the heater core outlet hose. Pop the outlet nozzle into the radiator fill. Connect to your garden hose to the tee with the included adapter, and open the faucet. Start the engine, I generally run it at fast idle, with occasional bursts to higher RPM--you're using water-pump surge to "scrub" the rust out of the water jackets. Once the water shooting out of the outlet nozzle is clear, pinch off the heater hose on the engine side of the inlet tee you just installed, you'll back-flush the heater core in addition to flushing the engine.

Getting rid of "brown" coolant (it's not burnt, it's rusty) will go ten times faster if you locate and remove the BLOCK DRAIN PLUGS, which you'll also need to remove in order to drain the anti-freeze. The originals are probably steel or iron. Nice upgrade is to replace them with brass draincocks that can be opened or closed with a few flips of the wrist.

When the flush water spraying out of the exit nozzle on the radiator is clean enough for you, shut off the engine, stop the water flow from the garden hose and disconnect it and the adapter from the flush tee. Pull the block drain plugs, or open the draincocks including the draincock on the radiator. When the flush water has drained out, cap the flush tee, install the block drain plugs or close the draincocks, pour in the proper amount of anti-freeze, add distilled water as needed...you should be done.

Wouldn't hurt to verify that the rad cap holds pressure, and to inspect all hoses for deterioration. If they're old...this is the time to replace 'em.

Remember, all that rust that's contaminating your coolant, used to be part of your engine. While the cast-iron of the engine block can sacrifice some surface iron, deep pitting of the cylinder barrels, or excessive loss from the "wet" side of the core plugs can lead to leakage.
 
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