Decarbonizing an engine
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Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
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From: Hesperia, CA
Decarbonizing an engine
I rebuilt the engine on my 77F250 460 C6. (Valves, rings, bearings, cam, roller lifters, double roller timing chain, etc.)
After 15K I decided that the engine needed better breathing so I pulled the heads and installed Manley oversized S/S valves, hard seats, porting, polishing, etc.
What surprised me was the amount of crud on the old valves after only 15K. I know they were clean when I put the engine back together because I polished them my self. I talked to the machine shop about this and they said it was the crud gas you get now days.
The thought of that crud building up on my new valves really bothers me. Does anybody have any surefire way of keeping the valves clean?
Years ago we used to run Risoline through the carb at about 1500 RPM. The blue smoke poured out of the exhaust pipe while you were doing it. I suppose you would get arrested for air pollution if you tried this now days. I have seen people run water through the carb in the same way to clean out the carbon.
Does anybody have any suggestions? Gary
After 15K I decided that the engine needed better breathing so I pulled the heads and installed Manley oversized S/S valves, hard seats, porting, polishing, etc.
What surprised me was the amount of crud on the old valves after only 15K. I know they were clean when I put the engine back together because I polished them my self. I talked to the machine shop about this and they said it was the crud gas you get now days.
The thought of that crud building up on my new valves really bothers me. Does anybody have any surefire way of keeping the valves clean?
Years ago we used to run Risoline through the carb at about 1500 RPM. The blue smoke poured out of the exhaust pipe while you were doing it. I suppose you would get arrested for air pollution if you tried this now days. I have seen people run water through the carb in the same way to clean out the carbon.
Does anybody have any suggestions? Gary
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i heard one good way is to let it suck steam while running,or water mist from a spray bottle,,i took apart a efi 460 that i purchased from the local junkyard,found extreme carbon in the chambers,couldn't beleive how much it had.wonder how these new fuels made from corn are going to effect the older engines,i heard ethanol fuels promotes engine wear,
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From: Idabel, OK
Try Seafoam or GM Topend Cleaner. I think they are both about the same product and have similar directions. The Seafoam you can get at most auto parts stores and the GM stuff at the GM dealerships. The Seafoam is a little cheaper I think.
You can put some in the gas tank or allow it to be sucked in through a vacuum line. I usually use the brake booster hose. I put it in as fast as possible without killing the engine, once the bottle is empty, turn off the engine and let it set for several hours or over night. When you drive it the next time, be aware, there will be lots of smoke, especially if there is lots of build up in the engine.
I have heard great reviews of both these products, time and time again.
You can put some in the gas tank or allow it to be sucked in through a vacuum line. I usually use the brake booster hose. I put it in as fast as possible without killing the engine, once the bottle is empty, turn off the engine and let it set for several hours or over night. When you drive it the next time, be aware, there will be lots of smoke, especially if there is lots of build up in the engine.
I have heard great reviews of both these products, time and time again.
Postmaster
Joined: Nov 2001
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From: Escondido, CA
When I pulled my engine apart after 2000 miles the valves were all carbon covered as well. After I cleaned them off again and rebuilt the engine I found my choke set wrong and was dumping fuel in the engine. That maybe a reason that it is doing it.
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Fleet Mechanic
Joined: Mar 2004
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From: Hesperia, CA
Thanks for all of the suggestions guys, but to stngh8r if you put it through the brake booster line on a 460 it will only go into the #4 & #7 cylinders. That is, if you have the factory manifold. I don't know about any of the aftermarket performer manifolds. 
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From: Idabel, OK
oops
hmmm? well, guess I only cleaned a few cylinders then. That is how I have always heard of everyone doing it, including some friends of mine who are techs, but I suppose I could see how that it might would only get to a couple of cylinders.
What would be the best way to get it to all the cylinders? Through the throttle body?
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From: Rome, GA
Take the breather off and use a spray bottle with water. Pull engine up to about 2000-2500 and mist it into the opening. Will run very rough for a short time. I have seen this done numerous times on carbed engines, should work through a throttle body as well.
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From: Rome, GA
I have always seen it just sprayed in a few times you dont want to run enough through to kill the engine. You just want the water to turn to steam in the combustion chamber. I wouldnt spray it more than a few times letting the engine return to normal running between sprays. The steam is what I was told knocks off the carbon build up. They also make some fuel additives that is supposed to keep carbon from building.
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Fleet Mechanic
Joined: Mar 2004
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From: Hesperia, CA
Originally Posted by stngh8r
hmmm? well, guess I only cleaned a few cylinders then. That is how I have always heard of everyone doing it, including some friends of mine who are techs, but I suppose I could see how that it might would only get to a couple of cylinders.
What would be the best way to get it to all the cylinders? Through the throttle body?
Look on the top of your manifold and see if you can see a ridge from the rear of the manifold where the booster fitting enters the manifold going to the #4 & #7 cylinders. This ridge is very prominent and easy to follow to the intakes on the #4 & #7 cylinders. If it is there then it is the same as the carbed 460.
Again, thanks to everybody for their ideas and suggestions. The thought of all of that gunk building up on my fancy new vales is very disturbing.
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