Best Way to Get the Carbon Build-up Out of My Engine?

It's been eating away at me since I rebuilt the carb and saw exactly what the intake looked like. Pure black, and thick hard carbon pretty much all over. Definitely not doing myself any favours running like that, but I just haven't got around to it. So the questions are:

1. Is this something seafoam/water can solve or will I have to take apart the top end a bit and get to chiseling?

2. Is the water trick real? It makes sense, but goes against some primal notion to not put water anywhere near my intake.

Any input would be appreciated. Thanks!

 

The cheapest way that always helps is to reload a Windex bottle with water and at about 2000 rpm spray enough mist into the Carb to start to drop the rpm some.

While Seafoam does work what I have seen with the stuff is it loads up the ring grooves with crap and that starts off a whole other issue!

 

The best trick is to rebuild / overhaul the engine. If there is carbon build up in the intake manifold then it's probably all caked up in the heads, under the valve covers and in the combustion chambers, too. I had / have an engine that had lots of carbon and it turned out to have a broken piston. The rings were frozen in the lands and I'd guess the thing smoked like crazy. The valve seals were non - existent.

 

Easy solution,
BG44K
Cleans while driving.
Cleans slowly so you have no worries about big chunks breaking off.
Go to BGProducts website for more info.
Been using this for 30+ years with no problems & seeing the results with my own eyes.
Regular customers cars have NEVER had to replace an injector because of "fouling" or clogging with debris.

Tom T.

 

I’ve used Seafoam and water to good effect, mostly on fuel injected engines, but a few carbureted smogger engines. Don’t expect miracles, it only really cleans out partially fouled combustion chambers and areas around the valves, any really built up gunk in the runners will still be there. You will need to take it for a good highway run at higher rpm’s afterwards to expel the loosened bits so they just don’t reattach themselves to the chambers and ring lands.

I used it mainly on cars that have done a lot of city driving and idling. At work it was Military Police Crown Vic’s, they drove around small postage stamp sized areas and rarely get driven hard. I’d do the Seafoam and take it off base for an hour long highway trip. It’s sort of like a chemically enhanced Italian Tune Up.

 

I was thinking the same thing.
If you have any carbon build up in your intake it’s not normal.
Inside the intake should be raw iron or aluminum depending on what you have, and slightly damp with fuel, that’s it.
Sounds like you have leaky intake valves allowing exhaust into the intake manifold, or there’s something screwed up in the exhaust crossing passage.

 

I used Marvel Mystery Oil in a high mileage 327 Chevy. Poured some right down the carburetor while running initially. What a cloud of smoke! I am sure the neighbors were thrilled. Then added it to the fuel and drove the car a couple thousand miles. The motor was just plain wore out, but when I tore it down, the combustion chambers, piston tops, and intake tract were clean and free of carbon. Looked like it had been recently rebuilt from that stand point.

 

I was sort of anticipating this given the amount of build-up. Pulling everything down to the heads and cleaning/replacing what needs attention then?

 

Is this for the car on your avatar?
‘76 Riv w/455?
That’s as far as you should have to go tear down wise.
Have the heads done.

 

Saw this at a shop once - Old School - rice. Dump some down the carb with the idle about 1200. Chunks of carbon coming out the exhaust. Don't know if it ran better, but it did have a nice smell...

 

'75 yeah. I'm hoping I won't have to put too much money into the heads but we'll see what it's like. Thanks for the reply I'll update this thread with some pictures once I dig in.

 

Any engine with PCV or EGR is going to have icky stuff in the intake manifold. A '75 will have both. Some "icky stuff" is normal, and of no concern.

The AMOUNT of icky stuff could be cause for concern. Reversion from a leaking intake valve can make this much worse. A PCV system that is sucking oil because of a failed PCV valve, or excessive blow-by will make it worse. An EGR problem that could make this worse, would also make the engine run poorly. You'd be complaining about misfire and stalling, not crap in the intake manifold.

Consider a cranking compression test, and perhaps a cylinder leak-down test to rule out valve leakage. Verify the PCV system is in good condition, and there's no oil in the hose to the carb.





Water-down-the-carb does wonders for steam-cleaning the combustion chambers. I would not expect liquid water to do anything at all in terms of cleaning the intake manifold. And it doesn't "smoke", so the neighbors don't call the Fire Department. I jack the engine RPM up to 2000 or even a little higher. Then pour a "urine stream" of water, alternating between the two primary venturis. If the engine RPM drops too much...reduce the water stream. I use a gallon or more of water. Probably want to change oil afterward, as it'll have moisture in it.

If you want to clean the manifold, you'll need a petroleum solvent of some kind. Seafoam has an aerosol product with a gigantically-long "straw" that allows you to direct the spray. Overall, I wasn't that thrilled with Seafoam BEFORE they silently and sneakily changed the formula.


GM Top Engine Cleaner used to be a good product. I don't know that it's the same formula now--the EPA may have gotten to them. But that's a "pour it down the carb" deal, and it'll smoke enough that the neighbors will be peeved.

I would do testing and exhaust all the possibilities BEFORE I started disassembling things.

 

I prefer Berrymans over Seafoam as no smoke and it does clean well. It’s really fast acetone per the material description sheet.

 

Good call. I'll see about a compression test tomorrow and maybe I'll pop the carb off to give you guys an idea of the buildup. From what I can remember it was pretty gnarly. Car runs fine though, no misfires, no rough idling and no stalling. Main reason I'm taking a look into the top end is because I know there's build-up and there seems to be some kind of slight knocking noise (yikes) only when the car warms up which is leading me to wonder about a combustion issue. I would love to be able to get away with not having to pull the whole thing apart so one step at a time here. Suppose I probably could have mentioned that to begin with

 

I’d think he’d be burning oil pretty bad.

 

It surprises myself that no ones mentioned the BG44K I mentioned.
ALL GOOD & NO BAD.

Tom T.

 

https://public.spheracloud.net/images/ledger/icons/icoSDS_Large_EN.gif
SDS says:
Naphtha (petroleum), hydrotreated heavy 15-40 64742-48-9
Distillates (petroleum), hydrotreated light 15-40 64742-47-8
Solvent naphtha (petroleum), heavy arom. 10-30 64742-94-5
1,2,4-trimethylbenzene 1-5 95-63-6
naphthalene 0.1-1.0 91-20-3

Probably a very decent solvent. Don't get it on your skin, eyes, or breathe the vapors. Don't drink it. The SDS is worryingly vague about the effects of short- or long-term exposure.

I'm pretty fond of Chevron Techron Complete Fuel System Cleaner. A bottle in the gas tank at every oil change for my vehicles. And, of course, buying Top Tier fuel whenever possible. Neither is going to do anything for intake manifold deposits on "Port" fuel injected vehicles, but downstream of the injector--cylinder head ports, intake valve, combustion chamber--should be reasonably cleaned.

 

I'm familiar with the BG product, however, if the extent of the carbon build up is as the OP says then pouring money down the carb seems like wishful thinking to me. As posted previously, he should do wet/ dry compression test, leak down and vac test. It's not like he will chemically remove all the carbon and the root problem will be gone, too. Spend the money on some gaskets and get those parts into a hot tank.

 

Alright here are the results from today.

Here's a video of that knocking sound (car is warmed up as the noise doesn't happen at all cold), starting underneath the passenger side and making our way over to underneath the drivers side with a scenic view of the engine. Please excuse the cinematography



I found some oil when I pulled the vacuum line off the PCV valve, and there was also some around the outside of the vacuum line where it connects. Seems like a replacement is in order.

I also did a wet/dry compression test. Injected each cylinder with ~5ml of 15w-40 through a syringe, so quantity shouldn't be throwing off any readings.

Dry:
1: 135 2: 125
3: 120 4: 115
5: 125 6: 130
7: 130 8: 130

Wet:
1: 160 2: 130
3: 140 4: 125
5: 140 6: 145
7: 140 8: 135

Now the readings seem pretty uniform to me, except for a couple anomalies such as cyl 1 wet and cyl 4 dry. With all cylinders but 4 the psi initially shot to around 90 then settled at their reading by the 5th crank. Cyl 4 took about 3 puffs to get past 90. I'm not sure what would be an expected pressure for this engine at this age. The service manual I have tells me compression is satisfactory since there aren't any readings below 70% of the highest one. I trust that you guys would be able to interpret the data better than I can.

I have to say I've never truly appreciated the amount of compression that goes on inside an engine, even in mine which belongs to a model year known for low compression. That all changed tonight as I ducked behind my fender to try and shield myself from the clouds of atomized residual 15w-40 shooting out of the spark plug holes. My first time doing a wet compression check might I add. I guess if you don't have oil on you somewhere, did you really do any work on your car?