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Carb/Injection and Carbon removal

Started by kevinanderson, September 08, 2016, 04:45:16 PM

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kevinanderson

Does anyone here run any additive to help remove carbon deposits in their older low mileage cars? I started my '76 CDV up after a 3 month slumber. After spinning the engine over until the  oil light went out, I hit the gas to set the choke and it started right up as usual. After about 45 seconds it started to hammer in the 5-7 cylinder area. Sounded like a cracked ring/piston, wrist pin or rod. Deep knock.  I shut it down and restarted it. Same thing. Didn't rap on opening the throttle but did upon returning to idle. Shut it down again. Repeated it self again upon restart the 3rd time. Well, drove it onto the trailer which required decent rpm's to pull onto. Upon unloading, nothing. quiet as always. I'm hoping it was carbon and blew itself out while running up the ramps. Almost afraid to restart it now. The car has 50k miles, about 8k put on by me. The original owner used it to run between Kansas City and Omaha to ball games. Oil and filter changes every 2k miles by me. Oil is always clean and full. Always use 91 premium unleaded fuel. Bought a can of Seafoam to stick in the tank and going to change oil, which has about 1k miles on it. Opinions on additives? Overhaul in the works?  What do you guys do/use in your original low mile cars?
Kevin

Dave Shepherd

We used tp use GM top engine cleaner, poured into the carb per instructions, must be done correctly not to hydro-lock the engine.

SixDucks

Hi Kevin,

I believe a deeper investigation is required here. It is unlikely that carbon build-up is causing this. I base this on your description of the knock appearing after 45 seconds of run time. You may have a rocker arm loose, or a flexplate bolt loose. A loose flexplate bolt can sound nearly identical to a rod knock.
As far as additives go, water works great but the RPMS need kept up to prevent hydro-lock. I would caution against any additives poured down the carburetor as the discharge may contaminate or clog the catalytic converter.

Terry
Current:
1941 coupe
1962 Fleetwood
1988 Brougham
Previous:
1956 Series 62 Sedan
1963 Fleetwood
1975 Fleetwood Brougham D'Elegance
1989 Brougham