Valves / top of piston color & carbon deposits

[Gary K.]

Pulling heads on '73 454ci and I see orangy-tan on a couple cylinders which I believe is pretty normal after +/-50k miles. Next cylinder getting blackened, then last chamber (#1 cylinder) exhaust valve caked w/carbon and top of piston is black and oily. Piston tops themselves look in good condition just the color / coating variations. Head gasket looked fine and no corrosion or issues on any of the surfaces. Anyone have any diagnosis ideas, I believe at the least I may be looking at new rings.

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[Terry M.]

Re: Valves / top of piston color & carbon deposits

Pulling heads on '73 454ci and I see orangy-tan on a couple cylinders which I believe is pretty normal after +/-50k miles. Next cylinder getting blackened, then last chamber (#1 cylinder) exhaust valve caked w/carbon and top of piston is black and oily. Piston tops themselves look in good condition just the color / coating variations. Head gasket looked fine and no corrosion or issues on any of the surfaces. Anyone have any diagnosis ideas, I believe at the least I may be looking at new rings.

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What was your oil consumption?

This is a case where a cylinder leakdown test BEFORE disassembly would have been a decided diagnosis advantage.

Unless your oil consumption was unlivable, I would have a good valve job done with new valve stem seals, check and replace the valve springs and/or valves only if they are out of spec. Put it back together and roll the dice.

How much do you drive it each year?

[Gary K.]

Re: Valves / top of piston color & carbon deposits

Not burning oil at all, motor pulled because it was time, lots of tired parts, and rough running which I diagnosed as a valve train/valve job type problem. Indeed one of the push rods was slightly bent on an intake valve and cam lobes worn somewhat. I really do not want to fix what's not broken - I don't want to do a full/complete engine rebuild but I am also not experienced enough to diagnose problems like this. Two of the eight cylinders are blackened and smell burnt. Pistons, bores, everything else looks OK. I plan to measure the bores and check everything out, bearings, etc. and if it's okay re-use most of the rotating assembly. Drives about 3k a year tops. Thanks for any advice///

[Joe L.]

Re: Valves / top of piston color & carbon deposits

Not burning oil at all, motor pulled because it was time, lots of tired parts, and rough running which I diagnosed as a valve train/valve job type problem. Indeed one of the push rods was slightly bent on an intake valve and cam lobes worn somewhat. I really do not want to fix what's not broken - I don't want to do a full/complete engine rebuild but I am also not experienced enough to diagnose problems like this. Two of the eight cylinders are blackened and smell burnt. Pistons, bores, everything else looks OK. I plan to measure the bores and check everything out, bearings, etc. and if it's okay re-use most of the rotating assembly. Drives about 3k a year tops. Thanks for any advice///

Gary-----


If the cam is worn, you'll need to replace it and the lifters. This can be done with the engine in the car (but you'll need to remove the radiator). I'd also replace the timing set when the cam is replaced.

Otherwise, I'd just do 3 angle valve job and replace whatever valve train parts need replacing. De-carbonize the piston crowns.

[Terry M.]

Re: Valves / top of piston color & carbon deposits

Not burning oil at all, motor pulled because it was time, lots of tired parts, and rough running which I diagnosed as a valve train/valve job type problem. Indeed one of the push rods was slightly bent on an intake valve and cam lobes worn somewhat. I really do not want to fix what's not broken - I don't want to do a full/complete engine rebuild but I am also not experienced enough to diagnose problems like this. Two of the eight cylinders are blackened and smell burnt. Pistons, bores, everything else looks OK. I plan on the cylinder walls to measure the bores and check everything out, bearings, etc. and if it's okay re-use most of the rotating assembly. Drives about 3k a year tops. Thanks for any advice///

How much of a ridge at the top of the cylinders? That would tell me whether I would go into pistons/rings or not. Without too much oil burning I would be inclined to leave the cylinder case alone . If you have to go for rings then you might as well recondition the bottom end as well. If it isn't broke don't fix it. look at the cam and some of the lifters. As Joe says if changing the cam, do the timing set. See how much play is in the chain. It might be worth doing the timing set if there is much play.

[Timothy B.]

Re: Valves / top of piston color & carbon deposits

Gary,

Your problem may have simply been plug wires and spark plugs. Some lifter wear is normal, don't fix what's not broke.

[Duke W.]

Re: Valves / top of piston color & carbon deposits

So what valve springs? The OE second design dual spring setup with integral umbrella seal that this engine was originally built with are no longer available from GM and no one has found another source, so most are at the mercy of some "engine builder" to make the choice.

If the engine only has 50K miles then the old springs should be okay as long as the umbrella seal is not damaged. These second design dual springs were vastly superior to the early single spring/damper design that were prone to failure.

Also, if the engine is assembled with a thick composition gasket, what is probably now an 8:1 true CR will end up at about 7.5 - about the same as a Ford flathead.

It's always wise to do thorough diagnositics on an engine before it is disassembled/removed from the car. A low mileage original engine may need nothing more than valve seals if oil consumption is high.

The archives are full of poor and failed rebuild stories. The quality of the outcome is proportional to the amount of up front research and proper management of the "engine builder" - oh, don't worry, he builds great racing engines!

How many times have I heard that line?

Some fuel fuel additives leave an orangeish stain, and leaded fuel typically leaves off-white deposits. The blackened cylinder is probably using a little too much oil and the valve seal is the usual first suspect.

Duke

[Gary K.]

Re: Valves / top of piston color & carbon deposits

Thanks everybody - the heads are matching April 11 1967 which are not correct for March 1968 car. Plus they are the rare 3904391 castings so have been removed, put up for sale and I'll be looking for 3919840 heads and do a complete rebuild w/3way grind. If the bottom end is to spec I'm probably leaving alone, replacing cam, lifters, timing, etc. Clean it up as best I can and put'r all back together. Never burned oil so I believe pistons & rings are probably OK.