Hi everyone,

My 383 has 5k miles on it (a crate motor) and has been fouling plugs from day 1. I have it out of the car right now and decided to pull the heads and take a peek.

Piston tops, combustion chambers, and backs of intake valves have fair amount of carbon-looking buildup: certainly not good for 5000 miles.

One knowledgeable friend who saw it said it's an oil problem and to check for sloppy guides, seal failure/poor installation, or rings not seated/poor honing job. The other knowledgeable friend who saw it said it looked like a really rich mixture causing the problem.

Deposits feel "oily" and smell like dirty crankcase oil. Question is: can partially burnt, too-rich fuel mixture smell like that? Can fuel varnish appear wet and oily looking?

I should add motor never smoked oil except a little, short "puff" of smoke upon initial startup which cleared out immediately.

Seals appear to be in fine condition and stems in guides are a beautiful fit; one friend felt it and agreed it's nice and tight. Last possibility, I guess, is a cylinder/ring fit issue. It was professionally rebuilt by a supposedly good company; is it likely they were sloppy boring/honing all 8 cylinders? (There is fairly even buildup everywhere.)

Also, a friend adjusted the hyd. lifters when engine was new (I think I was complaining of some clattering) using, as I look back, the method to adjust solid lifters (motor-running, feeler-guage). I discovered one pushrod cracked at upper ball tip end. Could rockers have been too tightly adjusted, causing valves not to close all the way, explaining carbon build-up on valves and piston tops, fouled plugs, etc.? No miss at idle, though. Motor acted fine.

What about a too-rich fuel mixture? I never did touch the carb (original on '75, as far as I know) and nobody adjusted it. One friend said if that was the case, though, that piston tops and comb. chambers would be "washed" clean from the fuel...?

Just trying to decide if I should button her back up or look into further work.

I'd really appreciate some opinions!
Thanks, Patricia

Usually when you see a small puff of "blue" smoke on the start up with a small block chevy, oil is seeping around the valve stems. The oil will foul the spark plug and the cylinder will not burn clean or not at all. Therefore giving the impression that the carb setting is rich. Actual oil consumption will be very low.
If an engine is not honed properly, the rings will not seat and oil consumption is usually higher, pending the number of cylinders that are effected. If the rings do not seat, the engine "usually" burns oil continuously. Again this fouls the plugs, and the engine runs rich.
Since you have the heads off, I would have them checked by a good machine shop. Clean up the block and re-install the heads. Check your carb and make sure that it is in good working order. Also, check the settings and find out what size jets you have. Eliminate any doubts about running rich. Eliminate the possiblity of the heads, and then you will have narrowed it down to the rings or hopefully, you will have solved the problem. If you think it is the rings, you might as well pull the motor and have everything checked. Pending clearances, you can have the motor honed again and install new rings.

Agreeded. With the puff at startup it is indicating a valve seal problem. Weather you do the rings or not depends on you budget and luck. From you description I would be willing to check the heads, replace the seals and try it. Could be the wrong choice, but I would give it a shot unless you want to absolute sure and only do it once. Then do the rings.

When it is back together and warmed up, create a very small vacuum leak and slowly increase the leak. If the car is running rich it will speed up the engine with the extra air. After a point of increasing the vacuum leak it will go lean and start to slow down then run rough, so only a bit at a time. If it does not improve at all, it's not rich.

Ken Styer

Thank you SStanford and Ken,

It appears I should minimally have the heads checked; I was contemplating going that route anyway, so I'm glad for the confirmation.

If it is a ring/honing problem, would it eventually fix itself from use and further breaking in?

SStanford, your comment re: rings not seated usually causing smoke all the time: I certainly never had that problem. The motor ran beautifully, performance-wise, too. I'll think about some cylinder bore work, but I'm leaning toward crossing my fingers on that one and hoping for the best.

Thank you for the help!
Patricia/'75

I have not seen your motor or know the history. I only know what you have posted. Considering my budget, I would probably have the heads checked and valve stem seals replaced. Then bolt it back together and see what happens. This should fix your problem.

I not a professional, I just play one in my garage! LOL

Well, I took the heads out to a VERY impressive performance shop which builds custom engines and which I hear very good things about.

Ends up the seals look great, valves a fine fit in guides; he suspects ring trouble. I whipped out a pix of the piston tops and he immediately felt sure it was ring issues due to pattern of carbon deposits.

I showed him an exhaust valve I noticed had rust deposits and he found a crack on #2 exhaust seat area, leaking water. So the heads are trash.

Minimally I'm looking at some sort of work on the rings/cylinders (if block is still useable) and new, aftermarket heads with the associated new valve train components. :(

I'm out of warranty and out of $2800 purchase price, with only 5000 miles of use and 1-4000$ expense ahead. Don't buy a crate motor from Motorworks, Spokane, WA!!

I do thank you guys for pointing me in the right direction with regard to having my heads checked. I'd rather find the problem now than put it back in the car and have to deal with it later.

Thanks,
Patricia

You may not have to replace the heads. Depending on the crack it may be able to be welded and remachined. If so you can save a lot of bucks. The flip side is you may want to use some high performance heads. Just food for thought.

Ken Styer