After a recent cam change/head rework (seals,spring & milling), I noticed that all spark plugs exhibit dark discoloration on the upper half of the insulator/electrode. While the lower half of the electrode/insulator is a tan/white color. I know the cam profile (Crane hydraulic special)likes a rich idle, but would'nt the entire insulator exhibit darkness under a rich condition? Also, oil consumption has increased (approx 1 qt/1000miles)and i think that is the source of the upper insulator plug darkness. However, it is unusual to me that only the vertical upper half (facing upwards) of the insulator reveals oil/fuel discoloration, while the vertical lower half (facing downwards) reveals normal combustion. All plugs exhibit this condition and engine does not smoke, either cold, under heavy acceleration, or up to temperature. Does the unusual plug condition indicate valve seal leaks or ring wear,oil control ring seal problems?

69 camaro, 350cid, s/r (67cc heads),2.02/1.6 valves, air gap rpm manifold, demon 650 dp carb, 1 3/4" hooker headers, Crane hydrualic special @106* centerline, TRW forged (flat top) pistons, M21 trans/ 3:55 posi.
thx to all that respond.

What you are seeing is pretty common for a light oil burner with valve seal or guide trouble. Probably not what you wanted to hear with the fresh head work but thats what it sounds like to me. Which cam do you have, and how does it idle? Just curious as I have been considering using one of those "saturday night specials"

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

Hey Travis, its a Crane Part # 110591 @480/494 lift and 228* / 234*. Idle produces 10" of vacuume @ 800 rpm. with a Noticable chop. (streetable for sure) THis replaced a comp 262HE and performmes much better at 2000 rpms and above. AT highway speeds (3000rpms)it is much quieter than the comp262he. However, when you give it the throttle, acceleration and exhaust noise increase dramatically. THe exhaust exhibits a kinda "pop" to it at rpms during accelleration, then screames as the RPMS exceed about 4000, much cooler to drive than before. I wished i would have done a complete rebuild of the heads thought. They only have 30k miles since i bought them new 3 yrs ago (along w/ a complete engine rebuild). So, i just replaced the springs and seals. I did point out to the machinist the " globs" of black gook on top of the intake valves when i brought them to him. He ended up convincing me that it was today's gasoline and dod not do a complete valve job, and there for the guides were not replaced. However the seals were. But they were not the large umbrella type that were on them. I agree w/ you. the seals and or guides are not up to par to keep oil out of the combustion chamber. I belive it only occurs during operation, since it does not smoke even after not being used for long periods of time. I was also told that with the high volume oil pump, the valves and seals are literally " swimming in oil" and can make oil control difficult with a high lift cam.
DO you have any recommendations for valve guides and seals to control the oil entering the cylinders. any further suggestion, I plane on redoing the heads soon!

It sounds like heavily worn guides from what you describe. That heavy black carbon on the back of your valves kills power. It could be seals too. Does those heads use PC seals, or just the little rubber o-ring? If they dont have PC seals, I would get the guides machined for them...I have never seen anything work better. Even the best seal cant help with shot guides. My machine shop doesnt use guide liners, they just replace the guides. Whatever you do, make sure that they arent just knurled...knurling the guides just doesnt last. Also, I would dump the hi-volume oil pump...they are totally uneccesary and just eat up power and can easily cause higher oil consumption. Unlike Fords, chevys have such a good oiling system they dont need the hi-volume pumps. I use a standard TRW oil pump in my truck and after 3 years on the shortblock, I still get 55-60 pounds of pressure at a cold idle and 45-50 at normal temps and 5500 rpms.

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

<BLOCKQUOTE>quote:</font><HR>Originally posted by travis:
Does those heads use PC seals, or just the little rubber o-ring? If they dont have PC seals, I would get the guides machined for them....

<HR></BLOCKQUOTE>

I know there was more than an O ring. What is a "PC" seal? I'm not familiar with the types of seals or guides either . Do you have specific Brands of seals / guides that i can request the machine shop install? The heads Are World products S/R's that were purchased new in 1999. I assume the seal is more than an "O" ring since i could see them (were orange in color)inside the inner damper spring and was almost as tall as the spring itself. He replaced tham w/ a blue set that were half the size of the spring. Is there a simple test to confirm seal/guide failures, or is the burn pattern on all the plugs a good confirmation of oil buring from the intake valves (upward vertical half of the plug fouled)

thanks for all your help'
joe c

pc means perfect circle