read my plugs- please

[vtwinsport]

Morning,
I have #5 & #6 getting packed with light tan colored deposits that completely coat the insulator. They look like bubbly white/tan scabs. My other plugs all look light tan / grey and no deposits. This happens about every two months and I have to change them.
I 'll have pics of my #5 & #6 plugs online soon but what do you think is causing this?
76 350, rebuilt 5K ago, 2101 edelbrock intake, 600 edelbrock carb on insulated spacer, hedman headers, msd diz, no vac advance since plug change, all mechanical for now & running better. Previous months, vac & mech.
Thanks in advance for comments.

[S10Fan]

Try this link......................

http://www.classictruckshop.com/club...park/plugs.htm

[watahyahknow]

maibe be a coolandleak intoo the intakesystem (leaking gaskets)

[vtwinsport]

Thanks guys,
Based on that link (great help), I have a valve guide/ seal problem. That makes sense as I've been monitoring mild white smoke from exhaust, both sides.
Might alos have an intake leak as I know I have felpro gaskets but I think ther are too hard and not suited for aluminum intakes. I should have bought the edelbrok gasket specifically for aluminum.
Thanks again.

[watahyahknow]

white smoke usually indicates water oilsmoke is a little darker i suspect theres either a leak on the intakegasket or a cracked manifold .
theres one other option for testing i forgot to mention , pressurizing the coolingsystem

any stumbling on a cold engine?

[vtwinsport]

wyk, yes there is a liitle stumbling until it gets to about 180 degrees. Then its down right perky until it hits operating temp of 210. I've had 210 since I had it rebuilt.

[vtwinsport]

just did some vacuum testing. 18 and steady at idle, full operating temp of 210. I think this rules out worn valve guides. If they were worn they would be fluctuating and lower.

[Desert1957]

Leaking valve guides are above where the valve seats on the head . They have no effect on engine compression at all or intake vacum readings.
What happens is the oil around the valve spring area seeps down the valve stem and is sucked into the combustion chamber (cylinder) on every intake stroke. This causes plug fouling over a short period of time depending on how bad the guides or stem seals are. This forms the small crusty coating on the plug that causes rough idle and misfiring under load.

You can prolong the plug life by installing umbrella style seals over the valve stems. this shields the valve guide and deflects the oil. it works fairly well untill that seal wears out. Only other way to fix this problem is to have the heads removed and rebuilt.

Desert

[watahyahknow]

that still doesnt explain the way the plugs look
with oil usage you'd expect them to be black with soot and oilresidue .
you told us that the engine was rebuild and i guess they would do the oilseals too they might be mounted wrong though

[vtwinsport]

Thanks guys,
now i know the reason for umbrella seals. I am adding a quart every 2.5 months, about 1000 miles. Plugs aren't oil fouled though. changed my edelbrock step up primary needle one richer and secondary jet one richer last weekend and will check my plugs again this sunday and compare. It was rebuilt and now I am questioning the quality. Sounds like I have a lifter or valve ticking on my drivers side. already checked the headers for leaks and their fine. May have to pull the valve covers next and have a look
Here is what my plug looks like exactly and even more buildup on the other one.

[xrcr]

Keep an eye on your coolant level. The middle cylinders on a small block are where your heating/water issues tend to show up first. 210 seems a little high. That plug looks to me like there is a water issue but not real bad, yet.
However there are a lot smarter people than me.

[Desert1957]

Originally Posted by watahyahknow

that still doesnt explain the way the plugs look
with oil usage you'd expect them to be black with soot and oilresidue .
you told us that the engine was rebuild and i guess they would do the oilseals too they might be mounted wrong though

Yes it does, Oil that passes by the piston rings will show up on the plugs as a wet oil residue, but oil that comes down through the intake port shocks the plug , sticks to the insulator and forms this white crusty junk, trust me on this one...

Desert



A build-up of combustion deposits stemming primarily from the burning of oil and/or fuel additives during normal combustion, normally non-conductive. When heavier deposits are allowed to accumulate over a longer mileage period, they can "mask" the spark, resulting in a plug misfire condition

[jchav62]

The engine in my '73 has bad valve seals/guides. Once every couple of months the #6 plug fouls the exact same you that you are explaining. Light colored build up. As soon as it starts missing a little on acceleration, I know it's time.

Desert knows his schtuff... Thanks for the info!

[watahyahknow]

youre never to old to learn to me the plug looked like it was coated with kettlescale (waterresidue mostly minerals)

[Desert1957]

Originally Posted by jchav62

The engine in my '73 has bad valve seals/guides. Once every couple of months the #6 plug fouls the exact same you that you are explaining. Light colored build up. As soon as it starts missing a little on acceleration, I know it's time.

Desert knows his schtuff... Thanks for the info!

I feel your pain Brother, I use to own an 83 G20 van with a 300K 5.0 , (POS) same thing once every 2 months number 8# for me , Idle would go away then the stumble and hesitation.
I had the dog box removal down to about 2 minutes...

Desert

[vtwinsport]

Thats reassuring guys. My coolant level has hardly moved but it does drop in the reservoir about an inch in a two month period. Oil is clean in the pan when I drain it. So, at least I know what to consider for repairs when I next have the time. Valve seals, guides and probably some time at the machine shop or aftermarket heads.