Valve guide or valve seal?

[Hozer 88GTConv]

I am trying to diagnose an oil consumption problem on #5 cylinder of my 10,000-ish old 306.

It seems to hold compression well, w/in 10 percent of all other cylinders.

I pulled the valve cover but could not tell if the seal was seated improperly.

I also have sneaking suspicion that I am losing a little power there.

My question is if there is any other way short of pulling the spring or cylinder head that might hint at one or the other.

Thanks for any replies...

[bad85gt]

A stem seal shouldnt cause a power loss, what heads are you running? Stockers or aftermarket? If they are aftermarket, what push rods are you running? Certain manufacturers require diff. length than stock push rods, because the geometry is different it will wear the guides prematurely, how that would cause a power loss I have no idea, but worth argueing over

[Hozer 88GTConv]

They are TFS TW heads only 18 months old...
with TFS 6.025" push rods and 1.7 FMS rockers...

I don't have any evidence that I am "losing" power in that cylinder, just a feelig

A dry compression check I did showed no appreciable difference in any of the cylinders in that head.

The only reason I know something is going on is an oily plug with lots of residue on it. I am definitely consuming oil in that cylinder.

I have no leaks anywhere else, checked several times...

[bad85gt]

I would drop tfs an email (techinfo@trickflow.com) and see what they say, doesnt sound like a long enough push rod but I may be wrong. Im running tfs hi ports and ran a stock roller push rod, like 6.250 or something, and they said I needed like an adjustable 6.400 and see what length I need, because the stockers wore my valve guides out. Also, have you done a leak down test on that cylinder? Could be possible you broke a ring or something

[Hozer 88GTConv]

they are actually 6.75" rods...

I guess I'll read about a leakdown....

thanks

[Old Guy with 87 GT]

might be a leak in the intake gasket on the lifter valley side

i just tore mine down and discvered that my #3,4 and #8 cylinders were sucking oil in thruogh the lifter valley ,gasket didn't seal right.......i was kinda surprised that it could suck oil in through there ,but it was .......my #4 port was coated in oil and judging from looking at the gasket it looked like the others were drawling in some oil too

[Hozer 88GTConv]

did you have any indications before you discovered this?
Specifically, was oil saturating the threads of a plug?
Or was it just enough oil to get thru that would rapidly burn off and not even yield the dreaded death smoke?

I have no smoke at all, I mean none, despite what appears to be a consistent oil leak into #5 somehow.

I am going to do a partial tear-down this weekend and check the valve seal. I couldn't do it before because I didn't have a functioning spring compressor.

Thanks again...followed by a leak-down

[Old Guy with 87 GT]

yes there was remnants of oil on the plugs .......the plugs were dry for the most part but the was a little oil on the threads of two of em

the tell tale sign was burnt oil smell at wide open throttle ..........i couldn't see oil burning or blue smoke....... the exaust had kinda a funky smell and you could tell it wasn't tuning it self right .........i knew it was burning oil from a friend telling me he smelled it when he was behind me every time i opened it up

i kinda knew to look for this problem cause it didn't burn oil before i did my intake swap and it was the only thing i could think of that woulda fit the symptoms i was having
(another symptom was when tuning ,it acted like it had a vacuum leak , but i couldn't find any vacuum leaks)

on another note ......the tell tale sign of oil getting by the valve seals is smoke at start up .............if you seals are bad what happens is when you shut the moter down oil runs down the valve and builds up in the cylinder .......when you start up the car it burns off that build up letting out a small blue smoke cloud till the exess burns off

[Hozer 88GTConv]

I am really thinking about this now...the fact that I have no death smoke at all is really making me think about the lifter valley option.

Plus the fact that I don't have to pull the cylinder heads...I really don't want to have to do that.

So, was it obvious when you pullled the lower manifold where the leaks were?

Thanks...

[Old Guy with 87 GT]

yep .........gasket was saturated with oil on the inside of the port sealed area (did that make sence)

plus the inside of the ports were coated with oil (you could run your finger on the inside of the port and feel the oil coating )

i've never heard of anybody else having this problem but on mine it seems like the only logical explanation for it's symptoms and for what i found when i tore it apart

maybe one of our engine guru's can jump in and give an opinion

[matt1190]

I had a similar problem on my 351. No smoke just greased spark plugs. The intake and heads (both alluminum) did so much "walking" during temperature changes that it ripped the intake gasket to shreds. No matter what gasket I tried it would still destroy them but I finally found one made by felpro that had a sheet metal core. Haven't had any problems yet, and my plugs are clean. Good luck.