possibly bad valve guides?

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Dec 18, 2006 | 03:43 AM

muscletruck7379

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Joined: Apr 2003

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From: Harrisburg, NE

possibly bad valve guides?

I have a 68 302 with some performance goodies, got a good deal on it, but when it finally ended up into a vehicle it wasn't as powerfull as a 10.0:1 comp 302 w/4bbl and ignition should have been, that and it smoked(blue=oil), alot. my neighbor said it sounded like it had a miss.

so it got put away and i indulged into my 351 w, - a 69 that turned out to have valves really badly burnt, as in egg shaped guides and seats on a couple cylinders.

we all know from car guy 102 that this happens with unleaded gas in engines with the soft seats. but what i got to wondering is if its possible that the same happened to the little 302. and am trying to see what others think before I really tear it open.

so, to tear or not to tear...

Dec 18, 2006 | 09:25 AM

P51D Mustang

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Joined: Mar 2004

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Run a compression test (or a leak down) first. This should tell you if the valves seats are bad. The oil could be coming from bad rings, or bad guides, or both. You will have to tear it down and inspect the cylinders to determine this for certian. It's probably just worn out. Un-leaded gasoline does require hardened valve seats though.

Usually when the guides are the culprit, you will get a lot more smoke when you blip the throttle after it's been idling, and/or if your on compression (de-ccelaration or down hill in low gear) and/or going around corners at high speed. If it's the rings, it will usually give smoke more continously during acceleration or lugging a load. If the power is down, it's probably got plenty of blow-by past the rings. A miss could be explained by a lot of oil simply being in the cylinders, and not always a result of poor valve seating.