Thread: Boy Was This Strange

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When I started my Jeep truck tonight to leave work, it cranked, and then I got a huge backfire, and some smoke rolled out from under the hood. I popped the hood pins, and expected to see a fire, but there was none. So I closed the hood and started to drive home.

After about 2 miles I noticed smoke coming out of the back of the truck.....a whole lot of smoke, so I pulled off the first exit and went to a gas station where I knew they had a water hose to fill up radiators. I thought for sure I had a fire brewing under the hood. But what I found was oil coming from the bottom of the passenger side valve cover on the 302 Ford, and running down onto the exhaust manifold, and smoking away. You know how one drop of oil can produce smoke as if it were a gallon of the stuff? Well, I had a fair amount of oil leaking onto the manifold, so it was really putting out the smoke.

Here is where it gets really strange. I thought the valve cover gasket was just leaking, so I got out some tools and started to tighten the bolts up, but then I noticed a piece of cover gasket laying on the fenderwell. AND THEN I NOTICED THE MOROSO VALVE COVER WAS BOWED OUT BETWEEN THE 3 BOTTOM MOUNTING BOLTS !!!! It was bowed out about 3/8 of an inch in two places, so a new gasket would never seal.

Called my Son, and luckily he was home, so he went to our shop and picked up a new set of gaskets and a new valve cover, and we put it on, no more leak.

What is strange to me, is how did that backfire create that kind of force in my crankcase to blow out the valve cover? My dipstick was also popped about 3 inched up out of its tube. I've had backfires before, but they are usually limited to the carb throat. How did this work its way into the crankcase? Could gas have gotten past my rings and into the oil and created fumes? (the engine is getting tired, so it isn't too far from being replaced)

Does anyone have an answer? Hope it doesn't happen next time I start the engine when it's cold.


Don

Do you have a lot of oil in your gas maybe??? Could have been fuel vapors in the oil flashing and blowing the gasket out??? Dunno, kind of weird....

I just thought of something. I'm not running a PVC valve, just a piece of hose from the breather on the other valve cover right to the carb. Aren't PVC valves supposed to close to keep this sort of thing from happening? I have never had one in there, but maybe now that the engine is getting more blow-by it is setting up a path for the fumes to ignite?

Don

If I was guessing I'd say the pvc system was plugged. When I got back from over the pond in '64 my Dad had a '57 Ford Custom waiting for me. California was just starting their smog BS and the '57 had been converted. A couple of months later as I was driving down the street a hell of a noise erupted from under the hood. The dipstick was blown out and oil was all over the right side of the windshield, made a hell of a dent in the hood and for all pratical purposes wiped out the bearings. You should have seen the mess it made on my Dad's driveway when I pulled the rubber plug that had been shoved up the road draft tube.

Great suggestions guys. I think the combination of my engine starting to get tired (and probably getting some gas leaking down past the rings) and no pvc valve, created a way for the backfire to ignite the fumes in the pan. It had been sitting in the hot sun all day, so it probably was ripe for this to happen.

I'm going to add a pvc valve, because I think I remember that they are supposed to have the check ball in there to close in case of a backfire. I will also change the oil and filter. I have been noticing my oil gauge flickering at red lights, as if the oil is thinning out, and letting the pressure drop.

Once I get a couple other projects out of the way I plan to build a fresh 306 for it. But this engine owes me nothing, it has been ridden hard and put away wet for 3 years, and it probably has 150 to 200,00 miles on it. Just hope it hangs in there for a little longer, don't need that hassle right now.

Thanks for the replys, all.


Don

If it's fuel in the oil, and isn't the carb over fueling, it could be the fuel pump (if you have a mechanical, block mounted) beginning to fail too.

i have had a backfire liket this once also, fuel in oil is probably why along with a non pvc setup. as the engine warmed up gas fumes accululated in the engine and a little backfire from the engine or something and wham. your engine compt is one lttile bomb.
mine blew one valve cover right off off a chev 305 and left the other hanging plus ballooned the pan never did find the dipstick .