Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

My recently rebuilt 92 5.7 350 is having blow by, is my engine bad?

I have A 1992 Camaro Z28 with a recently rebuilt 5.7 350. The car sat a lot for two years. When I get up around 40 mph, the pcv valves blow out and once the oil cap blew out. I was told it was blow by. Oil runs down the valve covers and into the starter, then the starter won’t do anything until the oil dries up.

Sounds like a bad rebuilding job. Or the rings are sticking and letting gasses by.

This sounds like as clear a serious blowby problem as I’ve ever heard. I’ll bet this will even show up with a compression test as seriously low readings, and perhaps you can even watch the pressure drop with a leakdown test.

BUT, I’ll offer another possibility… you may have a valve problem wherein the compression and/or combustion is blowing past the valve stem seals and seriously pressurizing the spaces under the valve covers due to valves not closing. Yeah, I’m trying to offer an optimistic theory.

Question: was it rebuilt before or after it sat for two years?
Was it professionally rebuilt?
Were there changes made to the engine in rebuild, such as being “stroked” (lengthening stroke for increased compression)?
Was the head rebuilt with stronger springs, rollers, etc?

Post back.

If that image is your actual phone number you need to edit it out. Things like that on an open web site are never good.

Does this engine have aftermarket valve covers? You need a vent in the valve cover opposite the cover with the PCV valve. There should be a 1/2" breather hose vented to the air cleaner to vent the blow-by, the PCV valve has little vacuum during hard acceleration and can’t handle the amount of blow-by a normal engine has.

Did some lay person line the grooves up in the rings ,when reassembling,some 350s had a little oil leal problem from the valve covers ,I forget the fix .Some people think that every line and wire you can yank off an engine will make it perform better .(you Folks do understand why most diesels dont have PCV systems right?)

The intake manifold gasket could have been installed wrong. Exhaust maybe getting past the crossover passage under the throttle body if there is a passage on a 92.

Has the pcv system been evaluated for proper function? Varies design to design, but on my cars – both have just one pcv valve, so not quite like yours apparently – but I just remove the hose which has the pcv valve in it, shake it to make sure it rattles, then feel the end of the pcv valve to make sure there’s a strong suction there at idle. It could be something simple, like the intake manifold connection to the pcv system isn’t connected or clogged, or the pcv valve(s) themselves are stuck closed or otherwise malfunctioning. It’s so simple to verify, if I had this problem that’s the first place I’d check.