My father in lay has a 64 Malibu ss with a stock 283 . He just put 2 solid finned aluminum valve covers on it and now it keeps blowing the cap off the filler tube. He bought this at the auction and whoever put this car together the cheapest chrome filler tube with a push on breather cap . If I get an oem style tube with the twist cap and put a twist on breather should this correct the problem? Sent from my iPhone using The H.A.M.B. mobile app
hmmm....there might be more to the story. What valve covers did it have before? and do you know what year block it has? like, does it have the fitting at the back of the block for the breather? if so, what is connected to it?
It had those cheap chrome valve covers on it before . I’ll have to look for the old breather hole on the block Sent from my iPhone using The H.A.M.B. mobile app
The old covers had a pvc in it but shouldn’t this breath fine through the filler tube Sent from my iPhone using The H.A.M.B. mobile app
It does have the breather port in the back of the block , it has a hose that runs to the back of the carb Sent from my iPhone using The H.A.M.B. mobile app
No his engine but this clearly shows how his is hooked up Sent from my iPhone using The H.A.M.B. mobile app
I believe there should be a pcv in that hose to prevent the pressure from building up and blowing off your cap. Originally the road draft tube connected to this rear port. Therefore it was an open system where the pressure didn’t build up. There’s a thread on here that discusses this a lot. What is the other line attached to the top of the intake rearward of the carb for? Here’s another thread: https://www.jalopyjournal.com/forum/threads/pcv-systems-revisted-with-more-questions.55422/ Sent from my iPhone using H.A.M.B.
As I said it originally had pc. Valves in the cheap valve covers but the new ones have no holes at all. Sent from my iPhone using The H.A.M.B. mobile app
So it worked fine with the old valve covers with two PVC's in the them. Then, You changed to valve covers with no PVC's and now you are building up crankcase pressure and blowing the filler tube breather cap off? Is that correct? Chappy
Basically your engine is developing the same crank case pressure it always has, but you have removed the major path for that pressure to escape...and it is now finding the next path of least resistance. Either put the old valve covers back on, or get some valve covers with breathers in them. Study the picture that mgtstumpy posted above. The crank case needs to vent. Chappy
He wants to keep the valve covers he has on now there has to be a way to vent this pressure they used to run d solid valve covers before. Sent from my iPhone using The H.A.M.B. mobile app
OP says he has the hose adapter that goes in the block where the road draft tube was and apparently either the right carb or a spacer under the carb where a hose fitting will go. The PCV valve that GM originally used had one end threaded with 1/4” NPT and a hose barb on the other end. If you can't find the valve with the pipe thread one with a hose barb on both ends will work too. With an oil breather cap that is in fact vented (and not sealed) in the filler tube it should work as GM designed the PCV on that car, it was a vented system not closed. If the cap you have is sealed, with no holes around the bottom, that is a closed PCV system and those got air through a hose connected to the valve cover drawing through the air cleaner. With the new covers having no holes for a fresh air hose you must use a vented filler cap. Squirrel asked if the engine was up to snuff, if it has worn bores and rings it may have excessive blow-by that could be pressurizing the crankcase and popping the cap off. Check to see if the PCV valve rattles ( is free, and not gummed up) and be sure the hoses are clean and cannot be collapsing when under vacuum.
Your breather cap should be about twice the diameter of the filler tube and look like its stuffed full of steel wool. Easy way to check the PCV is to pull the hose off with the engine running and put put your finger over the opening in the PCV. You should feel the vacuum. Also with enough crankcase pressure to blow the filler cap off, the pressure should come roaring out the hose. If no pressure out the hose, start disassembling down to the root cause or change valve covers
When you are talking twist off not these are you https://www.ebay.com/i/392063655125?chn=ps that would be don't
Found the problem, the hose was to short and had kinked, new hose with a longer bend and problem solved Sent from my iPhone using The H.A.M.B. mobile app
Ain't it great when you've got all those worse case scenarios rolling through your head that it turns out to be something dirt simple.
Be sure the spring steel retainer is attached to the cap and not loose as to move around. I had my cap come off a few times, but the retainer was not held in place properly. A couple of tacks with the welder fixed it.
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