Car: 1982 Cutlas Calais
Engine: 77 350 Olds

Late model small block I know. Love the thing runs strong and sounds terrific. Onto my problem, top hat oil cap keeps popping off while I’m driving.. giving it quite a bit of a throttle at times so obviously not good. Made sure the breather wasn’t plugged so don’t think crankcase pressure is the issue. Anyone have experience with these caps going bad and this happening? Should I try replacing the cap or should I invest in one of those nice billet oil necks with the screw on cap? Any insight would be appreciated thank you and god bless.

 

I don't know what type of oil cap you have based on your description. My car has a cap with two ears that is a "twist to lock" style and can't possibly come off unless it is physically turned 30º or so. This style was used for decades so it should be easy to find one of these fill tubes and cap.

 

I have never heard of the top hat style caps blowing off. Do you have a PCV that is working properly? There should not be that amount of crankcase pressure to blow that cap off. Does your cap have the retainer clip inside and is it tight?

 

Thank you for the comments. Verified PCV is in fact working. Above is the said cap. It will screw tight but is finicky by this I mean once it’s “locked” it will easily turn a few degrees to the point where it can come off. Maybe when it takes a bump in the road it’s getting knocked around who knows.. was also blowing donuts yesterday so could have had something to do with it. Probably going to try a new cap and see what happens.

 

Sounds like you may only need to purchase a new cap... Have you checked the internal ridge of the tube itself??? That also may have some wear so that the cap does not secure properly... Both tube and cap are readily available from several sources... Fusick shows a listing for both cap and tube...

http://www.fusickautomotiveproducts....s.asp?dept=344

 

My bet would be the cap. I'm no expert on oil caps, but that looks like a valve cover style cap, and not a factory one at that. Get a quality cap for your application and your issue will likely be resolved.

 

New cap ordered. Thanks everyone for the help. Stay safe out there

 

The pic of your oil cap is not what is normally called a "top hat". The top hat oil caps do not twist on. They only push on and friction spring holds them on. I will try to remember to take a pic of a real top hat.

 

I installed a chrome aftermarket tube on mine and the friction spring cap kept going off. I replaced it with an expandable hole plug. Certainly not pretty but, very functional. If I ever get to put her in another car show I will put the chrome cap on.

 

This is the top hat used on early V8's.

 

That's the kind of spring my chrome cap has. Damned thing just won't stay on.

 

The thing really does look like a top hat haha. I had never seen one before so you’ll have to forgive my ignorance. While I’m waiting for the new cap, I ended up taking pliers to the inside flanges of the current cap and working them down. Seems to have secured it quite well for the meantime but still will be nice to have an oem quality cap. Thanks again everyone for the help!

 

Hey that brown sludge on the cap normal???

 

The cap you have is old school Chevy. They don't fit for $hit on an Olds.