Barebones

I have a 1970 BB 454 that seems to be having a problem with oil blowback out the dipstick,It doesn't do this under normal driving but if you get into it a bit it will blow oil out the dipstick..
75k miles mild cam,headers thats about it.
Say over 3500 rpms pushing it seems to trigger the blow back then when i slow it stops..
Some tips would be much appreciated..

427Hotrod

What's it got for breathers? Stock valve covers or aftermarket?

JIM

Barebones

Hi Jim;
it has the stock breather and the filter seems to be clean.Valve covers are stock.I might add it doesn't smoke through the exhaust either.

bobs77vet

......if the breather system is working properly you should not have this problem......replace the PCV valve and the problem should go away

Barebones

Thanks will change PCV and let you know

427Hotrod

I doubt PCV will help. At WOT the vacuum is very low in the intake and the PCV does nothing. It WILL help with low speed ventilation and keeping general oil leaks to a minimum. But you are chasing high crankcase pressures and that only comes from ring seal issues. It's very possible to have rings that will allow blowby into crankcase but not allow a lot of smoke out the pipes. If you have a lot of blowby then more/larger breathers will help the issue of blowing the dipstick out..but the real issue is it's rebuild time. You can also get dipsticks with o-rings on them or even some that lock in place...but the real issue remains.

A leakdown test will let you know if the issue is on one or more cylinders.


You were wanting to pull it out over the winter and add a stroker crank anyway right??


JIM

Speed Direct

And so you see how The Great Temptor begins...

...Roger...

I have seen several frequent oil changes cure ring sealing issues if the car is one that has sat not being used for a long periods of time which may cause the rings to be sticking.

427Hotrod

I'm just an *enabler*. I just help people do what they really wanted to do anyway!

Seriously..Roger has a good point. If it's been sitting a while you might be able to get the rings *unstuck* with a little effort.

JIM

zigvs

cam,alum heads,headers...oh wait wrong thread.Oh no its not.rip it out and rebuild time!!!

justaguy10825

I added extra venting to my valve cover on this little guy.... It is very high performance... (aprox 125HP out of a 1310CC)... Anyway... she builds up a ton of crank case pressure @high rpm(s)... I added a vented-chrome oil catch-can and some braided lines... Looks great, works great and catches the oil that would otherwise find another way out of the block... The can is located on the bottom left of the photo... Just a thought... I don't have anything like it on the Vette...

noonie

Have run into the dipstick being blown out several times. One was an almost new engine a guy brought to me that had no pcv or other breathers.

3500rpm can still be a cruising speed depending on the rear end and the pcv should still suck, but may be overcome by excessive blowby.

One thing that is common on older engines are the pcv ports on the throttle body of the carb. They can become completely coked shut. Check for suction at the pcv.

Barebones

Thanks for all the advice,would kinda like not to do a rebuild this winter,I will try some of the suggestions and let you all know.
Just got the go ahead from the front office for a new paint job and don't want to make the gods angry,if you know what I'm saying.

427Hotrod

Aww c'mon.....you're going to want to make sure you don't scratch the new paint when you pull the motor next year. Might as well get the mechanical stuff taken care of before paint. Then you don't have to worry about it.

Plus it's more fun when you stuff your foot in it!!


JIM

SH-60B

Lock the dipstick down like that and something else will give way to the pressure, like the rear main seal.