• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

stuck valve

Share this page

cdsmith

cdsmith

Jedi Hopeful
Country flag
Offline
Well...
It seems I have a stuck intake valve, number 4 cylinder and is stuck open. The engine is a 1275 (it's in a Bugeye -- not that it makes any difference). The car was running okay yesterday, but today not so...
So... any suggestions? It would be nice to get it unstuck, but I realize that just getting it "unstuck" may be little on the optimistic side, but gotta ask!
As always any suggestions/help will be greatly appreciated.
Thanks
CD
 
Hi CD,
Carbon buildup on the stems, especially the intake, can cause the stems to bind.

The valve likely has a bit more opening travel before spring coil bind. Apply a good penetrating oil such as "Kroil" to the valve stem & lightly tap the top with a lead hammer. Tapping moves the valve down, the spring returns it. Persistant tapping plus liberal quantities of oil should eventually free the valve. I would suggest removing the rocker arms first.

It would be possible to set the piston at BDC starting the compression stroke, fill the cylinder with small diameter nylon rope, & by carefully turning the crank, force the valve closed as the piston rises. If this works, then remove the rope & resume the first step until you are sure that the valve is moving freely. Fortunately, these engines have the valve stems set vertically so there is no sideways bending pressure during this process. It wouldn't hurt to apply some penetrating oil to the other valve stems & do them also.

It's like any similar stuck situation. If you can get just a little movement, alternate forward & reverse pressures will gradually increase the travel until the parts are free.
D
 
Hello CD,

a valve that is stuck fully open could be bent. The carbon on the stem usually only affects the final closing. Certainly there is no harm in Dave's suggestion of lubrication and trying to free the valve. I would be wary of using rope to push it back unless there is a sign that it is freeing off.
It is however, a small job to lift the head on the 'A' series engine so I would suggest that is the best course of action. If it is merely carbon that is the problem, then a head overhaul is in order, to ensure reliability for the future.

Alec
 
Thanks for the info... I plan on spending some time today "tapping" and "oiling" (there may some be "beer-ing" involved as well - attitude adjustment).
I'm keeping my fingers crossed, but I realize I just may have to pull the head.
Thanks again for the input.
CD
 
Well... the tapping and oiling didn't work... Uncrossed my fingers and pulled the head, seems the valve guide slipped....
It's now at the machine shop.
Thank's to all....
CD
 
Back
Top