Valve query

vue

#1

timing belt slipped. All intakes are bent. But exhaust valves look ok. No nicks on Pistons from any exhaust valves. Because they are smaller dia.? I have not removed exh valves yet.


#2

Yep.

Because the exhaust valves are smaller in diameter, they didn’t get bent.

Tester


#3

Seats look good. Fairly shiny. No pits or carbon buildup. If I lived in Mexico I might try to straighten the valves. Or maybe India.


#4

Did you check the valve guides to make sure none got cracked?

Tester


#5

That’s just a little kink @Cavell. I could straighten that on the anvil :frowning:

Yosemite


#6

Maybe the way it is configured inside, plus the difference in valve diameter, the intake valves take the hit, and that prevents or at least minimizes damage to the exhaust valves. With a little improvising and some wood-work, the bent ones could be repurposed into a good coat rack. Or a restaurant could use them to set on the tables with a little sign taped on top to advertise the soup of the day :wink:


#7

It’s easy to see daylight around the valves when I look thru the intake ports. But no light on the exhaust ports. Saw a trick where u pour water in combustion chamber and use an air hose to blast air in the port. Any bubbles around valve points to poor valve seating. Of course with no intake valves in head now it might only work on exh valves.


#8

Valves don’t cost much and exhaust valves should be changed anyway. Under normal conditions they won’t last as long without a few pits and wear.


#9

If you’re going to the trouble of doing a valve job on the cylinder head and replacing intake valves you would be better off as mentioned to replace the exhaust valves also.
If you examine the exhaust valves and seats with a magnifying glass you may well see some pitting. That microscopic pitting is what can lead to problems at some point.


#10

I’ve heard this method mentioned here before. But I’m having a hard time envisioning how it could work. The pressures the valves have to hold with the engine running seem like they are much higher than you could achieve with an air hose, even if you could somehow create a perfect seal for the hose. I guess it would be better than nothing.


#11

If the head is off and the valves installed, the quickest way to determine if the is a good valve seal it to position the head, combustion chamber down (sitting on a couple of blocks) and squirt brake clean in each exhaust port one by one. Look under at the combustion chamber to see if there is leaking, it will be apparent… Dump out the exhaust and do the same to the intakes. If it holds brake clean, the valve seal will work just fine. Minor leaks can be touched up by lapping the offending valve(s). Big ones, like bent valves, will be readily apparent.


#12

the method I saw was combustion chamber up and pour a bit of water into area. with valves installed and spark plug used to seal that hole, it should be water tight? than stick air hose underneath inside port and direct airflow at back of valve. this high pressure airstream will show any bubbles around edge of valve seat. you don’t seal the port and try to pressurize it. yes I have seen the method where you squirt brake cleaner or similar into port and see if it drizzles out around valve seat.


#13

Water is more viscous than brake clean but you could use it the same way I described. It would seem you’d need a fixture of some sort to pressurize the port rather than try to use a high pressure airstream. The leak-thru method is quick and simple.