did i bend a valve? and why is this happening?

[clutchdust]

i'm still working on my friends '72. i finally got it running the other day. i did a C/R check because #6 seemed to be weak and found the valve adjustments were all scattered to hell. i readjusted the valves per my haynes manual: .008"/intake and .010"/exhaust, cold as measured between the cam lobe and rocker. this is the way i read it in the book. the problem i'm experiencing now is that i continue to have rocker arms jumping out of the valve guide (what do you call that little cup with rails the rocker rides on?). so after i adjusted the valves intially last week, i got it running and it sounded pretty good. i had to move it and it sat for a week over christmas while company was in town. so i go out to work on it last week and had a hell of a time getting it to start. i was even pouring raw gasoline in the carbs and it would not fire. so i do a compression check again (that is how desparate:ermm: ) and i find that the #$4 intake rocker has jumped up and is riding on top of the valve guide thingy. so i think, "hmm, that's weird" and i fix it and reset the clearance. i finally get it running and end up moving the car, everything seems to be running reasonably well considering the car hasn't run in 3+ years. got late so i put it up for the night. the next day, i want to just run it some more to run some of that crappy gas out of it and it won't start...again. go through the litany: got fuel, got spark, got compression... on 5 cylinders. i check and find #2 has done the same thing. i reset it and finally get it running but it has a definate miss. i pull the valve cover....AGAIN! to find the #3 intake rocker is cocked now. so i fix it and adjust the lash but notice this time that on this valve, the ball stud is ~1/4" higher than the others. i remove the rocker and measure across the top of the retainers and find the intake valve is lower than the valves next to it by ~1/4". i still get the car running but #3 cylinder has no compression, definately missing.

so now for the questions: is valve to piston clearance tight enough that this 'cocked rocker' condition could cause valve to piston contact resulting in a bent valve? if the valve is bent, how did it bend #3 but not #2 or #4, which also jumped out of place? why do the rockers keep jumping out of place? is there a way, short of removing the head, to check the valve seat to see if the valve is bent or if it may just be a big chunk of carbon stuck in there? is there a good source on-line for valves and gaskets should this be the problem?

hellllpppp!!!

[Phred]

Ok I'll Give you my 2 cents worth. I have had some experience with a similar problem. First, after sitting unused for a long time, two different things can happen to the valves/guides. First is the carbon on the valve stem and guide I.D. will really harden with unuse. Combine this with an engine sitting around for a long time, and what oil there was on the valve/guide has completely drained off. Now you start it up and the valve momentarily sticks to the guide when its half open. Then the rocker arm jumps off, and the piston comes back up and trys to close the valve. So you end up with a bent valve. It just depends on how much lift the valve had when it stuck, weather or not the piston would hit it or not. Generally there is plenty of valve/piston clr. The only other thing that would cause V-P interferance is if the cam lost its timing due to a timimg chain jumping a number of teeth.

Quick test for damage. remove the rocker arm and spark plug from the cyl. in question. Turn eng. over so piston is at bottom dead center. Now with lash pad removed, tap on the end of the valve stem with a brass punch and hammer. You don't have to hit hard. It should pop up and down freely, and all retainers should be very close to the same relative height. When this happens it can also nick up the lobe when the rocker tries to jump out. So check for damage there too. More than likely the head is going to have to come off for proper repair.

Phred

[Zedrally]

Hate to be the bearer of bad news, but you've got a bent valve.

There is no cure short of pulling the head, checking for piston damage, [cross fingers and hope that it's only a nick and turning the engine over hasn't created more damage].

This happened to me once, the pin that holds the cam timing sprocket moved and strange tap tap noises eminated from the engine,as it quickly came to a holt.

Subsequent inspection revelled a couple of bent valves and one that had totally snapped and was floating free in the cylinder. Luckily the only damage was a slight nick in the top of the piston that I filed out.

Needless to say I check the cam and pin very often now!

[clutchdust]

hey guys, thanks for the input, even if the news isn't what i'd like to hear. i was afraid you were going to say that:ermm: this is a little bit of a new experience for me since i'm used to working on American iron, but engines is engines, right?

phred, i'm afraid at this point that it must be a bent valve since i have done like you suggested already and the valve will not come back up. i get no compression on that cylinder and when the engine does run it does really funky things to my vacuum. too bad it wasn't the exhaust instead, at least it would run and be semi-stable. the intake just screws everything all to hell.

so the next step as i see it is to talk to my friend and see if she wants to invest that kind of additional money in this car. if it were really straight and in very nice condition, there wouldn't be a question. unfortunately, that isn't the case though. she lived in colorado for a time and the winter salt has taken it's toll on the lower rocker panels and the floorboard appears to have been punched in from an improper jacking attempt.

i may just offer to get it running and if she doesn't want to pay what the final cost is, i'll buy it from her from what she put into it so far. i did some checking yesterday and it appears i can pull the head and replace a bent valve and springs and all the upper gaskets for >$100. that's not that bad a deal.

last set of questions (for this post) is if i do pull the head, as long as i have it off, should i have it milled? and how much will this bump compression? would it be worth it? if i do get this car i want it to be a little terror untill i can drop in my SBC:devious:

[Zedrally]

Originally posted by clutchdust

last set of questions (for this post) is if i do pull the head, as long as i have it off, should i have it milled?

SBC:devious:

This again you won't now until you pull the head.

Look at the coolent level, has it dropped, do you need to top it up every time it runs?

If the answer to this is no, then it is unlikely that you have a warped head and you can plan on not milling the head.

On the other hand if it's using water it could be the gasket, or a cracked head.

The worst that you would need to plan on is a head from a donor engine.

[Zedrally]

Clutchdust,

I should have added that working on 240's can be addictive.

List warning.

Proceed only if you do not want to become addicted to zed's.

[i wouldn't be surprised if you didn't fall in love with the car and buy it]!

:love:

[justaZcarguy]

Hey Zed,

My cam just moved on the pin a few days ago, took out some valves...

Don't feel alone.

I posted the experience under "well here's the damage"

So, Clutchdust, hang in there, I just took the head off, if you need any advice, feel free to call me at 503.357.9776.

Have a good day, and look at it this way, it's repairable and at least you'll know what the inside looks like...

Brian

[clutchdust]

hey brian, i used to live in vancouver, wa for a couple years and a friend of mine moved up to FG about three years back. so....how's the weather? (sorry for that)

[justaZcarguy]

You know how a sponge feels, right?

Actually, the last few days have been cloud free and it's gonna last thru Sunday!! Woooohooooo!!!:classic:

Too bad the fast one is not driveable.....

I wonder if I know the friend that moved here....

Bri

[clutchdust]

sunshine through sunday, ehh?

got sunblock?

FG is that small, huh? buddies name was neil. we lost touch a few months after he moved. he would forward stuff to me though until about last year and i haven't gotten anything from him in a while. went by 'testtune'.

i still miss vancouver... in july and august.

[clutchdust]

so if i do pull the head, how do i deal with the chain? i'm seriously not going to pull the front of the engine down for this crap. can i just mark the cam timing and pull the sproket bolt? any advise on this stuff?

[Zedrally]

Set up #1 to TDC, jam some heater hose to hold the timing chain in place and off you go!