Hello all,

Found a broken intake valve spring. My first inclination was to just put new springs on and roll. Valve lash was within a few thou of where I set it. Decided to do a compression check and it on shows 90 psi. Definitely leaking past the intake valve.

So stuck my camera in there, and it looks like the valve seat is all carboned up. No apparent contact with anything. So I was thinking, pull the spring and put my drill on the valve. Spin and and see if I can knock some carbon off and get it to seal.

I suspect it has been broken for a little while. I was chasing an issue with my transmission which masked the car was running off.

Do I just need to pull the head?

pull the head and lap the valve in

quote:

Originally posted by banjo:
Do I just need to pull the head?

Have you considered calling Chad?

Could not have been too broken since you won the no box shootout this past weekend...

Congrats on your win

Go ahead and pull the head. That way you can clean up the carbon much better and like said, lap the valve to check contact.

Forgot to add, use the finest lapping compound you can. Too coarse can be a bad thing.

I would pull the head. I also would check the valve guide for wear. Don;t forget to check the seat while there too.Time for springs maybe.

I would pull the head because it does not take much contact at all to bend a valve.

Thanks Steve, since I fixed the transmission issue, car is killer. Its alot easier to go rounds when I don't have a 2-4 number swing at the 330.

Based on the logger it has been broke for a while. I use a long extension and I listen to both sides of the valve train before every race and I didnt hear anything abnormal. The only symptom was that it was running a little slow, and that was masked by the transmission issue. It came up on the rev limitor clean and is very consistent.

This last race I was getting what felt like a high speed miss over 6800. Figured it was probably time for plugs and wires since I was going on 2 years and just lowered the shift rpm 200 rpms and it ran good. I put 27 laps on the car this weekend. I also got down to three cars in box the same night.

Definitely be replacing all the springs. Not sure how it lasted and ran like it did

Replace the lifter where the spring was broken. I'd also replace all the springs, and look closely at the lifter. If any of the other springs are really weak replace those lifters too. Every time I broke a spring I'd break that lifter within 50 runs.

quote:

Originally posted by banjo:
Hello all,

Found a broken intake valve spring. My first inclination was to just put new springs on and roll. Valve lash was within a few thou of where I set it. Decided to do a compression check and it on shows 90 psi. Definitely leaking past the intake valve.

So stuck my camera in there, and it looks like the valve seat is all carboned up. No apparent contact with anything. So I was thinking, pull the spring and put my drill on the valve. Spin and and see if I can knock some carbon off and get it to seal.

I suspect it has been broken for a little while. I was chasing an issue with my transmission which masked the car was running off.

Do I just need to pull the head?

First the intake valve chases the piston so it probably did not hit it,,, but you never know. What spring broke, outer, inner??

Next, if you put a new spring on and leaked it then without running it I'd toss that info out the window. Try running it first then leak it. If it does not get better and you can hear the air coming out at the carb then I'd pull the head,,, dropping a valve will hurt much more that pulling the head to find all is OK.

Good call on the lifters, didn't think about that. I got a set I need to send in to get rebuilt. Should I stick with the roller bearings or upgrade to the bushing.

I was thinking the same thing on the valve chasing the piston. Further I wouldn't expect the lash to be good if the valve was bent.

It was the outer spring that broke. I checked the opening pressure on all the other springs, and they were all in the 220 range, they start at 240, so they are all a bit tired.

quote:

Originally posted by Footloose:
I would pull the head. I also would check the valve guide for wear. Don;t forget to check the seat while there too.Time for springs maybe.

Me too. Often they loosen up with the low valve spring pressure for whatever reason.

One of the reason I swear b no such thing as working on car too much. Finding something small before it becomes huge.

As for lifters I would upgrade if can also no such thing as overkill on parts in valvetrain.

quote:

Originally posted by banjo:
It was the outer spring that broke. I checked the opening pressure on all the other springs, and they were all in the 220 range, they start at 240, so they are all a bit tired.

Bill, do you know about how many runs on this valve train prior to this problem?

They have around 1400 runs on them. The heads are definitely due for new valves, springs and hardware. I am talking with Chad, but by the time I replace all that stuff and get all the labor done, i will be a good way to an updated casting. Looking at possibly trading in what I have toward a fresh casting.

quote:

Spin and and see if I can knock some carbon off and get it to seal.

at 1400 runs ,bill?????

quote:

Originally posted by banjo:
...by the time I replace all that stuff and get all the labor done, i will be a good way to an updated casting. Looking at possibly trading in what I have toward a fresh casting.

You may be correct on that, but then you'll also need to get a lot of the same work done on your new castings so you won't really be money ahead.

I just went through that with a set of "bolt-on" heads from a major, reputable company in the industry. I'm sure they would have run fine, but you could see light past the closed valves. I had another $800 in making them right.

The cam was a custom deal that is very easy on the valve train. Up until this point, I have had zero issues with it. Valve lash never moves. You would probably fall over If I told what my cam guy said I should expect for life. All the other spring show good. Understand I will be replacing the lifters springs and valves at this point. I run my stuff hard, but I keep a good eye on things. I am not a fan of replacing things just to replace them. I know I will have the valve covers off a little more often as a result of this. I would have figured a broken valve spring would make more noise. I think my initial assessment that it was broke for a while is incorrect. Looking over the data further and the oil reports, I dont see anything that would indicate a problem as I would definitely think that a broken valve spring would introduce some metal into the oil.

quote:

Originally posted by Lenny5160:

quote:

Originally posted by banjo:
...by the time I replace all that stuff and get all the labor done, i will be a good way to an updated casting. Looking at possibly trading in what I have toward a fresh casting.

You may be correct on that, but then you'll also need to get a lot of the same work done on your new castings so you won't really be money ahead.

I just went through that with a set of "bolt-on" heads from a major, reputable company in the industry. I'm sure they would have run fine, but you could see light past the closed valves. I had another $800 in making them right.

I will get a ready to bolt on, complete head from Chad Speier, I have trust in his workmanship and should there be a problem, I have no doubts that he would remedy the situation.