Can I get a Freaking Break!!!!!!

[ArmyWarrant]

I must be f@#$ing cursed, doomed to not own a stang without having carnage happen! I was merging onto I-64 downshifted into 3rd and accelerated into traffic, got up to 5k RPM and heard a loud ping and the car start missing and carrying on. I pulled over and pulled off the hood and started the car and heard stuff banging off the drivers side valve cover so I shut it down quickly and waited for a tow truck. I got it home and here is what I found under the drivers valve cover.







I don't think there is any damage to the valve but I want to make sure that there was no contact between the piston and the valve. Can someone send me a link to the procedures to measure piston to valve clearance. Id appreciate it.

[ArmyWarrant]

Just to add I checked the pushrod and it straight as an arrow. The only thing I can figure happened was the rockers backed off on those two valves. I would think if there was contact with the valve and piston that the pushrod would have bent prior to the rocker stud snapping.

[Rodeheaver's]

why do those rockers say sbc???? have you checked the valvetrain geometry?? thats usually the cause of that, or way to much spring pressure due to a huge cam and no stud girdles.....

[Rodeheaver's]

it is very hard to check ptv clearence with the heads on the car, just about the only way to do that is to put a checker (real light) spring in place of the exhaust and intake spring of the #1 cyl and set up a dial indicator to touch the top of the valve retainer totally parallel (with the rockers off that cyl of coarse), then rotate the engine 15 degrees before and after tdc of #1 cyl, you must check it at 15 before and after TDC... Once you are at 15 degrees in either direction, watch the indicator and push down on the valve and see how far the indicator is moving, you want no less than .100 ptv clearence 15 before and after TDC...

[ArmyWarrant]

I don't know, they were on it when I got it. I just got off the phone with a friend in new york an he is sending me a set of crane full roller rockers 1.6. I have access to dial indicators and everything but I need a degree wheel for this process right? I also checked the pushrod and they are stock length pushrods and I just don't think that is right. I was told when I bought the car that it has a z cam in it so I really don't think stock length pushrods are right for it. correct me if I am wrong.

Does a z cam have enough lift to require stud girdles?

I am gonna try and check the geometry tomorrow and make sure that the tip is riding in the center of the valve stem

[Rodeheaver's]

yes you do need a degree wheel, and the lift didnt break the rocker stud, the stud broke from valve train deflection, that means the stud is moving back and forth till it breaks, i would find it hard to believe that a piston hitting a vlavel would break that stud, it will usually bend a valve or bend a pushrod... And there is no cam that requires stud girdles, there is only big springs required by a big cam that needs stud girdles...and i would think that the correct springs for a z cam would not be that bad, but i would have to look up the number to be sure, and who is to say you have the correct springs???

[ArmyWarrant]

Thanks for all the info Tim, is there a way to find out what springs are on the heads? Also I think I am going to pull the heads to make sure that there was no damage done and then use the clay to check ptv. It looks like its gonna be down for a while then, I want to make sure that everything is right, while I got the heads off I'll be able to verify that it is a Z cam in the motor. Again thanks for all the info

[Rodeheaver's]

the only way to find out what the springs are is to check the preasure on a spring checker..... valve springs usually have no markings.. i guess thats why there are only 2 places in the ENTIRE world that make valve springs.....or so i have been told ..

[SK@StreetLethal]

Sometimes sbc rockers are used on sbf's to get better valve train geometry. Been there done that, the engine or heads don't know that rockers were stamped sbc. It's not so much you want the pattern dead center on the valve but that you want the narrowest pattern you can get.

[ArmyWarrant]

I think my engine shop at work has a spring tester so I think I'll disassemble the one valve and bring it with me to work tomorrow and see if I can figure it out. I really hope that its just a matter of the rockers backing off, I know wishful thinking but I have to lol

[INSANELY CRAZY]

why do those rockers say sbc???? have you checked the valvetrain geometry?? thats usually the cause of that, or way to much spring pressure due to a huge cam and no stud girdles.....

he wanted to go fast so what better way then put chevy parts in the ford motor.....

[Rodeheaver's]

Sometimes sbc rockers are used on sbf's to get better valve train geometry. Been there done that, the engine or heads don't know that rockers were stamped sbc. It's not so much you want the pattern dead center on the valve but that you want the narrowest pattern you can get.

i know i know... i was just jackin his wires..LOL

[ArmyWarrant]

Well I won't be abel to get access to the spring tester until monday so i am gonna wait until this weekend to tear into the car.

[ArmyWarrant]

Well I couldn't hold off on working on the car so I just took the other rocker of that cylinder and I got another kick while I am down. The pushrod is bent on that valve.

I was wondering if I floated the valves would that cause the damage I have? I moved the valve that had the bent pushrod and it moves freely without binding so I don't think it is bent. Wouldn't the valve be bent also if there was contact with the piston? I am hoping so. I plan on taking the heads off for sure now just have to wait until after the holidays for the garage space in my buddy's garage. I won't have my garage until october or I'd wait til then.

[ArmyWarrant]

How do I determine what spring pressure my valve springs should have for my cam? I was told that the car has a z303 cam in it and I will hopefully verify that this weekend by using my dial indicator that is designed for the lifter hole and finding the lift at the cam lobe. The z303 is supposed to be .345 I & E at the cam and .552 I&E at the valve with 1.6 ratio rockers. I want to make sure I have the right valve springs before I reassemble the engine after tear down. Any help would be greatly appreciated.

[ArmyWarrant]

Well I haven't been able to get a trailer to tow the car to the garage yet so I did some work I could at my house today. I checked for coil bind and didn't find any. I also checked how the rocker was riding on the valve stem and think I have some geometry problems, shouldn't the roller tip of the rocker be riding more towards the center of the stem then it is in this pic?

[altoona]

It's a little hard to see exactly where it's riding in that picture, but I've always been told that getting the smallest possible contact patch on the valve stem is more important than having it exactly in the center.

You can take a sharpie and make a mark on top the valve stem, then reinstall the rocker and turn the engine a couple revolutions. You'll then have a witness mark that will tell where and how wide your contact area is.

[ArmyWarrant]

Heres a better shot of that rocker

[SK@StreetLethal]

Loosen the rocker arm stud and adjust the guide plates over a bit. That should solve that issue.

[ArmyWarrant]

OK, Also I am wondering if the pushrods I have are ok for guideplates? These are the ones I have. It doesn't say anything about being hardened

http://store.summitracing.com/partde...5&autoview=sku