cprstreetmachines

Do you have a solid cam ? Looks like you do. My guess is you broke it just putting around town no ? Look like you need the CM ones if so.

Can you take a pic of the top of your valve stem for me ?

urban_cowboy

The damage happened sometime while driving on the street and/or an open road course, so on the street yes but puttering...never. I never drive below 3k and often shift at 5500-6300. The motor does not really putter very well. Question, how can a solid roller cause damage while puttering on the street?

I can take a picture, but the valves are covered by hardened lash caps (previous disaster). They will not show much.

Since I confirmed that the spring rate is correct, I have to wonder if the random rich condition I experienced with the old DP carb, which has now been decommissioned for an HP, caused some crazy detonation that I could not really hear. If that is what caused it, holy cow it must have been bad! I would have thought I would hear these things splitting and cracking, but honestly you could not hear anything abnormal from the normal solid roller rocker valve train noise.

I have not noticed a close tolerance from the rocker to the stud...I determined the push rod length based on an adjustable push rod checker so that the roller movement pattern is centered on the lash cap. Even when the valve stems wore down, the horseshoe was even on the valve stem.

After talking with some street rod guys today, they all said the Jesel and Harland Sharp will be stout, but still have wear issues b/c they are aluminum. They suggested that since this was basically a race car on the street that I go with a stronger steel rocker. I have ordered a set of the Hi-Tech 15-5 PH Stainless Steel 1.7 rockers (high in nickel and chromium). I will try to give CC a call tomorrow and talk with them about the Pro Mag rockers and see which of the two are stronger and if the Pro Mag 351C 1.7 5/16" stud rockers will work for my Windsor AFR heads. If they suggest the Pro Mag, I will call and change my order. I like that the Pro Mag says, "Ideally suited for serious street, bracket racing, super classes, and circle track racing. You won't find a better roller rocker for the price." Of course the Hi-Tech rockers say, "Lifetime Guarantee
Hi-Tech™ Stainless Steel Rocker Arms are so strong that we guarantee the rocker bodies for life against breakage." Ha, we will see about that!

On another note, I find it interesting that both Jesel and Harland Sharp make both a SBF Windsor rocker and a SBF AFR Windsor head rocker. I wonder what the difference is even on the stud style rockers...?

67mustang302

You need to put one of the good rockers back on and go turn the engine over by hand and look for coil bind or some kind of rocker interference. Use a feeler gauge to acutally measure how much clearance is left in the springs at full open. It may just be that your setup is too much for aluminum rockers, but even the basic aluminum rockers still have a quite high tensile strength. Stainless is very strong though, as well as CM. And Jesel is pretty much the best valvetrain stuff around, bar none. It looks like it's something more than just aluminum not being strong enough, and you need to fix it before you break another set of rockers or start breaking studs, springs or valves.

JMD

there is something more going on thean meets the eye....

can't say what, but I don't think that your problem is really (or only anyway) the result of parts not up to task,,, I think something is breaking these arms... with your agressive solid cam, I can see parts breaking on their own, but not that quick...

Starfury

A lean condition can cause detonation, but a rich condition won't. Rich cools the mix, whereas lean would heat it up.

dnswwood

Hey Guys,

Urban cowboy I know you know a lot more about these classics than i do and when my painted 70 shell gets home this week i'll have lots of questions for you!!! FWIW I run fox body 4 banger on the dirt track ,I know they are OHC and all but we run solid lifters and have had nothing but problems out of aluminum rockers.We normally run these 4 bangers at 8500 rpms ..i know ..i know...But as soon as we went to the stainless rockers we had no more problems.I know its a different application but with the engine you are running ...and you've checked spring rates and push rod length..I would almost bet this is your problem

Jeff

my77stang

your making a good move by going to the steel rocker arms, they are supposed to be lighter than the aluminum ones at the tip anyways.

urban_cowboy

Thanks guys for all the great input. Since the CC Hi-Tech SS rockers are a different shape than my old CC aluminum rockers, I will need to check for clearance issues anyways so I will for sure do that. There is no coil bind going on here. I checked that before we fired up the motor the first time. I am also confident that the clearance was right because we had to clearance the rockers slightly on the spring side for the lift and spring diameter that I am running. The exhaust rockers look pristine, which you would think if there was an interference issue, they would so problems too. Keep in mind that these rockers have a few thousand miles on them. I would think interference issues would have shown up before now if that was the case.

I recently too 2 degrees of timing out of the top end to eliminate pinging at WOT during the summer months. How much pinging would it take to do this? I would think it would need to pre-ignite very early to slam the intake valve closed like that.

I am waiting on a leak down tester to see if I am going to have to pull the heads. If I have to do that, then I am going to tear this motor down completely and start over just to make sure everything is clean. If the cylinders are good, then I will pull the pan, get the debris out of it and flush it out real good before sealing it up.

This motor make me scratch my head a bunch, and I am really scratching at what caused this. Really glad I did not drop a valve!

jcoby

I don't understand why you think it's a pre-ignition issue? I could understand if it burnt a valve or broke a spark plug or something like that.

Now, this is all an uneducated guess, but it would seem like having the rocker split like that would be caused by vibration, not brute force. Force would break it in the middle or bend it.

Just as a guess, did you clay the piston? It's possible the valve is kissing the piston when the engine's warm? Just enough to cause minor binding but no damage?

67mustang302

Yeah, detonation won't do that. If you did detonate badly enough to vibrate and crack rockers, you'd rattle every bolt loose in the engine and break all kinds of stuff, cam, oil pump etc. It could be a ptv issue on the intake side as well, remember that when the engine is running 2 things happen, 1 is that the valve expands from the heat, reducing clearance, the other is that the momentum of the valvetrain causes slight expansion of the parts and the actual lift is a hair higher that advertised. It could also just be a spring vibration issue. What springs is it running, and do they have dampers? It could also be that the slightly larger intake valve which weighs more is just enough extra force to break the rockers, but again, you need to make sure it's not something else before you put a new set of rockers on and cause more damage.