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Author Topic:   Cam Break in Q's, continuation
Winland Racing
Member
posted April 16, 2004 09:45 AM
Continuation from previous post..
Purchased a HYD. cam, was recommended to break in with weaker springs and 1.6 rockers, break in complete, no problems.
Change valve springs yesterday to 300# (cam recommendation)and installed 1.5 rockers. Engine ran for 2 minutes, then #4 intake rocker pops off the valve, bent push rod, change it, happens again (2 more times), them #7 pops off both rockers, bent push rods, changed them.

What is causing this?
It is currently running but I am concerned this will happen again.
The only visual thing I can see is that the intake rocker on #4 appears to be slightly walking off the valve, it is more slightly skewed than all of the others????

Please advise,
Thanks,
WR#66


dirtbuster
Member
posted April 16, 2004 10:05 AM
You used 1.6 rockers for breakin? Then changed to 1.5 this seems backwards to me.

Did you check to make sure your not in coil bind on the springs? or hitting a valve guide or something? That could bend the pushrods then let them wander off and slip off the rocker tip.

racerman707
Member
posted April 16, 2004 10:19 AM
Just curious,what type of heads are they? Newer models have self aligning rockers.


Winland Racing
Member
posted April 16, 2004 12:05 PM
Hello DirtBuster,
I think I got it backwards. I used the stock 1.5 rockers for break in then installed the 1.6 after the springs were installed.
Racerman,
I have 041 heads with 194 valves. Nothing too fancy. I run enduros in the 200 lap range. I did have a valve job and I know that he had to shim the valves to get the proper seat pressure as directed by the cam card.
I spoke to Charles at Camcraft and he thinks I am experiencing coil bind, and it is possible that my head guy may not have gotten the screw in stud exactly perfect on #4 intake.
I am going to talk to the head guy this afternoon.

Any other ideas??
Thanks again,
WR#66


Raz_900
Member
posted April 16, 2004 01:34 PM
1.) Coil Bind
2.) GuidePlate misalignment
3.) Pushrods hitting factory guide slots in the heads. If the shop didn't drill the holes larger, 1.6 rockers WILL NOT clear a stock head.



dirtbuster
Member
posted April 16, 2004 01:34 PM
pick a cylinder and roll the enigne over by hand until you reach max lift on the intake and check to see how much if any gap is left between the coils of the spring. Then repeat for the exhaust side. If you find any that are completely closed up or close to it you are coil bound. To really check you should do this to all cylinders as your head guy may have shimmed every spring based on the worst case and that might cause problems on some sylinders but not others.



Winland Racing
Member
posted April 16, 2004 03:10 PM
My head guy left town for the weekend so I will have to wait till Monday!
Raz,
I didnt know that I would have to drill the guide plates using 1.6 rockers.
If they were rubbing, I would have some marks where it rubbed?? I didnt have any marks where they pass through the guide plates.
If I install the 1.5 stock ratio rockers, Charles said my lift would go from 491 to around 461.
Is the only thing that I will lose be the top end powerband?? Any other drawbacks?
The tracks are generally muddy and only come in after 80-100 laps??
Thanks for the input,
WR#66


racerguy500
Member
posted April 16, 2004 06:11 PM
I am agreeing with the coil bind theory if it didn't do it with the 1.5 rockers. You are also right that it will drop your lift to about.461" but if it is coil bind that may not be enough clearance, once you get a few thousand rpm it may still happen. Had it happen to a teammates car last year. Ran great till about 5000 rpm then it would hit, bend everything and fly apart. Shims are good for causing that too. But if you have the springs recommended by the cam manufacturer you shouldn't need shims should you? I was always taught you need .010" clearance between coils for every 1000 rpm, not sure how accurate that is but never had a problem that way. Good luck.


Raz_900
Member
posted April 16, 2004 08:57 PM
Not the guideplates... the slots in the heads themselves. They should be either slotted to about twice normal length or drilled with a 1/2" bit if using guideplates and screw in studs.


rico 08
Member
posted April 18, 2004 08:53 AM
I don't think .491 lift would bind any spring,my cam is .509 and i've got the old cheap z28 springs with plenty of clearance before it binds.I'd look at the stud height on #4.Seems like alot of spring for a .461 lift cam unless you're talking over the nose pressure.


autoshop
Member
posted April 18, 2004 10:10 AM
could also be valve to piston clearance... let's hope not.

I'll vote coil bind - assuming that your cam is .491 with stock 1.5's it would be about .524 with the 1.6's - if your springs were only good for .500 you've found the culprit...

Winland Racing
Member
posted April 19, 2004 08:57 AM
Thanks for all of the ideas.
I am going to talk to the head shop today.
I originally had heavy duty springs installed in the heads, then the cam arrived stating that it needed a 300# spring and a certain seat pressure. I had the head guy remove the HD spirngs and put light duty in for break in. It seems the more you try to do the more problems that arise...Typical cause and effect.
I will post what repairs my current delema.
Thanks again,
WR#66


Winland Racing
Member
posted April 20, 2004 12:18 PM
Come to find out the pushrods were 7.9" wheras stock is 7.8", this in addition to the 1.6 rockers was causing the pushrod to slightly rub causing the bending. I have gone to a stock push rod and the stock 1.5 rockers. I re-adjusted the valves last night and all seemd well.

My advice to anyone that wants to use 1.6 rockers, have your heads drilled before installing them. There is a tool called the LOUIS tool that is designed for this. Apparently it is a 50.00 tool that is good for one set of heads.
I currently have one set of 1.6 rockers for sale,used for 20 minutes (if that) email if interested.
Thanks for the replys!

WR#66

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