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jamdak
Dodge Dakota
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2/10/2007
22:00:12
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 Subject: Broken Rockers
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Message:
On my '93 318, cylinders 1 and 7 were not firing. I removed the valve cover and cylinder 1 and 7 intake rockers were completely broken off! Now these are the stock stamped rockers being driven by a .512 lift cam and held back by stiff RT springs. Perhaps these rockers simply couldn't can the pressure? Any other ideas why these would fail?
Also, a compression test showed zero compression on those two cylinders. Since these valves are always closed, shouldn't I have seen full compression on those two cylinders? Or is zero compression normal for broken rockers? Can a stuck valve cause it to burn and have no compression? However there was no fuel entering the cylinder with the intake valve stuck closed so it couldn't burn, right?
I have already have a set of roller rockers on hand that I was going to use for my 408 but not sure if I should install them and call it good or completely remove the head (lot more work...).
Thanks for any suggestions!
James
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Fasstdak
Dodge Dakota
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2/10/2007
22:10:08
| RE: Broken Rockers
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The factory rockers can't handle the change in geometry...let alone the spring pressure. You need to change them out.
If you either nicked or bent the valves (with the rocker broke), you wouldn't see any compression at all. One or the other is hanging open.
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jamdak
Dodge Dakota
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2/11/2007
14:12:10
| RE: Broken Rockers
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Message:
Yeah, I figured it was too much for the factory rockers.
I also wouldn't see any compression since the intake valve doesn't open to suck up any air, right? None of the other 3 strokes would allow air in either. I'm going to run compressed air into the spark plug hole (making sure the exhaust valve is closed too) to see if I hear hissing out the exhaust or intake (as suggested by others).
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OBIO3
Dodge Dakota
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2/12/2007
02:09:08
| RE: Broken Rockers
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Message:
If your going to put pressure to them cylinders, you best have the crank at BOTTOM DEAD CENTER or your likely to bend/break more. And the last post was correct. No air getting in, no compression.
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N56629
Dodge Dakota
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2/12/2007
06:36:37
| RE: Broken Rockers
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If you have NO air getting into the cylinder then you have a total vacuum. Not a likely situation.
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jamdak
Dodge Dakota
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2/12/2007
09:05:17
| RE: Broken Rockers
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Message:
OBI03, "If your going to put pressure to them cylinders, you best have the crank at BOTTOM DEAD CENTER or your likely to bend/break more."
What exactly did you mean by this? I'm not sure how compressed air will bend/break more if the cylinder is not at BDC.
Thanks for the clarification.
James
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