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Old 04-28-2014, 02:44 PM
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Please advise on valvetrain issue.

I had GT40 (not milled) Cobra heads with the factory 1.72 Crane pedestal rockers. I removed those heads and traded them (with cash) for a set of Edelbrock performer aluminum heads that look new but are used. I got sidetracked with life and other priorities and the mustang went on a back burner...a year later I decided this weekend to put it back together.

The Edelbrock heads came with the same 1.72 Crane rockers but had .030 shims. Even though the heads were not milled I put it back together with the shims left on. After I fire up the engine, it is running with a bad miss and the rockers are knocking like rocks in a can. So I take the valve covers back off and removed all the shims, as I was doing that I noticed on the # 2 cylinder on the intake valve the rocker was loose, even after removing the shim with the valve closed, it has almost 1/4 of an inch free travel even after being torqued to 20lbs.

I suspect a flat lobe but it ran fine and was quiet before I tore it down (90 roller motor) and I do not see how a collapsed lifter would do this. The push rod is straight as an arrow. I ran it for a few minutes and shut it down and now it sits again. What should I look for to diagnose this? Thanks in advance!!!


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Old 04-28-2014, 02:50 PM
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. See if your valve stem tips are all at the same height... see if the pushrods are all exactly the same length...
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Old 04-28-2014, 02:53 PM
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Quote:
Originally Posted by BuzzLOL View Post
. See if your valve stem tips are all at the same height... see if the pushrods are all exactly the same length...
I will check the valve stems, the push rods should be all the same, I bought them from Summit a while back but I will check to be sure.

Thanks!
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Old 04-28-2014, 02:55 PM
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Got a better close-up view, and multiple angles??

Pushrods all the same length, not one oddball in there??

Are all the valve stem heights the same when valves are closed??

Stuck lifter plunger could give you 1/16 gap or more at the pushrod.

Last edited by ericnova72; 04-28-2014 at 02:56 PM. Reason: Buzz posted same time I was typing
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Old 04-28-2014, 03:00 PM
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Shaft in rocker not upside down, with wrong side facing pedestal is it??
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Old 04-28-2014, 03:09 PM
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Quote:
Originally Posted by ericnova72 View Post
Got a better close-up view, and multiple angles??

Pushrods all the same length, not one oddball in there??

Are all the valve stem heights the same when valves are closed??

Stuck lifter plunger could give you 1/16 gap or more at the pushrod.
Quote:
Originally Posted by ericnova72 View Post
Shaft in rocker not upside down, with wrong side facing pedestal is it??
I will look tonight. I really did not measure all the pushrods, just assumed they were the same since it is the same ones as before but I will check. I have not checked the valve stem heights at all and I will see if I can get an exact measurement on what the gap is, I was guessing 1/4" but could be less.

Holy cow, an upside down plunger would be nice lol, I am going to check for that as soon as I get home.

Thanks for the advice!
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Old 04-28-2014, 04:47 PM
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I don't know anything about Ford parts, but the instructions that came with my Edelbrock heads for a Chevy said to use .100" longer than stock pushrods.
Did you check the contact pattern on the valve stems with either a sharpie marker or dyekem?
Did you check the retainer to valve guide/seal clearance?
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Old 04-28-2014, 06:36 PM
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I figured it out (I think). Not sure what to do about it or why the guy I bought them from did not tell me about this. It looks like at some point shorter valves were installed. No telling how many, this is the only set I took off.



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Old 04-28-2014, 06:46 PM
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It looks like those valves were installed to use different rocker ratios on the intake & exhaust.
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Old 04-28-2014, 06:49 PM
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I went ahead and took off the set next to it and they are at the same height.
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Old 04-28-2014, 08:27 PM
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If it is all 8 intake valves, I could see it being done, for some reason like the mentioned differing rocker ratio's.

If it is just that valve or two,..... I would suspect a previous owner of having a problem and a piston tagged the valve and bent it, and a wrong length replacement was installed, either by total ignorant mistake and didn't even realize it,.... or ordered the wrong one/had one laying around and used it just to pawn the heads off as complete. (shady, scumbag move ).

I would have the head checked by a machine shop if you aren't a machinist type and know what to look for....could be valve seat or guide damage hiding in there.
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Old 04-29-2014, 12:04 PM
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Quote:
Originally Posted by ericnova72 View Post
If it is just that valve or two,..... I would suspect a previous owner of having a problem and a piston tagged the valve and bent it, and a wrong length replacement was installed, either by total ignorant mistake and didn't even realize it,.... or ordered the wrong one/had one laying around and used it just to pawn the heads off as complete.
. X 2... order correct length valve(s) and check for any other damage... make sure all springs are also of the same spec.s... springs set up for the pressures you need... never go excess pressures if using flat tappet cams...
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Old 04-29-2014, 12:13 PM
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Thanks guys. I hate that the guy I got them from failed to inform me of any of this and I have been sitting on them a year...lesson learned. I will decide on dropping them off at the machine shop or just saving for a new set.
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Old 04-29-2014, 12:33 PM
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Quote:
Originally Posted by ericnova72 View Post
If it is just that valve or two,..... I would suspect a previous owner of having a problem and a piston tagged the valve and bent it, and a wrong length replacement was installed
Or didn't replace it at all and it's still bent which is why it's missing so bad.
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Old 04-29-2014, 12:41 PM
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Or didn't replace it at all and it's still bent which is why it's missing so bad.
You are exactly right, that's a real possibility, if the new owner didn't look close at things before installing them.
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