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Valve lash cap breaks right in half?
Hey big-block motorheads...,
any idea why a valve lash cap might break right in half, and all other caps look perfect? My builder is out of the country on business this week or I'd bug him first. Engine: 428CJ Valve Lash Caps: by Crower Crower Cam: Solid Lifter / .640 lift Rocker Assembly: Shelby / Stainless with end-stands Two 6,400 rpm shifts; and 20 minutes later one failed. Broke right in half. Another guy in our Shelby Club said he has heard of this happening to others before. Any thoughts? Bad materials? Who knows? Thanks. |
The heat treat could be too hard. How is the lash on the rest of the valves? Another possibility is that that valve lost the lash for whatever reason then the cap broke in half. My guess would be the first.
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Metal Fatigue, improper heat treat or fit. Pick your poison.......
Rick PS: Just an afterthought. The valve stems should have a very small chamfer on the end. If this is lacking the sharp corner could cut into the fillet machined in the recess of the lash cap creating a stress riser inside the cap itself. |
Too much cam for the set?
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Mismatch between the taper lock angles of keepers/ caps?
Can you even get different lock angle keepers for FEs? |
Duane -
What cylinder heads are you using and what has been done to them - I am noting the amount of lift your cam has.... pb |
Re:
Hi Pat,
Edelbrock heads, solid lifter, added a 2nd inner valve spring... because they only handle .600 lift stock. .015 valve lash with aluminum heads. I'm in Wisconsin this week, and hopefully looking at it closer when I return. Closer inspection of the cam/lifters, etc... Thanks. |
Same reason the pin on my pin Trigo pin drive wheel shattered the first time I applied an open handed slap to the allen wrench.. Crappy quality control.. What the hey.. It's under warranty..
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I have seen some lash caps (name brand) that were poorly made and actually had a little left over tit sticking up on the flat surface that the valve mates up to (inside). Anyway that coupled with a heat treat would create enough of a stress riser to break it IMO.
Dale |
lol broken aps?
i took my car to toe preformance for the same reason only weeks after my purchase. Tony the owner said the guy who did the wrench work overtightened it..oh yea I bought my car from you! l:LOL: :LOL: :LOL: maybe you should torque em......
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Dcooney, are you sure about the .15 valve lash?, If correct I would set at .17
to compensate for heat expansion. You might be down to .13 after it warms up. |
Hi Perry,
.15 would be extreme without a zero in front of it. We are talking thousandths, not tenths here - right? :) Up to .006 tighter (Initial set cold) on aluminum heads, per the cam MFG. I don't have iron heads... Yea, .017 hot would work..., My current cam calls for .022-I/.024-E hot and -.006 cold. Running it a little looser would seem safer to me too, but Crower says they'd like to see it even go tighter when set hot. |
FWIW, 0.015" should be OK. I've got the Edelbrock heads and Crane cam, also. Recommended lash for the cam is 0.022. Both Crane and the builder said subtract 0.008 for the aluminum heads, so I set them at 0.014 and it seems to be running OK. My experience anyway. Seems like you might have just gotten a bad rocker arm. Any further analysis?
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Hey Chopper,
as per your question, and to make a long story short some additional analysis was done on my cam profile, overall lift, valvesprings, dampners and retainers, and total valve lash itself. A few suspect areas such as the particular valve springs I used, in combination with my solid lifter cam, profile, and revisiting usability prompted me to swap out my cam last weekend. Also ordered a set of matched Crower springs, dampners, lifters. Nothing conclusive yet, but working to eliminate variables that have been noted as questionalble ones. So far so good. Thanks. |
didn't read the whole thread but
If you are loosing a cam lobe or you somehow adjust it too loose, the slapping could cause the problem, Take you time and just look, It will come to you. It always does,
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