Valve stuck again...

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zinser72

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I dont know if anyone remembers my other thread, but this is the third time this has happened to me. First two times were RHS heads and they didnt even last 10 min before sticking a valve. This set is EQ, ported with 2.02in/1.60ex. I have about 1000 miles on this combo. I have included some pics, i can only figure out one pic at a time on my phone so bear with me. Any input at all on why this is happeneing is GREATLY appreciated. Im getting really sick of changing heads with cheapo headers and power steering :banghead:
 

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Contact patch looks good as far as i know, i checked it at assembly and it was right in the center
 

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Pushrod is junk, probably bent too but i didnt pull it out. How tough are roller cams? When this happened with my solid flat tappet cam it took out a lobe. Im REALLY hoping thats not the case with my hydraulic roller. Sorry if pic size is off, stuggling with the phone here haha
 

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Couple of questions.... Has it always been the same valve? Is the valve bent? mark it before you remove it to see which way it was bent, what was the installed height versus full open?
One more thing. When you get the engine back together and running, hook up a timing light. Starting at #1 than going to what # your working one. The deal is that the timing light will Freeze a part in motion when you shine it on a part your looking at and you will be able to see if any of the parts are bending, rotating like they should, flexing or doing something strange. Also, it's a great way to find a bent fan blade in motion put a number in chalk on each one.
Any way hope this helps. Good Luck!Bill
 
Not enough guide clearance would be my first guess. ( and or ) Valve stem seals cutting off too much oil would be my next guess. I use metal clad blue viton seals as they allow enough oil by to keep things happy.
 
I agree with the seal thing, especially if it's an exhaust valve. Lots of engines run without exhaust valve seals. There's really no reason for them. Let the arguing commence.
 
1) carb too lean if its a exhaust valve swelling up and dragging in the guide.
2) something sticky in your fuel system ( sugar) did you piss someone off?

I have seen both cause this problem while working at the dealer
 
Ouch...

Skrews is likely correct--I don't want to insinuate anything, but did you have the heads looked at before you installed them, or did you bring heads to a machinist and have them assembled? I've seen similar issues with OOTB heads elsewhere...

Roller cams are pretty tough, so it should be OK-can you measure the lift the way it sits right now and compare to other lobes or your cam card?
 
Did any body check valve to piston clearance on any of these heads???

Were the spring, the recommended ones for each cam???

you can have the best guide to valve clearance.......and a bent valve will still stick in the guide!
 
I don't like the look of the contact patch on the valve stem. Notice that it is rectangular and not circular. That valve is not rotating. Possible causes:
- Tight guide or seal as suggested.
- Springs setting in the pockets in the head in a way that keep them from ever rotating.

Are the springs tight in the pockets perhaps? Are there any smooth shims under the springs to allow them to move freely or are the springs down against a rough pocket floor that is stopping rotation?
 
Thanks for all the replies! Let me try to answer some questions. The first time it happened it was ex #7, second time in #7. This time it is intake #5. The heads were fitted with bigger valves and ported by what i thought was a reputable shop but with this being the third time i definatley wont be going back to them.

Also piston to valve has miles of clearance (over .250 IIRC) but i will do some investigating when i have the money. Moving this weekend so ill be busy with the new house but i do know the previous two times the stem seized in the guides at low rpm. This time it happened about two seconds after winding it up in first (quick run to 6300 rpm) possibly couldve floated the valves and touched one? But it wasnt instantaneous. Like i said i shifted to third and started cruising away before it stuck.

I will post more pics and specs when i tear it down i was just looking for pointers on what to look for. Thanks again for all the replies! I will update with more pics and clearances as soon as i can
 
nm9stheham said:
I don't like the look of the contact patch on the valve stem. Notice that it is rectangular and not circular. That valve is not rotating. Possible causes:
- Tight guide or seal as suggested.
- Springs setting in the pockets in the head in a way that keep them from ever rotating.

Are the springs tight in the pockets perhaps? Are there any smooth shims under the springs to allow them to move freely or are the springs down against a rough pocket floor that is stopping rotation?
Click to expand...

Thats the insight i was looking for, i do not know about shims or clearance as i did not assemble them. Now i know what to check at disassembly, what should stem to guide clearance be?
 
Could not tell off the top of my head but I am sure someone here can. I'd be looking at all the valves wear patterns/guides/pockets/etc. Any chance the assemblers just did not clean the heads up fully and left cosmoline/other crap in the guides?? Probably no way to know now...
 
Well im hoping its a flaw in the headwork, otherwise im completely stumped because i carefully picked my combo. Obviously in hindsight i shouldve checked the heads but i trusted a shop that does them every day more than myself. Maybe i shouldnt have. Hopefully in a week or two ill have pics and clearances. At least i know what to mark and look for when i take it apart. Thanks guys!
 
I would have to say with two seperate brands, and different cylinders, you need a new shop. Chances are they assembled them too tight. Normally I use teflon seals but on the exh valves I remove the small wire spring that preloads the seal on the valve stem. The contact pattern looks fine to me as long as at mid lift the rocker is centered on the stem.
 
That pattern looks a little wide IMO, like the shaft needs to be shimmed a hair higher.
Whats the cam lift and the coil bind on the springs?
Seat and open pressure?
What wall thickness pushrods?
I'd also check seat runout if they did a valve job. Most shops don't do that either and the seat will **** the valve head and bend it and beat the crap out of the seat.
I run my guides tight- but their straight- and I don't have any issues with valves sticking or taking the springs off of seals. I see lots of shops use HSS reamers or just broach a guide and the guides aren't straight. So they ream or hone them bigger until the valve goes thru and now you have guides that wear out in 1k miles, the plugs get loaded with oil and it becomes a fog machine because in order to get the valve to fit they make it too big.
 
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