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Stumped. Miss when lifters pump up

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jakelandry

10+ Year Contributor
976
157
Oct 13, 2009
Minden, Louisiana
I rarely post anymore due to the outrageous amount of topics that have been covered on the forum but this one has me in a bind. I recently picked up a set of venom cam gears and Kiggly beehives for a good price. I degreed my cams and installed the springs and other head components after a good cleaning and whatnot. All seemed good so I cranked the car. Ran good for a minute till the lifters finally got quiet. Once they were primed the car sounded like it was only hitting on 3 cylinders.

Enter diagnosis mode. Before any of the following are suggested, let it be known I have narrowed it down to a mechanical part.

Spark, fuel, signals to both, wiring, ecu, fuel pressure, injectors, tune, all fine.

I narrowed it down to a single cylinder via turning the injectors off in link once at a time and listening for a lack of change. I also mechanically verified by manually pulling the plug off the injector also.

I did not set ignition timing yet but that is not the problem. The injectors are no longer dialed in 100% since I degreed the cams but that's not a problem. Dialing in the cams did not cause this because it is only on one cylinder. Thus it must be mechanical.

So I pull the VC off and rockers are still there. Lifters are hard as a rock. Everything seems normal. Nothing changed since the last time I had the car out other than what I listed so I assume the valves did not bend themselves. So I took out the lifters on that cylinder and bled them. Crank the car back up and runs good again. Obviously I'm getting closer. Assuming the lifters had an issue I bought a set of Evo 8 lifters. They are shorter than any of the other lifters but buscher runs them and I don't intend to call him a liar. So get them in and exact same scenario as before. The only thing I can think is a valve is hanging open once the lifters prime up enough to allow full lift from the cams. When installing them I had to shim a single lifter an extra .030 to make "comfortable" contact with the cam. Obviously something isn't right there, but the car ran 100% perfect before the upgrades and I don't recall doing anything valve bendingly horrible. I used the rope in the cylinder trick to hold the valves up when installing the valve springs but that's all I can think of. I'm open to any logical suggestions from you guys before I pull the head. I have tons of videos and photos but honestly I feel like I've described it well enough. As always, thank you for your time.
 
Is the lifter you shimmed on that same cylinder, it sounds like it is but you were not specific enough on that detail, I presume it is.
I would take the shim out and if the problem goes away I would try a different size and see what happens, of course you do not want to upset the geometry, so try it as a test only.
Another thing look real close at the keepers on valve movement as you may have one hanging on the re
tainer, as last resort, replace with what you had before and see if it helps.
Also doing a leak down test will narrow it even further, but you are correct a valve is staying open.
 
Yes, what appears to be the hanging valve is on that cylinder. I tried shimming all lifters (at different times) on the cylinder from no shim to .030, .040, .060, .070 just for testing and the results remained. I'll pull the cams and retainer off the valve I suppose and check for any oddities. I haven't done a leakdown because I know my valves are not sealing 100% as they're stock grind and I just lapped them until light, from a very concentrated light source, did not pass by them. So obviously I'll be losing some air through the valves. Thank you for the response though. I didn't think to double check the valve locks and whatnot. Honestly I'm just glad someone didn't chime in and say " have you tried new plug wires? Mine did that and that fixed it!!"
 
" have you tried new plug wires? Mine did that and that fixed it!!"

LOL at above, or boost leak test. That's another standard answer.
 
The tool was the style that bolts in place of the cam caps and uses a bolt to drive the retainer and spring down. Currently pulling the head. Will update within a couple hours
 
There is somthing holding the valve open or the spring is weak. Lifters don't pump up to hold a valve open, it would take like 300psi of oil pressure to do that. I would be pulling the head to inspect it.
 
Lash adjusters can and do pump up enough to hang valves open, happens all the time but at high RPM. I don't think that is the problem but wanted to mention it.

Can you pull the valve springs and move the valve in/out to see if it is binding in the guide? Could the valve stem been bent during cam install when the rocker wasn't installed correctly or got shifted during assembly?
 
Update 1:

I should have originally been more clear. I have regrind cams so I already have shims under each lifter. The lifter that required the double shim was on the bad cylinder. I pulled it first under suspicion from the need for the shim. The valve is not even remotely bent. Nothing abnormal anywhere to be found other than the act that the valve apparently is not as long.

I'll update more in a second. There are slight marks on the pistons from the exhaust valves which could just be from me using the rope method and the valve contacting the piston.

Update 2:

Slightly bent exhaust valve. Likely the problem, but still doesn't make sense how the car ran so well before the lifters primed. Will update once valve is replaced. For now the lesson appears to be "take the head off the car to change the springs". I assume the exhaust valves were the ones to contact due to the fact that they have a smaller contact patch with the piston, thus the rope has less chance of getting between the valve and piston. Either that or the amount of pressure required to break the locks free from the valves was enough to bend them.
 
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Maybe you should check the cam lobe to make sure it is ground properly and on center?

I considered that at first, but I never had an issue till now. About 10k ago I tossed a rocker and put a fair mark in 2 of the lobes. In that 10k I've been lucky to run all my fastest times with no ill effects, however I couldn't give a damn about the quality of the grind cause they've been trash for 10k now LOL.
 
Out of curiosity what regrinds do you have? I have DKS 272s and I was having a terrible idle vac. I've never seen the needle on the boost gauge fluctuate so much. I had to shim the intake lifters with .030 thick washers to make it steady. I've also tossed rockers out twice on different valves just from idling.
 
Out of curiosity what regrinds do you have? I have DKS 272s and I was having a terrible idle vac. I've never seen the needle on the boost gauge fluctuate so much. I had to shim the intake lifters with .030 thick washers to make it steady. I've also tossed rockers out twice on different valves just from idling.

This could be due to a number of things. I wouldn't blame the fact that the cam is a regrind though. If you've got your lifters shimmed where they are within their working range, the fail point is likely a lagging valve.
 
Im interested to know how this turns out, im having a very similar issue. Could be the lifters, or the cams not correctly diald in or maybe the height of the valve is not in spec causing it to hang. Did you thoroughly bleed the hla's before, cause I didnt LOL.

Yes I spent a solid hour bleeding them down. I didnt soak them or anything, just bled them as I've done numerous times previously. I'm fairly confident it was the exhaust valves. Nearly every exhaust valve made slight contact with the pistons. Only 3 were bent, but now I'm questioning how they all hit the pistons. I degreed the cams to the real hks 272 card's spec so I assume they didn't tap on startup. All I can assume is using the rope to support the valves when compressing the springs was a bad idea. I've already replaced the valves but I have to wait till Monday to get a head gasket and arp lube for my head studs so I will update once it's back together.
 
Lash adjusters can and do pump up enough to hang valves open, happens all the time but at high RPM. I don't think that is the problem but wanted to mention it.

Can you pull the valve springs and move the valve in/out to see if it is binding in the guide? Could the valve stem been bent during cam install when the rocker wasn't installed correctly or got shifted during assembly?

Your not implying that oil pressure alone can push a valve open are you? That's phyically impossible, the valve needs to float for the lifter to pump up and hold it open.
 
I got the car assembled yesterday. It runs fine again. It was the bent valves. I didn't change my cam gears any so they must have bent when installing the springs as previously assumed. Thank you all for he help
 
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