HELP! Bent valve issues with engine builder
HELP! Bent valve issues with engine builder I'm working with a builder here in Bakersfield, CA (No names) and continue to have issues with bending valves.
Specs:
408 Stroker
Comp Cams Custom Grind (234/242 .601/.605 LSA 112 +2)
Comp Cams dual Springs
HA-2281 (?) Roller Lifters
7.400 Comp Pushrods
CNC ported 243 heads - Engine builder rebuilt heads and installed new guides.
OEM rockers with CHE performance bushing upgrade
The engine has bent valves on 2 separate occasions. The first time was an Exhaust valve. The builder said the tune was bad as all 8 Ex valves were hot and that they got stuck in the guides. They charged me to rebuild it all.
Second time it bent a valve I was after getting the stall converter installed. We were test driving/datalogging (with a Tuner here in town that Builder recommended) and it bent an intake valve. The shop asked me about the valvetrain. He then checked the pushrod length and said the pushrods should be 7.375". We told the builder and they blew it off. From my understanding, they did not check the pushrod length on this engine. Truck went to the builder to pull the engine, who now says 4 Ex Valves are hot and galled (Not 8 like last time) He said they had opened up the guides 0.001" to give better clearance - yet it still happened. Also said fuel in the oil, typical excuses, etc.
Builder is saying the tune/electrical is what has caused this, and are not talking about the intake valve bending this time - just the exhaust valves being hot.
The tuner who datalogged the it didn't see any issues with the tune. Has anyone here had problems with valve guides being bad? If the pushrods are too long, would that throw off the valve train geometry enough to be the culprit? I'm sure I'm missing a few things, just feel like I'm being taken for a ride by the machine shop.
Thanks,
CptMidway
Specs:
408 Stroker
Comp Cams Custom Grind (234/242 .601/.605 LSA 112 +2)
Comp Cams dual Springs
HA-2281 (?) Roller Lifters
7.400 Comp Pushrods
CNC ported 243 heads - Engine builder rebuilt heads and installed new guides.
OEM rockers with CHE performance bushing upgrade
The engine has bent valves on 2 separate occasions. The first time was an Exhaust valve. The builder said the tune was bad as all 8 Ex valves were hot and that they got stuck in the guides. They charged me to rebuild it all.
Second time it bent a valve I was after getting the stall converter installed. We were test driving/datalogging (with a Tuner here in town that Builder recommended) and it bent an intake valve. The shop asked me about the valvetrain. He then checked the pushrod length and said the pushrods should be 7.375". We told the builder and they blew it off. From my understanding, they did not check the pushrod length on this engine. Truck went to the builder to pull the engine, who now says 4 Ex Valves are hot and galled (Not 8 like last time) He said they had opened up the guides 0.001" to give better clearance - yet it still happened. Also said fuel in the oil, typical excuses, etc.
Builder is saying the tune/electrical is what has caused this, and are not talking about the intake valve bending this time - just the exhaust valves being hot.
The tuner who datalogged the it didn't see any issues with the tune. Has anyone here had problems with valve guides being bad? If the pushrods are too long, would that throw off the valve train geometry enough to be the culprit? I'm sure I'm missing a few things, just feel like I'm being taken for a ride by the machine shop.
Thanks,
CptMidway
Obviously there's a P-V clearance issue here so start looking at things that could cause this. Much more information is needed regarding the engine and I'm referring to the engine's components, the camshaft installation and most of all the needed measurements to determine what the root cause is. GL
Obviously there's a P-V clearance issue here so start looking at things that could cause this. Much more information is needed regarding the engine and I'm referring to the engine's components, the camshaft installation and most of all the needed measurements to determine what the root cause is. GL
Now, I'm still not sure what caused the galled/stuck valves - put that would point to valve guide clearance being off. Never heard of a sticking guide from the valves getting too hot - which is what the builder is saying.
Builder put together the long block so I only know what I've been told. From that I only believe half now.
Anyway, if nothing other than morbid curiosity I'll update the thread, as the Greek tragedy of my engine build continues. Hopefully my lessons learned can help others.
CptMidway
No oil up top?
Guides still to tight?
Curious, stock type guides?
Stock valves?
I think it would be difficult to overheat the exh valves. The tune would be so far off the car would barely run.
Too long of pushrods isn’t the problem.
Going to be interesting!
Guides still to tight?
Curious, stock type guides?
Stock valves?
I think it would be difficult to overheat the exh valves. The tune would be so far off the car would barely run.
Too long of pushrods isn’t the problem.
Going to be interesting!
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I'm working with a builder here in Bakersfield, CA (No names) and continue to have issues with bending valves.
Specs:
408 Stroker
Comp Cams Custom Grind (234/242 .601/.605 LSA 112 +2)
Comp Cams dual Springs
HA-2281 (?) Roller Lifters
7.400 Comp Pushrods
CNC ported 243 heads - Engine builder rebuilt heads and installed new guides.
OEM rockers with CHE performance bushing upgrade
The engine has bent valves on 2 separate occasions. The first time was an Exhaust valve. The builder said the tune was bad as all 8 Ex valves were hot and that they got stuck in the guides. They charged me to rebuild it all.
Second time it bent a valve I was after getting the stall converter installed. We were test driving/datalogging (with a Tuner here in town that Builder recommended) and it bent an intake valve. The shop asked me about the valvetrain. He then checked the pushrod length and said the pushrods should be 7.375". We told the builder and they blew it off. From my understanding, they did not check the pushrod length on this engine. Truck went to the builder to pull the engine, who now says 4 Ex Valves are hot and galled (Not 8 like last time) He said they had opened up the guides 0.001" to give better clearance - yet it still happened. Also said fuel in the oil, typical excuses, etc.
Builder is saying the tune/electrical is what has caused this, and are not talking about the intake valve bending this time - just the exhaust valves being hot.
The tuner who datalogged the it didn't see any issues with the tune. Has anyone here had problems with valve guides being bad? If the pushrods are too long, would that throw off the valve train geometry enough to be the culprit? I'm sure I'm missing a few things, just feel like I'm being taken for a ride by the machine shop.
Thanks,
CptMidway
Specs:
408 Stroker
Comp Cams Custom Grind (234/242 .601/.605 LSA 112 +2)
Comp Cams dual Springs
HA-2281 (?) Roller Lifters
7.400 Comp Pushrods
CNC ported 243 heads - Engine builder rebuilt heads and installed new guides.
OEM rockers with CHE performance bushing upgrade
The engine has bent valves on 2 separate occasions. The first time was an Exhaust valve. The builder said the tune was bad as all 8 Ex valves were hot and that they got stuck in the guides. They charged me to rebuild it all.
Second time it bent a valve I was after getting the stall converter installed. We were test driving/datalogging (with a Tuner here in town that Builder recommended) and it bent an intake valve. The shop asked me about the valvetrain. He then checked the pushrod length and said the pushrods should be 7.375". We told the builder and they blew it off. From my understanding, they did not check the pushrod length on this engine. Truck went to the builder to pull the engine, who now says 4 Ex Valves are hot and galled (Not 8 like last time) He said they had opened up the guides 0.001" to give better clearance - yet it still happened. Also said fuel in the oil, typical excuses, etc.
Builder is saying the tune/electrical is what has caused this, and are not talking about the intake valve bending this time - just the exhaust valves being hot.
The tuner who datalogged the it didn't see any issues with the tune. Has anyone here had problems with valve guides being bad? If the pushrods are too long, would that throw off the valve train geometry enough to be the culprit? I'm sure I'm missing a few things, just feel like I'm being taken for a ride by the machine shop.
Thanks,
CptMidway
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Verdad Gallardo Still seems like there is 2 separate issues - the guide issue and the bent valve issue. Builder has absolutely avoided the fact that an intake valve bent this time and solely focused on the exhaust valves again.
Teching In
Joined: Dec 2020
Posts: 48
Likes: 29
From: DFW, TX
If you have a build sheet i'd be curious to see what guides/valves are and what clearances are set to. If the guides are set correctly, no tune up should get them hot enough for them to stick.
Bronze guides/Stainless valves for 8mm valves i like to see .0015 on the intake, .0018 on the exhaust. On bigger power adder applications i'll loosen the exhaust up to .002-0025"
Powdered metal guides will require a larger clearance, about .002 on the intake, .0025 on the exhaust
This is just my professional opinion, each engine builder likes their own clearances. I'd rather have the guides a tad lose and drink tiny bit of oil rather than stick a valve though.
Bronze guides/Stainless valves for 8mm valves i like to see .0015 on the intake, .0018 on the exhaust. On bigger power adder applications i'll loosen the exhaust up to .002-0025"
Powdered metal guides will require a larger clearance, about .002 on the intake, .0025 on the exhaust
This is just my professional opinion, each engine builder likes their own clearances. I'd rather have the guides a tad lose and drink tiny bit of oil rather than stick a valve though.
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
Does this guy have a rep of building LS motors that have been pushed and survive? If he's willing to make it right and give you a build sheet with all the setup specs for no $$ - you could try it 1 more time. If not, I'd move on to a reputable shop. 3rd times not a charm!
If your PTV clearance is .008" like you stated earlier, that is your problem. When I checked mine I had .040" on the intake and there was no way I was going to run with that. I retarded the cam to get the intake PTV clearance to .070" and helped my dynamic compression ratio at the same time. I wouldn't do anything else until I checked that or had it checked.
I spent a good part of the day yesterday at the machine shop and on the phone with others trying to figure all this out. I did ask the builder for a build sheet and was asked "What is that". /Facepalm.
Consensus on the bent Intake valve is that fueling washed out the valve. They have not completely disassembled both heads - just the cylinder that had issues. They use a metal guide with a groove in them that helps hold oil. On the passenger side, 2 of the cylinders had oil (or fuel) all inside the intake ports and you can see the difference between the chambers on the passenger side head. These are CNC'd heads so the threads/bolts for the intake rockers are exposed to the ports. When I asked them about if they sealed them they said it would make no difference.
The pistons look in good shape and the cylinders didn't look to be scored vertically. Kid who pulled the heads showed the plugs on the front 4 cylinders looked black - but not oily.
The injectors are factory decapped that were flow matched - These will be sent out to the be checked to ensure flow pattern and rates are correct. Current opinion is that either the injectors are bad, or not calibrated correctly to the tune and just dumping too much into the cylinders under FT.
Moving forward:
Consider throwing 317 heads on (milled slightly to keep CR at ~10.5:1) - I already have these at the house.
Replace decapped injectors with 42lb ls3s or similar.
This would likely be the quickest way to get the truck back on the road and replace what could could be the issue(s).
I appreciate everyone's comments and advice.
CptMidway
Consensus on the bent Intake valve is that fueling washed out the valve. They have not completely disassembled both heads - just the cylinder that had issues. They use a metal guide with a groove in them that helps hold oil. On the passenger side, 2 of the cylinders had oil (or fuel) all inside the intake ports and you can see the difference between the chambers on the passenger side head. These are CNC'd heads so the threads/bolts for the intake rockers are exposed to the ports. When I asked them about if they sealed them they said it would make no difference.
The pistons look in good shape and the cylinders didn't look to be scored vertically. Kid who pulled the heads showed the plugs on the front 4 cylinders looked black - but not oily.
The injectors are factory decapped that were flow matched - These will be sent out to the be checked to ensure flow pattern and rates are correct. Current opinion is that either the injectors are bad, or not calibrated correctly to the tune and just dumping too much into the cylinders under FT.
Moving forward:
Consider throwing 317 heads on (milled slightly to keep CR at ~10.5:1) - I already have these at the house.
Replace decapped injectors with 42lb ls3s or similar.
This would likely be the quickest way to get the truck back on the road and replace what could could be the issue(s).
I appreciate everyone's comments and advice.
CptMidway
Honestly it would take a **** ton of fuel to dilute the oil enough to not lubricate the valve and then somehow not hurt the main or rod bearings.
We have equipment at work that we lubricate with fuel. It's not like fuel doesn't have lubrcation properties.
I guess I am politely calling bs
We have equipment at work that we lubricate with fuel. It's not like fuel doesn't have lubrcation properties.
I guess I am politely calling bs
Would be interesting to see some data logs of the car while driving it. With wideband data. Your tuner says it’s fine, machine shop says there is fuel in the oil. Seems to be a disconnect.
Stock ecu?
With a stock ecu, decapped injectors are rather a mess. The only solid data the tuner has to work with is flow rate. If that’s even correct. You don’t get any of the other data that is critical in the GM tune. Tuned one last year and I was just chasing my tail until we put some flex fuel injectors in, added the data and it tuned up very easily.
Tuned correctly, your plugs should be Snow White, not black.
Many of us have been on here for years, I don’t remember any posts about galled valves/guides. Including many turbo cars with stock heads. A guy would think that those cars would punish the exh valves.
I’m also not buying the no sealant needed on the intake rocker bolts.
Ron
Stock ecu?
With a stock ecu, decapped injectors are rather a mess. The only solid data the tuner has to work with is flow rate. If that’s even correct. You don’t get any of the other data that is critical in the GM tune. Tuned one last year and I was just chasing my tail until we put some flex fuel injectors in, added the data and it tuned up very easily.
Tuned correctly, your plugs should be Snow White, not black.
Many of us have been on here for years, I don’t remember any posts about galled valves/guides. Including many turbo cars with stock heads. A guy would think that those cars would punish the exh valves.
I’m also not buying the no sealant needed on the intake rocker bolts.
Ron
.008 on the ptv.
No build sheet.
De capped injs.
Multiple failures.
"Rebuilt" heads.
Cam location is?
Would be too much
, for me to go back to that guy.
Glas beads do wonders on valve stems/guides.....
No build sheet.
De capped injs.
Multiple failures.
"Rebuilt" heads.
Cam location is?
Would be too much
, for me to go back to that guy.Glas beads do wonders on valve stems/guides.....