Valve train has broken apart TWICE in less than 800 miles!
Registered User
Joined: Feb 2000
Posts: 473
From: Lexington Park, Maryland, USA
I still think it's the tuneup and engine rattle/detonation. A strong hunch.
If you go to a hydraulic roller cam it can be just as hard or harder on your valvetrian if the lobe is aggressive and now the lifters are heavier than the mechanical roller lifter. So keep that in mind.
Hopefully my hunch on this is wrong and you have a simple problem with not enough valve spring.
Karl Ellwein
Ellwein Engines
If you go to a hydraulic roller cam it can be just as hard or harder on your valvetrian if the lobe is aggressive and now the lifters are heavier than the mechanical roller lifter. So keep that in mind.
Hopefully my hunch on this is wrong and you have a simple problem with not enough valve spring.
Karl Ellwein
Ellwein Engines
Registered User
Joined: Sep 2000
Posts: 211
From: Milwaukee,Wi
I'm taking the car back to him and demanding that he rebuild the engine; mainly because of the metal still present in the oil despite changing the oil twice. I'll definately get the springs that were on there and have them checked, even though it may be of little help after the fact. He's saying that the springs were tested with enough pressure (never gave any seat or open pressures) to handle the cam...for what that's worth.
I'll be switching the cam out for a hydraulic on the rebuild/clean up. Even though these springs may be fine for the newer smaller hydraulic, I might buy a set of new springs just to be sure.
I'll be switching the cam out for a hydraulic on the rebuild/clean up. Even though these springs may be fine for the newer smaller hydraulic, I might buy a set of new springs just to be sure.
Registered User
Joined: Feb 2001
Posts: 334
From: Daytona Beach, FL & Fort Lauderdale, FL
I had a similar problem with my SR 396 when I was first getting it going. It seemed after 1k miles something with the valvetrain would break and I could not figure out what was going on. The first time I was using comp 873 solid lifters and found more than one to be faulty. Engine had to come out because one of the lifters was stuck in the bore and I was afraid I'd have to get another block! Turned out that everything was fine and I had it refreshed anyway while it was out and went with the Crane 11522 solid lifters. Well after that was all finished, about 1,500 miles later I have another valvetrain catastrophe. Found 2 broke push rods and the tops of one pair of lifters were destroyed along with a broken 7/16 ARP stud. I figured it was due to stud flex and/or high spring pressure because both times I had studded rockers, but I was using a stud girdle. I was still dumbfounded that I kept having these issues.
So next time around got everything fixed and made some upgrades. Got some T&D shaft mount rockers (1.55 ratio), got some new pushrods (Trickflow chromoly .080" wall 7.9"L) and mocked everything up and inspected the **** out of all I could see. i was rolling the motor over and where the push rods wend down through the head into the lifter valley I could see that more than just a few push rods were making contact with the upper part of the cylinder head. I guess due to the change in lifter and push rod length it changed the geometry a little and the push rods were being put in a bind. The heads were already bolted down and I didn't want to go thru that whole process again, so I just took some blue painters tape and taped the hell out of everything and stuffed rags and taped off all possible openings where metal shavings could migrate. Proceeded to clearance all of the push rod through holes to more than they needed to be on the heads and then mocked everything back up for a re-inspection. Everything looked good, and now my solid roller 396 has close to 6k miles on it with out any valvetrain issues at all.
Cam specs are custom 260/266dur .672/.672 on 110, spring pressure closed is around 420~430# and open around 650+/-. The only difference is that I have stock LT1 casting heads, I don't know what the AFR's look like. But you may want to check that out. Sorry I didn't see this thread sooner, but good luck, I know it is frustrating as hell with all the $$ involved.
P
So next time around got everything fixed and made some upgrades. Got some T&D shaft mount rockers (1.55 ratio), got some new pushrods (Trickflow chromoly .080" wall 7.9"L) and mocked everything up and inspected the **** out of all I could see. i was rolling the motor over and where the push rods wend down through the head into the lifter valley I could see that more than just a few push rods were making contact with the upper part of the cylinder head. I guess due to the change in lifter and push rod length it changed the geometry a little and the push rods were being put in a bind. The heads were already bolted down and I didn't want to go thru that whole process again, so I just took some blue painters tape and taped the hell out of everything and stuffed rags and taped off all possible openings where metal shavings could migrate. Proceeded to clearance all of the push rod through holes to more than they needed to be on the heads and then mocked everything back up for a re-inspection. Everything looked good, and now my solid roller 396 has close to 6k miles on it with out any valvetrain issues at all.
Cam specs are custom 260/266dur .672/.672 on 110, spring pressure closed is around 420~430# and open around 650+/-. The only difference is that I have stock LT1 casting heads, I don't know what the AFR's look like. But you may want to check that out. Sorry I didn't see this thread sooner, but good luck, I know it is frustrating as hell with all the $$ involved.
P
Banned
Joined: Oct 2002
Posts: 6,518
Karl,
Only reason a Hyd Roller would be harder on parts is if the valve is not in control. For normal RPM range of a street motor, that's not very hard to keep them in control. Why are all you Imp guys always thinking that these hyd roller cams are so crazy?
As for this solid roller deal............
A solid roller for the street is not that hard, you just have to pay attention to the details of component mass and enough spring but not too much that it breaks things.
If you want it to be dead nuts 100% daily driveable for 30,000miles reliable it's possible to do but it's not cheap. That is the problem most have, the money problem.
FWIW most "Engine Builders" are far from understanding valvetrains to any high degree from what I have seen. If they are 50% there they are good, if they are in the 70-90% range they are excellent and EXTREMELY RARE! Most engine builders are probably in the 30% range of actually understaning valvetrains. By percentages I mean the amount of the system they actually understand.
Bret
Last edited by SStrokerAce; Dec 24, 2007 at 04:33 PM.
Registered User
Joined: Feb 2000
Posts: 473
From: Lexington Park, Maryland, USA
Karl,
Only reason a Hyd Roller would be harder on parts is if the valve is not in control. For normal RPM range of a street motor, that's not very hard to keep them in control. Why are all you Imp guys always thinking that these hyd roller cams are so crazy?
As for this solid roller deal............
A solid roller for the street is not that hard, you just have to pay attention to the details of component mass and enough spring but not too much that it breaks things.
If you want it to be dead nuts 100% daily driveable for 30,000miles reliable it's possible to do but it's not cheap. That is the problem most have, the money problem.
FWIW most "Engine Builders" are far from understanding valvetrains to any high degree from what I have seen. If they are 50% there they are good, if they are in the 70-90% range they are excellent and EXTREMELY RARE! Most engine builders are probably in the 30% range of actually understaning valvetrains. By percentages I mean the amount of the system they actually understand.
Bret
Only reason a Hyd Roller would be harder on parts is if the valve is not in control. For normal RPM range of a street motor, that's not very hard to keep them in control. Why are all you Imp guys always thinking that these hyd roller cams are so crazy?
As for this solid roller deal............
A solid roller for the street is not that hard, you just have to pay attention to the details of component mass and enough spring but not too much that it breaks things.
If you want it to be dead nuts 100% daily driveable for 30,000miles reliable it's possible to do but it's not cheap. That is the problem most have, the money problem.
FWIW most "Engine Builders" are far from understanding valvetrains to any high degree from what I have seen. If they are 50% there they are good, if they are in the 70-90% range they are excellent and EXTREMELY RARE! Most engine builders are probably in the 30% range of actually understaning valvetrains. By percentages I mean the amount of the system they actually understand.
Bret
Agree with you 100%, (I would like to put myself in the 30% range too showing that I only know enough to be dangerous at times).
But to rebut a little: on the hydraulic aggressive lobe dealie, I do think some people don't put enough valve spring on the aggressive lobe hydraulic cams. (some...not everyone). Terry Samakow has drilled into my head that even hydraulic roller cams need more valve spring than what is normally shown on the cam card.
You drilled into my brain that pushrod stiffness is very important.
Remember when spec-ing out my cam I told you I had some sort of massive 1.5" OD high spring rate valve spring on my heads that Terry Samakow set up for me (around 160lb on the seat)? Those springs worked wonderfully on the GM846 cam and now with the cam I have from you, (119+ mph in a 3800lb impy with stock bottom 350). Terry assured me that stock hydraulic lifters can handle a lot of valve spring and that failure is certain if there is not enough valve spring (loss of valve control). And we all know that but sometimes obvous things need to be stated.
To the subject of the poster's valve train failures, I know I cannot be the only one who thinks that the problem is not with the valvetrain (in this case) but with the tune, (engine rattle). Or am I the only one?
Karl
Registered User
Joined: Feb 2000
Posts: 473
From: Lexington Park, Maryland, USA
Detonation is big time engine rattle and it shakes the life out of everything in the engine. That is the most common cause of valve train failure, (in my opinion). Rockers fall off the stud, studs snap, valve springs break....
Other things that happen when detonating: oil pump drive gear flys out, oil pump pickup falls off, oil pump cracks/falls off main cap, piston pins get tight on the piston, piston skirts crack, optispark rotors fly apart...
Most of the time something in the valve train will break 1st.
The detonation is almost impossilbe to hear especially with a loud exhaust or open headers. For some reason the LT1 rattle does not sound like pinging. (you'll hear it as a dashboard rattle or similar sound).
Detonation is almost always caused by too much spark advance, (tune is too aggressive for the load on the engine).
Karl
Other things that happen when detonating: oil pump drive gear flys out, oil pump pickup falls off, oil pump cracks/falls off main cap, piston pins get tight on the piston, piston skirts crack, optispark rotors fly apart...
Most of the time something in the valve train will break 1st.
The detonation is almost impossilbe to hear especially with a loud exhaust or open headers. For some reason the LT1 rattle does not sound like pinging. (you'll hear it as a dashboard rattle or similar sound).
Detonation is almost always caused by too much spark advance, (tune is too aggressive for the load on the engine).
Karl
Registered User
Joined: Jun 2004
Posts: 411
Interesting, I was trying to figure out how it would apply a shock to the valve, but your saying thats its just like a very bad harmonic frequency shaking it apart? Wouldn't this show up in the upper rod shells as well?
Banned
Joined: Oct 2002
Posts: 6,518
Hi Bret
Agree with you 100%, (I would like to put myself in the 30% range too showing that I only know enough to be dangerous at times).
But to rebut a little: on the hydraulic aggressive lobe dealie, I do think some people don't put enough valve spring on the aggressive lobe hydraulic cams. (some...not everyone). Terry Samakow has drilled into my head that even hydraulic roller cams need more valve spring than what is normally shown on the cam card.
You drilled into my brain that pushrod stiffness is very important.
Remember when spec-ing out my cam I told you I had some sort of massive 1.5" OD high spring rate valve spring on my heads that Terry Samakow set up for me (around 160lb on the seat)? Those springs worked wonderfully on the GM846 cam and now with the cam I have from you, (119+ mph in a 3800lb impy with stock bottom 350). Terry assured me that stock hydraulic lifters can handle a lot of valve spring and that failure is certain if there is not enough valve spring (loss of valve control). And we all know that but sometimes obvous things need to be stated.
To the subject of the poster's valve train failures, I know I cannot be the only one who thinks that the problem is not with the valvetrain (in this case) but with the tune, (engine rattle). Or am I the only one?
Karl
Agree with you 100%, (I would like to put myself in the 30% range too showing that I only know enough to be dangerous at times).
But to rebut a little: on the hydraulic aggressive lobe dealie, I do think some people don't put enough valve spring on the aggressive lobe hydraulic cams. (some...not everyone). Terry Samakow has drilled into my head that even hydraulic roller cams need more valve spring than what is normally shown on the cam card.
You drilled into my brain that pushrod stiffness is very important.
Remember when spec-ing out my cam I told you I had some sort of massive 1.5" OD high spring rate valve spring on my heads that Terry Samakow set up for me (around 160lb on the seat)? Those springs worked wonderfully on the GM846 cam and now with the cam I have from you, (119+ mph in a 3800lb impy with stock bottom 350). Terry assured me that stock hydraulic lifters can handle a lot of valve spring and that failure is certain if there is not enough valve spring (loss of valve control). And we all know that but sometimes obvous things need to be stated.
To the subject of the poster's valve train failures, I know I cannot be the only one who thinks that the problem is not with the valvetrain (in this case) but with the tune, (engine rattle). Or am I the only one?
Karl
Karl,
Yes it comes down to standard dual springs with all that mass, they need 160lbs seated to work. I like to go the other way and lower the spring mass so I need less spring load, so less deflection is in the system. In valvetrains the general rule is don't underspring the motor! At the same time if attention is paid to the setup and you go in and watch you component mass then you can take load out of the system, which also takes out deflection and improves the valvetrain stability and life more!
Hyd lifters can handle WAY more spring load than most realize.
Other than the valvetrain being extremely hap-hazzard here it could just as easily be the tuning as well.
Bret
