Why am I breaking valves???
TECH Resident
Joined: Jun 2007
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gee's-u got to get on this issue quick smart-if it has happen twice-
hope it gets better-
that hurts-
like someone said-u must find a good engine builder with a good track record
as stated by others-about the engine eating up the oil-where is it eating up the oil-
was the ring gaps set-up good???
take care and take it easy-
hope it gets better-
that hurts-
like someone said-u must find a good engine builder with a good track record
as stated by others-about the engine eating up the oil-where is it eating up the oil-
was the ring gaps set-up good???
take care and take it easy-
Last edited by njc.corp; Aug 30, 2007 at 11:26 PM.
TECH Enthusiast
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Actually minor detonation will hardly bother a piston. However the heat cycling will absolutely kill a ti valve when its overheating that badly. retarded timming hardly ever cuases fialure with valves. It wouldn't take much in the way of knock to drive combustion tempatures sky rocketing.
Originally Posted by edcmat-l1
WOW. All that from a couple pictures. HUH.....
Yeah it was burnin oil, but ya think its gonna snap a one piece titanium valve due to elevated combustion temps due to detonation, before its going to burn an aluminum piston? OoooKaaayyy.......
Before I put it on something like that, I'd more say it was retarded timing, causing increased exhaust temps. That would more likely cook an exhaust valve stem. Detonation would more likely burn a piston, as its happening in the chamber. Increased exhaust temps occurring in the port would have more of an effect on the stem.
Besides, from the pics, no sign of severe detonation. It is going thru some oil though.
Yeah it was burnin oil, but ya think its gonna snap a one piece titanium valve due to elevated combustion temps due to detonation, before its going to burn an aluminum piston? OoooKaaayyy.......
Before I put it on something like that, I'd more say it was retarded timing, causing increased exhaust temps. That would more likely cook an exhaust valve stem. Detonation would more likely burn a piston, as its happening in the chamber. Increased exhaust temps occurring in the port would have more of an effect on the stem.
Besides, from the pics, no sign of severe detonation. It is going thru some oil though.
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On The Tree
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From: Braking Point, Turn In, Apex, Exit - Repeat
It would suprise me if the engine was knocking, I originally used Torco fuel additive when I first started running the motor, that is were the orange on the exhaust valves came from, at the last event I switched from Torco to a mixture of 1/3 98 octane race gas to 2/3 93 pump. So I would say that the octane was always up there, so detonation wouldn't likly be t he cause. Also wouldn't the knock sensors help me out there? It didn't seem like I was using that much oil, I would only use 1 quart over a 2 day weekend, which wasn't cause of alarm at the track.
Originally Posted by LS1curious
Actually minor detonation will hardly bother a piston. However the heat cycling will absolutely kill a ti valve when its overheating that badly. retarded timming hardly ever cuases fialure with valves. It wouldn't take much in the way of knock to drive combustion tempatures sky rocketing.
Combustion temps start to elevate before audible knock ever occurs.
But, looking at the pics, dont really know how you can come to that conclusion.
Not to mention the fact that nothings happened to the valve faces.
As far as retarded timing causing any of it, I was pointing to retarded timing as a cause of increased temps in the exhaust port.
Personally I think its just a case of really bad luck. I mean, who the hell breaks a one piece valve? and all the questions about valve springs? What about all the solid roller springs with 600+ open pressures? You dont see them rippin the heads off.
I know bounce aint good for em, but rip the head off a one piece?
The post about guides being too tight may be on to something.
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A guide being tight will not cuase a head to break off a TI valve. Heat working them and hardening them will cuase them to fial.
the valve springs if they had some bounce could have cuased some trouble but very doubtful it made a valve head pop off.
the valve springs if they had some bounce could have cuased some trouble but very doubtful it made a valve head pop off.
Originally Posted by edcmat-l1
I realize all that. Emissions/5 gas analysis is one of my specialties. I monitor combustion temps by monitoring NOX.
Combustion temps start to elevate before audible knock ever occurs.
But, looking at the pics, dont really know how you can come to that conclusion.
Not to mention the fact that nothings happened to the valve faces.
As far as retarded timing causing any of it, I was pointing to retarded timing as a cause of increased temps in the exhaust port.
Personally I think its just a case of really bad luck. I mean, who the hell breaks a one piece valve? and all the questions about valve springs? What about all the solid roller springs with 600+ open pressures? You dont see them rippin the heads off.
I know bounce aint good for em, but rip the head off a one piece?
The post about guides being too tight may be on to something.
Combustion temps start to elevate before audible knock ever occurs.
But, looking at the pics, dont really know how you can come to that conclusion.
Not to mention the fact that nothings happened to the valve faces.
As far as retarded timing causing any of it, I was pointing to retarded timing as a cause of increased temps in the exhaust port.
Personally I think its just a case of really bad luck. I mean, who the hell breaks a one piece valve? and all the questions about valve springs? What about all the solid roller springs with 600+ open pressures? You dont see them rippin the heads off.
I know bounce aint good for em, but rip the head off a one piece?
The post about guides being too tight may be on to something.
Originally Posted by LS1curious
A guide being tight will not cuase a head to break off a TI valve. Heat working them and hardening them will cuase them to fial.
the valve springs if they had some bounce could have cuased some trouble but very doubtful it made a valve head pop off.
the valve springs if they had some bounce could have cuased some trouble but very doubtful it made a valve head pop off.
And I agree, bounce shouldnt do it either.
On The Tree
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got any pics of the rocker arm geometry from before this happened? I think it may be a combination of rocker studs flexing causing the valve to be pushed open and an angle (Unless you got shaft mounts) and then the design of the cam letting the valve slam shut with the force of the stiff springs. Titanium is light and strong but prone to fractures.
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On The Tree
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From: Braking Point, Turn In, Apex, Exit - Repeat
There was a T&D shaft mount rocker system with roller tips on the the car the second time. I will have to let LPE take a look at the seat concentricity, I've already shipped them the motor to check it out.
Wow, had a bone stock 6.0 do that on a 2002 HD2500 last week. Here's the pull out. I'm thinking the valve stuck in the guide holding it open and the piston top dead centered thus knocking the tip off the valve?? Did yours break off like this one? This was an elderly lady that didn't even get it over 2500 rpm's probably.
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From: Braking Point, Turn In, Apex, Exit - Repeat
We sent the motor to LPE and they "suggested" that the motor was over reved, which is kind of a cop out. I hit the rev limiter (6800 rpm) once when I first got the motor, but since then it hasen't been reved past 6300 rpm. I shift at 6000 and it may see as high as 6300 when I blip the throttle coming into a corner for a downshift. What LPE told me was a lifter may have pumped up when I blipped the throttle and the valve hit the piston. I thought they had relieved the pistons since they knew I was going to road race the car. But it seems like there wasn't enough PTV clearance and the valve hit.
I think the lifter pumping up may be the best idea I have heard, because I switched from 5w30 to 15w50 just before the motors last event because I noticed the oil pressure was running low at the previous event.
Thanks for all of the responses, on top of all of the carnage there is a bent rod, and I haven't checked out the crank yet. Looks like I will be starting over from scratch.
The valves were not coated btw.
I think what it came down to was I was running too much lift on the cam, and I just didn't have enough PTV clearance. I had LPE design and assemble the motor because I wanted it to be reliable and put together start to finish by professionals. LPE has a great name behind them but road racing motors are not there thing if something as simple as PTV clearance wasn't checked. And even if it was checked it is obvious now that it was not sufficient. It is unfortunate and now I know better than to use such a high lift cam for road-racing.
I think the lifter pumping up may be the best idea I have heard, because I switched from 5w30 to 15w50 just before the motors last event because I noticed the oil pressure was running low at the previous event.
Thanks for all of the responses, on top of all of the carnage there is a bent rod, and I haven't checked out the crank yet. Looks like I will be starting over from scratch.
The valves were not coated btw.
I think what it came down to was I was running too much lift on the cam, and I just didn't have enough PTV clearance. I had LPE design and assemble the motor because I wanted it to be reliable and put together start to finish by professionals. LPE has a great name behind them but road racing motors are not there thing if something as simple as PTV clearance wasn't checked. And even if it was checked it is obvious now that it was not sufficient. It is unfortunate and now I know better than to use such a high lift cam for road-racing.
FWIW it's not always lift that causes PTV contact.
My first experience with a broken valve head was due to PTV clearance at .000 and I never checked. I had a high lift short duration cam during the engine build up and it had a ton of clearance. Then I swapped to a cam with .028 less lift but more duration and never checked. The duration caused the contact by opening the intake earlier. It ran three passes down the 1/4 mile and had about 500 street miles before it broke.
It was so close that the pistons that made it had a circle the shape of the intake valve with no carbon and no indication of contact.
Something else thats a bit disturbing are the posts I've seen here where people ask if there PTV will be ok with a certain cam. In the posts I've seen the person asking the question gets a few 'yes it should be ok' answers and never bothers checking.
My first experience with a broken valve head was due to PTV clearance at .000 and I never checked. I had a high lift short duration cam during the engine build up and it had a ton of clearance. Then I swapped to a cam with .028 less lift but more duration and never checked. The duration caused the contact by opening the intake earlier. It ran three passes down the 1/4 mile and had about 500 street miles before it broke.
It was so close that the pistons that made it had a circle the shape of the intake valve with no carbon and no indication of contact.
Something else thats a bit disturbing are the posts I've seen here where people ask if there PTV will be ok with a certain cam. In the posts I've seen the person asking the question gets a few 'yes it should be ok' answers and never bothers checking.
On The Tree
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Time to get some solid lifters in there. http://www.automotiverebuilder.com/ar/eb120524.htm is a good article on valves, seems as the conditions your car goes through coated valves might be a better option.
Staging Lane
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From: under the hood
Originally Posted by 8a8mfh
FWIW it's not always lift that causes PTV contact.
The notion of lift causing the V/P problem comes from the old school cams where more duration always meant higher lift values.
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From: Austin, Texas
Originally Posted by LT-4Play
I tried posting this in the Gen III internal page and haven't recieved much input I thought maybe some of you advanced guys would have a better idea. In the last year I have broken 2 valves on 2 different motors and I can't help but wonder why.
The car is a 2002 Z06 that I run road racing track events with, I'm not hard on the motor, I shift right at or a little after 6k, 6200 at the most. I haven't mis-shifted/overreved either motor. (Rarley I'll hit the gate instead of the gear but I never aimed for 4th and hit 2nd) I heel toe downshift and blip the throttle to match revs coming into corners but not anything out of the ordinary at the track.
Tunes are conservative running less than 13 to 1 AF usually between 12.5 to 12.7 on the WOT pulls.
The car has full bolt ons, 1 3/4 Melrose Motorsports headers, Random cats, stock Ti mufflers, DeWitt's radiator with internal engine oil cooler, Blackwing, ported throttle body (by LPE), ported LS6 intake (by LPE).
1st motor stock LS6 bottom end with LPE heads, LPE GT1-1 cam (229in/242ex .631"in/.631"ex 114 lsa) stock LS6 valves, Comp 921 valve springs, Comp push rods, and Harland Sharp rebuilt stock rockers. I put about 2k miles on the motor and the way I figure the head of the number 8 exhaust valve broke off and blew the motor, broke the timing chain and cracked the block. I've also entertained other ideas, such as valve float, but I don't think the lightweight valve floated with a 921 spring, if anything I think we had too much spring for that valve. So there I am with a blown LS6, I figure this time I will have LPE build me a motor from top to bottom so it's done right.
2nd motor LS6 stoker Callies Racemaster crank, Manley H beam rods, JE pistons, LPE heads, LPE GT11 cam (215in/231ex .631in/.644ex 118 lsa), (I think the valves were Manley but I do know that they were Titainium intake and exhaust, Ferrea 99100 valve springs (150#@ 1.800" 475#@ 1.250" CB 1.050"), Comp pushrods, and T&D shaft mount rocker arms. This time the number 3 exhaust valve head broke off and took out the head and the block.
So WHAT THE HELL!!!!! Both times I tried to keep the valve train lightweight to minimize the chance of valve float etc, I keep the revs down and both times a valve head breaks off. Do I just have the worlds worst luck or am I missing something here?
The car is a 2002 Z06 that I run road racing track events with, I'm not hard on the motor, I shift right at or a little after 6k, 6200 at the most. I haven't mis-shifted/overreved either motor. (Rarley I'll hit the gate instead of the gear but I never aimed for 4th and hit 2nd) I heel toe downshift and blip the throttle to match revs coming into corners but not anything out of the ordinary at the track.
Tunes are conservative running less than 13 to 1 AF usually between 12.5 to 12.7 on the WOT pulls.
The car has full bolt ons, 1 3/4 Melrose Motorsports headers, Random cats, stock Ti mufflers, DeWitt's radiator with internal engine oil cooler, Blackwing, ported throttle body (by LPE), ported LS6 intake (by LPE).
1st motor stock LS6 bottom end with LPE heads, LPE GT1-1 cam (229in/242ex .631"in/.631"ex 114 lsa) stock LS6 valves, Comp 921 valve springs, Comp push rods, and Harland Sharp rebuilt stock rockers. I put about 2k miles on the motor and the way I figure the head of the number 8 exhaust valve broke off and blew the motor, broke the timing chain and cracked the block. I've also entertained other ideas, such as valve float, but I don't think the lightweight valve floated with a 921 spring, if anything I think we had too much spring for that valve. So there I am with a blown LS6, I figure this time I will have LPE build me a motor from top to bottom so it's done right.
2nd motor LS6 stoker Callies Racemaster crank, Manley H beam rods, JE pistons, LPE heads, LPE GT11 cam (215in/231ex .631in/.644ex 118 lsa), (I think the valves were Manley but I do know that they were Titainium intake and exhaust, Ferrea 99100 valve springs (150#@ 1.800" 475#@ 1.250" CB 1.050"), Comp pushrods, and T&D shaft mount rocker arms. This time the number 3 exhaust valve head broke off and took out the head and the block.
So WHAT THE HELL!!!!! Both times I tried to keep the valve train lightweight to minimize the chance of valve float etc, I keep the revs down and both times a valve head breaks off. Do I just have the worlds worst luck or am I missing something here?
I've read your post and some of the responses; you have a couple of issues here. First I have built a bunch of motors with Ti valves, I was an engine builder for Cosworth for many years. Every motor coming out of that place had Ti valves.
I also build LS1 motors and have seen many problems with the timing chains breaking. We have it worked out and I would be happy to share the information with you.
There is no way you were floating a Ti valve with 150 lbs on the seat at 6200 rpm. Just can't happen, I have built more than a few road race LS1 motors. We use steel valves, Comp Cams springs and turn 7000 rpm all day. You have something else going on here. If you would like to give me a call I would be happy to go over some options with you.
It would be easier to go over on the phone, advice is free.
Harold
Port Pros LLC
512-257-0222
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From: Houston, Tx.
Without verifying the p to v and radial p to v there's no telling if that had anything to do with anything. Could have stuck a guide too or so many things. I agree wth Harold that the spring pressures and Ti valves "should" be fine at any rpm that it seems you were talking about. Could be many things.