[QUOTE=Richard Roupe (51187);n1575296]The rest of the story.....
I picked up my engine from the shop this week. They repaired the cylinder with a sleeve, replaced the pistons, valves, valve springs, oil pump etc. Kept the cam, crank, rest of the valve train. Replaced the one head that was toast with a good dated part. It is running sweet. Good oil pressure, good torque and HP. We left the flat top pistons in specifically for the fuel, at their recommendation. compression is at 10.5:1
Just as a reminder, this is an L46 original block to the car and when it was rebuilt the time before, we installed a roller cam and roller lifters.
But here's the interesting part - I have been talking to them on and off about trying to figure out what happened to it. My initial guess was a malfunctioning heat riser valve since I discovered that it wasn't opening properly, right before the engine let loose. But they couldn't find any heat related damage, anywhere. Upon assembly and initial run on the dyno, the builder noticed a slight noise and put his hand on the valve cover. He felt something that wasn't right. Removed the valve cover on the right side and noticed marks on the oil baffle, right below the PCV valve. This also happens to be above the valve that failed, #6. He removed the other side and saw the same thing although not as pronounced. He corrected the intereference with the rockers and it all appears and runs good.
His guess, which is probably correct, is the roller rocker interference caused the valve to hang and the piston hit the valve and snapped it off, causing all the other damage. The rest of the valves were fine. I don't have a better answer and since the previous shop installed the roller, I can only guess they missed the problem in the build. Which would explain also why the engine didn't last very long. They should have checked for interference and caught it. They didn't. Jerks.
I'm still going to replace the heat riser valve though. Can't wait to get it back in the car!
A couple pictures of the cleaned up piston are below.
Just though you may want to add this to the body of knowledge out there.
Best,
Rich
Unless I missed it earlier, this is your first mention of "roller cam" and "roller rockers". Do you mean roller tip rockers or roller trunnion rockers?
A lot of things in this thread don't add up. You said it's a '69 L-46, but it has 300 HP heads and pistons. Doesn't make sense. There were three different engine codes for '69 L-46 depending on the engine's front end accessories.
How about posting a photo of the block stamp pad, and at what RPM on the tach does the redline start?
Regarding the cam and rockers, roller cams usually have more lift than flat tappet cams, so piston to valve clearance may be insufficient, and if a valve kisses a piston it can bend the stem and leave an impression on the piston or even break the stem at which time the valve head becomes a "soccer ball" that considerably reworks the entire piston crown, along with the head chamber and usually the cylinder walls too, which is the case with your engine.
BTW, if you have basic specs for the installed roller cam can you list them?
If the "roller rockers" are of the roller tip variety with conventional ball and socket pivot you are another victim of one of the biggest scams in the aftermarket parts industry. Most think the rocker arm tip slides over the valve stem. This is not the case unless the valve train geometry has been totally screwed up by excess removal of block deck and head surface material. The OE rocker tip that contacts the valve stem is curved so that with nominal valve train geometry the rocker tip ROLLS across the valve stem. Sliding is non-existent or at most, minor, so all roller tip rockers do is add valve train mass and a moving part that can fail.
Consider modern LS engines. They have ROLLER TRUNNION rockers that replace the ball and socket with a needle bearing. The tips are plain, and curved so they, too, ROLL across the valve stem, not slide.
So it sounds like you fell into the typical "engine builder" trap... roller cam, roller (tip) rockers... probably a high volume oil pump, too. If the oil pressure gage pegs at 60 most of the time at over 2000 revs, you got had.
I'm not a fan of roller cams for vintage engines, especially small blocks. I know Joe recommends them especially for big blocks, but I'm beginning to come around because the BB valve train is much more heavily loaded than small blocks due to heavier valve train components, and the OE springs are much stiffer than small blocks; but given the same lifter diameter, lobe-lifter interface loading is much higher. Cam and lifter failures are controversial. Some blame the blanks. Some blame insufficient crown on the lifter surface, while others blame insufficient lobe taper; and there are also reports of roller lifters coming apart. I'm not sure what to believe!
In fact, right now I'm working with a '67 L-71 owner in Northern CA on a rebuild. I have a baseline in Engine Analyzer 3.4 for the OE L-71 (other than CR lowered to 10:1) as installed in the car... SAE net, water pump, clutch fan, and 500 CFM @ 1 5" Hg exhaust flow model, which has proved to be accurate from testing for the C2 2.5" under-the-car exhaust system for several other projects. The head model may change if the owner actually had his heads flow tested as it's been tough to come up with reliable flow data for the old closed chamber rectangular port 1.72" exhaust valve heads.
Fortunately the owner is not like most guys who only see engines as one dimensional, i.e. top end power. He understands that low and mid range power along with reasonable idle behavior and excellent throttle response, especially to small throttle changes, are more useful for a road engine, especially a large displacement one that will have substantial top end power with any reasonable road engine cam, which doesn't include the L-88 or ZL-1 cams!
So once we have a final OE baseline engine we will evaluate roller cams.
Just for the heck of it I decided to try an OE LS7 hydraulic roller cam, and as expected it made better power throughout most of the rev range while equaling the OE cam's peak net power, both at about 5500. Yes, I know the LS7 cam will not fit into a Mark IV block, but I'm sure we can find similar lobes that can be ground on a Mark IV roller cam blank.
When we get further along I'll start another thread on this project. It should be interesting.
Duke
I picked up my engine from the shop this week. They repaired the cylinder with a sleeve, replaced the pistons, valves, valve springs, oil pump etc. Kept the cam, crank, rest of the valve train. Replaced the one head that was toast with a good dated part. It is running sweet. Good oil pressure, good torque and HP. We left the flat top pistons in specifically for the fuel, at their recommendation. compression is at 10.5:1
Just as a reminder, this is an L46 original block to the car and when it was rebuilt the time before, we installed a roller cam and roller lifters.
But here's the interesting part - I have been talking to them on and off about trying to figure out what happened to it. My initial guess was a malfunctioning heat riser valve since I discovered that it wasn't opening properly, right before the engine let loose. But they couldn't find any heat related damage, anywhere. Upon assembly and initial run on the dyno, the builder noticed a slight noise and put his hand on the valve cover. He felt something that wasn't right. Removed the valve cover on the right side and noticed marks on the oil baffle, right below the PCV valve. This also happens to be above the valve that failed, #6. He removed the other side and saw the same thing although not as pronounced. He corrected the intereference with the rockers and it all appears and runs good.
His guess, which is probably correct, is the roller rocker interference caused the valve to hang and the piston hit the valve and snapped it off, causing all the other damage. The rest of the valves were fine. I don't have a better answer and since the previous shop installed the roller, I can only guess they missed the problem in the build. Which would explain also why the engine didn't last very long. They should have checked for interference and caught it. They didn't. Jerks.
I'm still going to replace the heat riser valve though. Can't wait to get it back in the car!
A couple pictures of the cleaned up piston are below.
Just though you may want to add this to the body of knowledge out there.
Best,
Rich
Unless I missed it earlier, this is your first mention of "roller cam" and "roller rockers". Do you mean roller tip rockers or roller trunnion rockers?
A lot of things in this thread don't add up. You said it's a '69 L-46, but it has 300 HP heads and pistons. Doesn't make sense. There were three different engine codes for '69 L-46 depending on the engine's front end accessories.
How about posting a photo of the block stamp pad, and at what RPM on the tach does the redline start?
Regarding the cam and rockers, roller cams usually have more lift than flat tappet cams, so piston to valve clearance may be insufficient, and if a valve kisses a piston it can bend the stem and leave an impression on the piston or even break the stem at which time the valve head becomes a "soccer ball" that considerably reworks the entire piston crown, along with the head chamber and usually the cylinder walls too, which is the case with your engine.
BTW, if you have basic specs for the installed roller cam can you list them?
If the "roller rockers" are of the roller tip variety with conventional ball and socket pivot you are another victim of one of the biggest scams in the aftermarket parts industry. Most think the rocker arm tip slides over the valve stem. This is not the case unless the valve train geometry has been totally screwed up by excess removal of block deck and head surface material. The OE rocker tip that contacts the valve stem is curved so that with nominal valve train geometry the rocker tip ROLLS across the valve stem. Sliding is non-existent or at most, minor, so all roller tip rockers do is add valve train mass and a moving part that can fail.
Consider modern LS engines. They have ROLLER TRUNNION rockers that replace the ball and socket with a needle bearing. The tips are plain, and curved so they, too, ROLL across the valve stem, not slide.
So it sounds like you fell into the typical "engine builder" trap... roller cam, roller (tip) rockers... probably a high volume oil pump, too. If the oil pressure gage pegs at 60 most of the time at over 2000 revs, you got had.
I'm not a fan of roller cams for vintage engines, especially small blocks. I know Joe recommends them especially for big blocks, but I'm beginning to come around because the BB valve train is much more heavily loaded than small blocks due to heavier valve train components, and the OE springs are much stiffer than small blocks; but given the same lifter diameter, lobe-lifter interface loading is much higher. Cam and lifter failures are controversial. Some blame the blanks. Some blame insufficient crown on the lifter surface, while others blame insufficient lobe taper; and there are also reports of roller lifters coming apart. I'm not sure what to believe!
In fact, right now I'm working with a '67 L-71 owner in Northern CA on a rebuild. I have a baseline in Engine Analyzer 3.4 for the OE L-71 (other than CR lowered to 10:1) as installed in the car... SAE net, water pump, clutch fan, and 500 CFM @ 1 5" Hg exhaust flow model, which has proved to be accurate from testing for the C2 2.5" under-the-car exhaust system for several other projects. The head model may change if the owner actually had his heads flow tested as it's been tough to come up with reliable flow data for the old closed chamber rectangular port 1.72" exhaust valve heads.
Fortunately the owner is not like most guys who only see engines as one dimensional, i.e. top end power. He understands that low and mid range power along with reasonable idle behavior and excellent throttle response, especially to small throttle changes, are more useful for a road engine, especially a large displacement one that will have substantial top end power with any reasonable road engine cam, which doesn't include the L-88 or ZL-1 cams!
So once we have a final OE baseline engine we will evaluate roller cams.
Just for the heck of it I decided to try an OE LS7 hydraulic roller cam, and as expected it made better power throughout most of the rev range while equaling the OE cam's peak net power, both at about 5500. Yes, I know the LS7 cam will not fit into a Mark IV block, but I'm sure we can find similar lobes that can be ground on a Mark IV roller cam blank.
When we get further along I'll start another thread on this project. It should be interesting.
Duke
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