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  #16 (permalink)  
Old 10-24-2012, 09:53 AM
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Originally Posted by timothale View Post
My room mate in college rebuilt his Ford Fe and the cam went flat in 100 miles, he pulled it apart at their farm shop and got another new cam from the dealer and it went flat again in about 100 miles. I went to his house for weekend to help and found that the cam was catching two lifters with the same lobe. Factory replacement cam and original block, it only got new rings and bearings the first rebuild. I ended up getting a transmission thrust washer from a box of spare pieces the dealer had in their parts room, and every since then I drop in one lifter at a time and rotate tthe cam to check.
That would be true of the early FE's, they came from the factory with a thrust button that had to go back in or the cam would jump around to where lobes could catch multiple lifters, another common error is to get the cam tunnel plug behind the flywheel/flexplate too deep which will hold the cam forward enough to where lobes are lifting multiple lifters. Ford finally learned its lesson and put thrust plates into the engine about the 1963-1/2 model when they used to do a lot of mid model year updates.

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Old 10-24-2012, 01:56 PM
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fe cams

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Originally Posted by oldbogie View Post
That would be true of the early FE's, they came from the factory with a thrust button that had to go back in or the cam would jump around to where lobes could catch multiple lifters, another common error is to get the cam tunnel plug behind the flywheel/flexplate too deep which will hold the cam forward enough to where lobes are lifting multiple lifters. Ford finally learned its lesson and put thrust plates into the engine about the 1963-1/2 model when they used to do a lot of mid model year updates.

Bogie
the rear cam corplug actually is a specel plug and it goes in backwerds to the normal core plug. some service manuals mention installing this plug corectley
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Old 10-26-2012, 01:02 AM
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I have always wondered if wiping cam lobes is a modern phenomenon, due specifically to modern oils or if it was always a problem, even back in the heyday of the muscle car era.

I'd imagine the risk was always present, but was less to worry about back then. Is the problem mainly that we are using cam's with very aggressive ramp rates, high lift, and heavy springs in the presence of "bad oil"?
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Old 10-26-2012, 07:04 AM
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We wouldn't build flat tappet engines for customers anymore. But back when we where,we told customers to use the oil additive for the entire life of the engine,not just for break-in.
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Old 10-26-2012, 07:41 AM
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But what about back in the days before there was engine oil additive? Back when the oil was good enough as is. How great was the danger of wiping cam lobes back then?
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Old 10-26-2012, 08:42 AM
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But what about back in the days before there was engine oil additive? Back when the oil was good enough as is. How great was the danger of wiping cam lobes back then?
It happened, but back in the '50s-'60s and into the '70s, the cam action was much more gentle than the ramps seen on today's fast acting cams like the XE and Voodoo series. Even the 'hot' solid cams were- for the most part- not very radical as far as lift to degrees of cam rotation went. The factory production high performance Chevy cams all the way up to the solid cams all used basically the same valve springs. All this kept the cams from wearing rapidly, and cam failures weren't as frequent as today- or so it would appear. And there were always additives and cam break in lube, at least when I was aware of it in the '60s.

So I think there were less failures back then, but that could be an illusion. When we consider the number of aftermarket cams installed today w/the number sold back when- and add the transparency of the internet drawing attention to the failures today, IMHO there's good reason to wonder if the percentage of failures per thousand, say, were that much different.

FWIW, during the '70s there was a rash of bad factory Chevy cams, IIRC due to bad hardening/surface treatment. This would have caused problems regardless of the additives. More recently, offshore lifters have compounded the problem. No amount of additives or careful break in will overcome a badly made part.
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Old 10-26-2012, 08:47 AM
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It happened, but back in the '50s-'60s and into the '70s, the cam action was much more gentle than the ramps seen on today's fast acting cams like the XE and Voodoo series. Even the 'hot' solid cams were- for the most part- not very radical as far as lift to degrees of cam rotation went. The factory production high performance Chevy cams all the way up to the solid cams all used basically the same valve springs. All this kept the cams from wearing rapidly, and cam failures weren't as frequent as today- or so it would appear.

But when we consider the number of aftermarket cams installed today w/the number sold back when- and add the transparency of the internet drawing attention to the failures today, IMHO there's good reason to wonder if the percentage of failures per thousand, say, were that much different.

FWIW, during the '70s there was a rash of bad factory Chevy cams, IIRC due to bad hardening/surface treatment. This would have caused problems regardless of the additives. More recently, offshore lifters have compounded the problem. No amount of additives or careful break in will overcome a badly made part.
I agree with everything here; but would like to add that I wonder how many cam failures are misdiagnosed by people who aren't versed in actual diagnosis of 50yr old engine technology
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Old 10-26-2012, 09:14 AM
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I agree with everything here; but would like to add that I wonder how many cam failures are misdiagnosed by people who aren't versed in actual diagnosis of 50yr old engine technology
auto gear is on the right track.also after talking to a camgrinder in the vancouver aria tells me that the cores for most grinders come from china and ar of poor quality to be polite. he also claims that gm engines make matters worse where there
is no positive controle of the cam wandering back and forth.
so combine autogears coments with poor cores,you have room for high failure rates.
then you add the oil and the high spring pressure radical grinds,a roller cam sure improves the ods. finally 90% of thes engines never hit the track and ar just for street use,some should cross a couple of plug wires for the sound. cliff
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Old 10-26-2012, 11:12 AM
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Originally Posted by Silver Surfer View Post
I have always wondered if wiping cam lobes is a modern phenomenon, due specifically to modern oils or if it was always a problem, even back in the heyday of the muscle car era.

I'd imagine the risk was always present, but was less to worry about back then. Is the problem mainly that we are using cam's with very aggressive ramp rates, high lift, and heavy springs in the presence of "bad oil"?
Actually if you go back and look at the cams used in the muscle cars, they tend to have a lot of duration and not a lot of lift. Then when you look at the .050 inch duration numbers you see that they have a huge amount of ramp in their total duration. GM tried to deal with the lifter lobe wear problem by Parkerizing the cam which is a phosphate conversion coating on steel used to harden the surface and provide some innate lubricity to the parent material. For you guys who are interested in guns this will have a very familiar sound to it as it is a common process to protect gun parts from corrosion and wear.

Going back to the days of the flat head which also had an appetite for camshafts the popular treatment at that time was chilled iron. This is a process that takes white cast iron and uses heating and cooling to create a soft core with what essentially is a nodular iron surface for better wear. This was the "Cat's Meow" back in the day for a long wearing set of cam and lifters.

The roller cam follower has been around for a very long time. The problem with the flat tappet cam and lifter is the one where you cannot have sliding contact even with lubrication in some cases of same/similar metals otherwise you get surface welding (galling). So where rubbing contact is concerned either the metals need to be a lot different with lubrication and or with different harnesses or wear coatings. For flat tappet camshafts this usually meant cast iron with conversion coatings like Parkerizing and or heat treatments like chilling, or a contact patch of steel on an otherwise cast part. A rolling contact between similar materials is much less prone to galling and will function quite well with just common oils or grease for lubrication. In the case of lifters and cams roller contact also allows the use of more aggressive lobe profiles as the design limit of the flat tappet is where the lobe is so aggressive the lifter edge would dig into it. This is not a problem with roller contact; the limit here becomes how much side load the lift rate puts into the lifter body which wants to jam it in its bore.

Cost is a predominate issue with the auto manufacturers; one has to realize that to a large extent cost containment is a businessís predominate driver. Sort of a race to the bottom. The theory is that creative minds will find technical solutions that are both cost and performance effective so things will get better while costing less. Sometimes this works sometimes it doesn't but that's blather for college econ classes. Aircraft engines certainly went to roller cam followers very early in the 20th century for the need to use aggressive lobe designs without the wear issues so steel was used for cams and the lifters became steel rollers on steel needle bearings. Harley Davidson has used roller tappets as far back as I can track into very early in the 20th century and I'm sure there are many other examples. Detroit ever cost conscious used the flat tappet forever which had the back side of developing lubrication technology that allowed the use of increasingly aggressive lobe profiles and stiffer springs but there was always a limit to this. The performance aftermarket developed roller cams and lifters back in the 1950s for production engines to get into the power available in more aggressive lobe profiles and lift rates, but these were and are expensive. Detroit had to figure out a cost contained solution to cam and lifter life as the EPA informed them that ZDDP as an oil additive would have to be discontinued. They went through a period of materials development starting with machined steel, going to cast steel with treatments and finally arriving at specialty alloy cast irons with wear treatments for the cam and low cost lifters with simplified roller systems. These are a lot different from race roller cams and lifters and you will get them into design limit trouble pretty fast if you use this stuff on a highly built performance engine.

Bogie
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Old 11-01-2012, 10:18 AM
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Any thoughts on how distributor shaft end play effects wiping lobes? I can't remember if DoubleVision or OldBogie like to use a cam button on flat tappet cams, but if you do not go this route I am thinking more shaft end play allows the cam to more fore and aft. If so, what is the targeted amount of end play? I am about to install a distributor with .013" of end play.
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Old 11-01-2012, 07:46 PM
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Originally Posted by Silver Surfer View Post
Any thoughts on how distributor shaft end play effects wiping lobes? I can't remember if DoubleVision or OldBogie like to use a cam button on flat tappet cams, but if you do not go this route I am thinking more shaft end play allows the cam to more fore and aft. If so, what is the targeted amount of end play? I am about to install a distributor with .013" of end play.
The distributor shaft endplay doesn't cause wiped lobes. It CAN cause spark scatter and the timing to move around.

I advise using 0.015" to 0.020". 0.013" will be OK, no need to go tighter.

The rotation of the distributor along w/the angle on the cam lobes tend to push the cam towards the back of the block on a SBC. It can move forward under certain conditions though, so using a cam button to limit the end play on a flat tappet SBC is fine.

The cam end play should be around 0.005", but actually measuring it and assuring the measurement is going to hold is another thing altogether. You can use clay between the button and cover to check clearance on an assembled and installed engine. If the engine is out of the vehicle you can measure from the rear cam plug using a dial indicator. FWIW I have set up cam buttons w/zero clearance, letting the flex of the timing cover provide clearance and had no problems by doing so.

Before installing a cam button, be sure the timing set is in alignment. An example is if the crank gear isn't seated (or the timing set isn't made right), the timing chain can cause the cam to be pulled forward by the too-far-forward crank gear. You will know if this is a problem if the cam gear doesn't want to seat lightly against the thrust face of the block.

Check the alignment of the timing gears w/a straight edge. Also inspect the thrust face of the block for unusual wear or damage. In some cases the surface needs to be machined and a thrust washer used to compensate.
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  #27 (permalink)  
Old 11-02-2012, 12:08 PM
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The distributor shaft endplay doesn't cause wiped lobes. It CAN cause spark scatter and the timing to move around.

I advise using 0.015" to 0.020". 0.013" will be OK, no need to go tighter.

The rotation of the distributor along w/the angle on the cam lobes tend to push the cam towards the back of the block on a SBC. It can move forward under certain conditions though, so using a cam button to limit the end play on a flat tappet SBC is fine.

The cam end play should be around 0.005", but actually measuring it and assuring the measurement is going to hold is another thing altogether. You can use clay between the button and cover to check clearance on an assembled and installed engine. If the engine is out of the vehicle you can measure from the rear cam plug using a dial indicator. FWIW I have set up cam buttons w/zero clearance, letting the flex of the timing cover provide clearance and had no problems by doing so.

Before installing a cam button, be sure the timing set is in alignment. An example is if the crank gear isn't seated (or the timing set isn't made right), the timing chain can cause the cam to be pulled forward by the too-far-forward crank gear. You will know if this is a problem if the cam gear doesn't want to seat lightly against the thrust face of the block.

Check the alignment of the timing gears w/a straight edge. Also inspect the thrust face of the block for unusual wear or damage. In some cases the surface needs to be machined and a thrust washer used to compensate.
I guess I cheated him a bit by leaving out these details, certainly setting up a cam button is not for the casual viewer, it does take a fair amount of effort to get it right.

Bogie
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