The .501" is the lift. 292o and 282o are advertised duration. Most people pretty much throw the advertised duration out the window because it changes with cam manufacturers. Look at the @.050" numbers. For those cams they should be in the 220o-230o range or so. The at .050" tells you the most about the attitude of the cam. Lift will not effect idle, it is the duration that changes the quality.

 

The part about "The engine was built 3 or so years ago and has just been cranked up on occasion during the car restore." might be a problem. Did a good cam break-in take place? I'll describe it below in some detail.

The other thing bothering me is that startups after sitting awhile can possibly have some moments of low oil pressure; the Chevy oil pump is fully excellent, but there are a bunch of places for that oil to go before pressure builds! Sometimes people start an engine and go vroom! vroom! with it before pressure is everywhere. This is hard on things. There must be oil to keep the opposing bearing surfaces from actually meeting; they are designed to run with a film of oil between them, because oil cannot and will not collapse under pressure (that's why hydraulics work). [This is why I went to synthetic, but... read on; this turned out to be a really severe error for breaking in an engine, and cost me a lot.]

Sometimes you do lose a cam when breaking it in, yes. The most frightening scenario is when you have to replace a lifter with a new one; that'll kill a cam lobe lots of times. If you lose a lifter, I would strongly recommend changing the cam. Besides, if you lose a lifter, you need to find out *why*. Was it junk in the oil system? Sometimes just the crud on shop rags will do it. I would recommend a very close, and I mean, magnifying glass inspection of the cam and each lifter. Make darn sure the lifters are kept in order so you can see what lifter did what. (The pros have a board that holds the lifters, because they know a lifter cannot be put into a different spot and work.)

Your lift values are a bit more than I'm used to in a small block, but Comp Cams does good cams. I looked and see .47 lift, 270 duration. But the problem is different places measure cams differently. One place will measure when the cam has just barely taken up the slack in the valve train, another will measure when the valve is effectively open..

Hmmm, did they put extra heavy springs into your heads?

I lost 2 cams in rapid succession not long ago at all. The answer was quite strange. On my big block 454, the factory cam had an oil slot all the way around the middle of the rearmost load-bearing surface. This created a path for oil to get from the bottom hole to the top hole, and thus to the other bearings. Without that slot, which isn't on any other cam, oil didn't get to the other bearings! Cams died.

Now, my databook says that this was only done on "early 427 L-88's (1965-67)". I bought this 454 LS-6 in the crate about 1988 or so (before Chevy started confusing everyone by re-using "LS-6" on another engine).

The cams my mechanic put in did not have that oil slot. The lobes went flat. We finally figured it out. We could not find a cam with that slot anywhere; in fact, the cam companies said, "You have WHAT? I've never heard of that!". Finally, we just got the block machined to not need that slot to get good oil flow to the cam bearings. Then it was compatible with all those big-block cams out there.

I still don't know how I ended up with an early block and cam. I can only speculate that Chevrolet made a bunch of big blocks without that extra oil drilling, and perhaps Chevy had a bunch of slotted cams to get rid of. It was definitely a 454 LS-6 in the crate, though, not a 427 L-88.


Generally the cam manufacturer gives you some very special grease & lubricant to put on the cam lobes and on the bottom of the lifters.

When it gets time to break in the cam, there is a set procedure. It's something like this, and different mechanics do it differently, generally on a "Here's what works for me" principle; it's a little bit of an art.

Prime the oil system the day you fire it up: Pull the distributor. You should use the metal part of a flat blade screwdriver in an electric drill, put it down the distributor hole to the oil pump, to thoroughly "prime" the oil pump so there's oil everywhere in the oil channels at the moment of startup. Doesn't hurt to see the oil actually coming out, either. Put the distributor back in.

Static time the engine so it'll catch immediately. Bring the engine (by hand) slowly around to cylinder #1. Before you reach #1, on a previous cylinder, put a piece of paper between the points of the distributor. Now, pull it towards TDC. The distributor should be roughly pointing at #1 (you've marked this or know it, right?), and the "timing light" slot on the harmonic balancer is also coming on to TDC. When the balancer is on TDC, very gently turn the distributor towards the rotation until you can pull the paper away; that's top-dead-center-setup ignition (see, when the points open, the coil fires). Tighten the distributor to "not final but good enough for now". You should do final timing with a timing gun to the specs for your engine after the cam is broken in.

Now attach a tachometer to the distributor; if you're running a souped-up ignition, attach it to the wire that's given for attaching tachs. Note: make darn sure the tach wires aren't anywhere they'll burn through (exhaust manifolds are particularly bad ... *grin*, imagine how I know this) and that you can see them from where you adjust the carb for engine idle speed. (For fuel injection, you may have to start and do speed from inside the car, if you don't have a tach, put the tach on the widshield, etc.)

The carb should also have gasoline in its float bowls and also be "ready to rock"; it isn't that much work to make sure the fuel line down to the fuel pump is full, too.

What you're trying to do is make sure that *nothing* interrupts the engine running for 30 minutes or so.

Think about: Will this engine overheat? You're going to be running it hard with no air blowing, like it's in heavy traffic. You may want to get one of those big fans and aim it at the radiator. Is the cooling system full and "burped" free of air? When the engine first is running, you may need to add fluid as the air comes out of it. (Don't do this when the engine is hot, or you'll get a face full of angry steam and coolant).

When the engine is fired up, it should be taken straight up to 2000-2500 RPM, and I mean STRAIGHT UP. This means use the tachometer in the engine compartment / windshield. Some people use the idle screw on the carb to hold this RPM; that works too. I used another tach, and found out the tach in my Camaro reads 1,000 RPM **LOW** at 4,000 RPM; e.g., 4,000 RPM indicated was 5,000 true RPM, and with a 454 big block, that's getting into yellow to red line territory.

If you have to sit in the driver's chair and hold the RPM, then do it, but this is not recommended. You want to be watching the engine, looking for leaks *especially* (with all those new gaskets, this is when it's gonna leak!). Some people vary the RPM a bit between 2,000 and 2,500.

After 30 minutes most people shut the engine down. Then while it's warm and the oil is nice and runny, they drain the oil, now full of little bits of "stuff", out. They also remove the oil filter, also full of little bits. They put in new oil and filter.

Then they tend to go around the engine with a torque wrench and see if any bolts feel strange. A "stretchy" bolt, say, that should tighten to 50 ft. lbs, but easily tightens to 45 for a full spin, is stretching way too far, and will snap off if you push it. The ft-lbs spec is actually the desired stretch spec from the mechanical engineers who designed the engine. You need a new bolt of the desired strength. You'll have to swap it out.

Please don't make the same mistake I made! I put in synthetic oil to break in the engine. Hello, scuff marks in the cylinders! Hello, scuffing on the cam, main, and connecting rod bearings! DO NOT DO THIS ! If you want to run synthetic, wait until the engine is broken in. My engine had to come out and all the bearings had to be replaced. Oh, joy. Imagine how happy I was. How thin my wallet. Now it's running 30W oil.

I hope some of this I'm passing along will help. If only the Don't Break In On Synthetic part, it'll have been worth it.

Take care,

Dave

 

I lost 2 cams in rapid succession not long ago at all. The answer was quite strange. On my big block 454, the factory cam had an oil slot all the way around the middle of the rearmost load-bearing surface. This created a path for oil to get from the bottom hole to the top hole, and thus to the other bearings. Without that slot, which isn't on any other cam, oil didn't get to the other bearings! Cams died.

Now, my databook says that this was only done on "early 427 L-88's (1965-67)". I bought this 454 LS-6 in the crate about 1988 or so (before Chevy started confusing everyone by re-using "LS-6" on another engine).

The cams my mechanic put in did not have that oil slot. The lobes went flat. We finally figured it out. We could not find a cam with that slot anywhere; in fact, the cam companies said, "You have WHAT? I've never heard of that!". Finally, we just got the block machined to not need that slot to get good oil flow to the cam bearings. Then it was compatible with all those big-block cams out there.Dave

Here's the story on the '65-'66 vs. '67-up big-block lifter gallery oiling from the rear cam bearing; I answered this reader's question in my "Tech Bench" column about a year ago (I'm the Technical Editor of "Corvette Enthusiast" magazine). Photos show the '65-'66 rear cam bearing, the matching groove in the '65-'66 rear cam journal, and the '67-up rear cam bearing.

TECH BENCH

John Hinckley


Reader’s Question: I’m in the planning stage for a stock rebuild of my 66’s original 427/390hp engine (block casting #3869942), and I’m gathering the parts required before I pull the engine. One of the problem parts so far is the camshaft, P/N 3883986; it supposedly has a groove in the rear bearing journal, and I haven’t been able to locate one yet. My mechanic says the ’67 390hp cam, P/N 3904359, has exactly the same specs and will work fine, and he has one, still in the GM Parts tube, with the matching bearings; he says he has used several of them in ’67 and ’68 396 Camaros with no problems. I’m confused about the grooved-vs-no groove rear journal and bearing thing, and don’t want to make a mistake; can you explain what works and what doesn’t?

Response: Oddly enough, this is almost a repeat of the ’55-’56 vs. ’57-up small-block rear cam journal and bearing change for lifter gallery oiling fiasco; makes you wonder why they’d repeat the same mistake eight years later on the new big-blocks.

At any rate, here’s the background on your issue:

’65-’66 Big-Block Lifter Gallery Oiling: In order to feed pressurized oil to the galleries that feed the lifters, the ’65-’66 big-blocks used a combination of a groove in the rear cam journal and a rear cam bearing with a matching groove on its inside diameter. Oil entered the bearing through a hole at the bottom, traveled around the journal through the groove in the bearing and the journal, and exited the bearing through two holes at the top that aligned with two holes in the block; those two holes fed the oil galleries on each side that fed the lifters. Both the cam journal and the cam bearing MUST have the groove in order to provide adequate oil flow to the lifters, and the bearing must have the two exit holes at the top.

’67-Up Big-Block Lifter Gallery Oiling: Starting in 1967, Chevrolet redesigned the oiling path to the lifter galleries. The groove was removed from both the rear cam journal AND from the I.D. of the rear cam bearing, and an annular groove was machined into the rear cam bearing bore in the block instead. With the smooth rear journal and cam bearing surfaces, oil entered the bearing through the same hole in the bottom, but part of it flowed around the outside diameter of the cam bearing, through the groove machined in the bearing bore, and exited through the same two holes in the block at the top that fed the lifter galleries. The cam bearing now had only one hole, at the bottom.

What This Means To You: Your block dictates what you can use. The 1967 non-grooved cam and non-grooved one-hole rear bearing will NOT work in a ’65-’66 block, period; you need the cam with the grooved rear journal and the rear cam bearing with the three holes and the groove on its I.D. The cam isn’t a big problem – any competent machine shop can cut the required groove in the rear journal of the 3904359 camshaft, and all you need then is the correct rear cam bearing, which will be included with a ’65-’66-only big-block cam bearing set.

The reason the 359 cam and bearings have worked before for your mechanic in ’67-’68 396 Camaros is because their blocks were designed for it, with the groove machined in the rear cam bearing bore. If he had tried that combination in a ’66 block, he’d have had no oil to the lifters.

 

Craig, to add to what the other guys have posted, when you said you were rotating a new, unstarted engine for the last few years, I had no doubt why the cam failed. Don't do that.
All that an assembled engine needs at startup is priming the oil system. (and do what Dave said)

 

My engine builder like to run Rotella 15w40 and the Lucas Oil Stabilizer. The Rotella still has zinc in it. That's what I'm running in the motor he built for me.

Don't know if the oil choice is your problem, but just thought I'd tell you what I've been told.

 

Good instructions, Dave. I'd add a can of GM's EOS for initial break-in.

 

Ditto, EOS!!

pdq67

 

What about a well broken in engine(years and 3-4000 miles) and a new hydraulic roller?
Meaning it has run several years on Mobile 1 but has a cam change in the near future.

 

Has anyone tried to purchase EOS at their local GM dealer lately? A few months ago I went to my Chevy dealer and asked for a can and was told it is no longer made. Is this true or was I given bad info by the "kid" behind the counter.
Bill

 

According to one of the Buick sites, GM lost their supplier for EOS for a while but it is back under GM P/N 88862586 (I didn't verify this!)

Most experts agree that one of the significant causes of premature cam failure, on flat tappet cams, is the change in modern oil formulations. What is mising in the new SM oils is an additive called ZDDP (Zinc Dalkyl DithioPhosphate). ZDDP is a great Extreme Pressure, EP, additive but it tends to poison the catalytic converters on cars so equipped. because of this ZDDP levels have been dropping steadily for the past 20 years to less than .08% in modern "SM" oil.

You can buy an additive like zddplus (http://www.zddplus.com/) or you can find an oil with sufficient ZDDP such as Royal Purple racing oils. ZDDPlus claims that there aren't sufficient detergents and dispersants in racing oils for street use with 3000 mile change intervals. I don't know, you decide based on all the data available.

I've always broken my cams in with a procedure similar to that described in the post above. I do rub Moroso Moly-Paste into the cam lobes and lifters and I always use mineral oil with either EOS, Comp Cams or other manufacturers recomended break in lube (melling, crane, etc...) for start up. I change the oil and filter right after the 1/2 hour break-in because the molybdenum tends to clog the filter. I've never had a cam fail prematurely due to break-in wear.

I've been running my personal favorite Mobil 1, 15W-50 (http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_15W-50_.aspx) synthetic in my own car for several years with two different flat tappet mechanical camshafts. (both Comps) Mobil claims that this stuff is the "E-Ticket" for older engines running high valve spring pressures. The cam and lifters that came out of the old engine had very little wear on it. In the 4000 miles I've driven the new engine, I've checked the valve lash 3 times and never actually had to adjust a valve so, I assume that this cam is wearing very nicely too!

 

According to one of the Buick sites, GM lost their supplier for EOS for a while but it is back under GM P/N 88862586 (I didn't verify this!)

True, It's an AC/Delco part now.

 

Well we pulled the engine last night and there are 2 cam lobes wore down as well as the lifters. My rod bearings are shot, my crank bearings are shot, so the engine is going back to the machine shop to get evaluated. I suppose the crank will have to be turned. I'll post some pics this afternoon of the wear and tear.
I'm thinking about stepping down a size or so in the cam but I don't want to loose that sound. Thanks for all the feedback.

 

Well we pulled the engine last night and there are 2 cam lobes wore down as well as the lifters. My rod bearings are shot, my crank bearings are shot, so the engine is going back to the machine shop to get evaluated. I suppose the crank will have to be turned. I'll post some pics this afternoon of the wear and tear.

YOWCH!!!

Ouch, Craig, the picture of your bearing there just hurts (and is all too familiar to me).

Chevrolet lower ends have a good reputation for holding up. Something is seriously wrong here. Seeing this in a engine with 5 hours of runtime really bothers me. It's also way too familiar!

I went through a lot of the same thing you're going through a few months ago -- all the bearings dinged, cam went flat. My mechanic and I never did nail down the cause for sure. [ I didn't know about these forums then. ]

There are some real experts here; time to ask for help.

I was running the 1970 LS-6 454 engine with stock solid lifter cam. I think possibly what helped ding things was, my son was getting ready to get a driver's license, so I took him out for skid practice. After one pretty hard skid, the engine sounded different. I wrapped up the skid practice right then.

My mechanic heard something too. While trying to adjust the rockers, he ran out of adjustment. You guessed it. Some lobes on the cam had gone flat. I didn't know about the 1965-66 grooved cam rear-bearing thing (and I still don't know how it made its way into a 454 crate engine I bought around 1988). Anyway. A new non-grooved cam got its lobes ground down, then he realized what was going on, and fixed the block to accept non-grooved cams.

It was torn down enough to pull the cam, so I asked him if he'd pull the oil pan and look at a few of the main bearings because I had a bad feeling about them. He did, and they looked like the ones in your picture there.( I'll take some pictures here after our blizzard moves along.) The crankshaft was still okay, but it was obvious the softer metal in the bearings had gotten really dinged. [And why is it a deep scratch going around the whole bearing? I'd almost think a piece of grit got in there.]

He and I looked at each other and said, "What on earth?!". I sure didn't have any clever ideas, nor did he. Never saw this before. So we finally just put in a new oil pump, all new bearings, the new cam and lifters (we went to a hydraulic cam that gave me a bit of vacuum at idle so the power brakes worked).

But we never did for-sure pin down -the cause- of the bottom end bearing damage, getting the scratches like those in your pic. He broke in the new cam and we went to a non-synthetic oil for break-in.

What is really bothering me, as I write this, is the rocker arms are rattling at me now; I'd say two or three are a bit loose. I really hope it's just the first adjustment needed after initial break-in. (But those are hydraulic lifters!)

Any ideas on this are sure welcome. I don't know what tagged the bearings on the bottom end on my big block. It's possible that the oil sloshed in the pan during skid practice long enough for the pump to cavitate or suck up foam. This seems unlikely to me. I don't really know.

And something sure got the bearings on Craig's engine!

This is very unusual on a Chevy, and here we're seeing the same thing.

This would be a great place for someone to arrive with the cavalry!

I *think* that one thing we might have in common is long sitting periods, then being started & run, then more long sitting periods. (In my case, the joy of modern divorce was part of it; I had to become sole owner.) Until the last year or so I didn't drive The Beast regularly.

It's also obviously time I got some zinc additive, and I really appreciate the people who documented it and told where to get it! Thanks!

Let us know what the machine shop tells you, Craig.

Oh -- In particular, please ask them if they see any vertical scuffing in the cylinders. We saw a bit of that in my engine. No idea how it happened, but ask 'em to look. ( I'm trying to give the real wizards all the info I can.)

-- thanks,

Dave

 

I really liked that 501 cam in my 355 way back. Really cool idle but a top end cam it seemed.

 

Guys,

Remember that we can't use duration at .050" to calculate DCR b/c the intake valve will be off the seat .050" so CAN'T trap any charge!

As for cams, I go by this.

8 to 1 CR, 250 advertised duration;

9 to 1, 260;

10 to 1, 270;

10.25 to 1; 280;

10.5 to 1, 285; and

11 to 1, 290 CR!!

As for a 292/244 Magnum vs a 280/230 Magnum hy-cams, its the hydraulic intensity (H/I) difference in them that make them different IF lift and every else is the same w/ the smaller cam being more intense!

Now if you keep everything the same as both are advertised, I figure that they will have darn near identically designed lobe "lifter" acceleration, (i.e., H/I), rates. UDHarold can tell you this in a NYM b/c he designed CC's 268HE way back then!!

pdq67

PS., come's from Mr. Harvey Crane from him subtracting duration at .050" numbers from advertised duration numbers. So the smaller numbers, the more intense the lobe designs! A 292/244 = 48 is more intense than an old-school 292/230= 62 and I have the old 292/230 in my Strong-Arm 406 SB ..

And the 292/244 = 48 vs the 280/230 = 50!!

 

Thanks for all the info. I'm not an engine guy so most of the info is foreign language to me. My brother in law is an engine guy and he actually specked my engine for me to start with. The 501 292 lift CC had a very good lick to it but maybe alittle too much. Anyways it's back to the machine shop today to have the engine gone through and checked. Here's a couple of pics of the engine innards. Still didn't get one of the cam though.

 

And the old junk motor -097 cam I had in my junk301 had a notch out in it that looked like it was done w/ a 4.5" angle grinder!

It was about 5/16" wide x 1" long x 3/16" deep b/c it came out of an early 283 block! I figure the guy did it b/c of the horror stories he had heard about from using them in the early 265 blocks that are made like the early 396 blocks!

Notch looked like a woodruff key slot.

You'd think GM woulda learned from the 265??

Probably the same F** passed over ME designed both and nobody caught it the 2nd time and he would go home each afternoon and laugh about it to himself!!

pdq67

 

Cam technology has advanced a lot. The old 292 sounded great but often disapointed in performance. I HIGHLY recomend if budget allows to go rollor. However money does no grow on trees so take a look at the Thumper line of cams Comp has. They are designed to give you that lick you are looking for but should perform better than the magnum. JMHO.

 

Naw, go a UDHarold cam!!!

Call Harold here

(662) 562-4933

and ask him to spec HIS version of a Thumpr cam and go!

And please say hello to him from ol' pdq67 if you do!!

pdq67

 

They are reliable Dave but it's not that rare to see bearing damage. Sure looks like some debris or dirt ran through that bearing. If the cam went South that could have done it. From what I've read around here, most guys are breaking them in on a straight 30 or 40w and using GM EOS or zinc additive. There are plenty of oils you can run afterwards with enough zinc. Valvoline VR1 is suppose to have enough along with Brad Penn and various others. Adding the zinc sure isn't a bad idea from what I've been reading around here.

 

One thing I've learned has to be done REGARDLESS and that is run something like a pipe cleaner through each oil gallery in the crank!!

Or if you can find one, a gun-barrel brush.

This should remove any and all crank-cleaning shot-blast crap!!

pdq67

 

One thing I've learned has to be done REGARDLESS and that is run something like a pipe cleaner through each oil gallery in the crank!!

Or if you can find one, a gun-barrel brush.

This should remove any and all crank-cleaning shot-blast crap!!

pdq67

:yes:
I've got a set of six from Summit.
And this reminds me of a story. Back when my L78 died, it was time to build the L88. Out came the aluminum rods. OK,,,,, out came everything. This is two kids working in the basement of the folks house, mid seventies, so go easy on me,,,,,.
But we had the 'Book'. "How to Hotrod the Big Block Chevy". I ground the casting fair in the cam valley oil returns. (A roller cam needs a screen kit there to contain failed parts). Then checked the oil filter hole. (67 block, oil canister, not spin-on) Remember, this is a 427 L88 block. Shocking! Black casting sand still stuck in several places inside the oil filter area. And it was hard to remove. We got it all but it wasn't easy. Without the 'Book' we would have missed it. Aren't engines fun?:hurray:

 

Block your oil filter bypass, and the only thing that will get damaged is the oil pump. Run a Wix filter, too. After break-in, you can change to a stock bypass oil filter mount.

 

I dropped the engine off at the machine shop yesterday. Said it would be 2-3 weeks out. He also said for a charge he had a stand and would brake the engine in correctly. Said he would use a smaller spring on the heads to break in and then change to my springs. Another machinist asked me about what kind of springs I used in the heads during breakin. My heads are 186 202 valve heads with roller rockers. I think I'll let him break in the heads. I'm certain the crank will have to be turned. Preciate all the feedback and comments.

 

Was reading through another post of "My DZ 302 cam Journey ends happily with a 140 off road cam setup". I love the sound and was wondering if this would work in my engine. Where do you find the 140 offroad cams? I've got some time to figure out what to go with. Any thoughts?

 

I hate to tell you this, but a 383 won't like the old -140 cam..

Spec's are something like 316/257/323/269, 112/108, .493"/.512" gross lift and need's .024" and .026" lash.

It's actually a high-winding, "balls-out", short-stroke motor cam, imho.

pdq67

PS., notice GM was out to lunch on their advertised duration numbers that they generally never mentioned what they were.

I think the 316/323 came from GM and the 257/269 from Crane!

 

(Admins -- JohnZ has made an excellent post here in this "Competition Cam Differences" thread, concerning big block camshafts, grooved and non-grooved. I wish I'd read this information before a couple of camshafts died in my 454!. Could I suggest it be marked and "put in our online library" here, so to speak?

Thank you for your time,
Dave