I have a survivor ‘66 Corvette 427. I selected the Factory Muscle solid flat tappet cam as I was trying to stay as true to the original build as possible. I am searching for a solution due to a cam/lifter failure during initial break-in. Not too many people have good things to say about the flat tappet cams available today, and several have suggested using a hydraulic roller instead. I really don’t want to spend the extra money on an entirely new hydraulic roller valvetrain but I also don’t want to lose another cam. The jury is still out on how much metal went through the rest of the engine. Do you have any recommendations? I’d appreciate your help.
Jeff Smith: It appeared from J.C.’s email that he would prefer to stay with the flat tappet cam, but was prepared to go with a hydraulic roller if necessary. We contacted him to obtain more information in order to properly answer his question. We wanted to find out what valve springs and break-in oil he used and what the break-in procedure was.
J.C.’s break-in procedure was good–he pressure lubed the engine before starting and used a high-zinc oil, a Valvoline VR1 10W30 racing oil. I think that the culprit for the lifter failure might be the valve springs. J.C. used COMP Cams’ CCA-26120 beehive spring, It would normally be a great choice, but not during break-in with a flat tappet cam. That’s because these springs offer a seat load of 155 pounds with an installed height of 1.880 inches, which is a bit too much load for a flat tappet cam.
Compounding the issue is the cam’s 0.520 inch intake and exhaust lift. This creates almost 350 pounds of load on the lifter at maximum lift. This combined load probably contributed to three of the cam lobes going flat. Recommended loads for a flat tappet big block Chevy cam during break-in would be closer to 100-110 pounds of seat load with a maximum peak lift load of 300 pounds or lower.
Many engine builders use a dual spring but remove the inner spring before starting the engine. That places seat load around 100 pounds for the duration of the cam break-in period. Once the cam and lifters are thoroughly seated, the inner springs can be reinstalled. This is more work, but less than replacing the cam and lifters after a failure.
COMP generally recommends using the CCA-911-16 spring for its flat tappet cams. This spring is rated at 122 pounds of load at 1.900 inch installed height and 309 pounds at 0.500 inch valve lift. This is substantially lower–14 percent–at maximum lift, which would make things much easier on the lifters.
J.C. provided photos which showed excessive wear on only three lifters. That means 13 lobes appeared to have survived. This could be evidence that he was right on the edge of this cam surviving the break-in period. Reducing the spring load is an excellent way to ensure the cam will survive the break-in process.
Another variable was the Valvoline VR1 oil. This is a good race oil with a high 1,300 parts-per-million (ppm) count for phosphorous and an even higher 1,475 ppm count for zinc. The zinc and phosphorous are better known by the term ZDDP, which is an acronym for zinc dialkyldithiophospate. However, the VR1 oil also has nearly 1,100 ppm of calcium as a detergent. Normally, detergents are a great addition to oil because they help keep the engine clean. However, one aspect of detergents that is generally not well known is that they also attempt to clean anti-wear additives like zinc and phosphorous off of the metal parts they are trying to protect.
The best oil to use during cam break-in is one with high ZDDP levels but very low or no detergent. This way, the ZDDP remains on the cam lobe and bottom of the lifter where it belongs, minimizing excessive wear and allowing the lobe and lifter interface to create the necessary wear pattern.
The old mechanics from the 1950s and ‘60s recommended a 30-weight non-detergent oil for cam break-in on new engines. I’m old enough to remember those days, and I always wondered why (and frankly didn’t believe) a non-detergent oil was the best choice. But now that I understand how detergents interact with ZDDP, it is now clear why these mechanics made this recommendation. It worked!
Oils I think would offer the best chance for a proper break-in would be COMP’s Break-in Oil, Driven Racing’s Break-In (BR) Oil, and Lucas Break-in Oil. All have sufficiently high levels of ZDDP while minimizing the use of detergents.
We’ve found a company called Speediagnostix that has performed a series of tests on new oil to determine their actual chemical makeup. This sheds light on some oils that have the proper chemical makeup, and also reveals oils that are perhaps fine for a late model engine, but a terrible choice for breaking in a new flat tappet camshaft. The information we’ve placed in the accompanying chart has come from this Speediagnostix testing.
We’ve listed five oils in the second chart to illustrate that looking at only zinc and phosphorous levels does not tell the whole story. For example, COMP’s Hot Rod oil has good levels of ZDDP, but the calcium level is also high, which would work against the ZDDP during break-in. The Valvoline oil’s calcium level is not excessive, but still in the four-digit range. The Driven Break-in Oil has very low detergent levels with high ZDDP, a good combination.
Note that we included an API SN category oil just for comparison. Any oil with high calcium and low ZDDP numbers would be a disastrous choice as a break-in oil for a flat tappet performance engine. The trick of using an off-the-shelf diesel oil instead of a dedicated performance oil is no longer a good idea. The CK or the new CJ diesel oils offer very low ZDDP counts.
It’s our opinion that changing to a lower spring rate single spring for break-in and using a quality break-in oil such as the ones we’ve suggested will let you use a muscle car-style flat tappet camshaft and reward you with a much better result.
Once the engine is broken in, you still must use a high-zinc oil to maintain the proper lubrication needed for your flat tappet camshaft. If an occasional quart of API SN oil is needed in an emergency like during a road trip that should not be a problem. But you certainly don’t want to use an API SN oil regularly for an engine like J.C.’s. You will need one of these specialty oils to help maintain the flat tappet cam’s integrity for years to come.
Recommended Break-In Oil for a Flat Tappet Camshaft Performance Engine
This list includes oil that we have had personal experience with. There are likely other oils that will also be successful, but we have not tested them and so are not included in this list.
|Comp Break-In 10W30||1590||Summit Racing|
|Driven BR30||01806||Summit Racing|
|Edelbrock 30W||1070||Summit Racing|
|Lucas 30W Break-In||10630||Summit Racing|
Speediagnostix New Oil Testing
|Engine Oil Additives||Valvoline VR1 20W50||Comp Hot Rod 10W30||Driven Break-In 15W50||Pennzoil APR SN 5W20||Chevron CK Diesel 5W40|
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Wasn’t there an oiling groove or passage required that was only on the ‘66 big blocks that dictated a grooved camshaft for the valve train and lifter lubrication? Seems I remember something of the sort.
You are correct. 1965 and 1966 big block engines required a grooved rear cam journal to lube the top end of the engine. This was changed in 1967 by Chevrolet adding an oiling groove in the engine block itself. You can use an early grooved cam in a 1967 and later block, but not a later cam in an earlier block unless you have a machinist cut the groove. I first encountered this when disassembling a 1966 396 that was given to me years ago.
All good advice, thanks. But camshaft manufactured where please? I read something years ago warning that camshafts and lifters mfd offshore were soft metal.
soft metal ? why only 3 failed, I belive the soft metal story but don,t think he would use cheap china crap you break them in with the right oil and RPM X min. run some of good cams come with break in instructions built a lot of motors NEVER lost a cam in 50 years iam 77 not bragging just saying good luck I like old things
hi jeff, could you possibly expound on this ?
had been using castrol edge 5w-50 in everything.
vehicles are, mkiv/454 hyd flat tappet now has about 500 miles on. 99 lexus sc400/4.0 stock – 180k mi, 01 tundra/4.7 stock -90k mi.
am concerned with the reduction in zinc since all vehicles are old.
Hi Jeff, i’m also planning to break-in a similar solid flat tappet cam using Valvoline VR-1 10W30 Conventional oil. With both Comp & Eldebrock BR oils having significantly Higher (4234 & 3452 ppm respectively) Calcium Detergent content compared to VR-1, why is VR-1 10W30 Conventional oil’s Lower Calcium Detergent content evulated as unsuitable for cam break-in compared to the 2 Higher Calcium Detergent content Recommended Break-in oils ? Can you plz elaborate & clarify this for me ? ..With my Plateau Honed cylinder bore finish + Moly rings, I’m Only Concerned about good normal New Cam-Lifter break-in process…Thx for any info,….tom.
With this Same 20+ yr old Flat tappet break-in fail ongoing issue with nearly a dozen Break-in & running Oil brand products All claiming to be superior, Why hasn’t a block & cam-lifter assembly been spun up with adjustable psi valve spring pressure to Lobe/Tappet Failure state, Systematically Evaluating & ranking All the Advertized oils using identical psi Controlled Lifter on Cam Lobe performance Testing ? Somebody probably Has & Knows ! …TIRED of playing this D#@M Oil product PR Marketing Scam game… tom
[…] changed with Valvoline VR1 10w30 weight High Zinc oil, which is something you should do with any flat tappet camshaft in the interest of durability,” Jeff […]
Agree 100% with using Valvoline VR-1 oil for classic car engines. Parts stores in my area are stocked with synthetic oils for newer cars. They have to order the Valvoline VR-1 for me. I have also used Lucas ZZDP additive when breaking in a new cam along with the VR-1 oil. No lobe or lifter failures whatsoever.
i have a question about cam end play while putting together a 5 bolt 289 with a cam that has 497 lift when i put the double roller gear on my dial said it moves .039 so i put on the old cam gear single tooth plus spacer only had .005 to ,006 end play so i measured spacer with dial calipers and the step on new cam gear their was .030 diff this way, how can i solve this problem i looked at a 302s retainer plate to see if it was thicker nope it wasn’t should i find another company that makes cam timing sets it could get expensive if i go trial by error dont no what to do ! ? the one i have now is a cloyes
Most flat tappet cams require initial breakin by setting valves at zero lash or as close to that as possible, then be sure to use a break in oil with Zinc. Start up with as few turns of the starter as possible,(set timing before start up (advance a little ) Do not allow engine to idle below 2,000 rpm for 30 minutes, So make sure coolant is full without thermostat. After 30 minutes, adjust valves and timing then change the oil and take for a test run. I’ve done it this way for years and zero cam failures. By the way that’s by the book. (Iskenderian Racing Cams).
It’s also recommended to remove one of the valve springs (use single springs), just for breakin if you have extreme spring pressures.
Why aren’t hydraulic lifters and camshaft not pre hardened before shipping wouldn’t the eliminate most of this!
I’ve been building solid flat tappet engines since in the 70’s, and never rubbed out any yet. In saying that, the last one in built was a 383 Cleveland aprox 10 years ago, that is still running fine with F256 Crane flat tappet.
I read all the disaster stories of people rubbing out lifters, and while I believe many are incorrect assembly, initial starting problems, or run in procedure, I also see people from shops rubbing out some as well. This makes me wonder if there is a quality problem. (One reason I’m hesitant building flat tappet engines at the moment)
I’m in Australia, and use Penrite running in oil, with Lucas zinc additive.
When I put cam lube on cam, I don’t just smear it on. If you look at the finish on a new cam lobe, it’s almost porous. I rub the lube into the lobe with my thumb, to get it into the lobe.
While building the engine, lifters go in last before fitting intake. Then pushrods and rockers go on when engine is ready for fire up, so the tappets aren’t pressing hard on lobes wiping off lube while your turning engine over to bolt up clutch/flexplate etc.
Use ignition that you’re certain works. And fill carb with fuel. Be certain that timing is set on #1, not 180 out. (This can be checked when setting tappets)
If all is correct, engine will fire instantly. Bring up to 2500 rpm. If there are any problems, shut it down, don’t let it idle. Fix what’s wrong, then start again.
Don’t go revving it up and down, or letting it idle to listen how lumpy cam is etc, until after run in period.
I got the .520 cam for my 454 In 2016 and still Going strong, I used 911 springs set to 122lbs, and full roller rockerd, used compcams break in oil and poured comp zddp additive over lobes, I put in a high volume pump and put solid galley plugs in so lifters would be flooded with oil, break it went bad but cam lives, 911 springs valve float at 5550 so pac hot rod springs did the trick with 130 seat pressure.