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How to Break in a New Cam

There are a couple of things that have changed. Read about them here.

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Why Break-In's Not a Crime

If your engine is equipped with a roller cam, this story really doesn't relate. But because a flat-tappet-style camshaft relies on a follower that slides across the cam lobe, it requires lubrication that can minimize this sliding type of wear. All off-the-shelf oils that have a current API SM rating have had the zinc levels reduced to protect catalytic converters. This is not to say that using the current SM-spec oil will eventually kill your flat-tappet camshaft. There are probably thousands of engines running around right now without difficulty.

There are some mechanical things that could predispose particular engines to wear problems. Excessive valvespring pressure will only aggravate these problems, since these higher spring rates create more load between the lifter and cam lobe. Crane Cams suggests flat-tappet cams not exceed 300 pounds of load over the nose of the lobe. Generally, most street hydraulic cams do not see this much load at max lift, since the open-spring pressure is divided by the rocker ratio. So, if the open-spring pressure is 400 pounds and the rocker ratio is 1.5:1, the load on the lifter is around 266 pounds.

Flat-tappet lifters are designed to spin in the lifter bores. This requires that the lifter bores be free of burrs or casting flash that can cause the lifter to stick and not rotate. Big-block Chevys are infamous for sticking lifters because of their angled pushrods. If you think there is a problem, place a color stripe on the pushrod and watch it with the valve cover removed as the engine runs. If the pushrod does not rotate, the lifter is not spinning.

High-ratio rocker arms also tend to place more load on the lifter and cam lobe. This is because higher rocker ratios open the valve farther, which increases the load between the lifter face and the cam lobe at every point on the lobe. For break-in purposes, you should break the cam in with a shorter-ratio rocker arm and then swap the rockers after the first hour or so of engine operation.

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59 comments
Brian Clausen
Brian Clausen

It will save your bearings when you add it into your oil when your going through the break-in period.

Jake Fitzpatrick
Jake Fitzpatrick

chuck gill, im with you there. same nightmare in an old 326

Kenneth Corbiere
Kenneth Corbiere

tried to put a 327 high lift cam into a 400 ci.....bad, bad, bad, and really, I knew better

Derek Bettencourt
Derek Bettencourt

did the same with a 350 and used 272 crane same lifters 4 months ago runs perfect lots of cam lube used though.

Nathan Britton
Nathan Britton

Oh, and don't try to support the cam by sticking your finger down the distributor hole... you will end up bleeding.

Nathan Britton
Nathan Britton

Just put a new Comp cam in my '79 Ford 300-6. Found out, literally just in the nick of time, that the lifter cover was upside down and puking all the oil out. ALWAYS check for oil leaks...

Page Crow
Page Crow

#1: Install that cam with the engine standing UP. That way, you don't bang it around inside the cam-bearings. It drops right in real sweet if you go vertical.

Kenneth Bircheat
Kenneth Bircheat

Trying to take a cam out that had snap in two in a 351 winzer.

Mike Edler
Mike Edler

installed new cams and trays in a 2010 BMW, it ran for about 8 seconds, then seized the motor. thank god after prying it back out the motor was o.k. still don't know what went wrong.....

Jason Wingnut Smith
Jason Wingnut Smith

wondered why i had a knock in the motor one mechanic said big end another said it was i was the gudgeon pin... pull the motor down and nothing to do with either of those turned out i had wore the lobes of the cam 3 where worn down into the cam and another was worn down even with the shaft fitted a new lumpy cam with new lifters and behold the beast was running perfect..

Steve Syvertsen
Steve Syvertsen

Too much spring seat pressure on a friends BBC, ate that Lunati Cam right up like the cookie monster. nomnomnom!

Nicholas Adams
Nicholas Adams

Had a few lobes go round on a 400sbc with a gear drive. Replaced the cam and lifters, broke it in with the Crane break in additive, switched to a timing chain, then I could hear all the noisy connecting rod bearings that got chewed up. The new cam broke in fine. Pulled the engine, tore it down, sent the crank back out, scrubbed every inch of it and did it again, the whole nine yards... Ran great after that.

Jake Lister
Jake Lister

Had a timing gear come apart at 5,000 rpm on a Chevy 350

Dodge Custom Royal Lancer
Dodge Custom Royal Lancer

I use Shell Rotella T with STP blue bottle ZDDP to break in cams, works like a champ every time :)

Elijah Rose
Elijah Rose

rebuild at school, "were going to try and reuse this cam, i dont want to spend the money for a new one" *slip* *bang*...... " well i guess i need a new one now... " great day -_-

James Doepel
James Doepel

Heavy duty truck oil . Rotella or. Dello will do .

Tim Howe
Tim Howe

I was pulling the cam out of a 75 Camaro and it came out fast and I smacked the back of my hand on the radiator support, drove myself the the ER and got 3 stitches!

Ricky Bobbie
Ricky Bobbie

Keep it above 2500 rpms for 30 minutes and use lots of break in lube and an additive in the oil

Dean Henderson
Dean Henderson

cheap summit cam and lifters. Break in oil with lots of ZDDP. 2000 rpm for 20 minutes with open headers. Neighbors calling because of the noise. priceless

Louie Eriacho
Louie Eriacho

I agree with you Mr. Timothy Bremm interesting ...

Cam Beaton
Cam Beaton

I instaled a Stock Elimiantor cam, that I got for free in a 350 Olds. It sounded tough, but it was guttless.

Timothy Bremm
Timothy Bremm

All of these answers are interesting.A learning experience.

Robert Bruce Carter
Robert Bruce Carter

Didn't have enough clearance on valve springs. Coil bind ! Expensive lesson..

Rick Maynhart
Rick Maynhart

Stephen.....when you do the cam and dizzy gear you need a matched set from Bulltear.

Christopher Doss
Christopher Doss

Had a lunati voodoo go flat on 3 exhaust in 5 days after doing everything I could and spending an extra 100 on all the best additives and lubes I could get and weak break in springs, that was my last flat tappet :-( got a comp thumper roller in the same motor (after ANOTHER rebuild and cleaning to get all the metal out) and it's been great and the only new thing I had to do was figure out custom pushrod sizing.

Gary Huddleston
Gary Huddleston

Went cheap..put in a used can with old lifters... Can you say flat lobes in 10 days?

William Schmitz
William Schmitz

270 Crower in a low compression SBC 350. 10 inches of manifold vacuum. A set of Rhodes lifters fixed it. Lesson learned.

Steve LaRiviere
Steve LaRiviere

The only cam problem I've had, and this was a long time ago (1980 or so) was with a Crane Fireball cam I put in a SBC. I took care to break it in right, but it still wore out in less than 5000 miles. I swear it must have been made of pencil lead. I've used Comp Cams, Isky, Crower, and Ford Motorsports cams and never had a problem with them.

Jon-David Jacobs
Jon-David Jacobs

rebuilt complete 350 and installed new valve springs at the wrong height. made the cam a whole lot smoother about 5 minutes into breaking in the engine. couldn't understand why the valves were so noisy!

Joe Jr Ferrell
Joe Jr Ferrell

If you knw the L.S.A of a cam and how they function and understand oil and viscosity. And knw what your doing ...you shouldnt have any problems. Unless its a manufacturing problem. .

Mike Gizzmo
Mike Gizzmo

not a problem but a funny/odd story. in 1970 I wet 2 work 4 the PA dept. of Trans.they had & still do have a engine rebuild shop. one of the old guys taught me 2 rebuild engines (gas at that time). so I'm installing a camshaft in a 450ci IHC 6 cylinder and it's a bit sung (high spot on a cam bearing). so one of the old guys says stand back.9this is the odd/wild/crazy part) and takes out a large long brass punch & a 5 pound hammre. he hits the camshaft on either side of all the cam bearings. on the lobes spins the cam 1/3 turn hits again .. the engine ran great on our dyno. Kids please don't do this at home. never on a stock Ford shaft they are very brittle !!! I retired with 35 years rebuilding engines. FUN WITH TOOLS. my hands are shot

Chris Pinney
Chris Pinney

This is 2013 buy a roller cam!!! Flat tappet hasn't been in SBC since '86 and SBF in '84 in mustangs.

Halim Amzika
Halim Amzika

Two successful swaps (xe268h and xe274h), no issues as of yet. Used resp. 10W40 dino diesel oil and 5W50 fullsynth Valvoline VR1. Of course break in with the moly lube and additive!

Chück Gill
Chück Gill

I runed two high lift flat tappet cams in a Pontiac 400HO before I found and article on zinc and phosphate. Third time and ZDDP was the charm.

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