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Old 03-07-2010, 09:04 PM
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Big blocks eat cams without roller lifters?

This is my understanding with big block chevys; if you want to hold on to your cam lobes, you better go roller lifter because of the spring tension required in high lift, big valve heads. Well, I am hoping that the case will be considered "Different" in the case of a 455 Pontiac motor.

If would be true that the 455 Pontiac is in the same displacement league as a 545 Big Block Chevy, but the Pontiac is hampered by small ports and the ports flow at a slower/less volume rate. Any need to spend the extra $$$ for a roller cam & roller kit for a build limited to any stock or close to stock lift?

Thanks.

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Old 03-07-2010, 09:41 PM
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WDCreech is more likely the local Pontiac dude. He should be along to answer this for you or you can PM him.
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Old 03-07-2010, 09:57 PM
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Yeah, I wiped out a cam lobe on my 454 ... but I took responsibility for it. Improper pre-lubing.

All flat-tappet cam engines are at risk of break-in related failue unless you read all of the instructions, use the right motor oil, which almost all require a seperate ZDDP aditive these days.

There are plenty of threads here at HR.com on this subject. If you can't find one, just say so, and someone will point you in the direction of one.

The other thing that you must do is to remove those inner valve springs during break-in. Just the outers will be adequate for the break-in RPM range (usually 1500 - 2500 RPM)

Roller cams are hella expensive in comparison.
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Old 03-07-2010, 10:04 PM
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Well, I may as well post my flat tappet precautionary piece while we wait....

The following list of do's and don't's didn't sit well with the troops when I posted it originally, but if it helps even one person to prevent mushin' a cam, it's worth it. I even posted a disclaimer at the top to satisfy some of the members of this board.....

DISCLAIMER: THE FOLLOWING INFORMATION WAS GLEANED FROM MANY DIFFERENT SOURCES. SOME OF IT MAKES SENSE TO ME AND SOME OF IT DOESN'T. USE WHAT YOU THINK IS REAL AND THROW OUT THE REST OF IT. I HAVE NOT USED ALL OF THE SUGGESTIONS LISTED HERE. THROUGH THE YEARS, I HAVE ACCOMPLISHED MANY SUCCESSFUL FLAT TAPPET CAMSHAFT BREAK-INS, BUT I HAVE ALSO ROACHED A FEW. USE THIS LIST AS A GUIDELINE SO THAT YOU REMEMBER TO CHECK ALL THESE THINGS WHEN INSTALLING A NEW FLAT TAPPET CAMSHAFT. DO NOT TAKE EVERYTHING POSTED HERE AS GOSPEL. IF THE MANUFACTURER OF THE CAMSHAFT YOU'RE USING RECOMMENDS PROCEDURES THAT DIFFER FROM WHAT IS SHOWN HERE, USE THE MANUFACTURER'S RECOMMENDATIONS AND DISREGARD THIS INFORMATION.

Mistakes that may "frag" a flat-tappet camshaft and lifters.

1. Failure to remove all rust-preventative from cam and lifters with solvent once you get them home. (This advice does not include removing coatings applied at the factory such as phosphates. It is only suggesting to remove rust-preventative grease that may or may not have been applied to the cam/lifters to prevent rust in storage. This grease will not have the extreme pressure characteristics that Molybdenum Disulphide has and should be removed so that MD can be applied properly. MD is the black, tar-like extreme-pressure grease that is recommended by some camshaft manufacturers to be applied to the lifter crowns/cam lobes for initial camshaft break-in).

2. Failure to wash the cam and lifters with hot soapy water to remove the remainder of rust-preventative not removed with solvent. CAUTION; WASH ONLY THE CROWN OF THE LIFTERS. (THE VERY BOTTOM OF THE LIFTER WHERE IT CONTACTS THE CAMSHAFT LOBE). DO NOT ALLOW WATER TO GET INTO THE INTERIOR OF THE LIFTER BODY. BE VERY CAREFUL HERE IF THE LIFTER HAS AN OILING HOLE THAT HAS BEEN EDM'D INTO THE CROWN TO PROVIDE OIL FROM THE INTERIOR OF THE LIFTER BODY TO THE CAMSHAFT LOBE. Dry the cam and lifter crowns thoroughly with hot air from a hot air gun or hair dryer to remove all traces of moisture before applying Molybdenum Disulfide.
WARNING: DO NOT USE ANY ABRASIVE MATERIALS SUCH AS SCOTCHBRITE PADS OR SANDPAPER OF ANY KIND TO ACCOMPLISH THESE SOLVENT AND SOAP CLEANING OPERATIONS. USE ONLY SOFT, CLEAN RAGS. THE WHOLE INTENT OF CLEANING THE CAMSHAFT IS SO THAT WE CAN REMOVE RUST-PREVENTATIVE OILS AND GREASES THAT MIGHT HINDER GETTING DOWN TO THE BASE METAL IN ORDER TO PERFORM OPERATION #3 SHOWN HERE.

3. Failure to properly massage an extreme pressure lubricant such as Molybdenum Disulfide into the pores of the metal on all lobes and lifter faces. Moly will actually bond with the metal and give maximum protection to the lifter crown/lobe.

4. Failure to use an extreme pressure lubricant additive in the engine oil for camshaft break-in. Each cam grinder has his own specific product to facilitate valid cam break-in.

5. Failure to use the proper valve springs for cam break-in. You can't use the 300 lb over-the-nose springs that you'll eventually use in the motor and expect the cam to live at break-in. Assemble the heads with stock or weak single springs to break in the cam, then use one of the many tools available to change the springs with the heads on the motor. Alternately, assemble the heads with the springs you will run and use reduced-ratio break-in rockers, then change out the rockers after break-in. These rockers are available from Crower in different ratios for different motors. A popular ratio for a small block Chevy would be a 1.3:1 rocker. In other words, let's say the lift at the cam is 0.350" and the theoretical lift at the valve with 1.5:1 rockers is 0.525". Using the 1.3:1 rockers would result in lift at the valve of only 0.455", thus reducing stress at the camshaft/lifter interface during the crucial break-in period.

6. Failure to check for valve spring coil bind at max lift. If you cannot tell by eye, verify by inserting a .010- inch feeler gauge between the coils. A .010 space between five coils would give a total of .050 safety margin before stacking solid. If you cannot pass the feeler gauge between the coils, the spring is either coil bound or dangerously close to this condition, and you have probably overshimmed the spring (the fitted dimension is too short).

7. Failure to check for retainer to valve guide/seal clearance. 1/16"-1/8" clearance at full valve lift is considered sufficient.

8. Failure to check for binding at the rocker/stud interface with stamped steel rockers. Long slot rockers are made specifically to cure this problem.

9. Failure to check for piston/valve clearance..... 0.080" on the intake and 0.100" on the exhaust is considered by many to be the minimum clearance acceptable. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat.

10. Failure to run the motor at high rpms (2500 or higher, alternating 500/1000 rpm's up and/or down to allow the crank to throw oil in different places at different revs) for the first 40-45 minutes of its life. NO IDLING. NO IDLING. NO IDLING. The motor should not be run at less than 2500 rpm's for a minimum of 40 minutes. If a problem develops, shut the motor down and fix it, then resume break-in. The main source of camshaft lubrication is oil thrown off the crankshaft at speed, drainback from the oil rings and oil vapors circulating in the crankcase. At idle, the crank isn't spinning fast enough to provide sufficient oil splash to the camshaft/lifters for proper break-in protection.

11. Failure to clearance lifters in their bores so that they spin freely. Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one/half thousandths) considered close to ideal. Too loose is as bad as too tight.

12. Failure to initially adjust the valves properly. Using the "spin the pushrod until it feels tight" method will normally result in valves too tight. Holding the rocker arm tip down against the valve stem tip with one hand, jiggle the pushrod up and down with your thumb/forefinger of your other hand until all play is removed, then turn the rocker nut 1/2 to 3/4 turn to set the preload. Builders who have done hundreds of engine builds may have the "feel" to do the "twist" method, but those fellows who are doing their first few builds lack the experience to do this and will have better results with the "jiggle" method.

13. Failure to inspect the distributor drive gear for wear. Too much wear can allow the cam to walk in its cam bore and contact an adjacent lifter.

14. Failure to have everything ready for the motor to fire on the first few turns. Fully charged battery, good starter, known-good carburetor with full fuel bowl, source of fuel to the carburetor to allow minimum 40 minutes of uninterrupted running. Ignition timing set. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER.

15. Failure to prime the oiling system prior to firing the motor. Prime until you get oil out of the top of each and every pushrod. Observe the oil pressure gauge to be sure pressure is registering. Priming will aid lubing the valvetrain at initial startup. It's the last area of the motor to get lubed on dry start.

16. Failure to use new lifters on a used cam. Used lifters should only be used on the very same cam, in the very same block and in the very same positions they were removed from. Chances that the lifter bores will be machined on the very same angles on a different block as the block the lifters came out of are about equal to you hitting the lottery.

Now, this last bit of advice comes from Racer Brown, world-renowned camshaft manufacturer/engineer who ground the hot cams for Chrysler Corporation during the horsepower wars of the 60's.
"Overfill the crankcase by at least 4 or 5 quarts of oil so that the oil level comes to within an inch of the top of the oil pan. Install a set of fairly hot spark plugs with a gap of 0.050" to 0.060" to prevent oil-fouling of the plugs, which is otherwise inevitable under no-load conditions with all the extra oil aboard. During this operation, we want near-maximum oil flow, together with a maximum of oil vapors and liquid oil thrashing about in the crankcase so that the cam lobe and lifter interface lubrication is considerably better than marginal."

This advice from the Racer is too scary for me, but I included it so that you know someone, somewhere has done it.

Just a note to make you aware of the loading between the camshaft lobe and lifter crown. That pencil-point of contact, if carried out to a square inch, would be somewhere between 250,000 and 300,000 POUNDS PER SQUARE INCH.
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Old 03-08-2010, 03:59 AM
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Quote:
Originally Posted by DENCOUCH
This is my understanding with big block chevys; if you want to hold on to your cam lobes, you better go roller lifter because of the spring tension required in high lift, big valve heads. Well, I am hoping that the case will be considered "Different" in the case of a 455 Pontiac motor.

If would be true that the 455 Pontiac is in the same displacement league as a 545 Big Block Chevy, but the Pontiac is hampered by small ports and the ports flow at a slower/less volume rate. Any need to spend the extra $$$ for a roller cam & roller kit for a build limited to any stock or close to stock lift?

Thanks.
A Pontiac engine is much the same as a SBC, AFA the valve train layout/geometry goes, and nothing like a BBC. So the same things apply to any size Pontiac as it does to a SBC.

On a BBC, the push rod angles are different, and this can 'help' to make matters worse as far as breaking in a cam goes, because of the tendency for the lifters to not rotate at start-up. Plus the oil now sucks- as I'm sure you're aware.

ZDDPlus has to be added along w/a moly break in lube on JUST the lobes and lifter foot- NOT on the sides of the lifter body or cam bearing journals- you want nothing but motor oil there, to keep from gumming up the lifter in its bore. Moly lube also gets used on the pivot ball and rocker if you use stamped rocker arms.

The cams used in Pontiac engines are usually not super high lift, because a Pontiac cast iron D-port head doesn't need a ton of lift to get the job done. So, because of this, the valve spring rates are moderate- just like the cam lifts are. This means the tendency to lose lobes at break in isn't bad at all on a Pontiac engine. This also means that there isn't a special need for a roller cam in a Pontiac- unless there's a need for it other than the worry of breaking in a flat tappet cam and lifters. Like if you are shooting for mega HP numbers and RPM.

The only other consideration is, the Pontiac intake valves are 2.11", and are a bit on the heavy side. But as long as you go w/the springs spec'ed for the cam you want to use, there will not be any issues w/breaking it in, IMHO.

Bottom line- roller cams are nice. But not a necessity.
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Old 03-08-2010, 08:37 AM
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Excellent post techinspector1.

I may get flamed, but I feel compelled to add two items.

On techinspector1's #15, certain engines may need to be SLOWLY turned over BY HAND through one complete revolution to assure the passages line up to provide oil to the top end.

I would assume that if you are using a cam grind that has you this concerned that you will be using at a minimum roller tip rockers if not full rollers. Check the contact patch on the valve stems and install the correct length push rods before starting the engine and breaking in the cam.
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Old 03-08-2010, 03:27 PM
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I always question any method - Im not saying anything is wrong with the above methods but this is what my current opinion is on the following two methods - -

1. Use a lower ration rocker arm
2. Take out your inner spring and only use the outer

These both seem like you're extending your break in period and increasing your chance of grinding a lobe.

The concept seems sound I want to put less pressure on the lifters so they can spin and get rubbed/worn in with the cam lobes I get that...
BUT when you reinstall the springs or rocker arm with high ratio in you plan on using for the rest of the motors life, you put that extra pressure on those lobes/lifters that wasn't present at break-in and are essentially breaking those lifters and cam in again right? WITHOUT the assembly lube/grease this time just hopes that there's enough zinc in your oil now to keep life in those parts.

Here's just an example: You torque down your mains to 70 ft lbs and break your engine in - - you dont go back and retorque those mains to 85 ft lbs for the rest of the engines life do you? What sense does that make? What sense does it make to remove the inner spring or lower your rocker ratio to break in a flat tappet cam when you plan on increasing that 'pressure' after the first 30 minutes of that motors life???? Pressure creates added friction and wear it doesnt matter if its now 'broken in' both parts were brand new and had 'perfect' surfaces rubbing against each other.

Opinions? Educate me i guess?
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