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  #1 (permalink)  
Old 10-20-2008, 10:29 AM
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Why flat tappet cams?

After reading some recent posts asking about special lifters and oils with high z levels to allow running big lift - big spring pressure flat tappet cams for street engines I find myself wondering why? I can see if you were racing in a class where the rules dictate them, but other than that???

This isn't an attack on folks who want to do this! Just trying to understand the rational. I haven't touched a flat tappet cam in 20 years and can't think of a reason to select one over a solid (preferred) or hydraulic roller.

IMHO, The price difference when buying all new high performance parts isn't that much compared to the very real benefits in performance, oil temp reduction, and profiles. If it's just a cost thing I get that.

I really am just curious. I'm sure there are valid reasons my little brain just hasn't figured out. I do tend to get my way of doing things and that's that. I've had roller on the brain for so long I could well be over looking something..

Looking forward to some education!

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Old 10-20-2008, 11:16 AM
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The reason I run flat tappet cams is the cost.
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Old 10-20-2008, 11:47 AM
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Price is the only reason--- and the way cams are going flat, not a good enough reason. A roller is the only way to go.
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Old 10-20-2008, 12:09 PM
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I'm just looking to change out my cam in my 350 S10. I can do that for about 200 bux, as opposed to about 500+ for roller. If I were building a new HP engine, sure, roller makes sense. But not now. And I have never had a new cam flatten a lobe yet. The only cam that went south on me was an OEM buick 350 in a 74 Century.
Coat them with a clay based teflon grease (QMI) when you install them, run Valvoline VR1 oil and break them in for 20 minutes at 3 grand......no problems. Ever.
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Old 10-20-2008, 12:45 PM
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I do it for cost. If I had a roller block I'd be tempted to go roller, but I don't as of now. A solid flat is almost as good as a hyd roller for most hot street builds anyway. You may give up 10 hp but you can spend that $300 saved on something like a MSD box or a better intake to make up the difference.

Out of curiousity how radical of a cam can factory roller lifters take? Can they take .600+?
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Old 10-20-2008, 01:02 PM
How fast is fast enough?
 
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Another reason- a lot of these solid tappet cams with high ratio rockers have higher lift tahn a roller cam would with factory rocker arms- again money more wisely spent IMO. But yea, you have to watch the oil.
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Old 10-20-2008, 01:55 PM
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If you really want a roller, you can buy a roller block, or pay for insanely expensive retro rollers. Sometimes, retro rollers are the only choice. All of the pontiacs, most of the Olds, the big caddys, traditional BBC, BBF, Clevelands, AMC, Wedge... many of the builds I want to do REQUIRE retro rollers if I'm going to do it.

So, since I know how to break in a flat cam and what oil to run to keep it alive, I almost always choose the flat.

Retro rollers (depending on the application) can cost well over $1000 until you factor in the cost of springs, pushrods, lifters, cam, thrust button, distributor drive gear.

Cripes, for $1000 I can buy a completely remanufactured spare BBC longblock, so if you're asking why I do flat cams, its because for what I do there is no justification to spend $1000 just to get a little more torque.

Another thing... for $1000 I can buy 30 flat cams and just put a new one in if it goes flat.
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Old 10-20-2008, 02:14 PM
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The things I think you are missing is that when a flat wipes, the bearings and everything else are at risk of being wiped out. It all depends on what you are trying to do with the engine.
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Old 10-20-2008, 02:34 PM
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Solid rollers have problems when ran on the street due to roller failure, hydraulic roller won't make the power of a solid lifter due to valve float .And solids are cheaper, failure is usually not a problem with correct oils and break in procedure.
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Old 10-20-2008, 02:51 PM
How fast is fast enough?
 
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yep, solids have in many casesmore agressive ramps and more stability at higher rPM tahn factory hyd. rollers- because of that I have actaully "retro-fitted" a roller engine with flatt tappets before- they're just easier and cheaper to work with.

Solid rollers on the other hand are the king- but few of us can afford to play in that game. They're great for the strip and maybe on a car that only sees 3,000 miles a year, but I can't afford to run .650 lift when I'm running to get the groceries, and for anything under that work fine.
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Old 10-20-2008, 03:26 PM
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I run a solid flat tappet, because I like the sound, same with a gear drive-If it's a old school hot rod, it has to make noise and have a 4-speed-IMHO, if I wanted a Lexus, I would buy one
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Old 10-20-2008, 03:28 PM
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Last years circle track setup: $65 solid flat tappet cam, $90 lifters, $30 pushrods, $150 roller tip rockers, $60 springs, $40 retainers, $20 locks (pricing approximate - I would need to double check receipts to be sure). So that was $455 in my total valve train - turned it 6500-7000 every night all season with no failure using $3/qt Brad Penn oil.

Next years proposed setup: $250 solid roller cam, $300 lifters, $100 pushrods, $300 roller rockers, $150 springs, $40 retainers, $20 locks (again pricing approximate). So that adds up to $1160 - more then twice the cost of last years setup and I still plan on using the same $3/qt oil as last year so no cost reduction there.

Losing a flat tappet cam isn't fun mid-season, but it's been predictable as you start to see lash go away on one or two lobes - and it's fixable over a weekend. I can't wait to see the damage that a solid roller does to my engine when I let one go too long and it fails from fatigue and pushes needles throughout my engine without warning!

To each there own - my new engine odds are will be a solid roller to get the hp, but a hydraulic or solid flat tappet is pretty darn cheap and they can hold up.
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Old 10-20-2008, 04:07 PM
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Quote:
Originally Posted by Koolaid

...Next years proposed setup: $250 solid roller cam, $300 lifters, $100 pushrods,
$300 roller rockers, $150 springs, $40 retainers, $20 locks (again pricing
approximate). So that adds up to $1160 - more then twice the cost of last
years setup and I still plan on using the same $3/qt oil as last year so no cost
reduction there....
Don't forget to add a few $$$$ for a stud girdle.
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Old 10-20-2008, 05:12 PM
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retro roller setup far too expensive
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Old 10-21-2008, 12:22 PM
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Why flat tappet?

For some of us flat tappet cams are all that are available for our engine.
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