Thread: Mechanical flat tappet cam

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How many of you guys run them out here? I'm looking at one for my next upgrade in my K5. I'm not realty worried about the life because I don't really drive it that much, more of a play toy. I'm gonna bump up compression as well.

Engine specs as it sits right now
Holley 750dp
Huricane single plane intake
990 heads w/ 2.25/1.88
.060 over forged pistons
9.5:1
Cast crank
Thumb rods

Here's the cam I'm thinking....
11-611-5 - Puller & Mud Race Mechanical Flat Tappet Camshafts

Imho... the only real problem with'em is that the oils aren't made to support the loading. So you need to use an oil that can handle that load.

But why?? Why not use a roller cam that reduces the friction and is easier on the timing chain for instance?

Since you aren't using the ride daily, if it wipes a lobe or two ( and it's been known to happen almost instantly) I guess it won't be such a bother except for all the fine metal particles that'll be passing around in the oil... and lodge into the main and rod bearings...

It's your money / choice.. I'll be curious what you decide and how it works out.

Price of a roller cam is a lot more. That's why I was looking at the mechanical series instead.

Seen too many flat tappet cams go bad.....If you lose a lobe and the particles off the cam wipe out the crank, rod, main, and cam bearings, then how much money did the flat tappet cam save you?????

You can do the flat tappet---you just need to use Brad Penn or Joe Gibbs oil

Personally, if I were forced to use a flat tappet cam, I'd rather do the flat tappet solid than I would a flat tappet hydraulic.
You can purchase solid lifters today that have a small 0.012" hole EDM'd in the crown that delivers pressurized oil directly to the cam lobe. You can't do that with a hydraulic lifter.
http://www.jegs.com/i/COMP-Cams/249/...oductId=753217

You can however, use a tool to cut a groove into the hydraulic lifter bore that will deliver pressurized oil directly to the cam lobe.
http://www.summitracing.com/parts/cc...FY9eQgodoGQAHQ

As far as the cam you posted a link to, note that Comp advises a minimum 11.0:1 static compression ratio for that stick. At 9.5:1 SCR, the intake valve would close too late to trap enough air/fuel mixture to make a good BANG. This would result in the motor being (as one of my buddies used to say) "a weak-suck operation". At 9.5:1, you would want a lobe that closes the intake valve at around 35 degrees after bottom dead center @0.050" tappet lift. Be careful when comparing solid cams to hydraulic cams. Most solids are rated at 0.020" tappet lift rather than 0.050" tappet lift. Bottom line: The 11-611-5 is too much cam for 9.5:1 SCR. Read this to get an idea of what I'm talking about.......
http://www.crankshaftcoalition.com/w..._compatibility

If it were my motor, I'd use 11-218-4 for some snappy street action. Comp suggests minimum 9.0:1 SCR. Your motor, at 9.5:1, would be perfect.
http://www.compcams.com/Company/CC/c...?csid=457&sb=0
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What does brad penn & joe Gibbs oil have that others don't? Like a zinc additive or something like that. I already run oil that has a zinc additive because i run a hydro flat tappet extreme 4x4 comp cams. Also I'm gonna be pushing the compression up to 11-11.5:1 on the next rebuild, sorry for not mentioning that!

Wow! Mechanical flat tappet, and then on top of that 11.5 to one compression?? Where do you plan to find fuel for your occasional use? I'm at 10.3 to one with aluminum heads, and I wish I'd gone closer to 9 to one so I didn't have to worry with finding gas stations with 91 or better octane gas, and then worrying how long it's been sitting in their tanks....

Couple gas stations in Boyne City have 93 octane so that's not a big deal.

Originally Posted by rspears

Where do you plan to find fuel for your occasional use? I'm at 10.3 to one with aluminum heads, and I wish I'd gone closer to 9 to one so I didn't have to worry with finding gas stations with 91 or better octane gas, and then worrying how long it's been sitting in their tanks....

Sorry for the hijack... I didn't know this RSpears.. makes me glad I targeted 9:1 even with the aluminum heads on my 347.. now back to our regular broadcast schedule! Sorry for the hijack...

Originally Posted by rspears

and then worrying how long it's been sitting in their tanks....

Yep, and worrying about what percentage of it is water. Smart money would build for 87/89 octane.
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Originally Posted by techinspector1

Yep, and worrying about what percentage of it is water. Smart money would build for 87/89 octane.
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I couldn't agree with your more, Richard.

Originally Posted by techinspector1

Yep, and worrying about what percentage of it is water. Smart money would build for 87/89 octane.
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Originally Posted by rspears

I couldn't agree with your more, Richard.

So you would tells this to a drag racer that keeps getting beat as well? Don't worry you keep throwing your money out there and continue to lose! In my mud bog/run class I'm in, I'm right in the middle of the class. The people above me are running more power. I'd like to start getting some money back in return for going to events....

Originally Posted by Hoss Blazer

So you would tells this to a drag racer that keeps getting beat as well? Don't worry you keep throwing your money out there and continue to lose! In my mud bog/run class I'm in, I'm right in the middle of the class. The people above me are running more power. I'd like to start getting some money back in return for going to events....

Nope, my comments are more attuned to the street. For a competition vehicle you're in a different situation, but consider the problems with ethanol blends in your logic, too, like how much fuel to keep on hand between outings, how to store it (small volumes, less air), etc, etc. It's a different time than it was back in the day...

Originally Posted by Hoss Blazer

So you would tells this to a drag racer that keeps getting beat as well? Don't worry you keep throwing your money out there and continue to lose! In my mud bog/run class I'm in, I'm right in the middle of the class. The people above me are running more power. I'd like to start getting some money back in return for going to events....

You're not being real with us. You didn't say anything at all about being in competition when you opened this thread. Here is your statement:

"How many of you guys run them out here? I'm looking at one for my next upgrade in my K5. I'm not realty worried about the life because I don't really drive it that much, more of a play toy."

We wil answer one way for a street cam (playtoy) and another way for a mud bog cam (competition).
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