Just wiped a lobe. Wanna try a non-thumpr now. Any suggestions so I don't lose power? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-19-2013, 10:13 PM
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Just wiped a lobe. Wanna try a non-thumpr now. Any suggestions so I don't lose power?

Basically, I had the hydraulic flat tappet thumpr cam. (smallest, not mutha, etc.) Here are the specs for it.

What should I look for in a non-thumpr cam to offer close to equal power as what I have now? Just make sure it has the same lift duration?

FYI It's a 350 sbc basically stock but with upgraded aluminium heads, edelbrock air gap intake, and holley 650 dp.

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Old 02-19-2013, 10:30 PM
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Are you saying the cam lobe wore off the cam?
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Old 02-19-2013, 10:31 PM
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110941-11 CL110941-11 279 279 225 225 .465 .465 111 108 Hyd. Hyd. 1
1500-5600 Fair idle, Strong mid-range performance.
or step up to

113215-10 CL113215-10 270 278 217 225 .495 .500 110 106 Hyd. Hyd. 1,2
1300-5500 Good idle, Street Performance. Strong lower mid range. Stock converter OK.
depends on money
second choice here would be nice and idle better,but make more power
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Old 02-20-2013, 12:25 AM
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Thats what I keep fearing although maybe unfounded but to have a wreck with a flat tappet cam rather then going the roller way. I assume you've been looking in the Comp catalog online and go to page 170 where it mentions getting a cam nitrided which will hopefully help with a cam starting the wear process and wiping a lobe. Worth asking about anyway.
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Old 02-20-2013, 02:01 AM
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Quote:
Originally Posted by Zerocyde View Post
Basically, I had the hydraulic flat tappet thumpr cam. (smallest, not mutha, etc.) Here are the specs for it.

What should I look for in a non-thumpr cam to offer close to equal power as what I have now? Just make sure it has the same lift duration?

FYI It's a 350 sbc basically stock but with upgraded aluminium heads, edelbrock air gap intake, and holley 650 dp.
Howard has been known for a harder surface core this should be a good match: Howards Cams Hydraulic Flat Tappet Camshaft and Lifter Kits CL110041-12 - SummitRacing.com
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Old 02-20-2013, 02:55 AM
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Originally Posted by 33Willys77 View Post
Are you saying the cam lobe wore off the cam?
Yes. Noticed a ticking and saw that one rocker wasn't moving as far as the rest. Pulled the lifter out and it was beat to hell and domed. Looked down at the cam and that lob was basically gone.

Thanks for the good suggestions, guys. All I want is a cam that will (at least) match the power that I got from the thumpr, but without the whole "give up driveability for a cool sound" aspect.
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Old 02-20-2013, 11:19 AM
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It's prolly gonna be more about what oil and additives you're using than just replacing the cam. If you don't have enough zinc, ZDDP, phosphorus, etc in your oil, the new cam will meet the same fate as the current one.

Russ
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Old 02-20-2013, 11:40 AM
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Quote:
Originally Posted by Zerocyde View Post
Yes. Noticed a ticking and saw that one rocker wasn't moving as far as the rest. Pulled the lifter out and it was beat to hell and domed. Looked down at the cam and that lob was basically gone.

Thanks for the good suggestions, guys. All I want is a cam that will (at least) match the power that I got from the thumpr, but without the whole "give up driveability for a cool sound" aspect.
Below are a couple pages w/info that should help you have a successful cam break in. If you don't read anything else, be sure to check out the first page listed. Good luck.
Cam break in
Adjusting hydraulic lifters
Valve train points to check
Valve train geometry
Valve spring installed height
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Old 02-20-2013, 11:44 AM
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Below are a couple pages w/info that should help you have a successful cam break in. If you don't read anything else, be sure to check out the first page listed. Good luck.
Cam break in
Adjusting hydraulic lifters
Valve train points to check
Valve train geometry
Valve spring installed height
I had the cam for 3 years before the lobe wiped. I thought cam break-ins were only like 200 miles...
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Old 02-20-2013, 12:06 PM
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why not upgrade to a small roller hydraulic like I posted?make more power with a much nicer idle
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Old 02-20-2013, 12:14 PM
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I had a roller lifter arm break and the lifter spun and took out the roller and cam. All that metal went into the motor and chewed the bearings and pump up. Take a close look and do not just throw in a new cam. You might want to consider a rebuild!
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Old 02-20-2013, 01:18 PM
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Quote:
Originally Posted by Zerocyde View Post
I had the cam for 3 years before the lobe wiped. I thought cam break-ins were only like 200 miles...
Generally the cam is broken in for at least 20 minutes w/the engine at or above 2000 rpm, varying the rpm, w/o idling. So it's not really a matter of how many miles, unless you're able to meet the above criteria while driving the vehicle. Which isn't recommended.

The oil that is available from gas stations and parts stores is not generally going to have the additives present that are needed to keep a performance flat tappet cam and lifters from wearing at an increased rate. Using an oil specifically formulated for flat tappet performance engines, or adding ZDDPlus (or other similar additives) to OTC motor oil will help in this regard.
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Old 02-20-2013, 07:13 PM
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33Willys, I assume that was a retrofit style roller set then and what brand and model type were they as I know with roller cams a lot of mix and match can be done so one brand cam with another brand roller lifter and even used rollers for that matter.
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Old 02-20-2013, 09:15 PM
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They were an old style. It was more like sprung steel in an arch that held the 2 together. One little tab broke on it and it turned. Very costly when it happens to a 392 Hemi - solid roller too.
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Old 02-21-2013, 05:54 PM
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Quote:
Originally Posted by Zerocyde View Post
I had the cam for 3 years before the lobe wiped. I thought cam break-ins were only like 200 miles...
It never really ends anymore because the chemistry of oil has changed greatly and the old levels of ZDDP just aren't there to protect the flat tappet style cam and lifters. This is one reason (and a big one) the OEMs started to replace the flat tappet cam with rollers back in 1985. Others are reduced oil pressure and viscosity, elimination of indexed streams from the rods to pressure lube the cylinder walls and the cam, less drain-back and throw-off from lower pressures and tighter clearances, the use of a windage tray which cuts the mist flying around with the crank assembly. This combines in a hot rod engine with a more aggressive modern cam profile which is to cut back on long ramps that ease the tappet into motion and the use of higher lifts, cams like the Thumper, Extreme Energy, Voodoo, etc. get right too it with short fast acting ramps. This adds a lot of power and makes better use of compression ratios with unleaded fuels and high overall gearing but it's hell on the valve train parts.

Certainly nitriding or Parkerizing the cam will put a permanent hard wearing surface on it but to be safe it would continue to be a good idea to use a ZDDP booster. ZDDP forms a sacrificial coating on the cam and lifters similar to the chemical/heat hard overlay surfaces which by the way GM used for many years before ZDDP became popular in oils. But the ZDDP has to be constantly renewed as it gets used up between oil changes. GM had a lot of flat tappet cam and lifter wear problems when they stopped Parkerizing the cams and lifters of production vehicles back in the 1970's.

I have never been enamored with Chevy's idea of using the angle of the lobe and convex surface of the lifter that is there to cause the lifter to spin on its axis as also a method to preload a thrust force on the cam to stop it from longitudinally travelling in its bearing bores. I have forever build the Chevy with a roller cam thrust button to pick up that load as I figure the lobes and lifters have plenty enough to do without keeping the thrust load against the cam's movements.

Bogie
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