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Old 07-26-2013, 03:07 PM
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Comp Cams Magnum 280h vs xe274h

Hey everyone. Im looking for a little help with cam selection. Everytime I talk to someone about the math I hear Charlie Brown's teacher.
I'm not looking for a super high HP number(I wont complain about one either), I'm looking for the car to be an absolute beast from as low as possible to about 6000-6500RPM. Its a Saturday night toy, not a drag car, but I also dont want to get beat by some 18 year old kid at a traffic light.

Here's what I've got:

350 .030 over 4 bolt
Speed pro l2256 forged pistons
stock crank and rods, rods resized crank polished rotating assembly balanced
Brodix race rite 200 heads port matched
going to use an edelbrock rpm air gap intake
edelbrock 750
compression(by my math)is about 9.85:1
M21 trans
4.11 rear
stuffing this in a '70 Chevelle

The magnum 280 and xe274 were the recomendations I got so far. The first from summit the second from comp. What do you all think of these two for what I want or is there something better out there?
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Old 07-26-2013, 04:37 PM
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Comp Cams K12-433-8 Retro-fit Hydraulic Roller cam and kit.
236 I / 242 E degrees duration @ .050"
.520" I / .540" E valve lift w/1.5:1 rockers
110 LSA
9.1:1 min. compression ratio.
2500 - 6000 RPM cam range

Beware of an 18 year old kid at a traffic light with a 2013 Camaro ZL1 with 580 HP V8.

Last edited by MouseFink; 07-26-2013 at 04:44 PM.
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Old 07-26-2013, 04:54 PM
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Oh id love to go with a roller cam but its just not in the budget right now.
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Old 07-26-2013, 07:09 PM
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I currently have the xe274h with 10:1 compression and a rear gear ratio of 3.73

I freaking love it, Idles at about 900rpm and it sounds amazing

good midrange power from like 1600rpm and up in my engine

great torque too, in my particular engine it only likes being revved to about 5800 rpm max
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Old 07-26-2013, 08:20 PM
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That's right where is like to be as far as rpm. Like I said, I'm not building a race motor. With the low gears do you think I should go up a size for the cam or will that hurt my low end torque?
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Old 07-26-2013, 08:37 PM
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Quote:
Originally Posted by Fire60 View Post
That's right where is like to be as far as rpm. Like I said, I'm not building a race motor. With the low gears do you think I should go up a size for the cam or will that hurt my low end torque?
In my honest opinion the xe 274 was about as big a cam as I would ever want to go in a street driven car

if you're looking for a cam with streetability that gives you more power than the xe 274 you're gonna have to look at roller cams I'm afraid

bigger is not always better. it's nice have a little bit of the power curve below 2000 rpm
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Old 07-26-2013, 08:53 PM
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I'm with ya. I want it to move and shake whenever I punch it. That'll be mostly on the lower end. Thanks for input
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Old 07-26-2013, 09:26 PM
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Look at the isky Cams Hi rev street strip solids
EG Isky Z-27 #201027 camshaft. Can use a 1.6 or 1.65:1 rocker for more lift .550" ish net lift with the Brodix RR-200 heads.
ISKY Racing Cams - Do It Right. Race with the Legend. Camshafts, Connecting Rods, Valve Springs, Lifters

if your Chevelle has tall tires consider more 4.30:1+ gears.
For 4.10's use a short sticky 26" tire.

You are best to CC the chamber on those Race Rite heads as they will probably check larger than spec.
You don't want to come up short on real compression ratio.

Last edited by F-BIRD'88; 07-26-2013 at 09:50 PM.
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Old 07-26-2013, 09:39 PM
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I am running an XE274H in my SBC. 9.9:1 on Factory iron Vortec heads. Initial timing 26* and 35* total. Idles at 900RPM, makes 11" vacuum at idle. Runs my power brakes OK. I have 4sp manual trans and 3:73 posi. Truck is about 4,000 lbs. I love the cam, makes power all over. I was concerned it was too much cam for this heavy truck, but I think its great in the end. The 280H cam has slower ramps rates so it is not as sporty as the XE series.

Here is a good video to hear the idle sound. Note that I still had some carb issues at this time, and the linkage was right, not hitting WOT.

Here is the video that shows a lot more power output. At :07 you can see the rear end squat and tires break loose as the secondaries open. Carb is still lean in this video.
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Old 07-26-2013, 09:47 PM
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you are comparing a very small grape to another very small grape.
what mousefink said,at least use a roller cam,it will make more power everywhere in the RPM range.
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Old 07-26-2013, 11:37 PM
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Fbird, ill defiantly cc the heads. Thanks.
Surfer, what you got is exactly what I'm looking for. Smoke em thru second gear and then some. Thanks for all the input
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Old 07-27-2013, 07:37 AM
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You cannot get any camshaft that will make good power above 5,500 RPM without using high load valve springs. If you try that with a flat tappet camshaft and use no-lead pump gas, you are asking for a flat camshaft.

Save your money until you can afford to install a high performance roller camshaft and the appropriate high load valve springs. Then you can use 93 octane pump gas with out any problems.

Last edited by MouseFink; 07-27-2013 at 07:42 AM.
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Old 07-27-2013, 11:50 AM
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Quote:
Originally Posted by MouseFink View Post
You cannot get any camshaft that will make good power above 5,500 RPM without using high load valve springs. If you try that with a flat tappet camshaft and use no-lead pump gas, you are asking for a flat camshaft.

Save your money until you can afford to install a high performance roller camshaft and the appropriate high load valve springs. Then you can use 93 octane pump gas with out any problems.
This is 110% complete BS

The unleaded gas has nothing to do with camshaft wear.

These Isky flat tappet cams are very reliable and perform great. Use the recomended Isky springs or correct equal.
use the right oil and break in method. Excessive valve spring pressure is not required. look at the Isky cam card.
The spring pressures and installed heights are shown and they are not excessive. If you need help with the springs for these cams call or email Isky Cams.

Reducing the valve spring pressure for the initial cam break in is a good deal. (remove inner spring or install springs at a tall max installed height or use a lighter spring for break in)

I use this stuff in my oil for easy cam run in. and long engine/cam life. Molyslip E
www.molyslip.com

apparently this stuff is real good too. www.oilextreme.com
I have no experience with it, but knowledgeable people do, and recomend it. The technology looks very good to me.
David Vizard really likes this stuff.

99% if flat tappet cam problems are incorrect user install and break in method.
Like not bothering putting the Moly paste on the cam lobes or starting it with the valve lash all screwed up. etc

Last edited by F-BIRD'88; 07-27-2013 at 12:10 PM.
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Old 07-27-2013, 12:23 PM
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I bet your heads will check closer to 67cc. But you can CC them and prove me wrong and post your result.
They are real good heads for this build. Hard to go wrong with Brodix. Correct the chamber volume and quench/deck height as required.
Getting the details right makes a difference.

When selecting a Isky Cam for your engine, (or any other Cam brand for that matter) if you don't see exactly what you want or need help with camshaft specs/selection
call Isky and they will make you what you want. Remember the Cam catalog is just a catalog and only a very limited view of what is available in any combination you want. "Custom cam grind".

Last edited by F-BIRD'88; 07-27-2013 at 12:47 PM.
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Old 07-27-2013, 01:47 PM
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The refineries started reducing tetraethyl "lead" (ZDDP) from all gasoline stocks following the 1970 Clean Air Act. Starting in the 1971 model year, American automakers started reducing valve spriing pressure in all their production engines in an attempt to prevent valve spring seat erosion and camshaft wear. . By 1980, ZDDP (zinc) was completely eliminated from gasoline and automakers redesigned the engines to use roller camshafts in ordeer to prevent camshaft wear along with the weak valve springs to reduce valve seat erosion. Roller lifters completely solved the problem of camshaft wear when using no lead pump gas. The factory roller camshafts are not radical high lift camshafts and can get by with weak valve springs. If high lift (over .470" valve lift) aftermarket camshafts are used, you must use higher rate valve springs or risk engine damage at high RPM and that is especially true with high lift roller camshafts.

Supercharged engines such as the engine in the 2013 Camaro ZL1 require higher valve spring pressure in order to seat the valves with the supercharger boost trying to keep the valves open. . Supercharged engines require high rate valve springs and induction hardened exhaust valve spring seats.
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