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Old 03-25-2005, 07:01 AM
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Cam Choice

I am running a 330 HP GM 350 crate motor with Vortec heads. The long block is as it came from GM Performance Parts. On it I have a Edelbrock RPM AirGap intake, Edelbrock 600 CFM carb, MSD distributor & AL6 box, exhaust is thru blockhugger headers in to dual 2.25 exhaust. I have a T56 bolted to it and running a 3.90 rear gear in a 2800lb car. It runs & drive great but mid range needs more grunt.

I am looking at a cam upgrade to firm up the mid range and give me a little more RPM. The cam I am looking at is a Competion Cams Extreme Energy cam part #XE274H-10. This is an 1800-6000 rating with .490 lift on the exhaust side. With 9.1 compression and the need to keep lift under .500 for the stock Vortec heads this looks like my best choice. I plan on changing the lifters, push rods & valve springs at the same time. Is there a roller rocker that will work with this setup using the pushed in 3/8 rocker stud & center bolt valve covers?

My concern is getting a matched setup that will work together & last.

Thanks for your input.

Rusty

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Old 03-25-2005, 07:44 AM
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That cam will match your combo perfectly, but I am not sure that the stock springs in the vortec heads can support that cam. I have heard that around.440-.450 is the most lift you can go with with the stock springs.

Adam
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Old 03-25-2005, 07:45 AM
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roller rockers

Use aftermarket, stamp steel, long slot rockers. The HP gain with that cam is not worth the money.

You'd get more HP gains spending the money on reduction pulleys, standard steering box, or electric fans.
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Old 03-25-2005, 08:03 AM
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Based on how my vortec motor ran with the xe268h, and the combonations below, I think that the new cam would give you around a 40 hp increase.


look at combos 73, 78, 83 and 84
http://www.ryanscarpage.50megs.com/combos11.html

Adam
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Old 03-25-2005, 12:03 PM
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Cam Selection

I Built A Similar Motor W/vortec Heads And Cc 268xe And Am Very Happy With It. What Model Car Are You Racing, 2800lb Sounds Like A Early F-body...
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Old 03-25-2005, 12:20 PM
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First of all, I think about .460-.470 lift is the limit on lift w/o modifying your heads, check that closely.You also might want to read this article before you make any cam change,www.carcraft.com/projectbuild/116_0403_mail/ . Long story made short, Car Craft didn't get any significant torque or HP increases when changing to the Comp Cam XE-262 or XE-268 from the stock cam (they did get 370HP/410-torque w/the XE-268).They did get 400HP when they installed the GM roller "hot cam" w/1.6 rocker arms. Your block should be roller ready like the one in the article.

Last edited by acr; 03-25-2005 at 12:28 PM.
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Old 03-25-2005, 01:31 PM
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Cam Selcetion.

The XE268 would probably give you more mid range power in your combination than the XE274.
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Old 03-25-2005, 01:31 PM
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Thanks for the input. I already went to electric fans, manual steering box & reduction pulleys. Looks like I will need to modify the spring seat to safely run more lift & proper springs. Thanks again
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Old 03-26-2005, 06:57 AM
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Assuming you are going to a flat tappet cam and stiffer valve springs, you should consider replacing the stock rocker studs with ARP screw in type. While you have the heads off to have the valve guide seats "clearanced"... you may also consider having the valves unshrouded and radiused (a competition valve job), and push-rod guide plates installed. Comp Cams makes a Magnum roller rocker that is relatively inexpensive and works well with the push-rod guide plates installed. Just more options to consider... good luck!
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Old 03-26-2005, 07:06 AM
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Here is a link to the Comp Cams dyno test for a 350 c.i. SBC running the XE268H camshaft. Thought this might be beneficial...

http://www.compcams.com/Technical/DynoSheets/XE268H-10_001.asp
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Old 03-26-2005, 07:21 AM
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Here is what I would use from Lazer Cams.

HYDRAULIC
Lopey idle, performance use, dual exhaust and headers, 3.55-4.10 rear gear, manual trans. or 2000 stall speed for automatic trans.

1800-6300
2300-2700


2750116


275
280


225
230


.483
.471


108


104
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Old 03-26-2005, 12:30 PM
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Surprisingly, if I didn't goof up the calculation... the Lazer cam has a bit less overlap than the Comp Cams XE268H (66.5 degrees Lazer vs. 68 Comp Cams at 36 degrees advance) with a lesser lobe centerline angle. The Lazer looks like to be a good grind and for a hot yet "streetable" setup.
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Old 03-26-2005, 10:54 PM
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if you want to swap the cam out, which probably isn't necessary, I'd go with the XE 268. I put that cam in my sister's 69 Camaro, 350 RPM and ProAction 2.02 S/R Torquer heads and it is great. I recently chucked the Edelbrock 600 in favor of a Holley Street Avenger 670 and WOW. Easy to setup and the seat of the pants dyno showed a healthy improvement. especially above 2500 rpm it pulls waaaay harder and faster.
just my $.02
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