Theoretical cam question

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gliderider06

gliderider06

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All things in an engine being the same, would there be any noticeable difference in power between the 268 and 274 Comp Xtreme cams in a small block? From what I think, the larger would move the power band up some and maybe a few horsepower more. I already have the 268, and wondering if it would be worth trading it for a 274, or run what I already have.
 
I would think the 274 would have power falling off some on the bottom side. I wouldn't want to give that up in favor of the upper RPM power gain the 274 would give, so I would stick with the 268. Does that help?
 
gliderider06 said:
All things in an engine being the same, would there be any noticeable difference in power between the 268 and 274 Comp Xtreme cams in a small block? From what I think, the larger would move the power band up some and maybe a few horsepower more. I already have the 268, and wondering if it would be worth trading it for a 274, or run what I already have.
Click to expand...

Glider,

I was at the SEMA Show in November in Las Vegas, and was at the Comp Cams
Tech session.

The Comp Cams XE-274 is the 'most' popular Camshaft out of the Xtreme Energy
profile series.

But, there are a few upgrades that are required to make the XE-274 work to its
optimal performance level, as compared to an XE-268.
 
The difference would be minimal at best.

The recommended spring for the 274 is a double spring (995) and would require some machine work to a stock head. A really good single w/damper may work as well.

The 268 work well and is stock rocker friendly.
 
I was thinking along the right tracks. Got playing around on Comps website last night and did the desktop dyno thingie. The 268 and 274 cams were very close in power, as was the old 280/.480 grind. Just the power bands were mostly different. IIRC the 280 and the 268 grinds were almost the same, producing power that is. the small thumper made the least amount of power of the cams mentioned above.
I will put that money I was going to use for the cam, into something else.
 
Even with the xe268 I needed a converter, and suddenly the 3.23 gears werent fun. In went 3.73's. The 274 will be less fun off the line unless you have a 3000 converter and at least 3.55s. Course I dont have headers, either.
 
If you were trying to squeeze a little more for some kind of competition then maybe depending on the results.
But for street driving, even with the odd track time, going over around 270 degrees starts trading bottom end for top end power that your engine will rarely see, in most driving circumstances you'll have a slower car. There two main ways to increase power cam and heads, in classes that demand stock heads you'll see them use crazy amounts of duration and compression to squeeze every last amount of flow potential. But where you can use any heads you want, that's the better alternative to make power but obviously more expensive but gains are a lot higher to.
 
Thanks all! Would there be any benefit from installing 2.02 intakes over the 1.88's, while using the 268 cam? I have heard before that adding larger valves, loses bottom end some, on a mainly street motor. I am also toying with the idea of having the valves done in the heads too; however, if the benefit of that expense is marginal, i will skip that idea too.
So far this is what I have
69 Dart. 360 standard rebuilt short block. #587 port matched heads cut .050", 901 comp springs. Weiand Stealth intake port matched, 750 Holley, Hei Ign, 18*Initial,36* total. headers/duals... 727 w/2500 B&M converter, 8-1/4 SG 3.55 (have 3.92 not installed yet) Steel shim head gaskets (? thickness) I am planning on changing pistons to the Sealed Power H405cp. I don't want to go too high in compression cause i'm nervous of detonation or I would go to the h116. The car is only street driven. no track nearby. Does my plan sound good so far, and should I include larger intake valves?
 
If you're just wanting some more compression, why not just spend the money on the heads? I'm no expert on the older small blocks (myself and all my friends run magnums) but I'd look into seeing how much the heads can be milled before spending money on swapping pistons. With a good mill and thin head gaskets you can get a decent bump. I don't know how much compression your trying to gain but anything over 10:1 the benefits of more compression start decreasing.

It's something to look into at least before dropping a bunch of cash on the short block. I'd also be in favor of going to the larger valves with some minor bowl cleanup work.
 
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