XR274R vs XR280R in 383 - Team Camaro Tech
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  #1  
Old Apr 27th, 10, 07:38 PM
hp fan hp fan is offline
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hp fan
 
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Default XR274R vs XR280R in 383

Hi Guys,

Looking at using one of these cams XR274R or XR280R in a street 383 (will order on billet not cast core). Have checked things out and both will fit my bill as far as my performace goals go with the rest of my combo.

274 236/242 @ 50 110, 280 242/248 @ 50 110

But just curiuos if anyone has first had experince with either of these on how idle quality and vacumn would be for power brakes

Would like it to have tough idle and nice exh sound but not over the top.
Car is just a tough cruiser with a once a year run down the strip.

Buddy has a XS274S soild in a 355 and it sounds great reasonable vacumn, so I would think with the extra cubes the XR280R would sould simliar in a 383 ?
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  #2  
Old Apr 27th, 10, 07:52 PM
Steiner Steiner is offline
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Steiner
 
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Default Re: XR274R vs XR280R in 383

Just wondering....any reason why you're doing a solid roller if it's mainly a cruiser? Seems like both of those cams are small enough that you'd be within the RPM range of a hydraulic roller.

I did a custom grind based off the XR276HR which comes as a 224/230 @ 0.050", 110 LSA. Had it ground as a 224/224 on 108 LSA and ran 1.6 rockers for 0.536" lift. It's in a 400 with 10.11 compression and vacuum was 11.5" at 700 RPM which is more than I was pulling with my old 355 and that engine was still working great with four wheel power discs.

We were going to put the same cam in an identical 383 but Uncle Sam decided I could have some extra allowance so I did a Dart 400 block instead. Figure an identical 383 would only lose around 20-25 lb ft and hp at the most.





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'69 Camaro X11 Street Car
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TKO-600 - Moser 3.42 - Detroit Truetrac
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  #3  
Old Apr 27th, 10, 08:14 PM
makoshark makoshark is offline
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Jeremy
 
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Default Re: XR274R vs XR280R in 383

What kind of heads do you have?
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  #4  
Old Apr 27th, 10, 10:54 PM
6D9 6D9 is offline
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Ron
 
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Default Re: XR274R vs XR280R in 383

Im running the XS274S in my 408 sbc . My vaccum is right at 12 to 13" at 750-800 rpm idle. Not the same as the others listed but kinda close!
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  #5  
Old Apr 27th, 10, 11:20 PM
BPOS BPOS is offline
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Al
 
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Default Re: XR274R vs XR280R in 383

Kind of agree on the HR thing, esp for a street car. Mine is similar to Steiner's, but in a 383. A custom Comp grind based on the XR282HR. 230/236 @ .050, 110 LSA, and .515/.515 w/1.6 rockers. I like the set-it-and-forget-it feature, the thing runs hard but can also just putt around town and is pretty mellow. Very subtle with x-pipe and Magnaflows. 10" - 12" vac @ idle. Worked fine with the Delco booster - changed to Hydroboost just cuz it's cool.
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  #6  
Old Apr 28th, 10, 05:12 AM
hp fan hp fan is offline
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hp fan
 
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Default Re: XR274R vs XR280R in 383

Quote:
Originally Posted by 6D9 View Post
Im running the XS274S in my 408 sbc . My vaccum is right at 12 to 13" at 750-800 rpm idle. Not the same as the others listed but kinda close!
What does the XS274S sound like in the 408?
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  #7  
Old Apr 28th, 10, 05:22 AM
hp fan hp fan is offline
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hp fan
 
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Default Re: XR274R vs XR280R in 383

Quote:
Originally Posted by BPOS View Post
Kind of agree on the HR thing, esp for a street car. Mine is similar to Steiner's, but in a 383. A custom Comp grind based on the XR282HR. 230/236 @ .050, 110 LSA, and .515/.515 w/1.6 rockers. I like the set-it-and-forget-it feature, the thing runs hard but can also just putt around town and is pretty mellow. Very subtle with x-pipe and Magnaflows. 10" - 12" vac @ idle. Worked fine with the Delco booster - changed to Hydroboost just cuz it's cool.
Was sold on the HR deal myself but have seen a few of late with lifter noise issues and plus while they maybe set and forget, they still wont turn as much RPM as a solid roller or solid flat.

While it maybe only a cruiser I still want to see peak power at around 6300/6400 and be able to turn it to 6800/7000 if the urge hits.
Both the XR280R or XR282S will do that while the HR versions will struggle
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  #8  
Old Apr 28th, 10, 08:09 AM
rumrumm rumrumm is offline
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Lynn
 
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Default Re: XR274R vs XR280R in 383

If you want more rpm with a hydraulic roller, use CompCams beehive valve springs and a rev kit from AFR. 6500 rpm or so will be no problem.
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  #9  
Old Apr 28th, 10, 09:25 AM
sik68 sik68 is offline
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Steven
 
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Default Re: XR274R vs XR280R in 383

Here's my 355 with the XR274R in it. Only driven the car a couple times so far (still don't have mufflers on it so I gotta be careful on the street).

It idles down to 600rpm but gets pretty choppy there; I keep it set to about 800rpm. My car's a stick, and the car does buck at less than 1500rpm. As far as making power, the powerband is a little soft at less than 2000rpm. Of course, it is still making power there, but relative to how much it's making at say, 4000rpm, your torque curve is not a table-top by any means. I haven't taken the car past 5000rpm yet, nor have I taken it full throttle...I'm still breaking everything in.

I was also debating between the 274R and the 280R, and my engine builder decided for me that the 274R suits the 355 a little better for what I was planning to do with it. Keep in mind that since these cams are so close together, you can run a tight lash on the 274R and get about halfway between the 274R and the 280R. Comp recommended me a tight lash of 0.012" Intake, 0.014 Exhaust, which gives you a bit more cam.

You probably can't go wrong with either in the 383....if you're going automatic you might be looking for a loose-ish converter. Sorry, no comments on vacuum brakes, I am running manual.


Please no teasing on the "OMG I can't believe it" dorkiness

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  #10  
Old Apr 28th, 10, 09:35 AM
wildman926 wildman926 is offline
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Walter
 
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Posts: 266
Default Re: XR274R vs XR280R in 383

Why not consider the Voodoo line? They were designed to outperform the XE series from Comp Cam. Here is a good one -

Lunati 60133
Solid roller, rough idle. Excellent cam for high performance street/strip applications. Excellent mid to upper RPM torque and horsepower in 355-383 cubic inch engines. Needs 3000-3500 RPM stall speed converter, 10:1 or better compression, aftermarket exhaust system and 3.90 rear gear ratio.

•Advertised Duration (Int/Exh): 279/285
•Duration @ .050 (Int/Exh): 249/255
•Gross Valve Lift (Int/Exh): .585/.600
•LSA/ICL: 110/106
•Valve Lash (Int/Exh): 016/016
•RPM Range: 2800-7200
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69 Chevelle SS
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  #11  
Old Apr 28th, 10, 04:22 PM
6D9 6D9 is offline
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Ron
 
Join Date: Jul 2003
Location: stockton,ca
Posts: 2,309
Default Re: XR274R vs XR280R in 383

Quote:
Originally Posted by hp fan View Post
What does the XS274S sound like in the 408?
It has a nice mellow rough idle.
__________________
69 Camaro
491/AFR 315'S/Straub hyd roller
TH400/GV OD
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  #12  
Old Apr 28th, 10, 04:30 PM
hp fan hp fan is offline
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hp fan
 
Join Date: Jul 2008
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Posts: 102
Default Re: XR274R vs XR280R in 383

Quote:
Originally Posted by rumrumm View Post
If you want more rpm with a hydraulic roller, use CompCams beehive valve springs and a rev kit from AFR. 6500 rpm or so will be no problem.
Yeah had thought about that, but rev kit is more money and another thing to have problems with, plus none of this fixes lifter noise issues that I have seen about on several hyd rollers of late. A tight lash solid is quieter.

Thanks
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  #13  
Old Apr 28th, 10, 08:21 PM
6D9 6D9 is offline
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Ron
 
Join Date: Jul 2003
Location: stockton,ca
Posts: 2,309
Default Re: XR274R vs XR280R in 383

Quote:
Originally Posted by sik68 View Post
Here's my 355 with the XR274R in it. Only driven the car a couple times so far (still don't have mufflers on it so I gotta be careful on the street).

It idles down to 600rpm but gets pretty choppy there; I keep it set to about 800rpm. My car's a stick, and the car does buck at less than 1500rpm. As far as making power, the powerband is a little soft at less than 2000rpm. Of course, it is still making power there, but relative to how much it's making at say, 4000rpm, your torque curve is not a table-top by any means. I haven't taken the car past 5000rpm yet, nor have I taken it full throttle...I'm still breaking everything in.

I was also debating between the 274R and the 280R, and my engine builder decided for me that the 274R suits the 355 a little better for what I was planning to do with it. Keep in mind that since these cams are so close together, you can run a tight lash on the 274R and get about halfway between the 274R and the 280R. Comp recommended me a tight lash of 0.012" Intake, 0.014 Exhaust, which gives you a bit more cam.

You probably can't go wrong with either in the 383....if you're going automatic you might be looking for a loose-ish converter. Sorry, no comments on vacuum brakes, I am running manual.

YouTube- Trackday...Coming Soon

Please no teasing on the "OMG I can't believe it" dorkiness

YouTube- Trackday: First Drive
Cool vid man way cool! Lets meet up sometime an run at sac raceway.
__________________
69 Camaro
491/AFR 315'S/Straub hyd roller
TH400/GV OD
9" 3.50
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  #14  
Old Apr 29th, 10, 09:49 AM
69duskblueX33 69duskblueX33 is offline
Tech Team

Alex
 
Join Date: Jul 2009
Location: Dallas, TX
Posts: 87
Default Re: XR274R vs XR280R in 383

I'm running a crower 00423, which is a 277/283 advertised, 244/253 @ .050, and 564/582 lift ground on a 110 LSA. Solid roller.

In a 302, it makes enough vacuum for brakes above 600 rpm. I have idle set to 750 and have yet to have a problem with it. The car does buck below about 1500-2k, but with 4:11's and the muncie that isn't a problem above 7-10 miles an hour.

Personally, unless you are actually going to build something as a daily driver, the benefits of a solid outweigh the ease of a hydraulic all day long.
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