comp cam xr274r vs 288ar BB - Chevelle Tech
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post #1 of 15 (permalink) Old Dec 10th, 10, 3:30 AM Thread Starter
 
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comp cam xr274r vs 288ar BB

Hi!
Iam building a 454 Hi-per street, large ported cast iron heads, 11.0 cc comp, Holley 800 dp, dual plane intake, 2.73 gear in 12 bolt end..now to the problem..i thougt i find the best cam for this comp cam Xtreme Energy 11-770-8 but a friend told me that its problem whith Xtreme Energy cams and i should go for a more proven concept a magnum 11-692-8..then i put this cams in comp cams "CamQust" i ll get better curves with the "Xtreme Energy 11-770-8 " = very low end peak torque.. Do someone have experiance about this 2 cams??

Regard Mattias
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post #2 of 15 (permalink) Old Dec 10th, 10, 4:23 AM
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Re: comp cam xr274r vs 288ar BB

I know a 396 with the first cam(11-770-8) it dynoed 511 hp. 2.73 may be a little low, personally I would like 3.73. What trans and if auto stallspeed? Also get the cam on a billet core with cast gear option.

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post #3 of 15 (permalink) Old Dec 10th, 10, 4:34 AM Thread Starter
 
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Re: comp cam xr274r vs 288ar BB

th350 stall 2500 - 3000 some holeshot maybe..lägger upp den på chevelleforum ochså : )
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post #4 of 15 (permalink) Old Dec 10th, 10, 6:59 AM
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Re: comp cam xr274r vs 288ar BB

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lägger upp den på chevelleforum ochså : )
Hell, yeah, that's what I'd do, maybe more!!!

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The correct spelling is
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post #5 of 15 (permalink) Old Dec 10th, 10, 7:22 AM
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Re: comp cam xr274r vs 288ar BB

Bit of a mismatch with such high compression and no rear gear. Your going to need a larger cam to bleed cyl pressure off, but the larger cam wont like the 2.73's.

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post #6 of 15 (permalink) Old Dec 10th, 10, 10:36 AM
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Re: comp cam xr274r vs 288ar BB

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Bit of a mismatch with such high compression and no rear gear. Your going to need a larger cam to bleed cyl pressure off, but the larger cam wont like the 2.73's.
Vinny, lets not forget, they have no speed limits in Sweden.

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post #7 of 15 (permalink) Old Dec 10th, 10, 12:10 PM
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Re: comp cam xr274r vs 288ar BB

I heard the comp magnums are old technology. I have the xe274 in my 9.7:1 454 aluminum heads .30 over TH350 and 4.10 gears with a 2700 stall.
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post #8 of 15 (permalink) Old Dec 10th, 10, 1:15 PM
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Re: comp cam xr274r vs 288ar BB

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Vinny, lets not forget, they have no speed limits in Sweden.
Ha - your right! The cam should start to smooth out by 80-90mph

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post #9 of 15 (permalink) Old Dec 10th, 10, 7:14 PM
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Re: comp cam xr274r vs 288ar BB

I've run the 288AR-10 Astra-Tempered (8 Suffix) Solid Roller with CC-933 Springs in a 9.8:1 454 & 3.08 Gears with Good Results but it really doesn't start hauling until 3000rpm and liked to cruise above 2400rpm.

With Gears between 3.31 to say 3.08's I suggest you look at the Lunati LUN-502A1 and A3 112 LSA SR Billet Cams with CC-933-16 Springs (200/500 ftlb - 490 Rate Springs) and Dial In an 8.2:1 DCR with an .036" to .044" Quench.

All the above SR Cams with the 933 Springs with a Forged Rotating 454 will will hit 7000rpm.

If you're NOT running a Forged Rotating Assembly, and considering the 10.5 or 11:1 Static Compression and Hwy Gears, I suggest the HFT XM278H-12 or XM288H-12 with CC-925 Springs for a Strong 6200 rpm 454.

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post #10 of 15 (permalink) Old Dec 14th, 10, 1:36 AM Thread Starter
 
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Re: comp cam xr274r vs 288ar BB

Sorry checked my rear axle code and i have a 3.31 ~ 12-bolt Positraction rear end...a little bit better
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post #11 of 15 (permalink) Old Dec 14th, 10, 9:03 AM
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Re: comp cam xr274r vs 288ar BB

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Originally Posted by holgerth View Post
Sorry checked my rear axle code and i have a 3.31 ~ 12-bolt Positraction rear end...a little bit better
Little? I think alot better give it at least 3000 in stall and go for the 11-770-8. If you hav´nt bought pistons yet buy a set that will give 10-10.5 instead.

Marcus

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post #12 of 15 (permalink) Old Dec 15th, 10, 8:49 AM Thread Starter
 
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Re: comp cam xr274r vs 288ar BB

ok! I bought KB257-100 from summit -26 cc dome so the compression should not been 11:1 ..maybe 10 - 10,5 much better i'll hope..
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post #13 of 15 (permalink) Old Dec 16th, 10, 9:22 PM
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Re: comp cam xr274r vs 288ar BB

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Sorry checked my rear axle code and i have a 3.31 ~ 12-bolt Positraction rear end...a little bit better

==============================

FYI,just because the code on the rear states it was 3.31 gear when built new means it still has a 3.31 ring & pinion in it 35-40+ yrs later.

A quick & dirty chk that will get you somewhere close is to jack up rear of car and then put on jack stands.

Then mark a tire and also drive shaft using masking tape.

Now put trans in neutral & turn the driveshaft to see how many times the d-shaft spins fully artroun to make 1 full turn of the tire/wheels.

For ex if the d-shaft turns approx 3.4 times for 1 full turn of the wheel/tire then you likely have a 3.42 or maybe 3.55 ring & pinion.

Another example 3.75 (3 & 3/4) turns of d-shaft vs 1 tire rotation = approx 3.73 ring & pinoin.

But also keep in mind cond of posi unit /posi clutch slippage if in bad cond can affect results when doing this quick/dirty rear gear ratio chk too.

The only real way to nail it exactly is to remove the cover on the rear end and count the teeth on ring & pinion .

Scott

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post #14 of 15 (permalink) Old Dec 16th, 10, 9:55 PM
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Re: comp cam xr274r vs 288ar BB

I am currently running the XR274R 11-770-9. The specs are the same except the -9 is a solid core cam (I special ordered it, $300). The cam has a nice but subtle lope, I still have about 12lbs of vacuum which I need for power brakes. It idles good around 850 rpm and I have been twisting it up to 7000 rpm with no problems.

My motor is a 410 cubic inch Big Block with 10.4 compression, Muncie M22W, 3.73 gears with 28" tall tires. The car has run high 12's at 108mph so far.

Feel free to ask me any other specific questions.

Kurt

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post #15 of 15 (permalink) Old Dec 17th, 10, 4:05 AM Thread Starter
 
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Re: comp cam xr274r vs 288ar BB

I'll belive its the original rear end because i'm the third owner ant its all original and it was order new whith trailer hitch. i'll will measure it to the spring..
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