Comp Cams HE268 or XE268 - Team Camaro Tech
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post #1 of 19 (permalink) Old Mar 13th, 03, 06:09 AM Thread Starter
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I'm trying to decide on a cam for my 383 (S/R Torquer Heads 67cc, 2.02/1.60 valves 350 tranny, 2400 stall converter, 3.42 gears in a 70 camaro - street use only). I've narrowed it down to either the Competition Cam High Energy 268H or the Xtreme Energy 268H. The HE268 has a single pattern 218/218 duration at .050". The XE has a dual pattern 224/230 with more lift as well.

Based on those numbers, the XE should make more power but when I plugged the numbers in on a dyno program, the HE made more power accross the board. Did I miss something? Can someone verify my results?

Thanks.
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post #2 of 19 (permalink) Old Mar 13th, 03, 10:42 AM
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Hello,I have used both of the cams in 350,s and liked them both,with the 218/218 giving a smoother idle.I think your 383 would like more duration though.I ran the same set-up that you have with a RPM and a 750 edelbrock and a 280 magnum in my s-10 for a while.It was nice on the highway,lots of mid range power.How much compression do you have?
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post #3 of 19 (permalink) Old Mar 13th, 03, 10:55 AM
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I've had both also in my pickup with a 327, stock converter and 3.08 gears.

Driveability is better with the HE268, but the XE probably has a little more power up top.

For a 383, with the converter, and lighter vehicle, I'd go with the XE if I were you.

'01 Formula 6 speed...a few mods<br />321 RWHP/338 Tq with just a lid<br /><a href="http://www.ksfba.org/forums/" target="_blank">Kansas F-body Association</a><br /><br />'72 GMC pickup...what is stock is a shorter list than what isn't.<br /><br />Looking for 1st gen camaro
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post #4 of 19 (permalink) Old Mar 13th, 03, 01:23 PM
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Im going to say the reason the HE made more power than the XE is because the bigger cam wants bigger heads, probably a 200cc, especially with the added cubic inches. The smaller cam is probably more optimal with those heads, and thats why it made more power. Just my 2 cents...Nick

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post #5 of 19 (permalink) Old Mar 13th, 03, 02:23 PM
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I will pass along my thinking on the subject (it's free and you can ignor it if you want, ha ha ha)
Being that you are running a 383 I'm under the impression you won't be spinning it to the moon so I would think you would be happier with the broad range in power vs the peak #'s which is what I always tend to lean towards in choice.
The Extreme Energy cams give good #'s however they are harder on the valve line (traditionally) then the other series of cams. And I really don't think you need a dual pattern cam with those heads.
You have the cubic inches to step up a bit in cams and still be quite streetable. Richard mentioned the 280H Magnum (awsome cam, I'm running it now of course I have more stall and stiffer gears but less cubes) plug this stick into your computer and see the results. You should have lots of vac. for your brakes and I thought mine was going to be a lot lump pump pa pump pier than it is, you can tell it's cammed but not rank by anymeans.
Depending on your compression and quench (with your 67cc heads you should be able to be fairly tight) I can see you making 425 to 435 lbs of torque.
Hope this helps bud. Post your #'s when you get it plugged in. - Barry
[img]graemlins/beers.gif[/img]

68 Camaro, 355, Forged pistons, rods and crank, Edelbrock Alum Heads, Air Gap w/Street Avenger, CC 280H, MSD Dist & Digital Box, T400 w/brake & 4200 stall, 513 gears, 11.66 @ 120 (with 150 shot) Street driven (occasional strip use)
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post #6 of 19 (permalink) Old Mar 13th, 03, 05:31 PM
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I think that the XE268 would be a better choice myself. The 268H would be great for a stock converter and taller gearing and will in a 383 give you more off the line torque than you can do much with on the street. The XE268 will still have you blistering the tires, but is better matched to your converter/gearing combo.

Also, what computer dyno program did you use? I plugged the two cams into the DD2000 and used the exact measures for each cam and the XE268 matched the 268H on the low end, but kept pulling on the high end to the tune of 30 more horses.

John

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post #7 of 19 (permalink) Old Mar 13th, 03, 05:33 PM
 
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Angry

as qouted above:
------------------------------------------------
You have the cubic inches to step up a bit in cams and still be quite streetable. Richard mentioned the 280H Magnum (awsome cam, I'm running it now of course I have more stall and stiffer gears but less cubes) plug this stick into your computer and see the results. You should have lots of vac. for your brakes and I thought mine was going to be a lot lump pump pa pump pier than it is, you can tell it's cammed but not rank by anymeans.


I would agree if your mind is set on a hydraulic cam.I have used this cam with perfect results on driveability & reliability.
I built a 355 sbc. in 1989 & as far as I know,it is still running today.I owned this motor for 5 years & drove my 72'Chevelle to & from work & to the track every weekend.It had plenty of vacuum & I never had any problems with brakes or etc.

If you really want to get into some horsepower,why not use a CompCams XTreme Energy Solid lift flat tappet cam???

They are made for street driven cars & will really outperform a hydraulic cam.You will only need to check the valves once a year.

Just run a new thread & ask a few people that know.I have been running an aggressive solid lift flat tap. CompCam in my 406 for 6 years now & never had a problem & only run the valves once a year.Only a couple of valves is .002-.003 loose & that is the honest to God truth. [img]graemlins/thumbsup.gif[/img]

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post #8 of 19 (permalink) Old Mar 14th, 03, 02:16 AM
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Your example of the HE268 vs the XE268 is a perfect example of how Desktop Dyno can be dangerous and wrong! The reason they LOOK the same (except on the high end) is because you entered the cam into the program using advertised duration numbers. Based on only ONE data point the program calculates output, that's clearly a downpoint in this case since the two cams are VERY different when you compare .050" lift. Cylinder heads don't flow significantly between .004" lift and .050" lift anyway so who cares what advertised duration is in this case.
This is why I almost always enter cams into DD2k using 050 duration numbers even though the program instructions say otherwise.

and my point is . . . the larger 383 with a 2400 stall and 3.42 gears the XE268 is more apropriate, especially if your static compression ratio is about 9.5:1. If your compression is higher, like 10:1, I would use the XE274.

You should have an RPM range of about 1800 - 5200 RPM with the XE268 and 9.5:1 compression. With the XE274 and 10.0:1 compression your RPM band changes to 2000 - 5500 RPM.

Hope this helps.

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post #9 of 19 (permalink) Old Mar 14th, 03, 04:36 AM
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For a street only car I would go with the 268H installed at 110° ICL. I had a similar Crower cam in my 383 and it worked very well.

RPM···········1500····2000····2500····3000····3500 ····4000····4500····5000····5500····6000
Brake_Tq······217·····293·····361·····400·····413· ····432·····432·····408·····355·····293
Brake_HP······62.1····111·····172·····229·····275· ····329·····370·····388·····372·····335
Exh_Pres······0.0·····.1······.2······.3······.4·· ····.6······.7······.9······1.0·····1.0
Int_Vacuum····.2······.4······.6······.6······.6·· ····.6······.7······.9······1.0·····1.0
Vol_Eff_%·····61.4····69.6····78.3····84.5····88.4 ····93.0····95.2····94.2····89.4····83.5
Actual_CFM····110·····166·····233·····302·····369· ····443·····511·····561·····586·····597
Fuel_Flow·····40.1····60.6····85.3····110·····135· ····162·····187·····205·····214·····218
A/F_Mix_Qal···73.3····90.5····95.7····100.0···100.0· ··100.0···100.0···100.0···100.0···100.0
BSFC··········.645····.544····.496····.483····.489 ····.493····.505····.528····.576····.652
BSAC··········8.097···6.825···6.223···6.061···6.13 5···6.181···6.330···6.624···7.222···8.175
Friction_HP···12······20······29······40······53·· ····69······90······115·····144·····179
Mach_#········.149····.198····.248····.297····.347 ····.396····.446····.495····.545····.594
Piston_Spd····938·····1250····1563····1875····2188 ····2500····2813····3125····3438····3750
Piston_Gs·····159·····283·····442·····637·····867· ····1133····1433····1770····2141····2548
Overlap_%VE···-1.6····-1.8····-.6·····-.7·····-.9·····.9······2.2·····2.1·····1.5·····.5
Int_AvgVel····100·····133·····167·····200·····234· ····267·····300·····334·····367·····400
In_InertiaPrs·.0······.4······1.0·····1.6·····2.1· ····2.3·····2.3·····2.2·····1.9·····1.6
In_ResTunPrs··0.0·····0.0·····.0······.0······.0·· ····.0······0.0·····0.0·····0.0·····0.0
Ex_AvgVel·····108·····145·····181·····217·····253· ····289·····325·····361·····397·····434
ExTun_Prs·····.4······.9······-.3·····-.1·····.2······-.9·····-1.8····-2.1····-1.9····-1.5
Lifter_Pump_UpNone····None····None····None····None ····None····None····None····None····None
Spark_Adv·····28······29······28······27······27·· ····28······28······29······31······32

The XE268H installed at 106° ICL shows less torque in the area you spend the most time, 1500-3500 rpm.

RPM···········1500····2000····2500····3000····3500 ····4000····4500····5000····5500····6000
Brake_Tq······194·····270·····350·····398·····414· ····440·····434·····411·····363·····299
Brake_HP······55.4····103·····166·····227·····276· ····335·····372·····391·····380·····342
Exh_Pres······0.0·····.1······.2······.3······.4·· ····.6······.7······.9······1.0·····1.0
Int_Vacuum····.1······.3······.6······.6······.6·· ····.6······.7······.9······1.0·····1.0
Vol_Eff_%·····58.4····67.1····77.3····84.2····88.3 ····93.9····95.2····94.2····90.0····83.8
Actual_CFM····104·····160·····230·····301·····368· ····448·····511·····562·····590·····599
Fuel_Flow·····38.1····58.4····84.2····110·····135· ····164·····187·····205·····216·····219
A/F_Mix_Qal···73.0····90.5····95.7····100.0···100.0· ··100.0···100.0···100.0···100.0···100.0
BSFC··········.688····.568····.506····.484····.488 ····.488····.503····.525····.567····.640
BSAC··········8.631···7.130···6.342···6.068···6.12 4···6.127···6.308···6.581···7.116···8.032
Friction_HP···12······20······29······40······52·· ····68······89······112·····141·····174
Mach_#········.146····.195····.243····.292····.340 ····.389····.438····.486····.535····.584
Piston_Spd····938·····1250····1563····1875····2188 ····2500····2813····3125····3438····3750
Piston_Gs·····159·····283·····442·····637·····867· ····1133····1433····1770····2141····2548
Overlap_%VE···-2.9····-3.0····-.9·····-.7·····-.9·····1.9·····2.5·····2.3·····1.8·····.4
Int_AvgVel····100·····133·····167·····200·····234· ····267·····300·····334·····367·····400
In_InertiaPrs·.0······.4······1.0·····1.6·····2.0· ····2.3·····2.3·····2.1·····1.9·····1.5
In_ResTunPrs··0.0·····0.0·····.0······.0······.0·· ····.0······0.0·····0.0·····0.0·····0.0
Ex_AvgVel·····108·····145·····181·····217·····253· ····289·····325·····361·····397·····434
ExTun_Prs·····.6······1.1·····-.2·····-.4·····-.3·····-1.1····-1.7····-2.0····-1.9····-1.5
Lifter_Pump_UpNone····None····None····None····None ····None····None····None····None····None
Spark_Adv·····28······29······28······27······28·· ····28······29······29······31······32

DRA showed identical 13.00 e.t.'s in a 3800# car, TH350, 3.42 gears, 2400 stall converter. With the smaller cam, the stall speed went up 90 rpm and the 60' time was .03 seconds faster.

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post #10 of 19 (permalink) Old Mar 14th, 03, 05:35 AM Thread Starter
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I used 2 different programs - Desktop Dyno and KB Dyno. Desktop Dyno allows you to enter much more parameters. As Onovakind shows, the HE268 makes more power on the bottem end which is where this motor will spend most of its time. Only expect to get on it every now and then to discipline the local Hondas.

I'm trying not to get sucked into going with a cam that makes high HP numbers up top knowing that I will rarely be running in that range. But then I don't want to make this motor too lame either.

Oh, compression should be around 9.5:1
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post #11 of 19 (permalink) Old Mar 14th, 03, 05:49 AM
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Oneovakind, Just out of curiosity, why do you think a 383 would NEED more low end TQ on the street with a 2400 stall and 3.42 gear?

I did several things to reduce low end TQ in my 383 because even with a cam that's bigger than the XE268 I had too much TQ, unless I just wanted to drive around town blowing the tires off all the time

IMO the HE268 is a pretty small cam for a 383, it has 050 numbers barely bigger than most stock 350 cams. I think a 383 would be really wheezing for more air by 5000 RPM. The XE268 is also on the small side but would have better mid range and top end.

I've had 3 different cams in my 383; the Comp 275DEH, the Comp 282s and the Comp 294s. The 275DEH was a real stump puller and ran out of steam about 5500 with a fairly flat power curve. the 282s still made big torque down low but had more midrange and top end than the 275 DEH, it pulled past 6000 R's. The 294s pulls harder on the top end and still leaves hard with a 3000-3500 stall; its the biggest cam I care to run on the street in a 383.

Whatever you decide, good luck.

[ 03-14-2003, 09:22 AM: Message edited by: Eric68 ]
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post #12 of 19 (permalink) Old Mar 14th, 03, 07:56 AM
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I have to agree that you won't be giving up any driveability with the XE268 over the HE268 in a 383. You'll have more low end torque than you need anyway, why not have some extra up top if you decide to wind it up every once in awhile.

John

- '68 Chevy Camaro (sort of done, but always subject to improvement)
- '63 Pontiac Tempest (work in progress)
- '72 Datsun 240-Z (back-burner for now)
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post #13 of 19 (permalink) Old Mar 14th, 03, 09:41 AM
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heres another theory. as eric said, torque won't be an issue with the 383, especially on the street. torque is nice, but how much can you use on hard street tires? i would personally consider a bit more duration, like an advertised duration in the 270's or even 280's. i ran a 268 in a fairly mild 283 i had years ago and it was just about right. slightly lopey, but still torquey, for a 283. just my .02 [img]graemlins/thumbsup.gif[/img]

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post #14 of 19 (permalink) Old Mar 14th, 03, 10:40 AM
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I guess I'm just a small cam kinda guy, use the smallest one that will do the job. Sitting at a light listening to my engine run poorly isn't on my agenda. My 406 driver cam is only 224° @ .05", 6° more duration than the 268H, and makes about 70#ft more torque at 2500 rpm, but still makes it to 11.75@117 mph in the quarter. When I hook the trailer on and lock the converter, I'm glad to have a torque curve like that. You will notice that the 268H cam is installed straight up, while the XE268 is 4° advanced. This puts the intake valve closing points and 39° and 38° respectively, and with the 83% I/E ratio of the head, you don't need a lot of exhaust duration. EA3.0 came up with suggestions for cams with 5° less exhaust duration than intake. Looking closely, there is very little difference between the charts, so I selected the one that had the best eficiency at the rpm's at which I would spend the most time.

Here's a link to another 11-second guy with a small cam:
http://temp.corvetteforum.net/c4/bea...eResults.shtml
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post #15 of 19 (permalink) Old Mar 14th, 03, 01:15 PM
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I can respect a guy that can go 11.75 with a "small" cam. [img]graemlins/thumbsup.gif[/img] Lingenfelter is big on combos that use little cams too.

I'm kind of the same way, except I kept blowing the tires off it every time I tried gassing it in 1st gear on street tires - maybe it's just time for tubs

I didn't realize you retarded the HE268 either, I've always been one to step up to the next size cam rather than retard the cam timing.

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www.horsepowerinnovations.com

68 Camaro, E85 powered 427" small block. 9.96 @ 133 MPH, 1.319 sixty foot on motor. 5.92 eighth @ 116 with a 1.42 sixty breaking beams with back tire on the bottle
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