NastyZ28 Forum



Go Back   NastyZ28.com > Drivetrain & Performance > High Performance Modifications
User Name
Password

Reply
 
Thread Tools Display Modes
Old 05-19-2005, 11:09:00 AM   #1
Greg Mc
Veteran Member
 
Join Date: Mar 1999
Location: Hernando, MS
Posts: 1,198
Comp Cams Dyno Sheets

Looking at Comps web site dyno sheet section it makes you wonder why all the mags praised the XE268. Unless I am missing something it looks like the XE262 or the XE274 are a much better choice. The 274 would be the cam of choice for a mild SBC with the 262 being second and 268 third. When I was freshening my 350, vortec motor I decided to go with the XE262 over the XE268...not a bad choice but apparently I picked #2 instead of the #1 choice for my combo. I don't know how Vortec heads compare to the Dart S/R head Comp used on their dyno sheets. Just thinking out loud guys.

http://www.compcams.com/Technical/DynoSheets/
__________________
1981 Z28
454 +.030
3.42 posi
Greg Mc is offline   Reply With Quote
Old 05-19-2005, 03:37:00 PM   #2
Damon
Veteran Member
 
Join Date: Nov 2000
Location: Philly area
Posts: 11,729
Link is down right now, but I get your point.

Sometimes a smaller cam will work a little better in a motor than one that's a little bigger. I don't think there's anything wrong with the XE268, but something in that combo probably liked a little less or a little more duration that it gave. It happens. I've put together some combos that just flat WORK, despite the fact they don't look like an optimum match on paper. Usually, I stumble across them because trial and error is my only teacher.

What I'm saying is that the XE268 may not have been that BAD, it's just that something about the smaller cam just WORKED with that combo and produced better numbers. But change one thing in the combo (especially something as important as the heads) and the results are likely to change again.

The Vortec heads are quite a bit better than the S/R Torquers in my experience. Better flow on the intake by quite a bit, and a much better combustion chamber.


[This message has been edited by Damon (edited May 19, 2005).]
__________________
1990 454SS pickup. Original "tow truck motor" 454 upgraded to something a little more "aggressive." Seems pretty stout but the fuel bill is nuts.

78 Malibu. Inherited with only 35K on the odo! Mild 383 with Weiand 142 blower on top. Mid 12s appears to be the best it's gonna do on street rubber. Runs so good I may never drive it again.

"Last remaining QJet tuner on planet Earth!"
Damon is offline   Reply With Quote
Messages from Our Sponsors !
Awesome NastyZ28.com Merchandise !!

T-shirts, wearing apparel

Drinkware, Mouse Pads, Decals

Old 05-19-2005, 04:35:00 PM   #3
Greg Mc
Veteran Member
 
Join Date: Mar 1999
Location: Hernando, MS
Posts: 1,198
I know what you mean about some combos working better than others. I was just surprised at the results posted. The engine on the dyno sheet.

355 CID
9.25 compression
Holley 750 VS carb
Performer intake
S/R heads

XE262 was 348HP @ 5300 415TQ @ 3700
XE268 was 342HP @ 5000 413TQ @ 3800
XE274 was 369HP @ 5900 410TQ @ 3900

What surprised me is the XE274 did that well with 9.25 compression, performer intake, same heads and carb. Plus it has a wide torque curve; is above 400 ftlbs from 3300-4500 rpm and is over 350 ftlbs 300 rpm sooner than the XE262 and 400 rpms sooner than the XE268. That sounds like a good cam for our heavy cars. If I get bored this summer, I may have to do a cam swap.
__________________
1981 Z28
454 +.030
3.42 posi
Greg Mc is offline   Reply With Quote
Old 05-19-2005, 09:40:00 PM   #4
Damon
Veteran Member
 
Join Date: Nov 2000
Location: Philly area
Posts: 11,729
You'll notice that the HP peak of the XE268 is at a lower RPM point than either of the other 2 cams. Peak HP with that cam should be between the other 2 cams in terms of raw number as well as the RPM point. Torque, however, makes a nice orderly progression to hither RPMs the bigger the cam.

That's a classic indication of some weird interaction of those particular parts together. For some reason the XE268 on THAT ENGINE took a little "dip" in the upper RPMs that the other 2 cams did not for whatever reason. If it didn't take that dip up top the peak HP would have occurred around 5600 and I'll bet horsepower would have come in right around 360.

A slightly different XE 268 (ground on a wider 114* LSA) in my roots-blown 383 peaks out a few hundred shy of 6000 and there are no abnormal "dips" in the the torque curve anywhere in the RPM range. Big, flat torque curve, slowly fading away as the RPMs climb.


[This message has been edited by Damon (edited May 19, 2005).]
__________________
1990 454SS pickup. Original "tow truck motor" 454 upgraded to something a little more "aggressive." Seems pretty stout but the fuel bill is nuts.

78 Malibu. Inherited with only 35K on the odo! Mild 383 with Weiand 142 blower on top. Mid 12s appears to be the best it's gonna do on street rubber. Runs so good I may never drive it again.

"Last remaining QJet tuner on planet Earth!"
Damon is offline   Reply With Quote
Old 05-20-2005, 06:54:00 PM   #5
1978LT
Veteran Member
 
Join Date: Feb 2002
Location: Poquoson, VA USA
Posts: 16,280
I noticed that also. Strange.

Oh, and Vortecs are 25-30 HP better than S/R Torquers usually.
__________________
1978 Camaro LT: 406, TFS heads (for now), mild hyd. roller, headers, ZZ4 intake, Qjet, TH350 with mild 2000 or so stall (aaargh!), 3.42 posi.

In the works: different heads, more stall lol, more cam, that's about it til painting season rolls around

Don't stop believin'
Hold on to that feelin'
1978LT is offline   Reply With Quote
Old 05-22-2005, 12:23:00 AM   #6
pdq67
BANNED
 
Join Date: Jul 2001
Location: Columbia, MO, USA
Posts: 10,498
I think it was CHP mag that did a test QUITE some time back using a decent street 350 motor and compared the XE268 to the good old 268HE and the 268HE beat the XE cam..

AND the Cam-Father himself, Mr. Ed Isky always said that a single pattern cam that was right for the motor would out power a dual pattern cam!!

pdq67
pdq67 is offline   Reply With Quote
Old 05-22-2005, 06:25:00 AM   #7
1978LT
Veteran Member
 
Join Date: Feb 2002
Location: Poquoson, VA USA
Posts: 16,280
Quote:
<font face="Arial,Verdana" size="2">Originally posted by pdq67:
I think it was CHP mag that did a test QUITE some time back using a decent street 350 motor and compared the XE268 to the good old 268HE and the 268HE beat the XE cam..

AND the Cam-Father himself, Mr. Ed Isky always said that a single pattern cam that was right for the motor would out power a dual pattern cam!!

pdq67
</font>

I remember that test! It was about 1-1/2 years ago. They were also using S/R Torquers, but they home ported them and did a before and after. They got a nice improvement! I believe the 268 HE cam with the ported heads was nearing 380 FWHP.
__________________
1978 Camaro LT: 406, TFS heads (for now), mild hyd. roller, headers, ZZ4 intake, Qjet, TH350 with mild 2000 or so stall (aaargh!), 3.42 posi.

In the works: different heads, more stall lol, more cam, that's about it til painting season rolls around

Don't stop believin'
Hold on to that feelin'
1978LT is offline   Reply With Quote
Reply




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



Copyright © 1997 - 2014 NastyZ28.com Inc.
Powered by vBulletin Version 3.5.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.