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#1
02-25-2010, 12:09 PM
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Comp Cams XE-268 or XE-274?
This is my first post so hello.
I have a question about cam selection. I originally bought a Comp Cams XE-268 cam for my 400 that I am building for My 67 Firebird. Now after changing my heads from #11s to 670s and adding headers to the mix I was wondering if I should move up to the XE-274 cam. The rest of the engine combination is Performer intake and the 8 valve relief jobber pistons. Compression should be about 9.1 to 1. Thanks Joe. |
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#2
02-25-2010, 01:27 PM
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I would go for the XE274, and I am running the XE268 in a 8.8:1 400 now.
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 "NSDQ"
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#3
02-25-2010, 02:32 PM
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The 8 valve relief pistons will certainly lower the compression ratio, but they typically end up .030-.050" below the deck at TDC. This increases quench, which is not a good place to go IMHO.
I'm much rather see a two valve relief flat top piston at zero deck, even if it yields up near 10.5 to 1 compression, rather than a "bathtub" piston .050" down in the holes making 9 to 1 compression. My experience with the latter has never been a good one. Even at relatively low static compression ratios, those engines can run hot/overheat and detonate on pump fuel, if/when you try to make any serious power with them (optimum timing, fuel curves, etc). As far as the question, the XE274 camshaft for sure, and run PLENTY of spring pressure on it, stiff pushrods and light components if/where possible.....my .02 worth....Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#4
02-25-2010, 03:15 PM
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Thanks for the replies on the cam choice. I hear you on the pistons. It is the one thing about this engine I really don't like but cant change this go around. I am going to remove sharp edges on the piston tops and hope for the best. I will CC the heads and chambers this weekend to get an actual compression ratio.
Last edited by cutlas; 02-25-2010 at 03:23 PM. |
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#5
02-25-2010, 06:18 PM
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Wow, seeing Cliff endorse a XE grind is like seeing snow in Panama...
__________________
 Johnny US Army Retired1978 T/A 463 Pontiac, KRE 74cc 292CFM D-ports, Lunati VooDoo, V-max lifters, TKII, ATM 850 E85 carb, TCI TH-350 race tranny, 3600 converter 3.73 12 bolt 11.63@116.68mph 1981 T/A 4-speed 406 Pontiac, Merrick ported 6X heads, Comp 270S cam, Crosswind intake 750 Street Demon, 3.42 30 spline Eaton posi street car. 1980 Formula 350 Pontiac back burner project 1972 LeMans 350 Pontiac |
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#6
02-25-2010, 06:40 PM
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I`d run the 274 also.
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#7
02-25-2010, 07:47 PM
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"Wow, seeing Cliff endorse a XE grind is like seeing snow in Panama..."
I didn't see any other options in the thread? Personally, I wouldn't touch one with a ten foot pole, but the question was which one of the two. Since I have DIRECT experience with the XE268 in a 406 we built here with ported #16 heads, I recomended the larger XE274 grind. I know for CERTAIN the XE268 is a "turd" for that particular combination of parts......FWIW.....Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#8
02-25-2010, 10:02 PM
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i ran the turd (xe268) on a 9.25 to 1 400.....stock intake, RA manifolds, qjet, 3.90 gears, 4000lb car....ran consistant 13 flats..
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71 GTO, 463, KRE 295 cfm heads ported by SD Performance, RPM intake, Qjet, Dougs Headers, Comp cams HR 246/252 ...11 to 1 , 3.55 cogs, 3985lbs.....day three- 11.04 at 120mph ....1.53 60', 6.98 1/8 mile |
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#9
02-25-2010, 10:32 PM
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Quote:
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#10
02-26-2010, 08:52 PM
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no...it was not zero decked....ran shaved (.080) and ported #96 heads...thing ran pretty darn decent with more than a few high 12 sec. timslips to boot...
still running the same heads on my 455 combo...
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71 GTO, 463, KRE 295 cfm heads ported by SD Performance, RPM intake, Qjet, Dougs Headers, Comp cams HR 246/252 ...11 to 1 , 3.55 cogs, 3985lbs.....day three- 11.04 at 120mph ....1.53 60', 6.98 1/8 mile |
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#11
02-26-2010, 09:10 PM
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Quote:
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"Having a 10 second Civic must be just like coming out of the closet; you'll surprise some people, but you're still gay" 1970 GTO, 455+.034", 0 deck, Wiseco's, Eagle rods, 60919, Rhoads, E-Heads, 1.65 Scorpions, RPM, Custom Qjet by Cliff, Doug's 1 7/8", THM 400, Gear Vendors OD, 3.55s.........Her name is Blandorf; after a girl I knew once, 'cause she's just Bitchin, always. |
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#12
02-28-2010, 10:33 AM
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XE274, the 268 has problems. I like my XE274 in my 9.4 400. You sure the compression is only 9:1?
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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 |
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#13
02-28-2010, 11:01 AM
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I wouldn't run either. There are better options out there. I had the XE274 in my 455 and it wasn't overly impressive. i think i was leaving some power on the table with that cam.
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Skinned knuckles and empty wallet! Could I be any happier? 66 GTO Convertible. LS3-525 HP. Legend LGT700 5-speed, Wilwood 4-wheel disc brakes, Ridetech coil over front susp, PMT rear susp, Hotchkis bars, Billet Specialties 18" Dagger's (18X9 rear, 18X8 front). 2002 Ram Air WS.6 convertible Trans Am. Wife's car. |
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#14
02-28-2010, 12:31 PM
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The compression is only a guess based on an on line calculator.
I will cc the heads and piston tops later on today. What problems do the XE 268 cams have that is addressed with the XE 274? What other cam would you recomend and why? I already have the XE268 but can sell it to get something else. Thanks Joe. |
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#15
02-28-2010, 01:31 PM
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Get the XE 274 its a good cam .some engine builders dont like it others swear by it. im a real beliver in these cams haveing imported 7 engine with XE cams and one in my own engine................
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#16
02-28-2010, 05:54 PM
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We continue to see less than desireable results with them. Starting with not making as much power as they should for the combination of parts, dyno pulls ending WAY too early in the RPM range for the size of the cams, etc. There is some good reading on the subject, we've been following them for some time, and have watched the trend continue.
Here's a thread on the subject, from the Buick board, and it saves me a lot of typing! http://www.v8buick.com/showthread.php?t=188048 The folks who rant and rave about them bought into the concept....ask them for some timeslips.....Dave? We've had dyno charts sent here and they clearly show a sharp drop in power right around 4800-4900rpms. Folks have posted dyno charts showing the exact same deal, but no one seems to notice.....and when you do, a couple folks come on telling us how good they work in their car, which beyond spinning the tires leaving Dairy Queen, had never been tested on a dragstrip or even a marked off 1/4 mile of deserted road with a stopwatch!.....FWIW.....Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#17
03-01-2010, 04:02 AM
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Cliff your getting silly. the man is asking witch one of the 2 XE cams would be his best chooice. so what are you doing???. can remember that not to long ago you said you would leave it alone. there are plenty of people and engine builders that DO have sucses with the XE line.
Your rambling against this cam umongst others have alredy cost us a engine builder leaving this board!!. from who you claim is your frind , Is ore whas that your goal!!!!!!!!!. you obsesion hase made you rediculess . To sutch a point that plenty of people are not takeing you serius anymore. yet you stil look for every single chanse to get your fix . asking for time slips everytime is rediculee while you know for a long time alredy im not in the 1/4 races (thats a warm up for me) . so let it go................ |
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#18
03-01-2010, 04:26 AM
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Joe, are you sure about the 9.1:1 comp ratio?
#670īs on a 400 should end up at 9.75-10.0:1? With more than 9.5:1 i would not use any XE-grind, it will only make a ping-sensitive narrowband rpm-range engine. I would look for a 225in 236ex @.050" and 114-115 LSA or in that neighborhood cam. |
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#19
03-01-2010, 04:34 AM
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Quote:
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#20
03-01-2010, 07:33 AM
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"there are plenty of people and engine builders that DO have sucses with the XE line."
Dave, one person who responded in this thread had a complete engine prepared by a shop who advocates the XE cams, and he HATES it, or hated it. He was actually so disappointed in the engines performance, that he pulled the engine out and sold it. I have direct evidence from at least half a dozen other customers who tried these cams with less than desirable results, backed up by dyno and dragstrip runs. BTW, we MEASURE success with vehicle performance. It is not possible to judge the success or failure of a camshaft by dropping your car out of a C-130 so you can achieve 180mph velocities! Seriously, there is enough direct evidence staring us in the face, that EVERYONE should take notice. I don't remember ever seeing any direct evidence from yourself as to how well these cams work in comparison to other designs. When is the last time you had your engine up on the dyno and changed the cam, and nothing else to see the results? To date, I'm the ONLY one (that I am aware of) who has done a back to back dyno test between two camshafts, and changed NOTHING else. We even did it up one better, we chose a flat solid cam to take the hydraulic action of the lifters OUT of the equation. We also increased the size of the camshaft by a full 10 degrees at .050", and it had .060" MORE lift. Even so, it came up 10hp and 22ft lbs short on peak power production, and more than that in "average" power, and QUIT at exactly 5200rpm's. Those are FACTS, not a bunch of speculation as to how well this technology actually works, backed up by testimonials from customers who are happy if they can spin the rear tires in a tight turn or leaving the Dairy Queen parking lot! Unless you can't read any better than you can spell, I suggest that you wonder over to the Buick board, they have had more troubles with these cams than the Pontiac crowd, simply because the valvetrain system in those engines isn't as effective at controlling valve action at high rpms....FWIW......Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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