[grivera]

Mikes455Wagon ran deep into the 11's with an XE274 in a 455 so clearly every combo is different and why generalizations should be avoided.

[Cliff R]

I don't deal in generalizations, just facts.

Nothing I post up here is Google'd/copied/pasted from the efforts of others.

If I'm sitting there waiting patiently in line at the dyno and there is a 455 ahead of mine with ported iron heads, XE284 cam, single plane intake, and aftermarket 850cfm carb and it can't make 400hp I'm taking notes. What do you folks need on here? You ask for details, information, testing, experiences with these things, even "butt meter" evaluations, so I'm giving you some of it.

So we're on the SAME dyno, SAME day, SAME operator, SAME correction factors and that engine isn't even close to mine even using all those "high performance" parts. I guess I should have told him to carry it to Westech so he could have a dyno sheet showing it made 500hp and 590tq instead.....FWIW.

About 6 months after I dyno'd my engine and did the KRE head testing a local customer here called and wanted to "duplicate" my combination, 6X heads, iron intake (modified), RAIV cam, high ratio rockers, Q-jet, factory HEI, etc.

He did just that and even asked to borrow my carb on dyno day and I let him.

He goes to the SAME dyno, same operator, etc and not making 360hp despite their best efforts that day.

So after getting all the air let out of his balloon he called the shop the next day and talked to me about it. I asked several questions.

Did you zero deck the block......."NO"

Did you check valve train geometry when ordering pushrods....."NO".

Did you use high ratio rocker arms....."NO"

Did you degree the cam....."NO" (At that point he tells me that instead of using the Crower 60919 cam he used the Comp XE-274 cam instead) He was told by several of the "big" Pontiac shops and at least one "guru" that the "modern" lobe profiles would leap taller buildings and walk on more water....blah...blah...blah.

I decided to quit being critical of his build at that point, it doesn't help anyhow.

Will is correct with these things, we should NOT make "generalizations" and also realize that the skill levels of some are not equal to others, nor is there attention to detail, ability to tune, or even set up the car to effectively use the power...FWIW......Cliff

[78w72]

Originally Posted by Will

If someone says "I ran 'X' cam and it ran fine" you have to realize that this is only one single data point. What does that person consider "running fine?" Did they try any other cams? Did they do any dyno or track testing?

Most guys build an engine, decide on a cam and as long as it makes the rear tires smoke and sounds good at idle, they're happy. they'll tell you the cam in their engine is great, even if the engine would make 50 more HP with a different cam. How would they know?

I ran an XE274 in a 9.2:1 400 with stock ports (just matched to the gasket, nothing more), headers, 2.5" exhaust, 3000 stall "tight" converter, 3.23 gears, 27" tires, and it ran mid 13s @ 101-102. I got best times shifting around 5000-5200 RPM. No idea if the carb was tuned optimally. Probably a lot of tuning I could've done to get a little better times out of it.

Would it have run better/faster with another cam? Maybe. If all I wanted was a decent running street engine with some attitude, it fit the bill just fine.

I wish I could've tried a few different cams in that combo. Also wish I could've put a wideband on it to see what the carb was doing.

my experience with the xe268 didnt have any back to back dyno testing vs other cams, but it did do some test & tunes to see what it would do at the track... "running fine" to me means that it doesnt have any signs of detonation & idles good, not so much sound wise but more of a easy starting & has zero hesitation off idle or at any other rpm range (but thats is more a sign of the carb being built right by cliff) & has good smooth vac for the cam size. it has a pretty nice idle lope too but not the stupid "thumper cam" sound.

also the general specs of the build in this 400 are far from ideal, probably just at 9:1 or a tad below, quench distance is bigger than most would prefer & no gasket matching, no cam degree just installed straight up with standard comp supplied lifters, old crane springs that lived in a 455 with a magnum 280 cam for almost 10 years with lots of hard street miles, they were tested before install to be within their specs but not as good as new.

with all that said, what i find interesting is that the car runs as fast or faster than other similar builds/cams, even one of the smaller crower cams mentioned above as a better cam or the bigger xe274 with more compression & 3000 converter. the car is all stock besides the very mild engine build, no drag radials or drag shocks, very hard older bfg tires that many on here wouldnt even run on the street due to age & crappy or no track prep on a street car t&t day. also not going for max launch/times due to being a lower mile #'s matching car & a 4 speed that we all know doesnt shift or launch as fast as an auto with a decent converter even with an above average driver that i consider myself. so the et & 60ft could have been much better with some drag radials & a clutch that grabbed a little better or an auto trans. 103+mph & mid 13's from this type of mild build & heavy 2nd gen t/a with a "turd" small xe268 is not too bad IMO.

again, there are probably better cams out there that would make more power on a dyno or be faster at the track. but all in all, for a lower compression motor the xe's arent as bad as some make them out to be & dont really deserve the bashing they get. maybe the negative examples given had other issues causing the problems but myself & many others with these xe cams have pretty good results & im sure the OP's friend will be happy with his xe in that motor for its intended purpose of only street driving & doing some burnouts leaving the dairy queen...

[KCTurbo]

I have run the XE268 in a 400. For a low compression motor it is okay. I thought it really started to fall off at about 5K. For a street motor I didn't mind it, just depends on what a person is looking for. I ended up pulling it and going with more compression and a 2802 and liked that combo much better. I was running 6X-8's with the XE268 so it was pretty darn low compression, and #13's with the 2802. No real #'s or times to back my opinion up.

[grivera]

Originally Posted by grivera

Mikes455Wagon ran deep into the 11's with an XE274 in a 455 so clearly every combo is different and why generalizations should be avoided.

Originally Posted by Cliff R

I don't deal in generalizations, just facts.

My comment wasn't directed at you or anyone specific for that matter

[Will]

why are Comp's cams almost all on 110 LSAs with 106 ICLs? Doesn't matter which brand engine they're for. I'm sure what's good for a Ford 351 is just as good for a Pontiac 455, right? Unless, of course, you go with one of their thumper cams, then they tighten up the LSA, and the reason is to make it sound different, not for performance.

There are reasons to run various LSAs. Certain combos will work better with the narrower powerbands that tighter LSAs produce. some cam lobe designs work better at different LSAs than others. The whole goal is to open and close the valves at certain points in the cycle while also achieving peak lift at some optimum point. Where those points are depend on a lot of different factors, both inside and outside the engine. Street cars with tighter converters and taller gears generally benefit from broader powerbands. Then compression ratio and the driving style of the owner comes into play.

Why is it, if you buy a set of heads and a cam from Dave at SD Performance, you're going to get a cam with Comp lobes but lobe positions that are different than what Comp offers off the shelf?

These discussions always go down this rabbit hole. There are so many variables at play. All I will say is that Comp XE series cams, as offered off the shelf, would usually not be my first choice but if the purchase is already made and the cam is not wildly inappropriate for the rest of the engine specs, go ahead and run it. If it doesn't run like you want and you put in the effort to tune your combo to it's potential, you can always try something else later.