my thoughts/your thoughts on my friends 400 build
 

Street only build for a 81 Trans Am.
1972 400 short block all bone stock ( he bought it with 42,000 original miles) very little wear evident so he very lightly honed with the cheap rigid hone and installed new rings.
Heads are #17 small valve with 7/16 studs and a 3 angle valve job set up by Kaufman for use with CC XE 268 hyd flat cam. Trans is a T350 . Intake is the standard performer.
He wants to use 24-2600 converter and maybe 3.42 rear end.

Here was my response: I estimate a 9.9 cr with those heads and told him that cr with bad quench(.060")with the XE268 will ping badly on pump gas. That cam will also be done by 5000rpm tops and that stall converter and rear gear is not helping his combo. I told him to keep the 308 gears he already has installed. He is hoping for near 400 hp. I told him that with good octane boost it will live and have a lot of torque in the low to mid range for a street car but that 400hp is in dream land. More like 320-330 tops.
What are your thoughts?
Thx., Larry

PS: I suggested the Summit 2801. Maybe the 2802 with better heads to bring the power RPM up. Dump the XE268

I don’t see how the compression can possibly be 9.9 with those heads which are stated to be 72 CCs.

9.5 is about it, in fact that 3 angle valve job has sunk the valves enough to add another 1.5 to 2 CCs to that stock 72 CC number, now add on top of that the fact that most heads stated to be 72 CCs where really 74 CCs and you can quickly see that 9.9 is not possible!

Also the lift of that Cam will not be enough to access enough flow to make anywhere near 400 hp with those small valve heads!

That would not be the path I would have gone.

but.

Here is a dyno image, engine did better than most would think.
400 with XE262
About 9.2 CR - cranking PSI was 190 to 200.
445 ft lbs @3400
361 hp @5100.
long branch manifolds on but no exhaust. Timing was 32

And what heads where used in that dyno test ?

Stock 16 dports

?
Sorry the heads were also decked .010" ( subtract about 2 cc from valve job for it.) 72cc +10cc( head gaskets@ .042')+ 4cc(piston below deck) +5cc valve reliefs +1cc( ring area)= 92cc + 819.36cc (for cyl volume)= 911.36 /92 = 9.906 cr

I have a set of virgin 17's. I measured one chamber on each head. Both were EXACTLY 83.5 cc's......
I've read here that the 2801 is a high lift version of the 068. I'd just use the old reliable 068, which ONLY needs stock spec springs (just make sure you use NEW springs).

Any cam with XE in it's part number is worth NOT using!!!

Get the block zero decked, or as close as possible.

I recently saw a 78 TA at a car show. 78's used a taller scoop than 77's. The car had a Performer intake. He had his hood initailly closed. The car was immaculate!!! BUT the scoop did not look correct to me (he bought the car recently, as is, his TA knowledge was zero...) I made no comments about the scoop...

An iron intake will perform GREATLY!!! Even a 77. 78. 79 iron EGR intake. 68-72's are always preferred, though...

Exactly, which rings??? I hope they are not plain iron rings...

Don't worry about a specific HP number. Do the right things, this TA will be a blast to drive!!!

Opinions.. lol
Not my favorite lobes either, flat tappet wise I'd go with a Brookshire design.
Yet the Jim Hand book displays 6 different engine combinations using XE cams from 4 different veteran Pontiac builders (including SD Performance).

More XE cam owners on this forum are / were happy than unhappy!
More than 20 years ago I did suggest an XE cam to a friend.. he lowered 1.5 seconds off his 1/4 mile time as a result.
That friend was a licensed auto mechanic and did it for a living.

Both Dave Bisschop's Revised Stump Puller and Old Faithful 2.0 cam use a XE lobe.

Ken Crocie's magazine featured All-Alloy Indian build used XE lobes.

Jim Butler, KRE, Paul Spotts and other Pontiac venders sell and use XE lobs themselves.

.

XE flat tappet cams are the ones I’d avoid.

I liked the XE274 in my 9.5:1 400 until it wiped a lobe while cruising down the highway after running it for a few months. Only cam I ever had a problem with. This was over 16 years ago.

The XE268 did OK in my 69 bird with old combo. 400 + .030, untouched 62 heads, TH400 with Hughes GM20 converter, 3.08 rear, Long Branch manifolds. First time out with no tuning ran 13.78

https://www.youtube.com/watch?v=EobSWI7Ngi4

I too question the stated stock 73 CC volume of the 1968 17 heads.
These 2bbl 350 F body motors where said to have had a 9.2 compression, and as we all know these days Pontiac exaggeration all of there compression ratios by 1/4 to 1/2 a point!
If you then consider 8.9 a more realistic compression then the 17 heads used would have to be larger then 73 CCs.

The XE262 is a "turd" in a 400 build just like the XE268 is in a 455 build.

I've been asked to tune more of them than I can count, and not overly impressed with any of those builds anyplace. They run OK so if being evaluated by the "seat of your pants" I guess some folks would think they make the grade. Snotty idle, throw some power at you then fade away. Larger cams on wider LSA's in the same build will make BUTTLOADS more upper mid-range and top end power and just as strong if not stronger off idle and lower RPM's.

Comp grinds that junk on 110LSA's for one reason, "bling". Who wants a smooth idle engine when you are rolling thru the Dairy Queen car cruise? It has to sound "bad-ass" to run well at the track...right?

If you want a comparison a local customer here built a 400 with ported #62's. I had him use the Crower 60243 cam with high ratio rockers and Rhoads lifters. It's topped with a STOCK cast iron intake and 1968 Pontiac Q-jet. I built his TH350 and supplied a custom torque converter for it, 3.73's out back. In street trim his Firebird on DOT's it runs into the 11's! Do the math on that at 3600lbs race weight as see if that cam makes just a little bit more power than the XE262 or 268 in the same build?.......FWIW........Cliff

"I recently saw a 78 TA at a car show. 78's used a taller scoop than 77's. The car had a Performer intake. He had his hood initailly closed. The car was immaculate!!! BUT the scoop did not look correct to me (he bought the car recently, as is, his TA knowledge was zero...) I made no comments about the scoop..."

Just put a Shaker hood and scoop on my 81 that has a mild 400 in it. Performer intake also-Performer is 1/4" taller in front and 1/2 lower in the back vs a factory HO intake.-Why the scoop looks slightly weird.

i have the xe268 in a .030 over 400 in a 1978 W72 TA, 6x-4 heads, 3.42, 4 speed. stock intake & cliff built q-jet. heads were shaved about .020 & block about .005. estimated ~9:1. car runs very good with zero detonation on 87 or 91 gas, pulls hard up to about 5500 & ran 13.8 at 103mph on old hard street tires & some clutch slipping off the line. its a lower mile #'s matching car so i was not going for max times.

i picked the cam about 10-12 years ago before reading that some on here dont like them & im sure there is a better option for the combo however, i dont see any of the negative complaints some mention & its far from a "turd." stock timing & no real tuning, just bolted the parts on to the rebuilt shortblock, i did everything else like install heads, cam, etc with basic tool, no cam degree etc. i am considering a cam swap but so far it runs so good i dont see any real reason to do it. there may be better cam options but the xe268 & other xe cams are not as bad as some make them out to be... if everything else on the motor is working right.

I am not at all familiar with a 17 head. But if it was 9.2 SCR rated from the factory in a 350, it does indeed sound like a mid 80s cc head like Jeff said (83.5). With a clean up cut on the heads and a valve job with a stock 72 short block, the SCR is likely in the upper 8s.

No port work, with small valves, and compression in the upper 8s using RA manifolds. Be pretty easy to over cam it, really no reason to try for power beyond 5k. Especially if the plan is to keep it fun to drive on the street. I think that 320-330 hp is a good guess for the plan as is…FWIW…400 hp needs some major port work on the small valve heads, and a cam like a Lunati 702 or add headers and run the 703 Lunati, comp 278 ah-10.

Honestly, as is, I think it would run about the best with that cam Cliff mentions from time to time on lower compression 400s. Can’t think of the number? Slightly smaller than the summit 2801 bigger than the 2800.. The way this engine is set up though Lunati 702 would be overall VERY hard to beat for overall power and drivability.

If the owner can tolerate the xe268’s valve terrain symphony it commonly creates, it is a fun cruiser Dairy Queen drive in cam. I think it would run well. The xe268 will cash in by 5000, appears to me that matches the head potential and the compression. They generally are not cams you can expect a lot of trouble free miles out of, most people don’t drive there cars enough to find out though. The hi energy lifters that comp sends with their cam kits are pretty sup par, suggest getting better lifters. fwiw

Keep in mind some offer opinions with direct experience while others simply repeat what they read.

No kidding?:caked:

I don't talk about it much but actually built a 406 with well prepared #16's back when the XE cams first came out.

We used the XE268 cam in it.

It was NOT overly impressive anyplace, idled with sort of a "deep/heavy" exhaust note. Thru some power at you quick and early, but pretty all over by 5000rpm's.

Not one of the better combinations I've put together here but we learn by doing things as mentioned.

Jump ahead a few years from that disaster and moved to the Crower camshafts for my Pontiac builds. Same #16 heads, untouched and not even a port match, just some really good valve/seat work, stock intake, Q-jet, etc.

The Crower 60916 cam made 419hp/453tq. The 60243 cam made 424hp/465 tq.

With KRE heads we saw 450hp for the 60916 cam and 460hp for the 60243 cam.

A 2802 cam in a nearly identical 400 build made 385hp if anyone is taking notes. I doubt if a Comp XE262 or XE268 would be anywhere near the Crower cams, but after getting singed by using it a few years earlier in the first 400 mentioned above I was NOT going to spend the extra time, funds and dyno day to find out.

While we are talking camshafts and lower compression, the Crower 60210 is a flat ars "home-run" in any of the later 400's with 46, 4X and 6X heads and 7.7 to about 8.5 to 1 compression.

I had one in the 400 using unported 6X heads that powered the Ventura back in the 1980's. The car ran 14.0-14.20's at 98-99mph on any outing. That's with a TH400, stock 13" converter and 2.73 gears on plain old BFG street radials (235/60-15's). Best pass ever was 13.87 @ 101mph with really good air and a little tail wind. I see folks with more compression, more converter and more gear converter not running better if as good at about the same race weight.....FWIW.......

I ran an XE274 in a 0.030" 400, stock 670 heads, 3.55 gear, 2500 stall converter, 3 tube headers in a 3858# car that did 13.0 in the 1/4, still got the motor. I think it needed a little more converter to take advantage of the cam but was an excellent all around driver and felt great on the street.

The #17 heads are shown to be 72CC's and found on the 9.2 compression 350CI. They are most likely about 74-75 CC's as Pontiac added a few more CC's to take into consideration the carbon layer that would build up on the chambers and piston tops with the leaded gas of the day.

The XE cams are good with lower compression builds as they tend to build cylinder pressure, pull hard, but peak out a little early. Ran the XE274 in a 1972 400 with the 7K3 heads and those rebuild kit 8 eyebrow pistons and the engine pulled extremely hard to about 5,400 RPM's and was done - but it would rev to 6K, but it was no longer making power. Had no issues smoking tires with the 3-speed, 3.23 gears, 28" tall tires and ran on regular gas without issue. I would use this cam again on any low compression 8.2-8.5 engine. I would not run this cam in a high compression engine unless I planned on high octane gas or an additive.

The concern for your friend should be the high compression. No problems in my book honing the block with a drill hone/stone if there is little wear/ridge. Have done this a couple times "back in the day" when many of us had no money and freshening up the engine to stop the high oil use with new rings and valve seals was what we did to get more miles out of the car/engine. So go ahead and hone the cylinders, just make sure to be anal at cleaning up the cylinders after the honing to get them clean.

The heads will also have the press-in studs which means being reasonable on lift. If you go over a certain lift on the cam, then you will want matching springs which mean higher spring rates and this could pull studs up. So I would select a cam having a stock lift or a little more, but can use stock spring pressures.

Small valves, screw-in studs, won't provide any big HP improvements, and add to that the high compression and an EX cam spec and you friend is building for disappointment. However, the heads can be upgraded at cost and that's where most will say to just go with the 6X heads and get the compression you need along with the improved upgrades - then he can go with a bigger cam and get more HP/TQ.

So point out that his choice of parts are not entirely compatible and he may wind up with time/money put into the engine with disappointing results.

In the first post it said something to the effect that KRE prepped the heads with 7/16 studs, valve job, and springs to match the cam. Should be good on that.

Only one way to find the compression for sure is to cc the heads. Pontiac’s actual head cc has some pretty large swings from what the were actually, especially on those heads that had the 72 cc rating.

The cam has its nitche with very peppy bottom end . I have always known that. My friends' idea of 400 hp or the ability to run it on pump gas using the advertised cc numbers is very unrealistic. ...and I told him so. The only solution here is to pull a head and cc a chamber. If actual cc puts the cr in the lower 9's or so then he's good to go.

My bad, you are correct and I even read that. Just got into the reply and it slipped my mind - the older you get................ LOL

Just to back pedal as I let this slip my brain, "Heads are #17 small valve with 7/16 studs and a 3 angle valve job set up by Kaufman"

Ok, so your friend is good to go with higher lift cams, just match springs to lift (and they may alraedy be good to go) and then make sure plenty of valve-to-piston clearance. I believe the consensus is to keep lift under .500" and there should be no issues.

Are the 7/16" replacement Big Block rocker arm studs? I am assuming so since Kaufman set them up. The heads should be using poly lock? This will allow the rocker arms to be "zero lashed."

Yes, CC one of the head chambers so you know exactly what the CC's are and then you can use the on-line Wallace Compression Calculator to get a good idea of what the actual compression will be.

Yes, no kidding Trash.
You missed the five people in this thread positivity speaking about their XE cam. I know of several others here, maybe they will chime in yet.

Ever consider why one member supposedly has more complaints than nearly 54,000 other members. LMAO.

I have a set of 17’s in my pile. I cc’d them a couple of years ago and I’m almost positive that they were close to 74/75 but have a little bit of valve sink I believe. I can cc them again if you want so you don’t have to pull the heads off? I wouldn’t anyway for a question of 2 or 3 cc’s lol.

Lol, I have kind of found it is a little late to provide much helpful advise on engine internals once the heads are bolted on..

I think I underestimated the power potential of a small valve head some. I got to thinking I remember Dennis Jenson ( SD455DJ) posted some dyno pulls for a 400 with small valve heads a while back. Pure stock type built, tight quench, upper 70s cc small valve head with 45* valve, summit 2801, 214/224 @.050” cam, log manifolds. 383 HP @5300 and 455 tq@3500. You can see there would be no need to jump up to the bigger 224/234 cam. FWIW..Personally, most my experience has shown heads with 45* valves can usually tolerate more compression than the 30* intake heads, especially on smaller valve set ups. If KRE did 45* seats, it will help the XE some. Hopefully the engine has the bigger cc’s than in the 70s.

No "supposedly" to it. My information doesn't come from regurgitating what I can Google up, the efforts of others, or trying to associate myself with big names in the industry to put some sort of meaning to useless comments on these subjects.

Anyhow, I've had them on the dyno, and scores of vehicles in here to tune using them (at least the ones that didn't wipe lobes early in life). Matter of fact there was a 455 on the dyno with an XE284 camshaft in it right ahead of me once. It was topped with ported 7K3 heads, single plane T-II intake and an aftermarket 850cfm carburetor. They pulled and pulled and pulled on that engine running around changing this and tweaking that and couldn't bust 400hp and 499tq. Finally with ALL the stops pulled out they hit around 430hp. Actually we did NOT know what cam was in it till a few days later as it was simply dropped off at the facility for dyno testing and the owner/builder wasn't present at that time. It had a "menacing" idle and sounded like it was going to do something, but didn't make the grade when they started making pulls on it. I do remember power ending ABRUPTLY at 4800 RPMs so it never had a fighting chance to use the 240-246 @ .050" duration because the valve springs gave up. I'm a quick learner with this sort of thing so after building a turd of a 400 a few years earlier with a XE268 cam and seeing that engine fall way short I've avoided them. There are simply better choices out there that do not require battleship valve springs to keep things in check at high RPM's and you don't have to deal with all the "clatter" in the valve train that I've witnessed with many of those engines.

As soon as we got that "turd" off the dyno I put my own 455 on the same dyno with 6X heads, Crower RAIV cam, iron intake, Q-jet and factory HEI and cranked out 455hp on the very first pull.

IF anyone reading this wants to have a good experience with an XE camshaft have the heads prepared with 45 degree intake seats and heavy porting under the intake valves. I've seen a few respectable dyno runs with the XE274 camshaft in builds where the engine builder did that, plus they use really light components above the lifters to keep them from "crashing" at high RPM's. I still wouldn't go in that direction, there are simply better choices out there these days and you woln't have to deal with potential noise, lobe failure and lifter "crash" at high RPM's....FWIW.....

Apples to oranges comparison.

T-II intake vs Iron Q-jet

850 aftermarket vs Q-jet

Cliff - "the valve springs gave up." = - "power ending ABRUPTLY at 4800 RPMs"

PJ - So how can the cam be the fault in this example when the valve springs crapped out?

What was the engine's compression?? And your 455?

Cliff - "there are simply better choices out there these days and you woln't have to deal with potential noise, lobe failure and lifter "crash" at high RPM's"

PJ - Blanket statement? What RPM does lifter "crash" occur? Never experienced any of this with the XE274 I ran - ticking noise? You mean like Rhoads lifters that are promoted here, or the roller lifter ticking of certain brands that are used here? Heaven forbid I bring up solid HFT and their ticking noise. I don't recall any annoying "ticking" but then again I did not build the car/exhaust to be B-body 4-Door old man quiet so I can listen to the single speaker AM radio. No lobe failure in my experience, but I also know how to break in a cam and match parts. I zero lash my lifters, so is the "ticking" always a cam issue or maybe a lifter choice or adjustment issue just like other cam/lifter selections?


Please, when posting, state this is your experience and opinion and don't discount others when their experience have had no issues with the XE cams. They have a place when used in some builds. Yes, there are better choices on cams, but that can be said on every build as cam selection IS SUBJECTIVE. I could choose one cam, but another builder might choose another, and so on and so on. I could select the "best" cam based on dyno results, engine simulators, recommendations, and then choose a different intake/carb or have different head flow numbers, or wrong timing curve, wrong gearing/converter, etc. and have a "turd" or lack luster performance and then question those who suggested the cam.

I think you should know by now the difference between a street car and race car. On the street, I don't need to squeeze out every lick of HP. I am most likely not going to twist the engine to its max RPM range each and every time I row throw the automatic or manual gearing. So a cam profile that works best up to 6,000 RPM's may not be in my best interest when most of my driving is going to be around town and to car events. I LIKED the XE274 cam in my LOW compression 400 engine because it woke it up, pulled very strong (and I like power), could light up the tires, and got 16 MPG on the highway at 70 MPH. Was a great stoplight-to-stoplight cam which was most of my local driving - FUN, which is why I own the car. A RAIV cam would have never worked. Yep, power was gone by around 5,400 RPM's. So what? Isn't that what the next gear is for? So maybe the lower RPM range also protects those not so skilled at driving from grenading an engine and less wear on parts.

I respect your opinions, experience, and words on this forum, so don't take this personal, but sometimes these "absolutes" just don't fly. How about building a low compression street engine with the XE cam and let us know how the seat of the pants feel is for you. Yep, it won't be 500HP and 600TQ, but I don't think it will be a "turd" either.

Our 406 with xe274 can did that which seems to me is closer to an apples to apples comparison vs the 262 or 268 cam

"Apples to oranges comparison."

You are correct.......with all those aftermarket "high performance" parts the engine ahead of us should have made a BUTT LOAD more power, at least if you are buying into all the excellent advertising the companies making them tell us about them.....FWIW......

I'm not into "seat of the pants" feel or testing, and avoid parts that don't make the grade or have issues associated with them.

The XE cams are simply a direction I will not go with these engines. Right to start with they recommend too much spring pressure, which is hard on everything above the lobes. They also throw the valves around with a lot of authority. Fine for reducing overlap and getting better .050" numbers but with Pontiac heads and flat chamber floors and 30 degree valves/seats you are NOT taking advantage of the excellent low lift numbers.

Comp and other cam companies tell us that we will make "more power" with fast-ramp designs, better vacuum, improved throttle response, fuel economy, etc, etc. That sells parts but the reality of the situation is that shorter seat timing and greater .050", .200" and more lift is easily trumped by the valves being off seat longer. Folks are quick to look at .050" number but fail to realize that "time" in milliseconds adds up quickly to more opportunity to move air as the engine increases RPM's and the cycles are happening more times per second.

If you really want to make more power with shorter seat timing move to a roller profile instead. When you take the limitations of the lifter diameter OUT of the equation, what they tell you becomes possible.

I actually have a customer who used an XE cam in a 455 build and made excellent numbers. To get them he changed to 45 valves and seats, and HEAVY porting under the valves and short-turn in the heads. He installed ultra light parts above the lifters, including pushrods, rockers, and titanium valves/retainers.

The dyno results were actually quite impressive. Even so having to do all that with your basic "street" engine doesn't make it from a business standpoint and why jump thru all those hoops when you can make the same power with slower ramp cams, lighter springs, less expensive valves, retainers, etc.......

Generous offer! Thanks a lot! This engine is buttoned up and still on a engine stand. As far as the cam goes I think it will be fine being only a street cruiser( after all torque is what moves a vehicle driven on the street anyway) . It's the c.r. that needs to be established. Numbers from 72-83.5 cc is just too much of a guessing game. If comp ratio is in the high 9's then the cam simply needs to go. I need to get back to him and advise. What he does is up to him. I will certainly strongly advise him to pull a head and get a chamber cc'd. then go from there.

Thanks for all the responses, Larry

Ok I dug out the 17’s and cc’d them. They came in at about 83cc’s. The valves sit better than I remember but I’m sure they’ve had at least one valve job so I’d say out of the factory they were 80cc’s. Hope it helps you out.

Here is a pic after I cc’d them to show you how the valves are sitting etc. Im confident they are 80cc new.

I used a XE 262 on a 112 on my 78's low CR 400. Did OK. Used a 2801 Summit in the low CR 400 in the 81 about the same as the XE 262. Click over a stock cam.

Thanks for taking the time n trouble. Confirms what other posters are saying. I'll pass the info on. Looks like good news for him. Thanks again for all who helped. Regards, Larry

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.

Those valves shown in post 36 are indeed at stock height in the chamber!

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.

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

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... ;)

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.

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

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.