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.......