So who's running a Comp XE268?!
I know this is a old post but want to get opinions on that XE268 i just recently bought for my engine, debating whether i should return and go for something else?
340 bored 30 over and stroked 3.58=372
650 double pump vacuum 2ndarys
Eddy closed chamber heads
904 tranny stock
Rear end to be determind
yur gonna need a 750 or better to feed that hungry brute, and I'd run a DP.
I have a 367 (4.04x3.58), same eddies, KB107s at .005 up out of the hole, .039 gaskets for .034Q.
I did run a Hughes HE2430AL cam, which was 223/230/
[email protected] were 270/276/110+4,lifts of .538/.549 @1.6 arms. I think very similar to the XE268, except the Hughes runs a bit more lift.
At 185psi cylinder pressure that was a fantastically strong off the line cam, a tremendous midrange, died early compared to the previous 292/292/108 Dc cam, but still pulled pretty good to 6000, and I regularly took it to 7000. I ran it with 3.55s and a clutch. It had so much off-idle torque, that it was a dump-it-and-go routine most of the time.
Later I added an od box and a GVOD behind it for a final drive of 1.97, and pushed the mpgs to over 30USg with a dedicated smaller carb. I ran it with a few different intakes and carbs, but finally settled with the AirGap and 750DP. She runs TTIs with 3" full-length duals. Try to keep the crossover, cuz I unsuccessfully spent the best part of a summer trying to find the missing torque when I cut mine out to fit the GVOD. If you don't have a crossover, then with 3.55s, you will need more stall .
I like to gear my combos to hit 60mph in second gear at about power peak plus 300rpm or so. But that cam is so flat over the peak that you can go a long ways over the top. I'll guess it peaks around 5200, but it's hard to pinpoint. Ima thinking she'll pull pretty hard thru those Eddies and a 750, all the way to 6000.
Unfortunately for you with a 904, the ratios (2.45-1.45-1.00) will not get you any where close to 60 in second gear, and 6000,lol. You could do it in first with 3.23s, at 6200, or with 2.94s at 5650. But you would need some stall to get off the line happily. Don't worry, at 185psi, and a lil stall, it will spin any street 275s, pretty much from start to finish.
But if your pistons are still .012 in the holes, you'll have to run .028 or less gasket to make that kind of pressure/ and Q.
I wouldn't run .039+.012=.051Q. With iron heads that would probably risk detonation with full timing and even best gas. With the Eddies you'd probably be ok with best gas. But with .034Q I run 87E10 with full timing no issues.
So for just a gasket swap, keeping the Q to less than .040, you can save thousands of dollars over the course of the engine's life, in the fuel cost difference.
185psi is a sweetspot for that combo, embrace it. Running aluminum heads at 160psi or less, IMO, is a total waste. To break even in absolute power, with the same iron combo, it has been written that you need at least a half point more compression. That might be right for drag-racing, but on the street, IMO that .5 hike should be changed to at least 1.0; and the aluminums will like up to 1.5 points with tight-Q. I have run 11.3Scr with the 292/108 cam, full timing, and 87E10, with no issues.
With my Hughes cam above, I think it was 10.95cr, still on 87E10 and full timing.
BTW; full timing with those aluminum Eddies is between 30 and 34 degrees; I run about 32....... most of the time.
After the tune is in,you are gonna love that cam.
Then you are gonna spend all your money trying to make it stick and launch. Save yourself some coin, and just go straight to 295s or better. If they don't fit; either make 'em or get you a traction aider... like slapper bars at the least. Otherwise, with a 750DP, yur gonna need to relearn some driving skills,lol. The turns are gonna be awful exciting. Be cool in traffic 'til you get the hang of sliding around. If you can't be cool, at least get rid of the Part-Throttle Downshift,lol, cuz it will never be in the right place; when it kicks down in mid-turn, around you will go smashing your rims on the median; ask me how I know,lol.
Do not bother with 245s, you'll burn 'em off in a couple of weeks, probably less. Without trying very hard, you can bald 245s out in a couple if days.
I think a 2800stall would be about right for 2.94s and a 2500 with 3.23s, 2200 with 3.55s and a stocker with 3.91s. 3.73s are in-between so I'd first try the stocker.
BTW
those Eddies will accept up to .550 lift IIRC,or was it .600? Yeah .600 I think, cuz my current cam is .549/
[email protected] arms and different springs is all. Jus saying
