[Cliff R]

9.3 to 10.3, still isn't going to work well. The cam is just too small, and with the "modern" lobe profiles and short seat timing too good at cylinder filling at lower rpm's. Keep in mind as you read this that a stock replacement CS-274 camshaft from NAPA for a 350 SBC engine that works fantastic in low compression 350 engines sports 274 degrees seat timing.

Here's a case in point, as I love real-World examples, that happened recently when an engine shop attempted their first Pontiac 455 build. It is a very similar combo as yours, using a well prepared short-block and ported #96's. Instead of the XE274 they chose the similiar Comp XR276HR cam. The shop is VERY knowledgeable with race engines, and builds a lot of BBC stuff, but no experience with any Pontiac builds.

Their 455 ran poorly on the dyno and pinged enough to damage some rod bearings when they tried to throw some timing at it to make decent power.

I got involved as one of my customers did the Q-jet for it, and of course it was taking some blame for all the "issues" they were having. I talked to the shop owner and recommended that they call Comp and order a larger HR cam with 290-310 seat timing on a 114LSA, basically an "Old Faithful" clone on a 114 instead of a 112.

The XR276HR cam only made about 428hp @ 4900rpms no matter how they tuned it, and they ran into audible detonation at 30 degrees total timing on the dyno.

The new cam made 514hp @ 5800rpm's and no hint of detonation anyplace, per my recommendation, they set the total timing at 30 degrees and left it there for the entire dyno session.

The larger cam also made MORE torque at every rpm, and idled better than the smaller cam on the tighter LSA! The best they could get out of the XR276 cam was 516tq and it was clear down to 441tq @ 5000rpm's.

The new HR cam made 559 ft lbs peak torque, and still making 519 ft lbs at 5000rpm's, and 500ft lbs at 5300rpm's. (This kind of power is why the big Pontiac 455's run so well at the track and still have great street manners).

The ONLY change to this engine was the camshaft. The #96 heads were professionally ported to apprx 250cfm, for those who are taking notes.

I've been telling folks this for years, the WORST cams for these engines are short seat timing on "tight" LSA's, but for the most part it goes on deaf ears.

What these little cams also do is make tuning for "normal" driving more difficult, as they make a LOT of cylinder pressure early in the rpm range, as problem that we NEVER see with larger cams on wider LSA's. They also produce a "quirky" idle, probably from closing the intake valve so early and "tight" LSA with short seat timing, so considerable "reversion" for lack of a better description.

I've had folks drive, flat tow, roll-back and trailer Pontiac cars here for us to tune that bought into the Comp Cam XE and XR cam technology. Not in one single instance have we been overly impressed with any of those builds, and have had difficulty tuning them to run well in the "normal" driving range......FWIW......Cliff