Comp cam XE 274 help
Hi folks I'm new to this site from B.C. Canada but have read many threads on engine builds in the past. Trying to find a new Comp Cam kit # K20-224-4 XE 274 h , cam ,lifters, timing chain , springs and such. I've searched many stores through Canada and the States without luck for a 318 LA build . Can anyone point me in the right direction please.
Keep in mind (and you may already know this/IDK), that Advertised numbers can fool you;
Some cams are spec'd at .006Tappet rise, others at .008, and still others at .001.. The closer to zero, the bigger a cam will read.
Therefore; not all 274s are alike.
You can take a specific cam that is spec'd as a
[email protected] cam, and respec it @.008 and it be "only" a 270 or something, yet it is the exact same cam.
The point is that long-period cams may have late closing Intake angles, which will reduce your cylinder pressure. This may or may not, be a good thing, depending on your Scr.. 318s are notoriously hard to get decent street cylinder pressure out of, with off-the-shelf parts.
Low CCP (Cranking cylinder pressure) manifests as; soft low rpm power, which usually requires a higher stall and gears to overcome, reduced fuel-economy, and a lazy throttle-response..
The difference can easily be in the range of 1.0 to 1.3psi per degree(or more); thus 4 degrees could be 4 or 5psi. If the pressure increases from say 160 to 165, then you may have to run a higher grade of fuel to avoid detonation. But if the pressure falls from say 135 to 130, then she becomes very lazy down at low rpm.
Some manufacturers take advantage of the spec'ing system, to sell you a say
[email protected] spec'd cam, that they can brag will outperform another manufacturers cam, also spec'd at 274 but at .006. and it might, depending on the rest of the cam specs.
It's not as bad as it used to be 50 years ago; but you still have to keep it in mind.
For a 318 to run that 274cam efficiently, with a Dcr of near 8/1, the Scr will need to be up around 10/1. This will drive your CCP to near 165psi, and your gas requirement into 91 at WOT. This is really only important if you are running a clutch, and street-friendly gears which, on the street, is gonna drag the rpm down below 3000rpm for a lot of the time. The manual-trans equipped 318 will not do well down there unless it has decent CCP.
You may know all this, IDK, so if you do, sorry to have wasted your time.
