Was checking out RHS those head do look like they would be better for a 318. Would you guys say the same head for a 360 or is that a different kettle of fish?
Brad
Not exactly Brad. Just handled differently. Being a 360 is a bit larger, mostly due to stroke, the engine makes more torque. It has a heavier draw of air and fuel through the head. The port size (In cc amount) reacts differently than with a smaller engine.
While the port size is a little large for a 318, it isn't to big. I think "Race Head" is a little over board of a description. But I also don't want to down play it ethier.
If I was next to you while looking at both engines, I'd tell you to do a 360 engine with the RHS heads for several reasons. Being it is a cruiser and with the idea in mind you don't wanna get whooped by something other than your buddies Mopar in mind. The 360 is much choice because of;
1. The longer stroke produces more torque. This is made in the lower RPM band and fades by the top end of the RPM scale where HP is made. (Keep that in mind for a second. We'll be right back to that.)
The longer stroke makes alot more torque which is good for get up and go. No matter what car you have or it's weight, the more you have, the easier it is to get going. More the merry, hands down. With less pedal effort, even better.
2. The longer stroke engines will make there peak HP earlier than a short stroke engine. The 360 will peak several hundred rpm sooner than a 340 at similar peak levels. Remember the 340 loves to rev. The 318 is no different in the way it acts. It just has a (Much) smaller bore but the same stroke.
3. You still can get excellent gas mileage from a 360. Of course, once you start putting performance parts in it, it'll fall, just like any other engine. But there is an advantage to running a 360 over a smaller engine for mileage concerns as well as what I allready listed.
Since the bigger engine is makeing more torque at the same RPM as the short stroke engines, it will require less pedal to maintain the same speed.
I had a '79 Dodge Magnum (Cordoba based car) with a 360 in it. After a few upgrades, Carter 4bbl on top of a iron intake, dual exhaust of the manifolds w/H pipe to twin cats going to the bumper and a MSD w/a OE vacuum advance distributor, the car was getting 20 MPG's Hwy. with 235/60/15's and a 2.76 gear.
Preety good for a 3700 lbs car IMO. I get in with a 1/2 tank of gas, were looking at 4000 lbs.
While not a tire frier, it did move well. Note, no headers, no cam change, no overdrive.
4. Most performance parts are 340/360 based. The heads, in almost every book, catolog and performance parts maker/seller are geared to the bigger engines. The 318 is largely ignored.
The heads have runners that will work great, with high velocity and shaped well for this type of application. The smaller valve will keep the velocity up and moving. Upgraded chambers help burn the gas better with more power. No valve shrouding on a small bore.
On a smaller engine, the big ports act a little more, "Lazy" in there air speed flow. They'll start to work alot better with RPM. But I'd rather have them working now instead of later.
In drag racing, street or strip, he who gets to the top of there engines performance arena gets going quickest and has a better chance to win.
On the street, the first one to 100 MPH will win because everyone else is playing catch up.
