1.5 to 1.6

[stroker mike]

with a crane 260-2 in a 318 an increase in rocker ratiofrom 1.5 to 1.6 should give me an increase to 455/484 from 427/454, theoretically. one guy says the true lift will be more like 440/468, but why? I wanted a profile like a mild voodoo or xe, but since this setup is new I didn't want to tear it open. what can I really expect with a ratio change in this case? I want it to be the difference between a performer and an airgap rpm, will this do it? You guys know this stuff from experience, I only know most of it from books. not the same. Thanks again!! you ahaven't steered me wrong yet!

[DartGT66]

Don't know what he means with the lift increase being less, maybe because the pushrod geometry in the LA's are a bit odd, you don't see "full lift" at the valve? Anyway, it's hard ot rpedict the effects of changing the ratio. Sometimes it helps some, and sometimes not.

[djwhog]

Mike there is so much mixed responce to this. I know many say on stock heads that you get into geometry issues etc. I think it has a lot to do withthe cam and on large cams it makes a bigged diff. , you can get into push rod hole clearance etc.

If you can maybe buy on rocker, put it on the shaft and setup a dial indicator and check the real total lift you end up with..

What heads are you using, exhaust, intake etc

[rumblefish360]

Mike, your both right to a point. Your right with the math. (I think, I didn't check.) But your freind is right because the actuall ratio of the rocker is not 1.5 The factory stamped rockers are as poor as 1.3 and good as 1.45.

IMO, I would seriously suggest a Voo-Doo cam or XE cam if thats what you want to have. Not try and make a small cam more intense "like" a XE or VooDoo cam. That's the way to do it. Adding ratio in the rocker is a good way to increase the intencity of a cam, but it will not be a "performer" to a RPM AirGap change. It never will be.

A lay-mans way to pick a cam is by the duration of cruise of the cam followed by as much lift as the head can handle.
OR, in other words;

You cruise at 3200 rpm, your heads air flow stalls at .500 lift.

Look at cams that cruise in the 3000 - 3200 rpm range with the most lift you can get. Without the added rocker ratio. You will be happeir in the longrun.

To order a custom cam takes a few minutes on the phone and no real added cost to have it done.

[stroker mike]

Rumblefish and djwhog, you guys always give me answers that make sense. I can do the math all day but real world results are what I'm after. I guess I should get the grind I want quick, the engine is supposed to go back in the car in two weeks. I am not gonna put an air gap on this 318 anyway, cause of the difference in port size, my only real choice is a performer, which is exactly what is on there now. Holley had a 318/273 specific single plane with a funny air crossover at the back but I sold the one I had for 100 bucks a few years ago and offenhauser hasn't made a batch of the 360 *equaflow for my engine for some time now, I had one recently and sold the whole engine. I seem to be mildly phobic about being common place, I want a step above the performer, but then that is why I love mopar. Never second place! Does anyone know of a manifold that would have correct port size for a 318 that isn't a performer? Or action plus? if there isn't there should be, if I could make one I'd make a small fortune. There does seem to be a small demand... for those who don't want to put 360 heads on their 318.

[rumblefish360]

Use the RPM and since your into a performance build, if you don't mind some home porting, open the heads window up to the intakes. Bowl port it and have some fun.
(Use a cam of about 8* or more in duration seperation between the intake and exhaust lobes,)
I have a link around here someplace for offy intakes. Ah, here it is;
http://www.offyparts.com/index.php?o...1ee4f72e4bd1d5

[stroker mike]

Hey I went to that link, they don't have the equaflow listed, did they stop making it for the 318? but the dual port is cooooooool.........Thanks!

[rumblefish360]

Skip the dual port.

[TK]

While I disagree with Rumble about the dual port....Once you get the carb tuned, you will love the low end response, and MPG. The dual port will never perform on top end like some of the other choices.
I am not a fan of dual plane intakes for small port heads anyway.

[TK]

Huh, I was looking at the link, the picture of the dual port they show, is actually just a plain old Offey 360* Go figure.

[DartGT66]

Offenhauser has some great "innovations", most of them seem to be built on the same basement, the 360* They have very seldom been top contenders in any area.

I still think that teh lift thing isn't because the inaccurate ratios. It shouldn't affect the lift with the "new" rockers at all, if they hold true. In a small block, the lifter angle is far greater than the pushrod angle. The lifter raises to one direction, and the pushrod pushes the rocker to slightly other. Therefore, the movement of the lifter doesn't turn 1:1 to the rocker arm, and the true lift is less than what the movement of the lifter multiplied with the rocker ratio.

[stroker mike]

Well you are right about one thing, that is an equa flow intake in the picture, and they want 401 for a dual port, well summit get's the 360* for 280. It's the only alternative to a performer that I know of except the street dominator for 273/318. The fit and finish of offy products is downright superb, and since this isn't a pro street project, but a cruiser, I think that the offy 360 is an excellent candidate for my purposes. The thing is, that link HAS the dual port in stock, summit says 4-6 weeks minimum wait for the 360*. I think that really bites. I got time, so back burner is where this one is gonna go for now. but about the rockers,don't you think chrysler was aware of the quadralateral disproportion when they engineered those heads? I am sure that the difference in angle was accounted for by the placement of the fulcrum in the first place. The relation of the two end points to the fulcrum is what gives us our ratio in the first place, regardless of the direction of travel of the rod and lifter, so if 1.5 produces x within these parameters then 1.6 has to produce a proportionate amount of lift. Or di I fail geometry? LOL!! it has been a minute, to be honest!

[DartGT66]

Originally Posted by stroker mike

The relation of the two end points to the fulcrum is what gives us our ratio in the first place, regardless of the direction of travel of the rod and lifter, so if 1.5 produces x within these parameters then 1.6 has to produce a proportionate amount of lift. Or di I fail geometry? LOL!! it has been a minute, to be honest!

In this case, I think you have. Or the other possibility is, that I have. If the lifter angle and the angle the rocker arm makes its movement are the same, the angle of the pushrod has no meaning, but if they are different, then the angle makes a difference. I think Sanborn might have some knowledge and measurements about this?

[stroker mike]

since the end of the rocker moves in an arc...that would make the geometry more efficient, not less, or would it? aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaahhhhhhhhhhhhhhhhhhhhhhhhhhh!!!!

[rumblefish360]

Stop all the thinking for a second. If the cam you purchase advertises .480 lift with a 1.5, then that's what you should excpect at the valve. The only problem is actual rocker ratio and the only reason you will not have the advertised lift.
Geometry angles and such be danmed here for a min.

[stroker mike]

LOL!! I think you are right, rumblefish. Right on.